Bpg (border gateway protocol)

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BGP (Border Gateway Protocol)
Presented by: Edgardo Andrés Rodríguez Meisel

Communication systems that use the protocol
• Mainly used in internet • Used to join very large OSPF networks •Companies that need to have to two Internet service providers (multi-homing)

Figure taken from www.skullbox.net

Services provided by the protocol
• Connection Oriented • Unreliable
• Packagelosses handled by TCP

Figure taken from www.boxoid.com

Framing? Error control? Flow control?

• TCP is used between BGP peers • ERROR, FLOW control and FRAMING handled by TCP

The FrameHeader

Figure taken from http://www.rhyshaden.com

The Frame Header

• Marker: 16 octet field, set to all ones (used for compatibility) • Length: Total length o message includes header, valuevaries from 19 to 4096 • Type: • 1 – open • 2 – update • 3 – notification • 4 - keepalive

The Frame Open Message

• Version: Displays protocol version, currently 4 • My Autonomous System: AS numberof sender

• Hold Time: indicates maximum time that can elapse between the receipt of successive UPDATE or KEEPALIVE messages from sender • BGP Id: IP address assigned to the BGP speaker
• OptionalLength: indicates the length of the OPTIONAL PARAMETERS field • Optional Parameters

The Frame Update Message

• Withdrawn Routes: List of IP addresses prefixes for routes being withdrawn fromservice • Attribute: Specify certain attributes in the network

• NLRI: Carries CIDR (Classless Inter-Domain Routing) information

The Frame Notification Message

• Error code: indicates type ofnotification (error)
• Error Sub-code: provides more specific information about the error • Diagnostic Data: used to diagnose the reason of the notification

The Frame Keepalive Message
• Usedto determine if peers are reachable • Consists of only the message header • Sent maximum once per second (depends on implementation)

References
• Cisco.com. (n.d.). Internetworking Technology...
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