Setting Up Routing Vectors in a Network of Bridged 1394 buses

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Setting Up Routing Vectors in a Network of
Bridged 1394 buses
Subrata Banerjee PHILIPS Research Briarcliff,
New York
P1394.1 WG Meeting, Milpitas, CaliforniaApril
26-27, 1999
PHILIPS Research
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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.

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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?

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Broadcasting via Flooding

• Each node repeats incoming information toall
  its outgoing linksexcept the link on whichit
  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 )

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Bridge
3
1
Network
2
4
5
Bus
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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

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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.

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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

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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

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Update Routes

• If there is a significant change in routing
  related information (such as available bridge/bus
  capacity, broken link, etc.) thenthe 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

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Joining two nets

• BRPs at the meeting point of two 1394 nets
  exchange topology information
• Relatively straightforward details ...