Report On Routers

Submitted By     

RASHMI SINGH RATI OJHA REKHA SHAKYA RISHI SINHAL ROHIT SINGOUR

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Submitted to

Lect. Agya Mishra

DEFINITION PURPOSE CLASSIFICATION ROUTING ALGORITHM ADVANCED TECHNOLOGY APPLICATION CRITICAL REVIEW CONCLUSION

A router is a device that actually delivers information to its intended destination, using one of several different routing protocols. Routers have access to network layer addresses and contain software that enable them to determine which of several possible paths between those addresses is the best for particular transmission. Routing is the process of delivering information to its intended destination.

Need of firewall features to isolate networks and provide security for private networks. Recovery of TCP/IP protocols from the local Ethernet protocols which are routed over PPP protocols for transferring data information over GSM, GPRS and PSTN networks. Routers are used to reduced traffic load through the network.

Internal Routers - routers with all directly connected networks belonging to the same area. Area Border Routers - routers that are attached to multiple areas. AS Boundary routers - routers that exchange routing information with routers belonging to other AS.

Designated Routers (DR) and Backup Designated Routers (BDR) Instead of each router exchanging database information with every other router on the segment, every router exchanges information with the DR and BDR (foe example- OSPF)

OSPF:- stands for Open Shortest Path First

Bellman-Ford Algorithm [Distance Vector Algorithm]:Basic idea:- each network node (router) maintains a Distance Vector table containing the distance between Itself and ALL possible destination nodes.

Dijkstra’s Algorithm [Link State Algorithm]:Basic idea:-Each router constructs a link state packet (LSP) .which is transmitted to ALL other routers. Each router stores the most recently generated LSP from each other router.

Routing table updates occur periodically or when the topology in a distance vector protocol network changes Routing loops can occur when inconsistent routing tables are not updated due to slow convergence in a changing network

Each router is responsible for meeting its neighbors and learning their names.

Each router constructs a link state packet (LSP) which consists of a list of neighbors’ names and the cost to reach each neighbor.

Each router uses complete information on the network topology to compute the Shortest path route to each destination node.

Correctness Simplicity and Low Overhead Robustness and stability Rapid convergence Flexibility

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Larger internetworks require the use of RIP, or Routing Information Protocol, to keep track of new routes. Why RIP is still with us today is for several reasons – first, the protocol has undergone vast improvements in Version 2, and second - it is really simple to configure and use! And, oh yes, when used in a network of appropriate size (small) – it actually works! RIP v2 does manage to solve many issues found in the first iteration of this distance vector protocol and this article is a celebration of these new features.

Off-chip Buffer Shared Bus CPU CP U

M em

Route Table

Buffer Memory

Li In ne te rfa ce

or

y

Line Interface

Line Interface

Line Interface

MAC

MAC

MAC

Line card DMAs into buffer, CPU examines header, has output DMA out Typically <0.5Gb/s aggregate capacity

CPU

Route Table

Buffer Memory

Bypasses memory bus with direct transfer over bus between line cards

Line Card

Line Card

Line Card

Buffer Memory

Buffer Memory

Buffer Memory

Fwding Cache

Fwding Cache

Fwding Cache

MAC

MAC

MAC

Typically <5Gb/s aggregate capacity

Moves forwarding decisions local to card to reduce CPU pain

Punt to CPU for “slow” operations

Third Generation Routers “Crossbar”: Switched Backplane

Li I CPnt ne Uerf ac e M em or y

Line Card

CPU Card

Line Card

Local Buffer Memory

Routing Table

Local Buffer Memory

Fwding Table MAC

Fwding Table

Periodic Control updates

Typically <50Gb/s aggregate capacity

MAC

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It is used to create a network with remote access to private networks. It enables Private networks to be inter-networked with other networks such as the Internet. Companies to create their own networks in customers' premises to eliminate reliance on the end customers' network. Routers are useful to provide security in military transmissions that require highly secure lines by using “Hop-count Algorithm”. A small network to be created in mobile applications, where fixed line solutions aren’t possible.

There is a drawback of a router that transfers , accepts and relays packets only across networks using similar protocols. The packet at the front of the queue experiences contention for the output queue, blocking all packets behind it. Software can only be repaired by redesign. Software bugs can be highly contagious. Still need protection against link failure.

Problem: The packet at the front of the queue experiences contention for the output queue, blocking all packets behind it. Input 1

Output 1

Input 2

Output 2

Input 3

Output 3

Maximum throughput in such a switch: 2 – sqrt(2)

Modern routers are very complex hardware and software systems with demanding requirements and constraints To achieve carrier class converged networks, router software and hardware architecture is going to have to evolve to better achieve scale and reliability

WEBSITES:  www.google.com  www.howstuffworks.com BOOKS REFERRED:  Behrouz A . Forouzan  Andrew S. Tanenbaum

Questions?