What are the various ways to extend a Local Area Network (LAN)

If you have a huge premises that has multiple blocks (like a factory or a college), then you would be wanting to extend the IP Network (LAN) to the various blocks and new blocks that might come up in the future. There are multiple ways of doing this.

Wired Options:

The best way is to use fiber cables between the blocks (assuming that a bigger premises has blocks seperated by more than 100 meters – if they are less than 100 meters, you can also use the Cat5/6 Copper UTP Cables).

The fiber cables can be laid in a star topology (as shown in the above diagram) where a central fiber distribution switch / distribution layer switch with fiber modules connect with fiber cables that go to the individual blocks where they can be terminated in the fiber module of a network switch or a media converter and then a LAN segment using a network switch/UTP cables can be created locally.

In some places, it may not be feasible to have the fiber cables running from a central location to all the individual blocks. In those locations, multiple interconnected star fiber networks (as shown in the above diagram) could be utilized, or the departments can be connected with one another directly by fiber cables (as shown below), which is called ring topology.

All the above mentioned topologies are expandable to accomodate more switches in the future.

If you do not want to lay expensive fiber cables/fiber modules for a particular segment, you can also extend the LAN by using a LAN extender pair. These are SHDSL/HDSL/VHDSL based broadband routers that can be configured to operate in the bridge mode. They connect to the LAN on either side through the RJ-45 interface/ Cat5/6 cables and they connect to each other using the copper single pair telephone cables which are cheaper to procure and lay. In many places, the telephone cable networks are already present. You can realize full duplex bandwidths of about 2 Mbps over a couple of Kilo Meters (this depends on the model) using such a set up (HDSL is different from ADSL as it provides equal bandwidth both upstream and downstream, which is better for extending a LAN segment). You can use DSLAM/CPE broad band equipments (Using ADSL2+) to create a complete LAN using existing telephone cables as explained in this post.

Wireless Options:

Wireless technologies today are not only used for Wi-Fi client access but are also used for backhaul/interconnectivity.

A wireless mesh network can be formed with dual radio / multi-radio access points where one radio in each access points connects the clients and the other radio connects neighbouring access points. A mesh architecture is shown below. The number of such wireless mesh hops is limited as the available bandwidth reduces by half with each hop.

For departments/LAN segments that need to be interconnected but are slightly far away, point to point wireless solutions are available. Basically, these outdoor access points are configured to operate in the point-to-point or point-to-multipoint modes and one such access point along with antenna/tower is required in each department/building which needs to be interconnected. They are generally kept over a tower so that line of sight is realized between the locations, for best performance. This set-up can be used to connect two offices that are even up to 50/60 Kilometers apart, provided that a line of sight can be established with a tower. A basic wireless point-to-multipoint architecture is shown in the below diagram.

Service provider options:

In many situations, it is not possible to extend a LAN across a big area as public roads/tracks might be crossing in-between or the locations to be interconnected might be very far away. In such places, the fiber networks of bandwidth service providers can be utilized. Basically it is a shared private network where a limited amount of network bandwidth and infrastructure (in the form of Leased lines, MPLS VPN, Internet leased lines etc) can be leased from the service providers (Usually they charge per Mb per year). In certain areas, metro ethernet might be available where the service privider has the infrastructure to connect two locations of a same branch located in different places at speeds of 10/100 Mbps using his public network infrastructure. This is also provided on a leased basis.

VSAT connectivity is a satellite based connectivity that can be utilized to connect remote locations that are not accessible by wireline/wireless internet/connectivity options. Some examples where such VSAT connectivity can be used are hill tops, ships etc. In branch offices and SOHO type of offices, even broadband/3G internet connectivity can be used to create a small LAN segment. But it is advisable in such situations (where LAN traffic is going through a shared network like Internet) to use VPN tunnels/Encryption between the sites.

So, do you think there are more innovative ways of extending a LAN? Do contribute your suggestions in the comments section below.

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