Principles of OSPF Protocol Verification

Speaking of routing protocols, we are familiar with RIP, OSPF, and other protocols. Now let's focus on the relevant content of the OSPF routing protocol. First, explain the meaning of OSPF. OSPF is a typical link status routing protocol. OSPF routers exchange and save the link information of the entire network, so as to master the topology of the entire network and calculate routes independently. Because the RIP Routing Protocol cannot serve large networks, ietf igp workgroup specially develops the Link Status Protocol-OSPF. OSPF version 2 is widely used. The latest standard is RFC2328.

AS an internal Gateway Protocol, Interior Gateway Protocol (IGP) is used to publish routing information between routers in the same autonomous domain. Unlike the distance vector protocol (RIP), OSPF supports large networks, fast route convergence, and less network resources. It plays a very important role in the current application of routing protocols.

1. Link Status

The OSPF router collects the connection status information of each vro in the network region, that is, Link-State, and generates a Link-State Database ). The router has the link status information of all the routers in the region, which means that it understands the topology of the entire network. The OSPF router uses the Shortest Path First, SPF algorithm to calculate the route to any destination independently.

2. Region

The OSPF Routing Protocol introduces the concept of "hierarchical routing", which divides the network into a group of independent parts connected by a "trunk, these independent parts are called "areas" and "trunk" are called "trunk areas ". Each region is like an independent network. The OSPF router in this region only saves the link status of this region. The link status database of each vro can maintain a reasonable size, and the route computing time and number of packets are not too large.

3. OSPF Route Protocol Verification

In OSPF, all route information exchanges must be verified. The OSPF Packet structure described above contains a verification domain and a 64-bit verification data domain, which is used for computing specific verification methods.

OSPF data exchange verification is defined based on each region. That is to say, when a verification method is defined on a vro in a region, the same protocol authentication method must be defined on all routers in the region. Other verification-related parameters can also be defined based on each port. For example, when a single password is used for verification, we can set different passwords for each network in a region.

In the definition of OSPF routing protocol, we initially defined two Protocol Verification Methods: Method 0 and method 1, which are described as follows:

Verification Method 0:

The verification method 0 indicates that OSPF does not verify the exchanged route information. The 64-bit verification data bit in the OSPF data packet header can contain any data. After OSPF receives the route data, it does not process the verification data bit in the data packet header.

Verification Method 1:

Verification Method 1 is simple password verification. This verification method is defined based on each network in a region. Each packet header sent to the network must have the same 64-bit length verification data bit, that is to say, the password of authentication method 1 is 64 bits or 8 characters long.