HP 6125G HP 6125G & 6125G/XG Blade Switches Layer 3 - IP Routing Confi - Page 128

Open, Update

Page 128 highlights

Figure 43 BGP message header Open • Marker-The 16-byte field is used to delimit BGP messages. The Marker must be all ones. • Length-The two-byte unsigned integer indicates the total length of the message. • Type-This one-byte unsigned integer indicates the type code of the message. The following type codes are defined: 1-Open, 2-Update, 3-Notification, 4-Keepalive, and 5-Route-refresh. The former four listed codes are defined in RFC 1771, and the last listed code is defined in RFC 2918. After a TCP connection is established, the first message sent by each side is an open message for peer relationship establishment. Figure 44 BGP open message format Major fields of the BGP open message are as follows: • Version-This one-byte unsigned integer indicates the protocol version number. The current BGP version is 4. • My autonomous system-This two-byte unsigned integer indicates the autonomous system number of the sender. • Hold time-When establishing a peer relationship, two parties negotiate an identical hold time. If no Keepalive or Update is received from a peer within the hold time, the BGP connection is considered down. • BGP identifier-An IP address that identifies the BGP router. • Opt Parm Len (Optional Parameters Length)-Length of optional parameters, which is set to 0 if no optional parameter is available. • Optional parameters-Used for multiprotocol extensions and other functions. Update The update messages are used to exchange routing information between peers. It can advertise feasible routes or remove multiple unfeasible routes. 118

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118
Figure 43
BGP message header
Marker
—The 16-byte field is used to delimit BGP messages. The Marker must be all ones.
Length
—The two-byte unsigned integer indicates the total length of the message.
Type
—This one-byte unsigned integer indicates the type code of the message. The following type
codes are defined: 1–Open, 2-Update, 3-Notification, 4–Keepalive, and 5–Route-refresh. The
former four listed codes are defined in RFC 1771, and the last listed code is defined in RFC 2918.
Open
After a TCP connection is established, the first message sent by each side is an open message for peer
relationship establishment.
Figure 44
BGP open message format
Major fields of the BGP open message are as follows:
Version
—This one-byte unsigned integer indicates the protocol version number. The current BGP
version is 4.
My autonomous system
—This two-byte unsigned integer indicates the autonomous system number
of the sender.
Hold time
—When establishing a peer relationship, two parties negotiate an identical hold time. If
no Keepalive or Update is received from a peer within the hold time, the BGP connection is
considered down.
BGP identifier
—An IP address that identifies the BGP router.
Opt Parm Len (Optional Parameters Length)
—Length of optional parameters, which is set to 0 if no
optional parameter is available.
Optional parameters
—Used for multiprotocol extensions and other functions.
Update
The update messages are used to exchange routing information between peers. It can advertise feasible
routes or remove multiple unfeasible routes.