Common View of the Telco Network
Common View of the IP Network (Layer 3)
Routing can happen at any level
IP is a Network Layer Protocol
Architecture of Dynamic Routing
"Topology information is flooded within..."
Autonomous Routing Domains (ARDs)
Autonomous System (AS) Numbers
Autonomous Routing Domains Don’t Always Need BGP or an ASN
ASNs Can Be “Shared” (RFC 2270)
A Bit of OGI’s AS Neighborhood
Partial View of cs.wisc.edu Neighborhood
Policy : Transit vs. Nontransit
Policy-Based vs. Distance-Based Routing?
Why not minimize “AS hop count”?
Attributes are Used to Select Best Routes
Shorter Doesn’t Always Mean Shorter
AS Graphs Depend on Point of View
AS Graphs Do Not Show “Topology”!
Implementing Backup Links with Local Preference (Outbound Traffic)
Multihomed Backups
(Outbound Traffic)
Shedding Inbound Traffic with ASPATH Prepending
… But Padding Does Not Always Work
COMMUNITY Attribute to the Rescue!
Customer installs a “backup link” …
The primary link is repaired, and something odd occurs…
Let’s look at “te” communities…