VCL-WIKI
Border Gateway Protocol

BGP is responsible for checking all the available paths that data could travel and picking the best route, which usually means hopping between autonomous systems.

Characteristics of Border Gateway Protocol (BGP):

• Inter-AS configuration: BGP can provide communication between two autonomous systems.
• BGP supports Next-Hop Paradigm and coordination among multiple BGP speakers within the Autonomous System.
• Path Information: BGP advertisement includes path information, along with the reachable destination and next destination pair.
• Policy Support: BGP can implement policies that are configured by the administrator.
• BGP runs over TCP.
• BGP conserve network bandwidth.

Functionality of Border Gateway Protocol (BGP)

BGP peers performs 3 functions:

1. The first function consist of initial peer acquisition and authentication. Both the peers agree to communicate.
2. The second function mainly focus on sending negative or positive reach-ability information.
3. The third function verifies that the peers and the network connection between them are functioning correctly.

BGP Path attributes

BGP best path election criteria depends on BGP Path attributes-

1. Well-known mandatory attributes: Recognized by all BGP routers and present on all BGP updates, and passed on to other BGP Peers.
2. Well-known discretionary attributes: Recognised by all BGP routers and passes on to other BGP peers, may not be passed on BGP updates.
3. Optional transitive: May or may not be recognised by BGP router and passed on to other BGP peers.
4. Optional; Non transitive: May or may not be recognised by a BGP router and does not pass paths to its BGP peers.

The above mentioned features are offered and supported by VCL-MX-50xx family of IP/MPLS Routers.

Reference:

Balchunas, A. (2007). Border Gateway Protocol. BGP (v2.07, pp. 1-3). Router Alley