[j-nsp] Load balancing: hash algorithm

[samuel.gay at bt.com]

In the Juniper documentation I can read:

"By default, or if you specify only the layer-3 statement, the router uses the incoming
interface index as well as the following Layer 3 information in the packet header to
load balance traffic:
- Source IP address
- Destination IP address
- Protocol" 

And:

"On routing platforms with the Internet Processor II ASIC, when per-packet load
balancing is configured, traffic between routers with multiple paths is divided into
individual traffic flows (up to a maximum of 16 equal-cost load-balanced paths).
Packets for each individual flow are kept on a single interface."

With this information I have two question:
- Is the key (generate with hash algorithm) always the same if the incoming interface, source IP address, destination IP address and protocol are the same? If yes is it possible to predict the next-hop?
- Is there a way to know the next-hop used for an individual flow (if I have an Internet Processor II ASIC)?

Samuel


-----Message d'origine-----
De : david.roy at orange-ftgroup.com [mailto:david.roy at orange-ftgroup.com] 
Envoyé : jeudi 17 juillet 2008 10:55
À : Gay,S,Samuel,JPECS R; juniper-nsp at puck.nether.net
Objet : RE: [j-nsp] Load balancing: hash algorithm


Hi,

The hash algorithm uses the source IP address, the destination IP address, the Protocol field and the Incoming Interface Index in order to generate a key. 

Regards
David 

-----Message d'origine-----
De : juniper-nsp-bounces at puck.nether.net [mailto:juniper-nsp-bounces at puck.nether.net] De la part de samuel.gay at bt.com Envoyé : jeudi 17 juillet 2008 10:46 À : juniper-nsp at puck.nether.net Objet : [j-nsp] Load balancing: hash algorithm

Hi Group,

Do you know how work hash algorithm used in load balancing (only layer-3)? Is there some documentation about it?

Thanks,
Samuel 

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