RIP to OSPF and BGP protocol agreement

RIP protocol:

https://www.bilibili.com/video/BV19E411D78Q?p=54

RIP is a - A distributed based on distance vector routing protocol is a standard Internet protocol, the biggest advantage is simple .
RIP protocol requires each router in the network maintains from itself to each other - a destination network from the single best record (i.e., a set of distance).
Distance: typically "hops", i.e. the number of routers through which, via a router hop number + 1 from a source port to the destination port. In particular, all the way from
the network to the distance from the device 1 is directly connected. RIP allows a route can contain up to 15 routers, a distance of 16 indicates that the network is unreachable .
RIP protocol applies only to small Internet .

RIP protocol and who exchange? How long exchange time? What exchange?
1. Only and neighboring routers exchange information.
2. The exchange of information is the router own routing table .

3. every 30 seconds once exchanged routing information, the router then updates the routing table based on new information. If more than 180s did not receive notice of a neighbor router, it is determined that
the neighbor did not, and update their routing tables.

When the router just started working, only know from the network directly connected (distance 1), then each - a router and only a very limited number of adjacent
routers exchange and update routing information.
After several updates, all routers will eventually reach this autonomous system know any network shortest distance and under - hop router address
that is "convergence" .

Distance vector algorithm:

1. Modify the neighboring routers send packets to the RIP all entries
to adjacent routers X address of packets sent by RIP, modify all items in this telegram: the "next - hop" field address to X, and put
all the "distance" +1 field .

Each RIP packets after the modification 2. - A program, the following steps: 
       (. 1) R1 Net3 routing table if not, put the item filled R1 routing table
       (2) R1 routing table if Net3 , look at - - hop router address:
              if the next hop is x, then replace the source routing table project using the project received;
              if the next hop is not x, the original is newer than the distance from x to go the distance, otherwise not be processed.
3 .. If 180s not receive X adjacent routers update routing tables, referred to as X put unreachable router, i.e., the distance is set to 16.

4. Return

Distance vector algorithm Exercise 1:

 Distance vector algorithm Exercise 2:

RIP protocol good news travels fast, bad news travels slow:

The good news may be a number of hops on the line. Bad news, update 30 seconds, 180 seconds was abandoned packet.

Mind Map:

RIP sends Based on UDP.

OSPF protocol:

Open Shortest Path First OSPF protocol: "Open" marked the OSPF protocol is not subject to the control of a single vendor, but published in; "Shortest Path First"
is due to the use Djkstra proposed shortest path algorithm SPF .
OSPF main feature is the use of a distributed link state protocol .
OSPF features:
and who exchange?
1. autonomous system into the flooding method using all routers send the message, the router port to send information to all neighboring routers by output, and
exchange |? Adjacent to each router again and this information is sent to all of its neighbors router. Broadcast
---------------- eventually the whole area all the routers have been a copy of the information.
What exchange?
2. Information sent by this router it is adjacent to the link status of all router (the router to router and which is adjacent to the link and degree of
volume / price - cost, distance, delay, bandwidth, etc. ).
How long exchange?
3. Only when the link status changes , the router only send this information to all routers flooding.

Finally, all routers can establish a link state database that the entire network topology .
 

Link-state routing algorithm;

1. Each router finds its neighbor nodes [HELLO hello packet] , and to understand the network address of the neighbor node.
2. Set the cost of each of its neighbors metric Metric .
3. The configuration [DD database description packets] , summary information is given its own link-state database for all items to link state neighbor station.

4. If the DD packet has its own summary, the adjacent station without processing; or if there is no update, sending [the LSR link state request packet]
request and information than their own without their updating.
5. received packet LSR neighboring station transmits [the LSU link state update packets] is updated.
6. After the update is completed, a neighboring station returns [the LSAck of link state acknowledgment packets] to confirm.
As long as a link-state router changes: 
The flooding transmitting [the LSU link state update packets] is updated.
6. After the update is completed, the other station returns a [the LSAck of link state acknowledgment packets] to confirm.

7. configured to Dijkstra's shortest path between other nodes according to their link state database.
 

OSPF area /:

OSPF transferred directly with IP datagrams.
OSPF Other features:

1. Every for 30 min , to refresh a link state database.
2. As a link-state router only comes to communicating state with neighboring routers, and therefore the size of the entire Internet with no direct relationship. Because of
this when a large-scale Internet time, OSPF protocol is much better than distance vector protocols RIP.
3.0SPF problem of slow Bad news does not exist, it converges fast .
 

 

BGP protocol:

Border Gateway Protocol ( BGP ) routing in a kind of autonomous systems on the TCP protocol . BGP  is the only one to handle the size of the network like the Internet protocol , is the only way to properly deal well with having multiple connections to unrelated routing domains agreement . BGP  builds on the experience of EGP. BGP  The main function of the system and the other is of  BGP  systems to exchange network reachability information.

And who exchange?
With other AS Neighbor BGP speakers to exchange information.
What exchange?
Information exchange network reachability, ie to reach a network to go through - Series AS.

BGP speakers exchange path vector:
backbone network also issued a notice: "To reach the network N5, N6 and N7 along the path (AS1 AS3)"

How long exchange?
Updated when there is a change part changes.

BGP protocol process of exchange of information:
information network reachability exchanged BGP is to reach a network to go through - Series AS . When BGP speakers to exchange information on accessibility of the network, each BGP speaker will find better routes to the arrival from AS routing information received in the strategy adopted.
 

BGP is an application layer protocol, TCP transport means.
 

BGP protocol features:

BGP supports CIDR , so it should BGP routing table including the destination network prefix, the next - hop router, and reach the destination network to go through
various ASs sequence.
In just running BGP, the BGP neighbors exchange the entire BGP routing table. But after only need to update when there is a change part changes . So
do to save network bandwidth and reduce the processing overhead of the router as a whole.

Four kinds of packets BGP-4:
1.OPEN (open) message: used to establish a relationship with another adjacent BGP speakers, and sender authentication.
2.UPDATE (update) message: Notice a new path or revocation of the original path.
3.KEEPALIVE (keepalive) packet: in the absence UPDATE, periodically confirming connectivity of neighboring station; and also as an acknowledgment of OPEN.
4.NOTIFICATION (notification) message: previously reported error message: also used to close the connection.
 

Key:

Comparison of three types of routes protocol:

RIP is a distributed-based Interior Gateway Routing distance vector protocols, by UDP broadcast packets to exchange routing information.
OSPF is an interior gateway protocol, the amount of information to be exchanged is large, it should be as short as possible packets, transport layer protocol is not used (e.g. UDP
or TCP), but directly using the IP .
BGP is an external gateway protocol to exchange routing information between different autonomous systems, due to the complex network environment, the need to ensure reliable transmission, is
to employ the TCP .

 

OK