Eogogics - Tutorials on Technologies, Techniques, and Tools http://www.eogogics.com/talkgogics/tutorials en-us Plone 2.0 Microsoft Exchange http://www.eogogics.com/talkgogics/tutorials/microsoft-exchange Mon, 02 Apr 2007 12:47:24 -0500

What Is Exchange?

Exchange is Microsoft Corporation’s premier email server.  In the world of Internet, there are email servers and email clients.  Servers are responsible for sending, receiving, and storing email messages and attachments; clients are needed to read these messages and download the associated attachments.


Ease of installation and graphic interface are among the reasons for Exchange’s popularity.  Exchange is ready to work right after installation, without the need to modify dozens of text files or settings to get the server up and running.  When implemented right, it allows for a robust email server for medium to large corporations.   This brief tutorial will discuss the installation requirements, integration with Active Directory, mailbox creation, storage management, web access, and the Outlook client.

History and Context

Exchange 4.0 debuted in 1996 as an upgrade to Microsoft Mail.  Version 5.0 was released in 1997 and soon 5.5 followed with its LDAP directory access method, a precursor to what would become Active Directory in Windows 2000.  With the introduction of Windows 2000 and Active Directory, Microsoft introduced Exchange 2000 Server, a robust platform which also allowed for chat and IM services.  In 2003, Exchange Server 2003 was released.  Chat and IM were removed and marketed as separate services using Live Communications Server.  The Outlook Web Access module which allows access to email using a browser was enhanced considerably to mimic the real Outlook client which installs as part of Office.  The next version of Exchange, name 2007, will add lots more features and expand the storage of this mail server even more.  The new version will have friendlier administrative tools and enhanced backup and restore, a sore point in versions of Exchange up to this point.

Historical Milestones

1996  Exchange 4.0 is introduced as a replacement for Microsoft Mail

  • Client/server architecture
  • X.400 based

1997  Exchange 5.0 is released in May

  • Adds administrative console
  • Support for stand-alone SMTP
  • Outlook is introduced as the preferred client

1997  Exchange 5.5 is released in November

  • Introduced in Standard and Enterprise versions to target different audiences
  • Provides “connectors” to allow Exchange to talk to any mail server
  • Introduces LDAP
  • Introduces clustering

2000  Exchange 2000 is released

  • Designed to work with Active Directory
  • Provides enhanced storage and administrative tools
  • Adds chat and IM services
  • Adds key management services for sending and receiving secure email

2003Exchange 2003 is released

  • Enhanced Outlook web access module is added
  • Management console is greatly enhanced
  • Support for blacklisting addresses is added
  • Enhanced spam control is introduced in the server and in Outlook 2003

Why Exchange?

Exchange is certainly not the only mail server out there; there are dozens of mail servers available.  In fact, Unix folks would probably speak of Exchange with disdain preferring Unix mail servers such as Sendmail.  While it is true that Sendmail is well-designed and robust, it needs a Ph.D. to set one up.  There are millions of small and medium size business who want to set up in-house email and with Exchange, in a few simple steps, they can be up and running.  In fact, small businesses who install Microsoft Small Business Server (with a series of Next clicks) have Exchange installed automatically and ready to go.  This simplicity and ease of use are the major contributors to Exchange’s success.

Principles and Operation

Exchange Server 2003 relies on Windows Active Directory services.  The installation process is rather straightforward.  The installation process modifies and extends Active Directory.  Existing users are given email accounts that match their logon names.  New accounts created are given the option upon creation as to whether or not email boxes should be created.  Outlook Web Access is automatically created for all accounts and ready to use.  For users preferring Outlook, the process or configuring all Outlook clients in an organization can be fully automated in minutes.  Once Exchange is installed and up and running, there is very little maintenance.  Clearly backups are recommended but for the most part, Exchange manages everything.

Strengths and Weaknesses

Exchange’s strength lies in its simplicity and robustness.  It installs and configures easily. Anyone can be trained in a short period to learn to use it effectively.  Since it also sets up web access automatically for all mailboxes, it makes it easy for its mail users to check email from home or while on travel.  All this has made Exchange a darling of many organizations.
If there is one weakness in Exchange, it is its difficulty in back-up and restore.  This is supposed to be addressed in the next version, i.e., 2007.  While the backup process is pretty straightforward, when it comes time to restore, the procedure is quite ugly and difficult.  While third party add-ons are available to address this one weakness, Microsoft has promised to address this issue in the next version.

Business Implications and Applications

Most business, small and large, the federal government, state institutions, colleges and universities, as well as non-profit organizations use Exchange.  While very popular, it is still viewed as a difficult topic to master and many administrators shy away from learning to work with Exchange.  Most training institutions that teach Microsoft MCSE tracks do not include Exchange.  Exchange instructors and administrators are hard to find and somewhat prized.  This is interesting since Exchange is not difficult to learn and use.  Because of its widespread usage, along with Outlook being the favorite mail client generally, Exchange can only become more and more popular and pervasive.  With Microsoft’s introduction of SharePoint services and its Calendar connector, both of which integrate with Exchange, this dominance in the market will last for the foreseeable future.


How to Learn More about It


Courses
Eogogics offers a five-day in-depth workshop called Exchange 2003 Server: Migrating to and Deploying Exchange Server 2003 for IT administrators and systems engineers.  For less technical professionals or managers with an interest in Exchange communications technology and administration, a one-day short course is also offered.  Please check out our IT curriculum for a number of related courses.

Books

Web Resources





]]> 3G, IMS, and the Carrier Network Evolution Economics http://www.eogogics.com/talkgogics/tutorials/3G-IMS Wed, 21 Mar 2007 03:37:49 -0500

What are 3G and IMS?


Third Generation (“3G”) wireless and Internet Multimedia Subsystem (“IMS”) are technologies which, in many ways, are very complementary.

In essence, 3G is a radio modulation technology that enables greater throughput of bits per Hertz, making it possible to offer subscriber applications and services that require higher bandwidth.  The two dominant 3G technologies in the marketplace today are WCDMA/UMTS and 1xEV-DO, which have evolved from different technologies and are the product of different standards bodies.

IMS, on the other hand, is a network technology based on policies that provide a common enablement layer for all applications and services.  IMS allows a network operator to rationalize much of the investment required for new services (and legacy services as well) across a shared, policy based enablement layer.

Standards


The Third Generation Partnership (3GPP) sets standards for both GSM/UMTS and IMS.  Third Generation Partnership 2 (3GPP2) defines CDMA2000 (1xRTT/1xEV-DO) and MMD, a CDMA variant of IMS.  Also involved is TISPAN, a standardization body of ETSI specializing in fixed networks and Internet convergence.  Ad-hoc and other working groups exist between both 3GPP and TISPAN sharing ideas and approaches toward the next generation technology, especially in the area of fixed and mobile convergence.

Historical Milestones

  • 1980’s:  AMPS – Advanced Mobile Phone System, also referred to as 1st Generation Cellular
  • 1990’s:  PCS – Personal Communication System, the first digital networks built largely on the IS-136, GSM, and IS95/CDMA specifications
  • 2000’s:  3G – Universal Mobile Telecommunications System (UMTS) and 1xEV-DO (Data Optimized) evolving the radio access network.
  • 2000’s:  IMS – Internet Multimedia Subsystem for both fixed and wireless networks, a standard still evolving with promising early deployments, designed to optimize network resources and cost.


3G, IMS, and the Economics of Network Evolution


Both 3G and IMS seek to help operators evolve data-oriented service offerings for their subscribers.  Both technologies are aimed at higher speed data applications.  What’s also important to consider, however, is the enablement of voice traffic over Internet protocol (“VoIP”), traversing the network in a packet oriented fashion rather than the traditional, legacy circuit switched environment.  Because the majority of traffic and revenues today in mobile networks are based on voice, the cost differential of VoIP versus legacy, circuit switched networks, is a supportive element of a carrier’s strategic investment for both 3G and IMS.

Obviously, engineers and network planners would want to look to investment strategies today that can be reused and leveraged in a 3G/IMS environment tomorrow to gain better overall capital efficiency.  Moreover, while both 3G and IMS have their own basis of admission control and quality of service, IMS provides the possibility of increased granularity with respect to quality of service, down to subscriber profiles, applications preferences, etc., where 3G today defines only four, rather coarse classes of services around streaming, interactive, conversational and background traffic.  In the 3GPP community, LTE, or Long-Term Evolution is currently working towards end-to-end QoS.

Why Is the Study of the Economics of Network Evolution So Important?


The mobile industry in the developed countries have reached or nearly reached maximum penetration levels.  To continue to drive growth, new traffic must be generated, which can originate from new services from existing subscribers as well as from machine-to-machine interfaces.  Moreover, for the industry to show increased margin over time, the cost per Erlang (or Erlang equivalent) must decline.  This can be done, relative to existing, 2G technologies, with 3G and IMS, making the financial justification for the migration and highlighting policies and control methods which will provide usage guidance for sales and marketing programs that does not cannibalize existing revenue streams nor decrease the effective ROIC of capital budgets for new applications on a per-dollar basis.

Challenges Ahead


While, on the surface, IMS paired with 3G radio modulation seems like an easy decision, there is still much work to be done in standards.  A great deal of work also remains to be done in designing, deploying and operating live networks.  Policy based decision control is intended to be hierarchical, and network designers of tomorrow will not only require mastery of traffic management, but also of issues such as policy management, access control, quality of service, and migration to IPv6.

Additionally, with LTE, the radio access network begins to operate almost independently from the core, handling all mobility management between eNBs in a flat IP architecture.  Understanding this as an end point relative to today’s 2G and 3G radio access networks can be challenging, especially for carriers who wish to avoid costly redesigns and major network overhaul projects with the introduction of LTE.

Business Implications


Carriers who want to further differentiate their services offerings will migrate both the radio access and core networks towards 3G, ultimately LTE (or potentially EVDO Rev C, WiMAX, or others) with an IMS core network.  Furthermore, carriers with both a wireline and wireless network will be able to offer a higher degree of integration between home entertainment services, communications, and data bundles which will incorporate the home telephone, the mobile telephone, televisions, etc., in a manner that is highly integrated and interoperable, allowing for greater degrees of flexibility than today’s technology for subscribers.

Summary


Carriers in the developed countries face a number of challenges today that include margin expansion, adding shareholder value while coping with a shrinking addressable market, and ongoing complaints about the quality of subscriber experience.  By understanding the margin-per-application for the 3G applications such as video, audio, SMS, and others, and while understanding the cost differences on a per-minute-of-use basis for voice in a legacy domain versus that of a 3G/IMS system, carriers can begin to set forth strategies that will address all challenges while continuing to grow their business.

How to Learn About It


Courses
  • 3G, IMS, and the Carrier Business Economics  (3G-IMS-STRAT, 2 days) is a fast-paced two-day briefing on the 3G/IMS business economics that will be of interest to telecommunications executives responsible for business strategy, marketing or service creation, engineering, deployment, or to industry analysts looking for what happens next in carrier spending and why.
  • If you are already familiar with 3G and 3.xxG technologies such as UMTS, HSDPA, and HSUPA, you can learn more about the evolving 3G LTE/4G technologies by taking the two-day  course on 3G LTE/4G: The Next Generation Mobile Networks
  • For an all-in-one-place comparative study of all of the major existing and evolving wireless technologies, consider the two-to-four day Technology Comparison and Evaluation course.
  • For a quick ramp-up to IMS, consider   IMS:  The Technology, Applications, and Challenges (IMS, 2 days). This intensive tutorial on IMS looks at the technology, its financial drivers, wireless/wireline standards, implementation issues,  security considerations, how traffic engineering is impacted by the network policy, and the future of telecommunications networks, including a flat, all-IP infrastructure. 


Books:
For books on 3G and IMS, check out the bibliographies at the end of our tutorials on 3G, 4G, and IMS.  Here’s the index to the available tutorials:  http://eogogics.com/talkgogics/tutorials/


Web Resources:




]]> Emerging 4G Mobile Wireless Technology http://www.eogogics.com/talkgogics/tutorials/4g-wireless-technologies Wed, 14 Feb 2007 05:28:43 -0600

What Is 4G Wireless?

4G, short for fourth-generation wireless communication systems, has engaged the attention of wireless operators, equipment makers (OEMs), investors, and industry watchers around the world.  4G refers to the next generation of wireless technology that promises higher data rates and expanded multimedia services.  Since, at this point, 4G is more of an aspiration than a standard, there is not an agreement yet on what should constitute 4G.   

Since the ITU is a major force in the standardization of telecommunications technologies, it’s worth looking at the ITU’s performance goals for 4G:

  • “The framework for 4G systems should fuse elements of current cellular systems with nomadic wireless-access systems and personal-area networks in a seamless layered architecture that is transparent to the user”

  • “Data rates of 100 Mbps for mobile applications and 1 Gbps for nomadic applications should be achievable by the year 2010.”

  • “Worldwide common spectrum and open, global standardization should be pursued”.

As another viewpoint, the Wireless World Research Forum (WWRF) defines a 4G network as one that operates on Internet technology, combines it with other applications and technologies such as WiFi and WiMAX, and runs at speeds ranging from 100 Mbps (in cell-phone networks) to 1 Gbps (in local WiFi networks). There is some debate among standards bodies and industry watchers as to whether WiMAX is, or will become, a full-fledged 4G technology competitive with 4G wireless.


From Performance Goals to a Standard

The process of developing a standard is a long one, carried out by several groups, which include Standards Development Organizations (SDOs), industry forums, and companies, such as OEMs, that have a stake in the end product.  Some of the major SDOs are nonprofit regional or governmental bodies, such as ETSI in Europe, CCSA in China, and the TTA in Korea. 3GPP and 3GPP2 are examples of industry SDOs that develop and maintain standards for current 2G and 3G technologies.  In 2007, the ITU will convene a global congress to set a course for the 4G standards development process.  It is doubtful that we will see an ITU standard before 2010 or beyond. Nor are standards necessarily the final word on the subject.  Standards are what various groups are willing to agree to after years of negotiation.  In the meantime, there is nothing to stop the various SDOs and wireless operators from deploying so-called 4G systems without waiting for the completion of the formal standards process.


Progress to Higher Data Rates -- But Short of a Defined 4G Standard

The CDMA development group (CDG) based in the United States is pushing the 1xEV-DO speeds to what they hope will qualify it as a 4G technology.   InRevision C they plan to use CDMA, TDM, OFDM and MIMO (Multiple Input Multiple Output) and even the Space Division Multiple Access advanced antenna to increase the download speeds up to 280 Mbps. This new standard will be called Ultra mobile Broadband.

Japan’s NTT DoCoMo and Korea’s Samsung are testing a 4G communication system prototype called Variable Spreading Factor Orthogonal Frequency and Code Division Multiplexing (VSF-OFCDM) at 100 Mb/s while moving, and 1 Gb/s while stationary (or “nomadic” in ITU terms).   NTT DoCoMo and Samsung both plan on launching the first such commercial network in 2010.

One alternative to 4G being proposed is the 3GPP LTE (Long Term Evolution) project.   It is the name given to an initiative within the Third Generation Partnership (3GPP) Project for the ongoing enhancement of the UMTS 3G standard.. The LTE project is not a standard, but it will establish a “4G like” capability for UMTS operators.Among all these technologies, several research organizations think 3G LTE holds the most promise.  3G LTE, sometimes called 3.99G, is also being hyped as “Super 3G”.


Emerging 4G Access and Capacity Schemes

Recent years have seen major advances in wireless access technologies.   Among the new schemes being proposed for 4G, 802.16e and 802.20 standards are OFDMA, Single Carrier FDMA, and MC-CDMA. The new technologies, while offering the efficiencies of the older technologies such as CDMA, also offer advantages in scalability.  Current working assumptions for physical layer multiple access schemes is OFDMA for downlink and Single Carrier FDMA (SC-FDMA) for uplink.

One way to increase system capacity is to implement a Multiple-Input Multiple-Output (MIMO) antenna scheme. A wireless system with single antennas obeys Shannon's classical limit for capacity, which can be expressed as C = log2(1+SNR). Ideal capacity therefore increases as the log of the signal-to-noise ratio. MIMO systems, on the other hand, increase capacity linearly with respect to the number of transmit and receive pairs that are used.


The Spectrum Bottleneck

The 4G migration, while holding great promise for high data rate services and a broad range of multimedia applications, will require additional radio spectrum. The FCC opening of the 700 MHZ band through the auction process is a possible solution for 4G deployment in the U.S.   However, use of this band for mobile wireless services is years away due to the complexities of reallocating existing broadcast licenses.  Moreover, there is little chance of establishing a common 4G spectrum plan on global basis. The lack of a unified spectrum plan for mobile wireless networks was obvious with the rollout of 2G and 3G networks.


Business Implications for 4G

4G technology will not be a major factor in the wireless market in the next four to five years.   During early 2007, operators will most likely be choosing between investments in 15 year-old GSM technology or newer 3G technologies like CDMA2000 1xEV-DO, WCDMA, and HSDPA which offer greater network capacity and lower cost to deliver emerging multimedia service as well as broadband data.  4G will not be available as a business option until the ITU and the national standards groups like the 3GPP and 3GPP2 organizations have completed the development of a formal 4G standard.


Recap and Conclusions

  • The Internet is the driving force for higher data rates and high speed access for mobile wireless users. This will be the motivation for an all mobile IP based core network evolution.
  • The market may not be able to support two incompatible wireless mobile technologies such as 4G wireless cellular networks and mobile WiMAX.
  • OFDM and MIMO are the largest strongest candidates for 4G access technologies.
  • NTT DoCoMo and Samsung are the world leaders in testing and rolling out so called “3.99G” technologies.   Lessons learned here may influence the direction and technology path for 4G in the next 4 years.
  • The lack of radio spectrum suitable for 4G deployments will be a major impediment to the migration of 3G to 4G networks, especially in the U.S.

How to Learn More about It



Courses

  • If you are already familiar with 3G and 3+G technologies such as UMTS, HSDPA, and HSUPA, you can learn more about the evolving 3G LTE/4G technologies by taking the two-day  course on 3G LTE/4G: The Next Generation Mobile Networks
  • For a great all-in-one course comparing and contrasting all of the major existing and evolving technologies, consider the two-to-four day Technology Comparison and Evaluation course.

Books and Other


  • Advanced Cellular Network Planning and Optimisation: 2G/2.5G/3G...Evolution to 4G  

by Ajay R. Mishra (Editor).  John Wiley Inc., 2007.

  • Wireless Technology: Waiting for 4G, Bernstein Research, September 25, 2006.
  • “Race for the future: The 3G mobile migration”, Telephony, September 11, 2006.

 

Web Resources

]]> Voice over IP (VoIP) http://www.eogogics.com/talkgogics/tutorials/VoIP Tue, 30 Jan 2007 04:03:33 -0600

What Is VoIP

VoIP, Voice over IP, stands for Voice over the Internet Protocol.   In VoIP, voice calls are packetized to allow the voice traffic to “ride over” the organization’s data network.  This eliminates the need for a separate voice network with its dedicated voice circuits, thereby saving resources and costs.

The enhanced functionality and attractive pricing of VoIP offerings is encouraging many consumers to migrate to VoIP services provided by their cable company or VoIP telephony companies such as Vonage.  You may already have a VoIP-enabled phone on your desk at work, too, as many businesses are adopting VoIP to replace their antiquated phone systems. Traditional business phone systems tend to have expensive proprietary interfaces and offer little flexibility for important business communications requirements such as disaster recovery.

VoIP’s use of the Internet Protocol puts it firmly in the realm of data networking. However, most systems and devices that use the Voice over IP protocol must support features and functions found in traditional telecommunications systems. Thus VoIP represents the convergence of voice and data.


History and Standards

While Voice over IP has taken off rapidly in the last several years, convergence of voice and data has been around for many years in one form or another. Voice over IP started in the early 1990s with “point to point” applications used on a multi-media PC between two parties over the Internet. H.323, a standard for these applications developed by the International Telecommunications Union (ITU, www.itu.com), enjoyed relative success in the market.  As businesses looked to adopt VoIP for their corporate phone systems, more complex capabilities were required.   Session Initiation Protocol (SIP), a standard developed by the IETF www.ietf.org several years back, has now emerged as the de facto VoIP standard for telecommunications carriers, software vendors, and equipment manufacturers for both consumer and corporate systems.


Historical Milestones

1950s  Long distance phone calls and mainframe computers

  • U.S. nationwide long distance dialing introduced in 1949
  • AT&T owns home private lines through “Bell Operating Companies”,   long distance lines, all business phone lines, and the manufacturing of all the telephone equipment
  • Mainframe computers introduced for large financial institutions with proprietary terminal equipment

1970s  US Government files lawsuit to break up AT&T; Internet Protocol gains acceptance

  • 1969 – ARPANET creates first packet-based network (first used for research sharing between universities and grew to government, military, and military suppliers in 70’s) 
  • 1974 – U.S. Government files anti-trust lawsuit against AT&T
  • Mid-70’s the Internet Working group is formed; by late 70’s ARPANET is widely used for data and file sharing
  • 1979 – CompuServ, a commercial e-mail and information sharing service, goes online

1980’s    Break-up of AT&T completed; personal computers Introduced 

  • 1984 – court decision to split AT&T, the Regional Bell Operating Companies, and equipment manufacturing into separate companies to introduce competition
  • Personal computers introduced on the market and first networks between these by Novell, Banyan, and other networking companies come into being
  • Late 80’s and very early 90’s – widespread adoption of TCP/IP networking by major corporations to implement standardized networks

1990s and 2000s

  • 1996 telecommunications act seeks to stimulate competition by allowing cable companies to offer telephone service and long distance providers to offer local service
  • Cisco enters voice market by purchasing a VoIP equipment manufacturer; in the late 1990s, other equipment manufacturers, such as Avaya and Nortel respond with their solutions
  • “Software-based” solutions, such as open-source Asterisk software and Microsoft-based Interactive Intelligence, gain market acceptance
  • In the early 2000s, first widely accepted standard for VoIP networking, called SIP, is adopted by all major manufacturers and VoIP phone service providers

Why VoIP?

Traditional telephony uses a dedicated circuit per call. This means that distributed organizations must install a lot of expensive equipment while still being subject to a limit on the numbers of calls that can be distributed to alternate sites.

Traditional telephony also requires the operation and maintenance of a separate voice network with its own equipment and personnel, in addition to the organization’s data network.  Obviously, if the voice traffic can utilize the existing data network, that would lower the cost of both hardware and personnel.

Also, traditional telephone systems tend to use proprietary interfaces. This “vendor lock-in” makes equipment and business communications applications extremely expensive to buy and maintain. The widespread adoption of VoIP standards holds the promise of a ubiquitous network for voice and data.

VoIP is now a mainstream technology adopted by approximately 75% of all companies purchasing new phone systems.   Adoption of carrier circuits by individuals is also growing rapidly.   Due to the dramatic savings that can be achieved by the elimination of dedicated voice circuits in a wide area network, the early adopters of VoIP tend to be distributed organizations such as banks, retail, and universities.


Principles and Operation 

As mentioned earlier, voice conversations in VoIP are “packetized” and sent on a data network using the Internet Protocol (IP).   Incidentally, that does not mean that the Internet itself is necessarily used for the transmission of this data, only that voice is carried on a data network using IP. Traditional telephony uses a dedicated voice circuit or “channel” per call and transmits calls to other devices using a voice signal on that channel. By using “packets”, many calls can be sent on the same data circuit as long as appropriate data bandwidth is present to handle the overall traffic.

 In carrying both voice and data on the same network, allowances must be made for the real-time nature of voice, or the call quality will suffer.  With most data applications, small delays are acceptable.  With a voice conversation, delays can be heard by the parties on the call and affects the quality of conversation.   However, the technology has evolved to the point where, with good planning and design, it is possible to achieve high-quality voice conversations on the data network.   For example, using the “quality of service” criteria as a guide, data routers and switches can optimize the flow of various kinds of data traffic within the available bandwidth, allowing the voice packets higher priority as needed.  Most organizations assess their data network and upgrade appropriate components and bandwidth prior to a VoIP deployment.   More information on the quality of service and other network design considerations can be found in our free CxO 5 Minute VoIP Guru Guide.


Strengths and Weaknesses

VoIP offers many advantages over traditional telephony.  Many of these stem from the fact that logical networking rather than dedicated circuits can now be used to transport conversations.   For example, users and their devices can be located anyplace on the data network and have access to both their phone calls and their data applications.  Previously, dedicated and separate phone circuits had to be present to handle the voice.  VoIP also works on a wireless data network, making mobility much easier.

One of the drawbacks of VoIP in the short term is that it requires expertise in both voice applications and data networking. IT experts with knowledge of both fields are not easy to develop.  There is a learning curve for data experts to master the features and functionality expected by their new telephone users. On the flip side, voice experts must become proficient with the unfamiliar data networking concepts and techniques.


Business Implications and Applications

The early adopters of voice over IP were highly distributed organizations that already rely heavily on wide area networks for their data and therefore also had significant bandwidth available between sites as well as reliable data networks.   Maintaining a separate voice network is expensive and offers little flexibility for routing call traffic among multiple sites due to the requirement for dedicated circuits.   Banks, retail organizations, and universities have all been widely moving to VoIP to save money on circuits between sites and route calls more flexibly.

Most distributed organizations want their “phone system” to operate as one virtual system. VoIP-enabled phone systems, often called IP PBX’s, are architected using a software model offering redundant processing, clustered operation, and standardized directories.   Business communications now appear to callers and users as one large system, independent of physical sites, just as the data applications do.  

Both single-site and distributed organizations gain significant business advantage by moving to Voice over IP.   One big advantage of VoIP is that it uses a “logical” connection to the network rather than a physical circuit. This means that users can move about the network without the administrator having to make physical moves, additions, or changes.   For some companies this can mean dramatic savings in system administration costs.   Due to the “software approach” of many VoIP systems, system administration is greatly simplified and sometimes streamlined with standard company directories such as Microsoft’s Active Directory and LDAP-based directory systems.

One of the “killer apps” for VoIP is disaster recovery.   Companies who maintain redundant networks and have disaster recovery options for their data can now use that same style of redundancy for voice communications.   Phone systems using VoIP are architected with a software model and offer redundancy and clustered server options. In a traditional telephone environment, if a dedicated circuit or set of circuits are not available, it takes as much as thirty minutes for calls to be re-routed.   And for back-up capability, physical circuits, hardware cards, and expensive systems must be in place.   With VoIP there is some requirement for additional hardware and bandwidth, but systems using a software approach offer disaster recovery back-up options that are much less costly.   Also, using the standard protocol of SIP, calls can be instantly redirected. Users can also log in from any location on the data network and have phone service.


How to Learn More about It

Courses and Tutorials

  • Communications, systems, and software engineers; network, IT, and marketing/sales professionals; technical or strategy managers or consultants, and others who plan to evaluate, design, build, or work with VoIP networks, applications, and services will benefit from the 2-3 day course on   VoIP: Protocols, Design, and Implementation.
  • Those interested in the security ramifications of VoIP, for instance network-security planning teams, network administrators, IT and telecom engineers, IT security management, crime prevention/investigation officers, and homeland security personnel should take a look at the 2-day VoIP Security course.

Books

  •  VoIP for Dummies by Timothy V. Kelly and Philipp Fockeler, May 30, 2006
  • Hacking Exposed: Voice Over IP Security Secrets & Solutionsby David Endler and Mark Collier, November 28, 2006
  • Practical VoIP Security by Thomas Porter and Jan Kanclirz, Jr. March 30, 2006
  • Newton’s Telecom Dictionary by Harry Newton should be in every IT organization’s library and on every engineer’s desk who will be involved with a VoIP rollout   The dictionary is updated regularly with new terms and industry issues.

Web Resources

  • http://www.itu.int   International Telecommunications Union is the standards body for H.323, the older VoIP standard that is still used in some equipment and software.
  • www.ietf.org    IETF is the international standards body for the Session Initiation Protocol (SIP) standard.
  • www.voipsa.org  VoIP security discussion group and forums
  • www.voip-info.org   Great resource for finding vendors and events as well as for general information.
  • www.eweek.com   Good source of news on VoIP technology and providers

Tradeshows

  • www.tmcnet.com    Internet Telephony, aimed at a wide variety of audience ranging from enterprises and carriers to contact centers  
  • www.von.com  VON Show, focused largely on the carriers


]]> Internet Multimedia Subsystem (IMS) http://www.eogogics.com/talkgogics/tutorials/ims Mon, 29 Jan 2007 16:03:08 -0600

What Is IMS?

Communications networks are rapidly evolving into policy-based, packet-oriented networks designed to provide a particular quality-of-services (QoS) for subscribers while reducing the costs associated with capital expansions, network operations, and management.  If you are involved with telecommunications planning, engineering, deployment, strategy, marketing, or services creation, it is critical that you understand the technology and business implications of IMS.

Internet Multimedia Subsystem (“IMS”) is a policy based system that provides greater flexibility to operators for the development and launch of multimedia applications.   While IMS has often been thought of as a data/application enabler, many operators are actually looking to it as the next generation technology for both voice and data, providing services to subscribers in a manner that has never before been seen.

IMS will provide carriers with a new set of operating capabilities, flexibilities, and challenges.  In the near future, network professionals will need to augment their knowledge of circuit switched networks with an understanding of packet oriented technologies.


Standards

Third Generation Partnership (3GPP), Telecoms & Internet converged Services & Protocols for Advanced Networks (TISPAN), and 3GPP2 (Third Generation Partnership 2) all have variants of the general IMS technology that address their specific requirements.   Since mobile networks have more demanding policy and signaling requirements, they need a somewhat customized version of the standard.  Similarly, 3GPP and 3GPP2 differ in a number of areas, e.g., authentication, which calls for different IMS strategies for 3GPP from those employed in Multimedia Domain (MMD), a close cousin of IMS in the CDMA 3GPP2 arena.   Also in the standardization mix is TISPAN, an arm of the European Telecommunications Standards Institute (ETSI) that deals with the convergence of Internet with fixed networks.  There are working groups that help 3GPP and TISPAN share ideas and approaches toward the next generation technology, especially in the area of fixed and mobile convergence.


Historical Milestones

  • 1999 - 3G.IP, the industry forum that developed the initial IMS architecture, comes into being.
  • 2000 - Work from 3G.IP is brought to 3GPP working group as part of their standardization efforts.
  • 2001 - 3GPP Release 4 introduces the capability of an all-IP core network as well as a bearer independent core network.
  • 2002 - 3GPP Release 5 introduces IMS and HSDPA.
  • 2004 - 3GPP Release 6 adds enhancements to IMS.
  • Mid 2007 - 3GPP Release 7 will reduce the delay that affects VoIP


Principles and Operation

It would be hard to do justice to the complex architecture of IMS in this short article.  What follows is a very high-level description of IMS.  The signaling protocol for IMS is based on SIP.  As a network technology, its architecture includes many other components.  As requests for resources enter the network, a P-CSCF, which may also include PEF/PDF and SBC functions, will route the signaling to the appropriate I-CSCF, and can be located in either the visited or home network.  The P-CSCF will also provide authentication and charging functions.

The P-CSCF is the first point of contact with the network and an IMS based terminal.  Resident in the P-CSCF may be the PEF/PDF (policy enforcement/decision point), and can be located in either the home or visited network.  Additionally, the P-CSCF may take on functions of a Session Border Controller.

The I/S-CSCF will handle SIP registrations, decide which application servers or SCIM need to be included, will provide ENUM lookups for routing, and enforces policies for load purposes.  Also, the S-CSCF is interfaced to the HSS where the subscriber data is housed for policy information relative to the subscriber's profile.  

Also involved are additional nodes such as media servers, BGCF, PSTN gateways, charging, SLF within SDM/HSS, and a host of other elements.


Business Implications and Applications

The coming fixed/mobile convergence offer the promise of a new communications paradigm where a subscriber could perform tasks such as using a cellular telephone as a TV remote control, programming a DVR while away from home, transferring calls from a mobile phone to a landline, all without interrupting communication.

It allows a network operator to rationalize much of the investment needed for new – and legacy – applications and services across a shared, common policy based enablement layer made possible by IMS.  Since the network itself is a contended asset, the challenge that operators face is how to provide policy management and support across all levels of the network while maintaining the quality of service parity.   IMS provides a way to meet that challenge as well.

Many operators are looking at IMS as being the new core network technology that will allow them to cap the (ANSI-41 or MAP) networks sometime in 2008 or 2009. 

In a nutshell, IMS changes the core network from a circuit switched environment to that of a policy based, packet domain.  Policy engines and definitions, from subscriber management and profiles to access policy and admission control to policies governing composite services and third party applications, define how the network is to function and operate.  Moreover, policy decision functions and policy enforcement functions reside within the network to dynamically control which traffic traverses the network, and how the traversal is to occur.

By understanding the basics of IP and networking, IPv4, IPv6, SIP, and VoIP, engineers can build a solid base of knowledge ahead of the roll out and commercialization of IMS networks and applications.


How to Learn More About It

 

Courses

  • Engineers, network designers, technicians, and specialists who work today with legacy circuit switched equipment and need to quickly ramp up their knowledge of IMS, should consider:  IMS: The Technology, Applications, and Challenges (IMS, 2 days).  This course studies IMS from all angles including the technology, status of wireless and wireline standards, key challenges posed by the technology, financial drivers for its adoption, deployment, security considerations, and the future of telecommunications networks, including a flat, all-IP infrastructure.  It also takes a look at the issue of network policy and how the different levels and types of policies for QoS and admission control have important bearing on traffic engineering in the evolving networks. 



  • Finally, if you come from a traditional telecommunications background and have not been exposed to the concepts of data networks and the increasingly important Internet Protocol (IP), you may wish to consider our courses on IPv4 or IPv6:  Internetworking with TCP/IP Version 6 (IPv6, 2-3 days).

Books

 
Web Resources:




]]> RFID: Radio Frequency Identification http://www.eogogics.com/talkgogics/tutorials/rfid Mon, 29 Jan 2007 16:03:08 -0600

What is RFID?

Radio Frequency Identification (RFID) technology is an automatic identification technology (Auto-ID) that uses radio waves to identify physical objects, whether animate or inanimate. Therefore, the range of objects identifiable using RFID includes virtually everything on this planet, and beyond.

Fundamental Concepts about RFID

An RFID system consists of the following components from end-to-end:


  • Tag: A mandatory component

  • Reader: Also a mandatory component

  • Reader antenna: Another mandatory component; some current readers available today have built-in antennas

  • Controller: Again, a mandatory component. Most of the new-generation readers have this component built in.

  • Sensor, actuator, and “annunciator”: Optional components are needed to make external inputs and outputs possible

  • Host and software system: Theoretically, an RFID system can function independently without this component. Practically, an RFID system is close to worthless without this component.

  • Communication infrastructure


Advantages of the Technology


The advantages of RFID can be broadly categorized as current or future:

  1. Current: These advantages are immediately realizable with the technology products that exist today.

    The most important advantage of RFID is that it is “Contact-less”; an RFID tag can be read without any physical contact between the tag and the reader.

    Writable data: The data of a read-write (RW) RFID tag can be rewritten a large number of times.

    Absence of line of sight: A line-of-sight is generally not required for an RFID reader to read an RFID tag.

    There are other advantages as well, e.g., variety of read ranges, wide data-capacity range, support for multiple tag reads, ruggedness, and ability to perform “smart” tasks.
  2. Future: These advantages are either available in some form today or will be available as improved features in the future as the technology matures.

    A discussion of the future advantages of RFID is beyond the scope of this introductory tutorial


Limitations of the Technology

The current limitations of RFID include poor performance with RF-opaque and RF-absorbent objects. This is a frequency-dependent behavior. The current technology does not work well with these materials and, in some cases, fails completely.

RFID is also impacted by environmental factors. Surrounding conditions can greatly impact RFID solutions. The impact of hardware interference may also be an issue. An RFID solution can be negatively impacted if the hardware setup is not properly configured for the environmental conditions.

Limited penetrating power of the RF energy and immature technology are some of the limitations that have the kept the technology from spreading wider than it has.

Application Areas

The potential application of RFID technology is limited only to one's imagination. Although a popular belief holds that RFID is best suited to supply-chain management or consumer packaged goods industries, the range of current RFID applications goes far beyond these areas. In fact, a variety of established RFID application types have already been deployed successfully in real-world environments. It has been used in the military, Medicare, factories, Super Malls, and a host of other places.


Privacy Concerns

Not surprisingly, privacy issues surrounding RFID represent a significant concern. After all, when a new technology is invented and is in the process of being developed, it must be analyzed from several viewpoints to determine whether and how its use will impact society. Consumer advocacy groups worry that RFID misuse might lead to the tracking of individuals, resulting in a loss of privacy.

RFID versus Bar Code

RFID is currently being touted as a "better bar code" and "smart bar code." The media regularly proclaims that the days of bar code are numbered and that RFID will replace bar codes "soon." In fact, RFID does have some clear-cut advantages over bar code, but bar codes also offer some clear-cut advantages over RFID. Unfortunately, in the media enthusiasm over RFID, the strengths of bar code are often ignored or misrepresented. As a result, the belief that bar codes are a sure loser to RFID has started to take shape. This belief is not founded on facts.


The RFID Strategy

An RFID strategy provides a roadmap to use the technology aligned with an enterprise's strategic vision and goals. For example, a business that strives to be a model of efficiency could use RFID to streamline its operations. An RFID strategy is strongly recommended for a large enterprise. A smaller scale company may also benefit from such a strategy. An RFID strategy also shows the extent to which a business is ready to use RFID within itself.

A one-size-fits-all strategy is generally not possible, which means that businesses must create their own unique RFID strategy, determine how RFID can create value that is aligned with its strategic directions, factor in such external drivers as meeting customer RFID mandates, all within the tolerable cost/risk ranges, and so on.


Creating Business Justification for RFID

Business justification is strongly recommended before rolling out RFID in an enterprise because it enables you to accomplish the following fundamental goals:

  • Provide objective data about the benefits of RFID. Objective data enables you to determine whether to use the technology. Indeed, if RFID shows substantial benefits, objective data might accelerate adoption of RFID in the business. Business justification will also build realistic expectations of the technology.

  • Maximize return on investment (ROI). Through a careful analysis of business cases, you can quantify the benefits and the resources needed to implement an RFID solution. You can select the areas that offer the maximum ROI as the potential candidates for RFID use.


Designing and Implementing an RFID Solution

Just how challenging can it be to design and implement a nontrivial RFID solution? Someone who has not implemented such an RFID system might think, "Not much at all! After all, what else do you need besides a few readers, antennas, cables, and some tags to build an RFID system?" The short answer is this: plenty. Suffice to say that designing and implementing a real-world, nontrivial RFID solution is not easy. Therefore, if you are expecting to use a plug-and-play RFID solution for your business needs, be forewarned: The unique needs of each business and the involvement of many context-dependent variables influence the appropriateness of an RFID solution. No single one-size-fits-all RFID solution exists. Depending on your business needs, you can find several solution components commercially available today from hardware and software vendors as well as integrators. The task is to know which of these components will provide the optimum solution and how you need to put these elements together to achieve the desired results.


Standards

A discussion of RFID technology would not be complete without a mention of the standards that seek to regulate different aspects of the technology and the organizations that set them. EPC and ISO lead the way in the process of defining standards for RFID. However there are other standards and protocols like R2T protocol, T2R protocol, anti collision protocols, and TTF protocol to name some.


Summary

RFID is a technology that can not be ignored. Whether you are in telecommunications, IT, or any of the following industries, you will be impacted by RFID:

  • RFID hardware, software, and solution vendors and related professional services companies

  • Managed services providers, outsourced RFID solutions and application providers, and RFID service bureau operators

  • Personnel responsible for automating Supply Chain Management (SCM), Customer Relationship Management (CRM), Manufacturing Resource Planning (MRP), Enterprise Resource Planning (ERP) and other business processes

  • Healthcare management personnel responsible for tracking patients, staff personnel, equipment, inventory, and other critical resources

  • Retailers and personnel responsible for merchandise inventory and ordering processes, Customer Relationship Management (CRM), Merchandise tracking and fraud prevention

  • Providers of value-added applications and services such as metering, telemetry, telematics, and sensor applications, inventory control and tracking such as merchandise control, asset tracking and recovery such as computing equipment monitoring, tracking parts moving through a manufacturing process, tracking goods in a supply chain, and payment systems

  • RFID Hardware Manufacturing companies

  • Companies interested in optimizing their RFID business process strategies

  • Venture Capitalist and Startup companies


How to Learn More about It


Courses

  • Check out the Eogogics Short Range Wireless curriculum for courses on RFID, Bluetooth, ZigBee, and WiFi.

Books

Web Resources

  • RFID Journal: http://www.rfidjournal.com/ Clearinghouse of news and information about RFID

  • RFID News: http://www.rfidnews.org/ Provides news updates of significance in the RFID Industry

  • EPC Global: http://www.epcglobalinc.org/ Specializes in the development of industry-driven standards for the Electronic Product Code (EPC) Network to support the use of Radio Frequency Identification in industry.


]]> SS7 or C7: Signaling System #7 http://www.eogogics.com/talkgogics/tutorials/ss7 Mon, 29 Jan 2007 16:03:08 -0600

What is a SS7?


Signaling System #7 (SS7), also known as C7 in Europe, is a critical component of modern telecommunications systems. Despite the upcoming migration to IP networks and evolution to IP-centric architectures such as the IP Multimedia Subsystem (IMS), it remains the glue that binds all telecommunication networks together. It is a communications protocol that provides signaling and control for various network services and capabilities. Being a layered protocol, SS7 provides various protocol levels for connection oriented and connectionless (database) signaling in fixed and mobile networks.

SS7 is a specific protocol utilized for inter-system signaling. Stated differently, SS7 defines a set of parameters for messaging between telecommunications "nodes". This signaling process takes place over telecommunications facilities called "links". The SS7 messages traverse the links between two or more nodes, enabling data communications between and among the system. There are different types of SS7 links and they are used for different purposes. We will discuss nodes and links more fully later in this article.

SS7 signaling is a form of packet switching. Unlike circuit switching, which utilizes dedicated data "pipes" for transmission of information, packet switching dynamically assigns "routes" based on availability and "least cost" algorithms. Another example of packet switching is TCP/IP, the protocol used for routing messages over the Internet. Unlike the Internet, which utilizes a vast public "web" of interconnecting facilities and routing equipment, SS7 networks are private and logically self-contained. The private nature of SS7 networks is critical for security and reliability.


Purpose of SS7


The major purpose of SS7 is to enable connection oriented as well as connectionless signaling. Connection oriented signaling is associated with establishing a temporary dedicated connection between two or more points. A common example is simply the establishment of an inter-office voice call between two telecommunications switches. Connectionless switching is database oriented. There is no dedicated connection established. Instead, information is requested (from a database), provided (by the database), and relayed to the point in the network where it is required.


SS7 Architecture


There are four major types of telecommunications nodes important to SS7:

Service Switching Point (SSP): A telecommunications switch that contains the control logic (software) necessary to send/receive SS7 messages to other nodes in the network. Telecommunications switches that can not send/receive SS7 messages are referred to as a Switching Point (SP). An SP must interface directly to an SSP (on a one-to-one relationship) in order to access SS7-based services.

Signal Transfer Point (STP): This is the "heart" of the SS7 network. Think of the STP as an electronic "post office". While all that the STP does is route messages from point A to point B in the network, the network would be lost without it. The routing of messages follows a scheme that we will discuss later in this section. STPs are ALWAYS provided in mated pairs. STPs operate in what is called "load sharing mode". This means that, at any given time, each STP should be processing 40% of the total signal-processing load. In the event of an STP and/or link(s) failure, the network is designed to change over to the remaining STP so that it can continue to operate at 80% load.

Service Control Point (SCP): This is the "brain" of the SS7 network. The SCP is nothing more than a database. However, utilization of an SCP offers profound enhancements for service delivery and network control. Service logic may be placed in the SCP (rather than the switch), creating the impetus for many improvements such as rapid feature deployment, mass customization of features, and improved utilization of switch resources. SCPs are almost always deployed in a "mated pair" configuration. This designed redundancy makes allowance for a back-up SCP should the other go out of service for some reason. Some non-call affecting, or otherwise non-critical, functions may be served by a single SCP.

Service Node (SN): Includes database functionality of the SCP along with additional capabilities such as voice interaction and control of voice resources. Generally speaking, SCPs work well with requirements that call for voluminous data transactions. SNs, on the other hand, are typically not designed for high volume data processing. Instead, SNs are best suited for special circumstance call processing involving voice resources and/or interaction.


SS7 Links


SS7 messages are carried by a physical medium referred to as a link. While there is some variation throughout the world, the traditional facility type utilized for an SS7 link is a DS-0 circuit, with a load carrying capacity of 56 kilo-bits per second (kbps). Some SS7 manufacturers have designed equipment and interfaces for DS-1 (24 DS-0 circuits) level interconnection for purposes of SS7-to-ATM signaling, but that is a subject for a more advanced tutorial.

There are six different types of links and they all have a different role in the SS7 network. SS7 links are typically provides in either pairs or quads, sets of four. The number of links or the number of pairs/quads, actually provided between nodes is based on traffic engineering considerations which we will discuss later.


A-links: Access links connect SSPs to STPs and SCPs to STPs.

B-links: Bridge links connect STP pairs that are at the same "hierarchical level". SS7 is required for signaling between different networks, just as it is required within a given network type.

C-links: Cross links provide the connection between a mated pair of STPs.

D-links: Diagonal links are utilized to connect STP pairs that are at different hierarchical levels.

E-links: Extended links are supplementary links providing back-up to primary link pairs in the event the latter experience a failure.

F links: Fully associated links connect an SSP to another SSP. Typically, F links utilize one channel (one DS-0) of a DS-1 between MSCs that share a "hand-off" boundary. The DS-1 is utilized for voice communications when a mobile caller "hands off" or traverses from one MSC to another during a call. This leaves 23 channels for voice and 1 channel for signaling. F links will become increasingly rare as greater dependence is placed on more network centric SS7 signaling based on STPs.

What Traverses the SS7 Link?


SS7 signal units traverse the SS7 link. There are three different types of signaling units:

  • Message Signal Unit (MSU) is the signaling unit that carries the actual message "payload".

  • Link Status Signal Units (LSSU): As the name implies, these signaling units provide status of the links operating condition.

  • Fill-in Signal Unit (FISU) act, as their name implies, to fill in the space between MSUs and LSSUs.

Due to the nature of their work, SS7 networks require very precise timing and synchronization. There is therefore a constant stream of signal units traversing an SS7 link. A link is a bi-directional circuit. This means that (in a DS-0) there is 56 kb of information traversing each direction every second. The bi-directional nature of SS7 links allows information to be transmitted and received simultaneously over the same link.

Summary


Despite the eventual migration to IP networks and evolution to IP-centric architectures such as the IP Multimedia Subsystem (IMS), SS7 does remain an important glue that binds all telecommunication networks together. Bridging technologies such as SIGTRAN will ensure a smooth migration to all IP networks with IP-based signaling such as SIP eventually taking over in many networks. However, it is critically important for telecommunications professionals to understand SS7 as it will continue to be a core element of telecom networks for the decades to come.


How to Learn More about It


Courses

Eogogics offers a host of courses on SS7/C7 and related subjects, including CAMEL, SIP, and IMS.

Books


Web Resources


]]> Tutorials on Technologies, Techniques, and Tools http://www.eogogics.com/talkgogics/tutorials/index_html Brief yourself on an emerging technology, technique, or tool with a free, short tutorial. Learn what it’s about, its principles of operation, strengths and weaknesses, applications, and more—along with suggestions on how to learn more about the topic. Mon, 29 Jan 2007 16:03:08 -0600 ]]> Simple Network Management Protocol (SNMP) http://www.eogogics.com/talkgogics/tutorials/SNMP Mon, 29 Jan 2007 16:03:08 -0600

What is SNMP?


Simple Network Management Protocol (SNMP) is a widely used protocol designed to facilitate the management of networked devices from a central location.  Designed originally for the management of devices such as routers and switches, its usage has grown rapidly to encompass the monitoring of nearly any electronic device one can think of.  SNMP is now  used to monitor and manage television broadcast studios, automated fare collection systems, airborne military platforms, energy distribution systems, emergency radio networks, and much more.


SNMP Architecture


The SNMP architecture is composed of three major elements:

  • Managers (software) are responsible for communicating with (and managing) network devices that implement SNMP Agents (also software).
  • Agents reside in devices such as workstations, switches, routers, microwave radios, printers, and provide information to Managers.
  • MIBs (Management Information Base) describe data objects to be managed by an Agent within a device. MIBs are actually just text files, and values of MIB data objects are the topic of conversation between Managers and Agents.

Before we go any further, we need to introduce the concept of Object Identifiers or OID’s. Each MIB object definition has a unique OID, which is a dotted listed of integers. For example, within the Host Resource MIB, the OID for data object “hrDiskStorageCapacity” is “.1.3.6.1.2.1.25.3.6.1.4”.

When Managers and Agents communicate, they refer to MIB data objects using OID’s.

An OID sent with a corresponding value {OID,Value} is referred to as “binding”.

Managers can be viewed as Clients; and Agents, as Servers. The operations between Managers and Agents are quite simple:

  • “get” commands are sent by a Manager to an Agent to request data values defined by a MIB. The Agent will respond with the requested values. Closely related requests are “getnext” and “getbulk”.
  • A Manager can also send “set” commands to an Agent. If the MIB defines a data object as read-write, then the Agent will accept the data value sent with the “set” command and process it appropriately (store it or execute appropriate action).
  • Agents will send unsolicited “traps” (alarms) to Managers to alert them to important events.

The basic operations of SNMP are quite “simple”, but the totality of SNMP is far from that.  The typical ramp-up time for an individual learning to use SNMP effectively on his or her own can easily stretch to six months or longer.

SNMP Standards and Versions


SNMP Standards are described in Request for Comments (RFC) documents published by the Internet Engineering Task Force (IETF).  Standards Topics can generally be categorized into:

  • Messaging protocols between Managers and Agents (which encompasses security issues)
  • MIB syntax standards
  • “Standard MIB” definitions

Messaging Protocols

Three messaging protocols exist:
  • SNMPv1 was the first protocol introduced, and it is still widely used. It implements “get”, “getnext”, “getresponse”, “set”, and “trap” operations.

    Security for SNMPv1 is based on a “community string” that is transmitted with each message. The community string acts as a password. If the Manger includes the correct password in a request to an agent, the agent will send a response. The community string is not encrypted and thus the security it provides is quite weak.

  • SNMPv2 usually refers to SNMPv2c (other v2’s were proposed, but only v2c survives today).

    It introduced the ability to transmit SMIv2 MIB-definitions of type “Counter64”.

    SNMPv2c also provides expanded messaging operations: “getbulk”, “inform”, “report”, and a new “v2trap” operation (same functionality as the v1 “trap”).  It also introduced enhanced error responses by Agents.

    SNMPv2c utilizes the same community string security as SNMPv1.

  • SNMPv3 is the most recent introduction, and it is a major step forward in improving security. Security enhancements include:

    User Authentication:  Verification of the identify of the SNMP Entity (Manager or Agent) sending the request. Managers and Agents share knowledge of valid users, and there is a shared secret key defined for each user. When an Entity sends an SNMPv3 message, the secret key is used to create a hash of the message, and this hashed value is included with the message. If the receiving Entity can recreate this hash, then the message is said to be “authenticated” as from a valid user.

    Encryption:  Message payload can be optionally encrypted based on a second shared key.

    VACM (View Access Control Model):  Agents can now be configured to control who can access which MIB Objects under agent management.  For example, User = “Operations Supervisor” can access critical read-write control data, while User = “Plant Monitor” can access only read-only status data.

    Message Timeless Checks ensure that messages are not delayed or replayed.

MIB Syntax Standards  


MIBs are written in either of the following two syntax standards:

SMIv1 is the earliest version and was introduced along with SNMPv1. SMIv1 MIBs are very functional and very common.

Data defined by SMIv1 MIB Objects can be transmitted between Managers and Agents by any of the three messaging protocols, viz., SNMPv1, SNMPv2c, or SNMPv3.

SMIv2 was introduced along with SNMPv2c.  Major enhancements include:

Introduction of new data base types, including the “Counter64” data type.

Although derived data types could be defined in SMIv1, SMIv2 formalizes this syntax and also defines some “Standard Textual Conventions” such as “Display String”.

Improvements that enhance the documentation of MIB files and objects, such as:

  • Module Identity Statement
  • Conformance Statements
  • Improved Trap Definition Syntax (“NOTIFICATION-TYPE”)

An SMIv2 MIB can usually be translated into an SMIv1 MIB.  The primary exceptions are: a) A Counter64 type object cannot be translated. b) An improperly coded NOTIFICATION-TYPE cannot be translated to an SMIv1 TRAP-TYPE with the same OID.

Data defined by SMIv2 MIB Objects can be transmitted between Managers and Agents by any of the three messaging protocols, viz., SNMPv1, SNMPv2c, or SNMPv3.  The only exception to this is that Counter64 Object data cannot be transported by SNMPv1 messages.

“Standard MIB” Definitions


Depending on the origin (author) of a MIB, we can categorize MIBs into either:

  • Enterprise MIBs
  • Or Standard MIBs

Enterprise MIBs are authored by non-standards-committee organizations, e.g., Cisco or HP. All such organizations must apply for a unique “Enterprise ID” issued by the Internet Assigned Number Authority (IANA).  Enterprise MIBs are then organized under these unique ID’s.

Standard MIBs are authored by persons associated with the IETF.  For example, a standard Printer MIB exists, and printer manufacturers commonly implement an Agent to support this MIB in addition to their own Enterprise MIBs.

Other Standard MIB examples include:

  • X.25
  • Modems
  • DS1, DS3
  • Bridges
  • ATM
  • Token Ring
  • Fiber Channel Fabric Element MIB
  • Ping, Traceroute, Lookup MIBs
  • Print Job Monitoring MIB
  • ICMPv6 MIB
  • Mail Monitoring MIB

Strengths and Weaknesses


Strengths

  • Widespread popularity
  • Many standard MIBs available
  • Agents have low impact on monitored system resources
  • Well suited to monitoring
  • Many products available

Weaknesses

  • Not as comprehensive as some other protocols
  • Not bandwidth efficient
  • Complicated message encoding rules
  • Security has been on on-going concern.  SNMPv3 was developed in response to this issue.
  • UDP, or other connectionless, protocol is used, which creates issues regarding verification of operations:  Trap-Send verification (did it really reach the Manager?); Verification (success) of any “set” operation to an Agent.  However, cleverly designed MIBs and Manager logic can overcome these problems.

Applications


Here are some typical uses of SNMP:

  • Monitoring device performance
  • Detecting device faults, or recovery from faults
  • Collecting long term performance data
  • Remote configuration of devices
  • Remote device control

How to Learn More


Courses

  • SNMP Essentials:  A Fast-Track Tutorial (3 days, SNMP-ESSENT):  The first of our series of three courses on SNMP, this course is designed to fast-track individuals and organizations wishing to become SNMP-competent.  It employs highly interactive lecture combined with hands-on exercises to help you effectively acquire the necessary knowledge and skills and apply them to real-life situations.
  • SNMPv3: Secure SNMP (1 day, SNMPV3):  Our intermediate level SNMP course, it deals with the security and other enhancements embodied in SNMPv3, the latest version of this protocol.  
  • SNMP Agent Development (1 day, SNMP-AGENT):  Our final course on SNMP, it is aimed at the software developers responsible for programming SNMP agents for deployed devices.

Books

  • Understanding SNMP MIBs by David Perkins & Evan McGinnis.  Prentice Hall, 1997
  • SNMP, SNMPv2, SNMPv3, and RMON 1 and 2 by William Stallings.  Addison-Wesley, 1996
  • Essential SNMP  by Mauro & Schmidt.  O’Reilly, 2005
  • A Practical Guide to SNMPv3 and Network Management by David Zeltserman.  Prentice-Hall PTR, 1999

Web Sites


]]> Microwave Line-of-Sight Systems http://www.eogogics.com/talkgogics/tutorials/microwave-line-of-sight-systems Mon, 29 Jan 2007 16:03:08 -0600

What Are Microwaves

Microwave frequencies range from 300 MHz to 30 GHz, corresponding to wavelengths of 1 meter to 1 cm.  These frequencies are useful for terrestrial and satellite communication systems, both fixed and mobile.  In the case of point-to-point radio links, antennas are placed on a tower or other tall structure at sufficient height to provide a direct, unobstructed line-of-sight (LOS) path between the transmitter and receiver sites. In the case of mobile radio systems, a single tower provides point-to-multipoint coverage, which may include both LOS and non-LOS paths.  LOS microwave is used for both short- and long-haul telecommunications to complement wired media such as optical transmission systems.  Applications include local loop, cellular back haul, remote and rugged areas, utility companies, and private carriers.   Early applications of LOS microwave were based on analog modulation techniques, but today’s microwave systems used digital modulation for increased capacity and performance.
 

Standards

In the United States, radio channel assignments are controlled by the Federal Communications Commission (FCC) for commercial carriers and by the National Telecommunications and Information Administration (NTIA) for government systems. 

The FCC's regulations for use of spectrum establish eligibility rules, permissible use rules, and technical specifications. FCC regulatory specifications are intended to protect against interference and to promote spectral efficiency. Equipment type acceptance regulations include transmitter power limits, frequency stability, out-of-channel emission limits, and antenna directivity.

The International Telecommunications Union Radio Committee (ITU-R) issues recommendations on radio channel assignments for use by national frequency allocation agencies. Although the ITU-R itself has no regulatory power, it is important to realize that ITU-R recommendations are usually adopted on a worldwide basis.


Historical Milestones

1950s     Analog Microwave Radio

  • Used FDM/FM in 4, 6, and 11 GHz bands for long-haul
  • Introduced into telephone networks by Bell System

1970s    Digital Microwave Radio

  • Replaced analog microwaves
  • Became bandwidth efficient with introduction of advanced modulation techniques (QAM and TCM)
  • Adaptive equalization and diversity became necessary for high data rates

1990s and 2000s

  • Digital microwave used for cellular back-haul
  • Change in MMDS and ITFS spectrum to allow wireless cable and point-to-multipoint broadcasting
  • IEEE 802.16 standard or WiMax introduces new application for microwave radio
  • Wireless local and metro area networks capitalize on benefits of microwave radio


Principles and Operation 


Microwave Link Structure.  The basic components required for operating a radio link are the transmitter, towers, antennas, and receiver. Transmitter functions typically include multiplexing, encoding, modulation, up-conversion from baseband or intermediate frequency (IF) to radio frequency (RF), power amplification, and filtering for spectrum control.   Receiver functions include RF filtering, down-conversion from RF to IF, amplification at IF, equalization, demodulation, decoding, and demultiplexing.  To achieve point-to-point radio links, antennas are placed on a tower or other tall structure at sufficient height to provide a direct, unobstructed line-of-sight (LOS) path between the transmitter and receiver sites.


Microwave System Design.  The design of microwave radio systems involves engineer¬ing of the path to evaluate the effects of prop¬agation on performance, development of a frequency allocation plan, and proper selection of radio and link components. This design process must ensure that outage requirements are met on a per link and system basis. The frequency allocation plan is based on four elements: the local fre¬quency regulatory authority requirements, selected radio transmitter and receiver characteristics, antenna characteristics, and potential intrasystem and intersystem RF interference. 

Microwave Propagation Characteristics.  Various phenomena associated with propagation, such as multipath fading and interference, affect microwave radio performance.  The modes of propagation between two radio antennas may include a direct, line-of-sight (LOS) path but also a ground or surface wave that parallels the earth's surface, a sky wave from signal components reflected off the troposphere or ionosphere, a ground reflected path, and a path diffracted from an obstacle in the terrain. The presence and utility of these modes depend on the link geometry, both distance and terrain between the two antennas, and the operating frequency. For frequencies in the microwave (~2 – 30 GHz) band, the LOS propagation mode is the predominant mode available for use; the other modes may cause interference with the stronger LOS path. Line-of-sight links are limited in distance by the curvature of the earth, obstacles along the path, and free-space loss. Average distances for conservatively designed LOS links are 25 to 30 mi, although distances up to 100 mi have been used. For frequencies below 2 GHz, the typical mode of propagation includes non-line-of-sight (NLOS) paths, where refraction, diffraction, and reflection may extend communications coverage beyond LOS distances. The performance of both LOS and NLOS paths is affected by several phenomena, including free-space loss, terrain, atmosphere, and precipitation.


Strengths and Weaknesses

Strengths

  • Adapts to difficult terrain
  • Loss versus distance (D)  = Log D (not linear)
  • Flexible channelization
  • Relatively short installation time
  • Can be transportable
  • Cost usually less than cable
  • No “back-hoe” fading

Weaknesses

  • Paths could be blocked by buildings
  • Spectral congestion
  • Interception possible
  • Possible regulatory delays
  • Sites could be difficult to maintain
  • Towers need periodic maintenance
  • Atmospheric fading


Business Implications and Applications

The tremendous growth in wireless services is made possible today through the use of microwaves for backhaul in wireless and mobile networks and for point-to-multipoint  networks.  Towers can be used for both mobile, e.g. cellular, and point-to-point applications, enhancing the potential for microwave as wireless systems grow.  Increases in spectrum allocations and advances in spectrum efficiency through technology have created business opportunities in the field of microwave radio.   Telecommunications carriers, utility companies, and private carriers all use microwave to complement wired and optical networks.

How to Learn More about It


Courses

  • For those who need a less technical discussion of microwaves, for instance sales and management personnel, a “friendly” version of the above two-day course is also available.
  • If your needs require a more detailed course on microwaves, please take a look at  Microwave and Fixed Line-of-Sight Link Design Workshop, a comprehensive four-day course which offers the option to add a hands-on workshop on the fifth day.

Books

  • Digital Transmission Systems, Second Edition, by David R. Smith.  Kluwer Academic Publishers, 2004.  Good introduction to microwave systems, including modulation, error correction codes, equalization, and diversity.
  • Microwave Radio Links: Theory to Design by Carlos Salema.  John Wiley and Sons, 2000.  Excellent treatment of all aspects of microwave systems engineering.
  • Federal Communications Commission Rules and Regulations, Part 101, Fixed Microwave Services, 1 August 1996.
  • TIA/EIA Telecommunications Systems Bulletin, TSB10-F, “Interference Criteria for Microwave Systems”, June 1994.

Web Resources


]]> Optical Networking http://www.eogogics.com/talkgogics/tutorials/optical-networking Mon, 29 Jan 2007 16:03:08 -0600

What Is Optical Networking?

As the name suggests, optical networks form a class of networks where optical, rather than electronic, components are the building blocks of the network.  Compared to metallic cable, fiber optic systems offer greater bandwidths, lower attenuation, and no crosstalk or electrical interference.  Those advantages have led to the dramatic growth of fiber optic systems worldwide.  Today, nearly all long-haul telecommunications depend on the use of optical networks for their large capacity and robust performance.
 

Standards   

Standards for fiber optic cable and other optical components have been developed over the last 20 years primarily by the American National Standards Institute (ANSI) and the International Telecommunications Union (ITU).   Standards for fiber optic transmission have been developed initially in North America under the name Synchronous Optical Network (SONET) and later by the ITU using the name Synchronous Digital Hierarchy (SDH).
 

Historical Milestones

  • 1958: Discovery of laser
  • Mid-60s: Demonstration of guided wave optics
  • 1970: Production of low-loss fibers, which made long-distance optical transmission possible
  • 1970: Invention of semiconductor laser diode, which made highly refined optical transceivers possible
  • 70s-80s: Use of fiber in telephony: SONET/SDH standards from ITU
  • Mid-80s: LANs/MANs: broadcast-and-select architectures
  • 1988: First trans-Atlantic optical fiber laid
  • Late-80s: Development of EDFA (optical amplifier), which greatly alleviated distance limitations
  • Mid/late-90s: DWDM systems explode
  • Late-90s: Intelligent Optical networks
  • 20?? Soliton transmission with optical TDM

Optical Networking: Why?

The “traditional" networks consist, for the most part, of a collection of electronic switches interconnected by point-to-point optical fiber links, which can span local, metropolitan, or wide area networks.  To accommodate continually increasing demand for bandwidth and flexibility, such networks are being enhanced by adding more fibers and switches, increasing the bit rate per fiber, and upgrading the switches' size, throughput and functionality.  Such enhancements eventually lead to very large and complex networks that are difficult and expensive to construct, operate and maintain.  Recent and emerging advances in optical technology promise revolutionary all-optical networks capable of providing improved economy, flexibility and robustness while still capable of making use of the large existing fiber base.

Principles and Operation  

An optical fiber is a cylindrical waveguide made of two transparent materials each with a different index of refraction.  The two materials, usually high-quality glass, are arranged concentrically to form an inner core and an outer cladding.  Different entry angles of the light source result in multiple modes of wave propagation.  Propagation can be restricted to a single mode by using a small-diameter core.
 
The choice between single-mode and multimode fiber depends on the desired repeater spacing or transmission rate; single mode is the preferred choice for long-haul or high data-rate systems.  The earliest form of multimode fiber was the step-index, where the core has a uniform index of refraction and the concentric cladding also has a uniform but lower index.  In this case the propagation velocity within the core is constant, so that rays traveling a longer path arrive behind rays traveling a shorter path, thus producing pulse spreading, or dispersion.  These dispersive effects may be remedied by constructing a fiber whose refractive index increases toward the axis, with a resulting refractive index profile that is parabolic.  With a graded-index fiber, rays that travel longer paths have greater velocity than rays traveling the shorter paths due to decreasing refractive index with radial distance.  The various modes then tend to have the same arrival time, such that dispersion is minimized and greater bandwidths become possible for multimode fibers.
  
Within the spectrum available in a fiber optic system, there are three low-loss windows, at wavelengths of approximately 850, 1300, and 1550 nm.  Early applications of fiber optics for communications applications were based on the short-wavelength band of roughly 800 to 860 nm.  Operation in the longer-wavelength bands, particularly at 1300 and 1550 nm, is attractive because of improved attenuation and dispersion characteristics at these wavelengths.  Typically today the shorter-wavelength band is used for short-haul, low data rate systems, and the longer-wavelength bands are applied to long-haul, high data rate systems.  Special fibers have been developed that shift the minimum dispersion to about 1550 nm to take advantage of lower attenuation as well as minimum dispersion.  These fibers are called dispersion-shifted fibers, and are important to single-mode fiber applications.

Low-data rate, short-haul fiber optic systems tend toward multimode cable, LED transmitters, and PIN diode receivers.  High-data rate, long-haul systems tend toward single-mode cable, laser diode transmitters, and avalanche photodiode receivers.   Latest generation fiber optic systems have introduced innovations that have significantly improved the bandwidth and repeater spacing possible.  Coherent detection via either homodyne or heterodyne techniques allows much greater bandwidths to be realized.  Several wavelengths can be transmitted simultaneously in wavelength-division multiplexing, analogous to frequency-division multiplexing used in telephony.  Optical amplifiers are now available that eliminate electronics and instead use specially doped fiber or semiconductor laser devices.  The use of optical amplifiers will allow a fiber optic system to be upgraded in bit rate without replacement of the repeaters.  Optical amplifiers have also been used to achieve ultra-long distances via soliton transmission, which is the transmission of an idealized pulse without loss of pulse shape.
 

Types of Optical Networks

Optical networks may be classified in several ways.  Opaque optical networks include optical-electronic-optical (OEO) conversion, while in all-optical networks each connection is totally optical (or transparent) except at the end nodes.

Optical networks may be single wavelength or multiple-wavelengths (WDM).  The use of SONET/SDH with a single carrier is a typical example of an opaque, single-wavelength optical network.

Finally, optical networks may be passive or active.   A passive optical network (PON) is an all-optical network that utilizes only passive optical components, e.g., fibers, directional couplers, star couplers, wavelength routers, wavelength multiplexers, and filters.  The intended applications are fiber-in-the-loop (local loop) and fiber-to-the-home (FTTH). The optical signaling formats in PONs can employ wavelength-division multiplexing (WDM), subcarrier multiplexing, time-division multiplexing (TDM) or any combination of these. An active all-optical network (AON) enables each of a large number of optical WDM channels (wavelengths) to propagate from source to destination over long distances and high bit rates without optical-to-electronic format conversion within the network.

Optical Network Architecture

There are two standard optical architectures, linear and ring, both of which can provide network protection and restoration of services.  SONET rings are the most widely deployed architecture.  They can be thought of linear networks folded back to create a loop or ring.  But unlike linear architectures, rings are designed to guarantee automatic restoration of services when cable or nodes fails, by use of loops around the failed component. Because of this automatic protection against failures, these rings are called self-healing.  There are several SONET ring architectures that depend on the number of fibers, transmission direction, and level of switching protection.

Originally developed in the United States, the SONET standard was adopted by the ITU-T but renamed as the Synchronous Digital Hierarchy (SDH).  These standards provide a complete set of specifications to allow national and international connections at various levels.  Optical interfaces are defined that provide a universal fiber interface and permit mid-span interconnection of different vendor equipment.  A standardized signal structure allows any existing hierarchical rates (for example, DS-1, DS-3, E-1, and E-3) to be accommodated.  Overhead within the SONET signals facilitate synchronization, add and drop multiplexing, electronic switching, performance monitoring and network management of the composite and tributary signals.  The SONET hierarchy is built on synchronous multiplexing of a basic SONET rate of 51.84 Mb/s, so that higher SONET rates are simply N x 51.84 Mb/s.  The basic signal structure provides sufficient flexibility to carry a variety of lower-level rates within the 51.84 Mb/s signal.  

Optical Networking vis-à-vis Other Technologies

  • Size and Weight: Since individual optic fibers are typically only 125 μm in diameter, a multiple fiber cable can be made that is much smaller than corresponding metallic cables.
  • Bandwidth: Fiber optic cables have bandwidths that can be orders of magnitude greater than metallic cable. Low data rate systems can be eas¬ily upgraded to higher rate systems without the need to replace the fibers. Upgrading can be achieved by changing light sources (LED to laser), improving the modulation technique, improving the receiver, or using wavelength division multiplexing.
  • Repeater spacing: With low-loss fiber optic cable, the distance between repeaters can be significantly greater than in metallic cable systems. More¬over, losses in optical fibers are independent of bandwidth, whereas with coaxial or twisted pair cable the losses increase with bandwidth. Thus this advantage in repeater spacing increases with the system’s bandwidth.
  • Electrical isolation:  Fiber optic cable is electrically nonconducting, which eliminates all electrical problems that now beset metallic cable.  Fiber optic systems are immune to power surges, lightning induced currents, ground loops, and short circuits. Fibers are not susceptible to electro¬magnetic interference from power lines, radio signals, adjacent cable sys¬tems, or other electromagnetic sources.
  • Crosstalk: Because there is no optical coupling from one fiber to another within a cable, fiber optic systems are free from crosstalk. In metallic cable systems, by contrast, crosstalk is a common problem and is often the limiting factor in performance.
  • Environment: Properly designed fiber optic systems are relatively unaf¬fected by adverse temperature and moisture conditions and therefore have application to underwater cable. For metallic cable, however, mois¬ture is a constant problem particularly in underground (buried) applica¬tions, resulting in short circuits, increased attenuation, corrosion, and increased crosstalk.
  • Reliability: The reliability of optical fibers, optical drivers, and optical receivers has reached the point where the limiting factor is usually the associated electronics circuitry.
  • Cost: The numerous advantages listed here for fiber optic systems have resulted in dramatic growth in their application with attendant reductions in cost due to technological improvements and sales volume.
  • Frequency allocations: Fiber (and metallic) cable systems do not require frequency allocations from an already crowded frequency spectrum.  Moreover, cable systems do not have the terrain clearance, multipath fading, and interference problems common to radio systems.

Business Implications and Applications

Today fiber optic systems are much more cost effective than metallic cable, satellite, and radio for long haul, high bit rate applications.  Fiber optic cable is also expected eventually to overtake metallic cable in short haul applications, includ¬ing metro facilities and local networks. One final cost factor in favor of fiber optics is the choice of material, namly silicon, which of course is one of the earth's most abundant elements, versus copper, which may someday be in short supply, or the radio spectrum, which is already in short supply.

How to Learn More about It


Courses
  • SONET/SDH: Principles and Design  is an intensive, two-day course that covers everything needed to understand and deploy this important technology, namely, the basic principles; system architecture, components, and operation; end-to-end network design process; and applications. 


Books
 

  • Digital Transmission Systems, Third Edition, by David R. Smith.  Kluwer Academic Publishers, 2004.  Good introduction to optical communications, including components, standards, and networks.  Good description of SONET and SDH.

  • Optical Networks by Ramaswami and Sivarajan: A Practical Perspective, Second Edition.  Morgan Kaufmann Publishing, 2002.  A practical textbook that offers   details on all aspects of optical components and networks.

  • Deploying Optical Networking Components by Gilbert Held.  McGraw-Hill.

  • Fiber-Optic Communications Systems by Govind E. Agrawal.  Wiley & Sons.



Web Resources
  • ITU (http://www.itu.int) ITU-T:  Telecom sector of the International Telecommunications Union, the United Nations treaty agency that sets telecommunications standards.
  • ANSI (http://www.ansi.org ) American National Standards Institute is the national standards body of the United States.  It coordinates and accredits standards development across the US.



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