1 Setting Up Routing Vectors in a Network of Bridged 1394 buses PHILIPS Research Subrata Banerjee PHILIPS Research Briarcliff, New York P WG Meeting, Milpitas, California April 26-27, 1999

Subrata Banerjee PHILIPS 2 Problem Statement While progress has been made in the format and syntax of routing tables, so far no discussion took place on computing and setting up the routing table entries Current SCAT item Linked with bus id assignment, prime portal selection, joining/breaking nets, etc. Goal is to make us start thinking on this topic.

Subrata Banerjee PHILIPS 3 Can the Internet Approach be Applied Here? Summary:  Determine network topology via neighbor discovery and local topology broadcast Have a flooding based broadcast mechanism! Why?  Works even during initialization/boot-up phase when no routing information is available  Well-known to be the most reliable routing approach So, how does it work?

Subrata Banerjee PHILIPS 4 Broadcasting via Flooding Each node repeats incoming information to all its outgoing links except the link on which it was received Lot of redundant messages! Yes. Makes it robust and work in unknown topologies No. of redundant messages is limited via sequence numbering and hop-counts (details …) Bus 5 Bridge Network

Subrata Banerjee PHILIPS 5 How can flooding work in 1394 Network? First each bus selects its bus representative portal (BRP) [ f (GUIDs), etc.] All “flooded” messages are handled by the BRPs GUID of the BRP = Temporary id. of the bus Now BRPs can employ flooding to exchange information Implementation can be optimized for speed/cost Used only for certain type of broadcast messages

Subrata Banerjee PHILIPS 6 Now what? Finding trees and picturing the forest Each BRP determines the ids. of its neighboring BRPs Broadcasts this local topology information via flooding Upon receiving these messages each BRP determines the “forest from the trees” Now each BRP has a complete knowledge of the network topology.

Subrata Banerjee PHILIPS 7 OK. What then? Compute Routes... Centralized approach  Elect NRP (Net Representative Portal, or Prime Portal) f (BRP Ids.)  NRP computes routes (based on some “least cost” algorithm)  NRP broadcasts the routing information in the net  BRPs, based on this information sets up the routing tables in all portals in its bus

Subrata Banerjee PHILIPS 8 Compute Routes Distributed approach  Each BRP has the same topology information  Based on that, each BRP independently executes the same route computation algorithm  Each BRP, based on its route computations sets up the routing tables in all portals in its bus

Subrata Banerjee PHILIPS 9 Update Routes If there is a “significant” change in routing related information (such as available bridge/bus capacity, broken link, etc.) then the relevant bridge portal sends a broadcast message to the network. Upon receiving this message all routing tables are updated after a selective route computation in a centralized or distributed manner. Periodic updates from BRPs as heartbeats

Subrata Banerjee PHILIPS 10 Joining two nets BRPs at the meeting point of two 1394 nets exchange topology information Relatively straightforward details...