1 Setting Up Routing Vectors in a Network of Bridged 1394 buses PHILIPS Research Subrata Banerjee...

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Setting Up Routing Vectors in a Setting Up Routing Vectors in a Network of Bridged 1394 busesNetwork of Bridged 1394 buses

PHILIPS Research

Subrata Banerjee

PHILIPS Research Briarcliff, New York

P1394.1 WG Meeting, Milpitas, CaliforniaApril 26-27, 1999

PHILIPS 2Subrata [email protected]

Problem StatementProblem 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.


Can the Internet Approach be Applied Here?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?


Broadcasting via FloodingBroadcasting 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 …)

0

1 3

2 4Bus

5

Bridge

Network


How can flooding work in 1394 How can flooding work in 1394 NetworkNetwork??

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


Now what? Now what? Finding trees and picturing the forestFinding 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.


OK. What then? Compute Routes ...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


Compute RoutesCompute 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


Update RoutesUpdate 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


Joining two netsJoining two nets

BRPs at the meeting point of two 1394 nets exchange topology information

Relatively straightforward details ...

1 Setting Up Routing Vectors in a Network of Bridged 1394 buses PHILIPS Research Subrata Banerjee...

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