Job descriptions that are generic

Job that demands skilled professionals with extensive experience in network administration. Candidates applying for the job must have hands-on experience on routers, switches and enterprise servers.

Day to day troubleshooting of common network problems, ability to handle help desk calls, interact with IT staff in remote locations and resolve WAN related problems.

Job descriptions that are specific about technology

Looking for a network engineer with experience in Cisco firewall products, Wan accelerators, F5 load balancing devices, Blue coat, MPLS etc. Must be at least a CCNP certified professional.

As you have read, there is no common job description to this profile. We recommend that you choose a specific area of networking such as security, switching or routing and increase your knowledge in that area. Also, consider taking up certifications in those areas and aim to become a specialist over a period of time.

802.11b Vs 802.11g

Both the WLAN standards use the unregulated radio frequency band of 2.4GHz which means they can interfere with other appliances using the same frequency.

802.11b supports a maximum bandwidth of up to 11Mbps whereas the 802.11g supports a bandwidth of up to 54Mbps. 802.11g is the best of the two for office use since 802.11b is slower than 802.11g cards.

802.11g costs more than 802.11b network adapters or the wireless cards.

So, if you want to buy a wireless card for your notebook or your desktop, if your wireless access point supports 802.11g, then you should choose a 802.11g wireless card over a 802.11b card. There are many companies that manufacture wireless cards such as Realtek, Broadcom, Intel, Linksys and D-Link.

Addition of this functionality will enable HP servers and storage resources to be shared between StorageWorks 8/20q based SANs and HP B-series fabrics. It also lets businesses start with an 8-port 8/20q fibre channel switch and add TR ports for more storage capacity without impacting their existing Storage Area Network (SAN).

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The energy management software from Cisco is expected to lower the energy consumption by about 15% to 20%. Since most of the companies in the world use Cisco’s network products, their software product could place them in a very good position in the market. The long term outlook of Cisco looks really good.

For more information on Cisco EnergyWise technology, explore the following links.

• EnergyWise Flash Demonstration
• Key features of Cisco EnergyWise [PDF]
• Business benefits by deploying Cisco EnergyWise [PDF]
• Download Cisco EnergyWise

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If your business depend on your computer and you make phone calls through Skype then the Surfboard comes highly recommended. The Motorola Surfboard SB5101 is reasonably priced and works with a vast majority of ISPs as most of them actually supply Motorola brand cable modem to their customers.

With the support for a network data transfer rate of 30 Megabits Per Second, this cable modem ensures that when your ISPs upgrade their network in the future, you will not have to upgrade your modem. This will suffice your needs of the future as well.

The model is currently available for around $55 from Amazon. Check Amazon for latest price of this product.

A computer network may be any set of computers or devices connected to one another exchanging data and information. There are three main types of networks:

• A Local Area Network (LAN)- described as a small network constrained to a small geographic area.
• A Wide Area Network (WAN)- typically a larger network that covers a large geographic area.
• Wireless LAN & WAN- a more popular approach to computer networking that involves communication over small or large geographic areas using electromagnetic waves to communicate between nodes without the use of cables.

Networks can be viewed both physically and logically. A physical perspective involves location, the actual cables, and network elements such as routers, bridges, and application layer gateways to connect the physical media. A logical perspective involves subnets, or maps of the physical media. Many campuses of buildings may use a set of LAN cables in each building to create a common subnet, using virtual LAN (VLAN) technology.

There are also distinguishing characteristics of networks which may describe them as an intranet or extranet. An intranet is a community of interest under a private administration which requires special access by users, which are most commonly employees of an enterprise. Intranets do not necessarily need to be connected to the internet. An extranet is the extension of an intranet which allows secure communications to users outside of the intranet community.

The term “repeater” originated with telegraphy and referred to an electromechanical device used to regenerate telegraph signals. Use of the term has continued in telephony and data communications.

In telecommunication, the term repeater has the following standardized meanings:

1. An analog device that amplifies an input signal.
2. A digital device that amplifies, reshapes, retimes, or performs a combination of any of these functions on a digital input signal for retransmission.

Repeaters are often used in trans-continental and trans-oceanic cables, because the attenuation (signal loss) over such distances would be completely unacceptable without them. Repeaters are used in both copper-wire cables carrying electrical signals, and in fibre optics carrying light.

In optical communications the term repeater is used to describe a piece of equipment that receives an optical signal, converts that signal into an electrical one, regenerates it, and then retransmits an optical signal. Since such a device converts the optical signal into an electrical one, and then back to an optical signal, they are often known as Optical-Electrical-Optical (OEO) repeaters.

A router can be used to either connect at least two networks, or to form a mobile ad-hoc network. A special variety of router is the one-armed router used to route packets in a virtual LAN environment. In the case of a one-armed router the multiple attachments to different networks are all over the same physical link.

A router that connects clients to the Internet is called an Edge Router. A router that serves to transmit data between other routers is called a Core Router.

A router creates and/or maintains a table, called a routing table that stores the best routes to certain network destinations and the “routing metrics” associated with those routes. In recent times many routing functions have been added to LAN switches, creating “Layer 2/3 Switches” which route traffic at near wire speed.

Routers are also now being implemented as Internet gateways, primarily for small networks like those used in homes and small offices. This application is mainly where the Internet connection is an always-on broadband connection like cable modem or DSL. These are not “routers” in the true sense, but the terminology has been confused with network address translation.

There are several manufacturers of routers including:

• 3Com
• Alcatel
• Belkin
• Cisco Systems, Inc
• D-Link Systems
• Juniper Networks
• Linksys
• Mikrotik
• NETGEAR
• Nortel
• Pivotal Networking
• Siemens AG
• SMC Networks
• Tellabs
• MRV Communications
• Zoom Telephonics

How switches work?

A switch can connect Ethernet, Token Ring, or other types of packet switched network segments together to form a heterogeneous network operating at OSI Layer 2.

As a frame comes into a switch, the switch saves the originating MAC address and the originating port in the switch’s MAC address table. The switch then selectively transmits the frame from specific ports based on the frame’s destination MAC address and previous entries in the MAC address table. If the MAC address is unknown, or a broadcast or multicast address, the switch simply floods the frame out of all of the connected interfaces except the incoming port. If the destination MAC address is known, the frame is forwarded only to the corresponding port in the MAC address table. If the destination port is the same as the originating port, the frame is filtered out and not forwarded.

Switches, unlike hubs, use microsegmentation to divide collision domains, one per connected segment. This way, only the NICs which are directly connected via a point-to-point link, or directly connected hubs are contending for the medium.

By eliminating the possibility of collisions, full-duplex point-to-point connections on the switch become possible. Virtual LANs can be used in switches to reduce the size of the broadcast domains and at the same time increase security. In redundant architectures, Spanning Tree Protocol (STP) can be used in switches to prevent loops.

Forwarding Methods used by a Switch

1. Cut through
2. Store and forward – the switch, unlike cut through, buffers and typically, performs a checksum on each frame before forwarding it on.
3. Fragment free
4. Adaptive switching

Hub can also be called a multi-port repeater. This is due to the fact that a hub will repeat the signals received from one port to all other ports excluding the port it received the signals from. For example, in a 10 port hub, if signal is sent from port # 10 then hub will repeat the signal to all other ports except port # 10.

In a hub every device connected to it will receive the broadcast traffic and thus makes it inefficient for larger networks. But for small networks with less than 20 computers, using a hub can be cost effective. All the devices connected to the hub are part of the same broadcast domain and also collision domain. That means, only one device can transmit the data at any given point of time and other system when try to transmit will result in a collision.

A ethernet network utilizing a hub behaves like a shared-medium, that is only one device can successfully transmit at a time and each host remains responsible for collision detection and retransmission.

Advantages of a Hub

1. A protocol analyzer connected to a hub allows it to see all the traffic on the segment but not when it comes to a switch as it will separate the ports into different segments.
2. Some computer clusters require each member computer to receive all of the traffic going to the cluster. A hub will do this naturally; using a switch requires implementing special tricks.
3. A cheap hub with a 10BASE2 port is probably the cheapest and easiest way to connect devices that only support 10BASE2 to a modern network. (Cheap switches don’t tend to come with 10BASE2 ports.)

Disadvantages of a Hub

1. The need for hosts to be able to detect collisions limits the number of hubs and the total size of the network.
2. For 10 Mbit/s networks, up to 5 segments (4 hubs) are allowed between any two end stations.
3. For 100 Mbit/s networks, the limit is reduced to 3 segments (2 hubs) between any two end stations, and even that is only allowed if the hubs are of the low delay variety.
4. Some hubs have special (and generally manufacturer specific) stack ports allowing them to be combined in a way that allows more hubs than simple chaining through Ethernet cables, but even so a large Fast Ethernet network is likely to require switches to avoid the chaining limits of hubs.