[OSPF] comparison between rip and OSPF

RIP Basic introduction

RIP It is a routing protocol based on routing vector algorithm , In large networks, the convergence speed is slow （ In case of failure , It takes a long time to solve the fault ）、 The measurement is unscientific 、 Poor scalability and so on .
RIP Update time 30s, Aging time 180s, If the route is in 180s No refresh within , The router will think that the route has failed . The route converges through the timer .
RIP There is no neighborhood maintenance mechanism , Judge whether the path is invalid by passively waiting for route aging .

example RIP The shortcomings of

• Slow convergence
  The goal is C–>A
  route 1：C – B – A, need 2 jump
  route 2：C – D – E – F – A, need 4 jump
  C Think of the path 1 Is the optimal route
  hypothesis B–A The switch between has failed ,C Failure cannot be sensed in time ,C Sent to A Of packets will still follow the path 1 Send out . At this time, packet loss will occur , wait until C Path in router 1 Reached the aging time ,C Will choose the path 2.
• The measurement is unscientific
  RIP Take the number of hops as a measure
  Suppose the path 1 Bandwidth of each link in 1M, route 2 Bandwidth of each link in 10M
  C–A The packets of will go through the path 1
• The anti ring mechanism has poor scalability
  The maximum number of hops is 16 jump （16 Jump to empirical value instead of calculated ）,16 A hop route is an invalid route
  When the number of hops is 16 Jumping time , The router will discard the packet , But doing so limits the size of the network ,RIP The protocol cannot support networks with too large diameter

RIP Features are some of the problems that come with them

RIP characteristic	The problems brought about by
Hop by hop convergence	Slow convergence , Long recovery time
Hearsay route update mechanism	Lack of understanding of global network topology
The maximum number of valid hops is 15	In ring networking , Make remote routes unreachable
With “ Hops ” For measurement	There is a risk of choosing a suboptimal path

RIP Solutions to related problems

RIP problem	A method of optimization or solution
Slow convergence , Long recovery time	“ Receive updates -> Calculate route -> Send updates ” Change it to “ Receive updates -> Send updates -> Calculate route ”
Lack of understanding of the global network	Routers are based on topology information , Independent computing routing
The maximum number of valid hops is 15	Unlimited hops
There is a risk of choosing a suboptimal path	Take the link bandwidth as the reference value for routing

OSPF

comparison RIP,OSPF Changes made

1. RIP： Receive updates -> Calculate route -> Send updates
   OSPF： Receive updates -> Send updates -> Calculate route
   RIP The routing result is passed ;OSPF Link state information transmitted
   OSPF The process of calculating routes has been postponed , The process of route delivery and route calculation are decoupled . Link state LS It is the material for calculating routing ,OSPF Notified LS Link state is the material for calculating routing , Not a routing result .
2. The topology computer system is different
3. Unlimited hops , But I will choose other ways to prevent the ring

OSPF Working process of

1. Build a neighborhood
2. Synchronize link state database （ Exchange status information with each other , Maintain database consistency between the two devices ）
3. Calculate the optimal route （ Calculated independently by each equipment ）