Routers

 

Routers – What is Router? Characteristics of Routers. Router Protocols

Routers are used to connect both similar and dissimilar LANs. Router operates on the network layer of OSI model using the physical layer, data link layer and network layer to provide connectivity, addressing and switching. These are highly intelligent devices. In case of TCP/IP network, Internet Protocol (IP) is used as addresses for network; this is the router which interprets the IP address and delivers the packet reliably.

Now, we may say that router transmits the network layer data and therefore, provides transmission of data between LANs that use different data link protocols but using the same network layer protocol. Because of this, Etl1ernet can be connected with token ring network using routers. Additionally, routers provide connectivity La MAN (SMDS) and WAN (X.25, Frame Relay and ATM). Routers are protocol sensitive; typically supporting multiple protocols and large and varying packet sizes such as might be involved in supporting both Ethernet and Token Ring.

Characteristics of Routers

Routers are multi-port devices with high – speed backbones

Routers also support filtering and encapsulation like bridges

Like bridges routers are also self-learning, as they can communicate their existence. to other devices and can learn of the existence of new routers, nodes and LAN segments

As explained earlier, they route traffic by considering the network as a whole. It shows that they use a high level of intelligence to accomplish this task. This characteristic makes them superior than hubs and bridges because they simply view the network on a link-by-link basis

The packet handled by router may include destination address, packet priority level, least-cost route, minimum route delay, minimum route distance, and route congestion level

Routers constantly monitor the condition of the network, as a whole to dynamically adapt to changes in the condition of the network

They typically provide some level of redundancy so that they are less susceptible to catastrophic failure.

Router Protocols 

Router protocols consist of both bridging and routing protocols as listed below:

Inter-router Protocols

These are router-to-router protocols that can operate over dissimilar networks. This protocol routes information and stores data packets during periods of idleness.

Serial Line Protocols

This protocol is widely used over serial or dial-up links connecting unlike routers. Examples include HDLC, SLIP (Serial Line Interface Protocol), and PPP (Point-to-Point Protocol).

Protocol Stack Routing and Bridging Protocols

This advises the router as to which packets should be routed and which should be bridged.