[j-nsp] juniper-nsp Digest, Vol 148, Issue 2

[Amarjeet Singh]

Hello Mark - On cisco i'm pretty sure they copy IPP to EXP bits while
imposing labels.

However i want to understand how does EXP classification happens on ingress
i.e coming from CE
What value is set on EXP bits while imposing label stack on IP packet in
Juniper Implementations?


>
> Date: Mon, 02 Mar 2015 07:45:37 +0200
> From: Mark Tinka <mark.tinka at seacom.mu>
> To: juniper-nsp at puck.nether.net
> Subject: Re: [j-nsp] <COS Query> While imposing MPLS labels what value
>         is set on EXP bits
> Message-ID: <54F3F901.6090101 at seacom.mu>
> Content-Type: text/plain; charset=windows-1252
>
>
>
> On 1/Mar/15 19:14, Amarjeet Singh wrote:
> > Folks - I've query on COS in MPLS VPN environment.
> >
> > While receiving Packets ingress from CE, let's say TOS field in IP header
> > is set to IPP-4.
> > And i've a MF that is classifying IPP-4 into FC-4 + PLP-LOW.
> > + There is MPLS Rewrite rule on egress interface that is matching
> > FC-4+PLP-low and setting EXP bits to 4 (100)  while relaying packet to
> next
> > hop.
> >
> > EXP rewrite happens only on MPLS encapsulated packets before that packet
> > should be MPLS encapsulated first.
> >
> >  While receiving IP packets coming from CE and imposing 2 Label stack on
> it
> > (Transport/VPN label) what value is set on EXP bits of Labels? Does the
> TOS
> > value in IP header of IP packet is copied to MPLS EXP bits?
> >
> > How does the MPLS classification happens to set FC+PLP on MPLS packets
> > before hitting MPLS EXP rewrite rule on egress?
>
> Most vendors, by default, will copy the first 3 bits of the DSCP value
> into the EXP field, if there is no explicit remarking of the EXP field
> on ingress.
>
> Since IPP is 3 bits only, the IPP bits get copied to the EXP field
> verbatim.
>
> I'm not sure how this works if you're remarking on egress (classic
> Junos). We remark on ingress, separately for DSCP and EXP.
>
> Mark.
>
>
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> End of juniper-nsp Digest, Vol 148, Issue 2
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