[j-nsp] per-flow load balancing hash and ICMP traffic

[Rafał Szarecki]

Mark,

It is interesting what U describe. I rather expect that removing
destination-port from hash will put all ICMP packet on same  link.
If U configure 'source-port' actualy ASIC is look at first 2 Bytes after end
of IP Header. This 2 B for ICMP are TYPE and CODE field. So they will should
do not varry.
The destination-port is matching 3rd and 4th Byte, where ICMP has checksum.
and this value of course can varry. So use of this for hash, will result in
load-ballancing.

BTW as ASIC just takes some bytes form packet, they are protocol unaware.
And if in FirewallFilter you configure some 'destination-port' without
protocol (tcp/udp), it can results in matching of ICMP, raw IP or other
packets which has no port at leyer 4.

2006/12/7, Mark Miklic <mmiklic at gmail.com>:
>
> Ok, problem solved (thanks Ray;).
>
> Seems like the source-port for layer-4 hash equals to datagram id for
> ICMP.
> Really interesting...
>
> Mark
>
> 2006/12/7, Mark Miklic <mmiklic at gmail.com>:
> >
> > Actually,
> >
> > it is enough if I exclude source-port from the hash. This is even more
> > confusing... I thought mtr had nothing to do with layer-4 source ports
> and
> > such, being ICMP. Is perhaps the sequence number treated as the source
> port?
> > Any ideas?
> >
> > Thanks,
> > Mark
> >
> >
> > 2006/12/7, Mark Miklic <mmiklic at gmail.com>:
> > >
> > > Anyone knows how ICMP is being treated when layer-4 hash option (any
> of
> > > them) is being turned on?
> > >
> > > I was doing some tests today, and the only way I could ensure a
> > > consistent path for MTR through the per-flow lb-ed network was to
> exclude
> > > layer-4 parameter hashing completely.
> > >
> > > The only thing that comes to my mind is that Juniper introduces random
> > > values if there is no layer-4 information in the datagram...Is there
> any
> > > option to bypass this, or perhaps I am barking at the wrong tree?
> > >
> > > Thanks,
> > > Mark
> > >
> >
> >
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-- 
Rafał Szarecki JNCIE
+48602418971