Thanks to Jay Borkenhagen, Randy Bush, Anja Feldmann, Matt Grossglauser, Madan Musuvathi, Jennifer Rexford, Shubho Sen, and Jia Wang for many helpful comments Errors are my own My opinions should not be taken to represent AT&T policy
Brick
Common View of the IP Network (Layer 3)
IP traffic This is the fundamental service provided by Internet Service Providers (ISPs) All other IP services depend on connectivity: DNS, email, VPNs, Web Hosting, …
IP ROUTING PROTOCOLS DO NOT DYNAMICALLY ROUTE AROUND NETWORK CONGESTION
A collection of physical networks glued together using IP, that have a unified administrative routing policy.
ASNs are 16 bit values. 64512 through 65535 are “private” Currently over 11, 000 in use.
BGP
Link State Vectoring
Link State IGP EGP Vectoring
Many Routing Processes Can Run on a Single Router
Which IP Addresses are Covered by a Prefix?
NET A
NET A
provider
provider
Peer Don’t Peering struggles are by far the most contentious issues in the ISP world! Peering agreements are often confidential.
Given multiple routes to the same prefix, a BGP speaker must pick at most one best route (Note: it could reject them all!)
i. BGP is routed (using IGP!)
135. 207. 0. 0/16 10. 10. 10 AS 1 192. 0/30 destination next hop 192. 0/30 10. 10. 10 destination EGP destination next hop 135. 207. 0. 0/16 192. 0. 2. 1 next hop 135. 207. 0. 0/16 192. 0/30 10. 10 AS 2
135. 207. 0. 0/16 10. 10. 10 AS 1 192. 0. 2. 1 127. 22. 33. 44 destination next hop 127. 22. 33. 44 10. 10. 10 destination EGP destination next hop 135. 207. 0. 0/16 127. 22. 33. 44 10. 10 AS 2
Import Export AS 1
Martian list often includes
xxxxxx cccccc xxxxxx
IP Forwarding Table
AS 1 AS 2 AS 3 AS 4
AS 1 AS 2 AS 5 AS 3 AS 4
Duh!
provider customer
provider customer provider
provider customer provider
IGP distances
Many customers want their provider to carry the bits!
This means that MEDs must be considered BEFORE IGP distance!
1 2 3 4
A Solution to a Stable Paths Problem
Scale Scale Scale Scale
AS 65502 AS 65503 AS 65500 AS 65501 AS 65504
AS 2 is “punching a hole” in The CIDR block of AS 1
2005? 2007?
1 3 2 4 1 3 5 1 2 4 5 6 3 1 2 2 6 4 5 3 6 4 5 6
The goals of (1) fast convergence (2) minimal updates (3) path redundancy are at odds
Rate limiting dampens some of the oscillation inherent in a vectoring protocol. Current interval (30 seconds) was picked “out of the blue sky”
This is “normal” --- exactly what dynamic routing is designed for…
A quote from some recent email: Is this true or false? How can we tell?
BGP is a moving target …
Скачать презентацию Thanks to Jay Borkenhagen Randy Bush Anja Feldmann
45fcffe4a719ee2675b28f3311dd2ed4.ppt