Routing Protocols in Computer Networks, Slides of Computer Networks

Download Routing Protocols in Computer Networks and more Slides Computer Networks in PDF only on Docsity!

Routing Protocols: Types,

Static, Dynamic, Distance

Vector, Link-state

Dr Yawar

Routing protocol goal: determine “good” paths (equivalently, routes), from sending hosts to receiving host, through network of routers

• path: sequence of routers packets traverse from given initial source host to final destination host
• “good”: least “cost”, “fastest”, “least congested”
• routing: a “top-10” networking challenge! Routing protocols mobile network enterprise network national or global ISP datacenter network application transport network link physical application transport network link physical network link physical network link physical network link physical network link physical (^) network link physical Network Layer: 5- 2

Routing Table

192.168.3.0 Frame Relay 192.168.1.0 Ethernet 192.168.2.0 FDDI

Network 192.168.2.

FDDI

Network 192.168.3.

Frame Relay

Remote

Location

Network 192.168.1.

Ethernet

Main Site

Routers—Layer 3

What is Routing Protocol in Computer Networks?

• Routing Protocols are simply a set of defined rules used by

the routers to communicate between source & destination.

These protocols do not move the information from the

source to a destination, but they update the routing table

that contains the information.

• Routes learned by routing protocol are known as dynamic

routes. The goal of protocols is to exchange routing

information between routers. protocols have a number of

advantages in your network.

Continue

• Routing protocols are used in the discovery of

remote networks, maintaining up to date routing

information, choosing the best path to destination

networks, and the ability to find a new best path

when the current path is not available

LAN-to-LAN Connectivity

• Routers encapsulate and de-encapsulate data packets

as they are transferred from system X to system Y

X Y

A A B B C C Presentation Data Link Physical Data Link Physical

A B^ C

Data Link Physical Data Link Network Transport Session Presentation Application Physical Data Link Network Transport Session Application Physical Network Network Network

Graph abstraction: costs

• c(x,x’) = cost of link (x,x’)
  • e.g., c(w,z) = 5 Cost of path (x 1 , x 2 , x 3 ,…, xp) = c(x 1 ,x 2 ) + c(x 2 ,x 3 ) + … + c(xp- 1 ,xp) Question: What’s the least-cost path between u and z? Routing algorithm: algorithm that finds least-cost path

u

x y

v w

z

2 2 1 3 1 1 2 5 3 5

Path Determination 1 2 3 4 5 6 7 8 9 (^10 )

• Routers find the best path through the network
  • Routing tables contain route information
  • Network addresses represent the path

of media connections to a destination

Which Path?

Routing Metrics Routing protocols uses different metrics to select the best route

• Path length
  • Total hop count or sum of cost per network link
• Reliability
  • Dependability (bit error rate) of each network link
• Delay
  • Useful because it depends on bandwidth, queues, network congestion,

and physical distance

• Communication cost
  • Operating expenses of links (private versus public)
• Bandwidth and load

Static Routing

Protocol

• When an administrator manually allocates the path from the source to the destination network, static routing protocols are employed. It improves the network’s security.

Routing

Protocols

• Packets p a s s through many routers from source to destination
• Dynamic nature of Internet; routes change and need to be updated
• Routing protocol – combination of rules and procedures allowing routers to inform one another of changes 17

Dynamic Routing

A network change blocks

the established path...

A B C D X A B C D X

…and an alternate route is

found dynamically.

• Most internetworks use dynamic routing

Dynamic

Routing

Protocols

• Running a dynamic routing protocol will allow our routers to share their network information with each other and recover from a network outage automatically.
• If a n alternate path exists and all of the routers are running properly configured routing protocols, they will eventually locate the alternate path and u s e it if the primary path goes down. 20