Quick Study Notes: Interdomain Routing With BGP

Interdomain Routing with BGP:
• BGP is used to exchange information between autonomous systems (AS)
• AS is a collection of networks under a single administration
• AS is identified by a 16-bit (or 32-bit) number
• public AS: 1-64,511; private AS: 64,512-65,535

BGP Characteristics:
• reliable, connection-oriented transport (TCP port 179)
• reliability: periodic keepalives, incremental triggered updates
• scalability: 800K+ routes, TCP sliding window (max. 65,576 bytes)
• stability: batched updates, slower convergence

Path Vector Functionality:
• BGP routers exchange network reachability information, called path vectors, which are made up of path attributes
• examples: AS path (list of AS numbers to destination), next hop (IP address to next AS), and origin code (source of route)

BGP Routing Policies:
• hop-by-hop routing paradigm (AS level)
• how a neighboring AS routes traffic cannot be influenced, but how a traffic gets to a neighboring AS can be influenced
• tight route filters required
• must address both incoming and outgoing traffic

** 24 May, 2020 UPDATE ** Quick Study Notes are also video format now. Part 1 is available!

** 29 May, 2020 UPDATE ** Part 2 is also available!