Chapter 2 route protocol Reading Notes and Chapter 3 route protocol

Chapter 2 route protocol Reading Notes and Chapter 3 route protocol

Chapter 2 route protocol Reading Notes

In a complex network structure, data needs to be sent to the target host through a reasonable route. The route control module determines the route.

7.1 definition of Route Control

7.1.1 IP address and route control

The Internet is composed of vro connected networks. In order for data packets to arrive at the destination correctly, the router must forward the packets correctly on the way. Routing control or routing is used to forward data in the correct direction.

 

7.1.2 Static Routing and Dynamic Routing

Route Control is divided into static and dynamic static routing and dynamic routing

Static Routing is a way to set the router and host in advance and fix the routing information. Dynamic routing is a method that allows the routing protocol to automatically set route control information during operation.

 

 

7.1.3 basics of Dynamic Routing

Dynamic Routing

Dynamic Routing sends the network information that is known to the neighboring routers, and the information is transmitted to other routers once like a relay, even when the entire network is known, the routing control table is created.

7.2 route control scope

IGP interior gateway protocol and EGP exterior gateway protocol are used according to the routing control scope.

7.2.1 various organizations connected to the Internet

No managers, no managers, and every organization maintains an equal relationship.

7.2.2 Autonomous Systems and routing protocols

Specify your own routing policy. The small unit used in one or more network groups is called autonomous system AS autonomous system or routing selection domain.

7.2.3 IGP and EGP

The routing protocol is divided into two layers: EGP and IGP. Without EGP, it is impossible to have communications between different organizations in the world. Communication is impossible without an IGP mechanism.

IGP also includes RIP routing information protocol, RIP2 OSPF Open shortest path first Open shorpath first, and many other protocols.

7.3 Routing Algorithm

There are various routing control algorithms, the most representative of which are Distance Vector Algorithm and link state algorithm. Distance-vector link state algorithm.

7.3.1 Distance Vector Algorithm

Distance Vector Algorithm DV is a method in which distance and direction determine the location of the target network or host.

 

7.3.2 link status Algorithm

7.3.3 main routing protocols

 

7.4 RIP

 

7.4.1 broadcast route control information

RIP periodically broadcasts route control information to the entire network. If no route control information is received, the connection is disconnected. However, this may be caused by packet loss, so RIP requires waiting for 5. If no route information is received for the sixth time, the connection will be closed.

 

7.4.2 determine routes based on distance Vectors

RIP decides the path based on the distance vector algorithm. The unit of distance from metrics is the number of hops. The number of hops refers to the number of routers passing through.

Generate a distance vector based on the distance vector, and then extract a smaller route to generate the final route control table.

 

7.4.3 RIP processing when subnet mask is used

 

7.4.4 handling of route changes in RIP

7.4.5 RIP2

7.5 OSPF

Open shortest path first IS a link-State Routing Protocol Based on OSI's IS-IS intermediate system to intermediate system.

 

7.5.1 OSPF is a link-State Routing Protocol

Switches the link status between routers to generate network topology information, and then generates a route control table based on the topology information.

If you select a RIP route, the smaller the number of routers in the figure, the better. In contrast, OSPF can assign a weight to each link and always select a path with the minimum weight as the final route. That is to say, OSPF always selects a path with the minimum total cost based on the cost of each link.

 

7.5.2 basic OSPF knowledge

In OSPF, a router connected to the same link is called an adjacent router.

 

In OSPF, there are five types of packages according to their respective functions.

Send the hello packet to check whether the connection is successful. To synchronize route control information, each vro uses the database description package to send route summary and version information to each other. If the version is old, a link status request link state request packet is sent to request route control information, and the link status update link state update packet receives Route status information, finally, confirm the link state ack packet package through the link status to notify everyone that the local device has received the package. Route control information.

 

7.5.3 OSPF working principle Overview

 

The connection validation protocol for OSPF is the HELLO protocol.

 

Send a HELLO packet every 10 seconds in the LAN. If no HELLO packet arrives, determine whether the connection is disconnected.

When the link status changes, the vro sends a link status update packet to notify other network status changes.

The link status update package contains two types of messages: Network LSA and router LSA.

The Network LSA generates information centered on the network, indicating which routers are connected to the network.

 

7.5.4 perform area segmentation Management

The potential problem of link state-based routing protocols is that when the network size is getting bigger and bigger, the topology database indicating the link state is getting bigger and bigger, and the more difficult it is to calculate the route control information. OSPF introduces the concept of region to reduce computing load.

A Zone refers to a group of Connected Networks and hosts so that an autonomous system AS can have multiple zones. However, Autonomous Systems with multiple regions must have a trunk region backbone area, and all other regions must be in this trunk region to connect.

The router in the connection area and trunk area is called the regional border router. The vro in the region is called an internal vro. The router connected only to the trunk region is called the trunk router, and the router connected to the outside is the AS border router.

In other words, it means that the internal router only understands the link status information within the region and calculates the outbound route control table based on the information. This mechanism not only effectively reduces route control information, but also reduces the processing burden.

 

7.6 BGP

Border gateway protocol: border gateway protocol. Therefore, it belongs to the external gateway protocol EGP.

7.6.1 BGP and AS numbers

The final route control table of BGP is represented by the network address and the router Group of the next stop. However, it performs route control based on the number of passed.

 

7.6.2 BFP is a path vector protocol

 

7.7 MPLS

Currently, in addition to routing technology, tag switching technology is also used in the process of forwarding IP data packets. The routing technology is based on the longest matching principle of the IP address, and the tag exchange sets a tag value for each IP packet, and then forwards the packet based on the tag. The most representative of label exchange technology is multi-protocol label exchange technology MPLS multi protocol label switching

Because the marked Forwarding is usually unavailable on the vro, it cannot be used across the Internet.

 

7.7.1 basic MPLS network action

The router that implements the MPLS function in the mPLS network is called the label exchange router LSR label switching router. In particular, The LSR that is connected to the external network is called the label edge router LER label edge router.

 

When a packet enters MPLS, a 32-bit gasket header (including a 20-bit mark value) is appended to the front of its IP address header ). When data leaves MPLS, the gasket header is removed. Here we call the action of adding a tag forwarding as PUSH, replace the action of marking forwarding as swap, and remove the action of marking forwarding as POP.

 

7.7.2 advantages of MPLS

 

The first is fast forwarding.

The second is to generate a virtual path using tags and implement IP address and other packet communication on it.