Re: [mpls-linux-general] Signification of some commands

[James R. L. <jl...@mi...>]

On Fri, Jun 10, 2005 at 04:25:47PM +0200, Bertrand Lemaitre wrote:
> Hi,
>=20
> Would it be possible to have the signification of the following instructi=
ons ?

Sorry for the long delay in responding, I've been forcing myself to work on
ldp-portable, getting it to a work state.  Hopefully more on that in a
subsequent email ...


>=20
> nffwd

Allows for branching to a differnt NHLFE based on the NF mark of a packet.

> nf2exp

Converts a NF mark of a packet into the EXP at the current level of the sta=
ck.

> tc2exp

Converts a tcindex on a packet into the EXP at the current level of the sta=
ck.

> ds2exp

Converts the DSCP in the IP header into the EXP at the current level
of the stack.

> dsfwd

Branches to a different NHLFE based on teh DSCP in the IP header of a packe=
t.

> exp2tc

Converts EXP bits at the current level of the stack into a tcindex on a pac=
ket.

> exp2ds

Converts the EXP bits at the current level of the stack into the DSCP
in the IP header.

>=20
> I think there is a link beteween the experimental bit, the quality and se=
rvice.
> Any help would be great.

You are correct that these are there for implementing QoS or CoS.
Specifically tcindex and NF mark can be used by iptables and/or tc to
influence Layer 3 routing descisions (on a egress LER) or queuing descision=
s.
The EXP bits allow for propogating QoS or CoS info across a Forwarding
Adjacency, hence the reason why these commands only affect the EXP at the
current level of the stack.

The *fwd operations allow for re-use of MPLS componetns (not always just
reuse of the NHLFEs pointed to by the 'fwd', but also of the NHLFE or ILM
which utilizes the 'fwd')

Let me know if you have any specific questions of how to use these.
One thing to note is that I have not tested these instructions in sometime
so some code rot may have occured.

>=20
> Thanks
>=20
> Bertrand Lemaitre
>=20
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--=20
James R. Leu
jl...@mi...