BGP Message Types

Border Gateway Protocol Message Types

Fig 1: BGP Message Types

Before the establishment of the Border gateway protocol peer connection the two neighbors perform the TCP handshake and that is the three-way handshake and that connection open to a port number 179. So, after the process of the TCP connection Border Gateway Protocol peers exchange the multiples messages and these are all the messages unicast so following are four Border Gateway Protocol messages types:

• Type 1 and that type is known as Open Message Type.
• Type 2 and that type is known as Keepalive Message Type.
• Type 3 and that type is known as Update Message Type.
• Type 4 and that type is known as Notification Message Type.

Open Message Type

Fig 2: Open Message's Field Size in Octets

So, after the establishment of the TCP session both the neighbors send the open messages that includes a set of parameters. This message is the message which is used for the full connection establishment with the peers. This message is used to identify the neighbor itself. And following are Border Gateway Protocol operational parameters that are including in the open message:

• BGP version #
• Autonomous System Number
• Border Gateway Protocol Identifier
• Optional Parameters

Keepalive Message Type

Fig 3: Keepalive Message's Field Size in Octets

Keepalive messages are the messages that sent between the peers in every after the sixty seconds by default for the maintaining of the connection. This message only contains on the only message header and that total size is 19 bytes.

Update Message Type

Fig 4: Update Message's Field Size in Octets

Updates messages are the messages that contain on all the information of Border Gateway Protocol uses to build a loop avoidance picture of the internetwork. The single BGP update message is the message that has the information on one path and for the multiples path we need the multiples update messages. This message contains on the unreachable routes’ information and the information of the path attributes and also the network layer reachability information.

Notification Message Type

Fig 5: Notification Message's Field Size in Octets

This message is sent when someone error is detected and after the delivery of that notification message the Border Gateway Protocol connection closed. This message is the message that contains on the error code, error sub code , and the data that is related to that error.