Tiểu luận môn mạng máy tính Seminar Network Computer RIP Protocol

Tiểu luận môn mạng máy tính Seminar Network Computer RIP Protocol Không gửi lại thông tin routing theo hướng mà router đó nhận được Cơ chế này sử dụng ngay cả khi không có hiện tượng một mạng bị down. Và cơ chế này giúp cho việc tránh được routing loop khi một mạng bị down Hạn chế : không khắc phục được hiện tượng count to infinity khi có nhiều router kết nối một cách gián tiếp. Ví dụ trong trường hợp 3 router kết nối theo hình tam giác

Seminar Network Computer

RIP Protocol

Sinh viên : Bùi Tuấn Anh

Lương Kim Doanh Nguyễn Văn Giang

 I RIP Introduction

 II Routing Loop Problem

 III RIP v1 vs RIP v2

 IV Summary

Contents

 Routing Information Protocol

 RIP is one of routing protocols based on Bellman Ford ( Distance Vector)

 RIP is most useful as an Interior Gateway Protocol (IGP)

Introduce about RIP

 Send the entire routing table to all the

 Slow Convergence

 Routing Loop

RIP’s Problems

 A condition in which a packet is

continuously transmitted within a series of routers without ever reaching its destination

Routing Loop Problem

Routing Loop Example

Routing Loop Example(2)

Cause by???

 Routing loop may be caused by:

◦ Slow convergence

◦ Incorrectly configured route redistribution

◦ Incorrectly configured discard routes

 Routing loop can create following issues:

◦ Count to infinity

◦ Excess use of bandwidth

◦ Network convergence is degraded

Cause and results

 Setting a maximum

 Split Horizon

 Split Horizon with Poison Reverse

 Hold down timer

 Triggered Updates

 TTL field in IP header

Solutions for routing loop

 Once the router counts to infinity it marks router as unreachable by setting a

maximum

Setting a maximum

Split Horizon

 A router should not advertise a network through the interface from which the

update cameSolution???

Only solves small routing loop and only prevents routing loop between neighbor routers

 A variation of Route Poisoning

 This is an enhancement of the basic split horizon feature

 The rule states that once a router learns of

an unreachable route through an interface, advertise it as unreachable back through same interface

Split Horizon with Poison

Reverse

 The hold down feature works by having

each router start a timer when they first

receive information about a network that is unreachable

 RIP’s hold down timer :180s

Hold down timer

Hold down timer (2)

Hold down timer(3)

Hold down Timer (4)

Hold down timer(5)

Hold down timer (6)

 When a route fails, an update is sent

immediately rather than waiting on the update timer to expire



Triggered Update

 TTL: Time To Live

 A 8-bit field in IP header

 TTL contains a numeric value

 The numeric value is decreased by one by every router on the route to destination

 When the numeric value = 0 , packet is

discarded

TTL field

TTL field (2)



RIPv1 vs RIP v2

RIP version 1 RIP version 2

Classful Routing Classless Routing

Not send subnet mask

information in routing table Sends subnet mask information in routing table Not support VLSM ( Variable

Length Subnet Mask)

Supports VLSM

Not support CIDR ( Classless

Inter-Domain Routing) Supports CIDR

Not has authentication to secure

routing update

Has authentication to secure routing

update(MD5authentication) Broadcast route updates by using

the IP address 255.255.255.255

Multicast route updates by using the IP address 224.0.0.9

Advantage and

Disadvantage

 Advantage

 Simple to implement

 Compatible with several network machines

 Process load is small

 Use in small network ( Autonomous System )

 Distance Vector and RIP