1 / 21

Dynamic Routing Protocols

Dynamic Routing Protocols. Why Dynamic Routing Protocols ? Each router acts independently, based on information in its router forwarding table Dynamic routing protocols allow routers to share information in their router forwarding tables. Router Forwarding Table Data.

feo
Download Presentation

Dynamic Routing Protocols

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Dynamic Routing Protocols • Why Dynamic Routing Protocols? • Each router acts independently, based on information in its router forwarding table • Dynamic routing protocols allow routers to share information in their router forwarding tables Router Forwarding Table Data

  2. Routing Information Protocol (RIP) • Routing Information protocol (RIP) is the simplest dynamic routing protocol • Each router broadcasts its entire routing table frequently • Broadcasting makes RIP unsuitable for large networks Routing Table

  3. Routing Information Protocol (RIP) • RIP is the simplest dynamic routing protocol • Broadcasts go to hosts as well as to routers • RIP interrupts hosts frequently, slowing them down; Unsuitable for large networks Routing Table

  4. Routing Information Protocol (RIP) • RIP is Limited • RIP routing table has a field to indicate the number of router hops to a distant host • The RIP maximum is 15 hops • Farther networks are ignored • Unsuitable for very large networks Hop Hop

  5. Routing Information Protocol • Is a Distance Vector Protocol • “New York” starts, announces itself with a RIP broadcast • “Chicago” learns that New York is one hop away • Passes this on in its broadcasts NY is 1 New York Chicago Dallas 1 hop

  6. Routing Information Protocol • Learning Routing Information • “Dallas” receives broadcast from Chicago • Already knows “Chicago” is one hop from Dallas • So New York must be two hops from Dallas • Places this information in its routing table NY is 1 New York Chicago Dallas 1 hop 1 hop NY is 2

  7. Routing Information Protocol • Slow Convergence • Convergence is getting correct routing tables after a failure in a router or link • RIP converges very slowly • May take minutes • During that time, many packets may be lost

  8. Routing Information Protocol • Encapsulation • Carried in data field of UDP datagram • Port number is 520 • UDP is unreliable, so RIP messages do not always get through • A single lost RIP message does little or no harm UDP Data Field RIP Message UDP Header

  9. OSPF Routing Protocol • Link State Protocol • Link is connection between two routers • OSPF routing table stores more information about each link than just its hop count: cost, reliability, etc. • Allows OSPF routers to optimize routing based on these variables Link

  10. OSPF Routers • Network is Divided into Areas • Each area has a designated router Area Designated Router

  11. OSPF Routers • When a router senses a link state change • Sends this information to the designated router Area Designated Router Notice of Link State Change

  12. OSPF Routers • Designed Router Notifies all Routers • Within its area Area Designated Router Notice of Link State Change

  13. OSPF Routers • Efficient • Only routers are informed (not hosts) • Usually only updates are transmitted, not whole tables Area Designated Router Notice of Link State Change

  14. OSPF • Fast Convergence • When a failure occurs, a router transmits the notice to the designated router • Designated router send the information back out to other routers immediately

  15. OSPF • Encapsulation • Carried in data field of IP packet • Protocol value is 89 • IP is unreliable, so OSPF messages do not always get through • A single lost OSPF message does little or no harm IP Data Field OSPF Message IP Header

  16. Selecting RIP or OSPF • Within a network you control, it is your choice • Your network is an autonomous system • Select RIP or OSPF based on your needs • Interior routing protocol

  17. Selecting RIP or OSPF • RIP is fine for small networks • Easy to implementing • 15 hops is not a problem • Broadcasting, interrupting hosts are not too important

  18. Selecting RIP or OSPF • OSPF is Scalable • Works with networks of any size • Management complexities are worth the cost in large networks

  19. Border Gateway Protocol (BGP) • To connect different autonomous systems • Must standardize cross-system routing information exchanges • BGP is most popular today • Gateway is the old name for router • Exterior routing protocol Autonomous System Autonomous System BGP

  20. Border Gateway Protocol (BGP) • Distance vector approach • Number of hops to a distant system is stored in the router forwarding table • Normally only sends updates Autonomous System Autonomous System BGP

  21. Border Gateway Protocol (BGP) • Encapsulation • BGP uses TCP for delivery • Reliable • TCP is only for one-to-one connections • If have several external routers, must establish a TCP and BGP connection to each Autonomous System Autonomous System BGP

More Related