[j-nsp] COS - dscp and ipprec default rewrite markers

Damon Pegg damon.pegg at uk.easynet.net
Wed Feb 18 12:02:35 EST 2004

If only mpls packets get rewritten by default on egress based on queue and
PLP why the dscp-default and ipprec-default rewrite rules?  The only time
you are going to use them is if you want egress IP packets' TOS to be
different to ingress TOS so its highly unlikely you are going to use these
unless, say if you are mediating QOS to another Service Provider and they
use the correct default values when you dont.  Pretty unlikely I would have
thought?  Ok, so maybe if you mediate on an access box to the core, but this
too is unlikely if you have Juniper at the access layer, since it only has
four queues inbound anyhow...

Naturally, this is very different in MPLS when you need to replace the
default if you use anything different from defaults for classification into
the forwarding queues (the default overriding your values otherwise since
MPLS always used a set of rewrite rules.)

Just trying to understand if I missed the point with these non-MPLS default
re-write rules.


Damon Pegg
Network Development
Easynet plc
t:    0207 900 7075
f:    0207 900 4443
m:    07931 406206
e:    damon.pegg at uk.easynet.net
w:    www.easynet.com  

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