Subject: RSVP LSP

From: [email-masked]
Date: Wed, 02 Aug 2000 09:55:42 -0400

Hi,

Thanks for your answer.

In (1) case, you mean two diffrent LSPs. I understand one is of LDP signaling, the second is of RSVP signaling. Is that right? 

If the LSP from A to B is LDP signalled, then it should use label stack at case (2), is that right?

In case (2), is LER1(LIR, Edward says) configured not use RSVP signaling?  

Is that possible that a whole LSP is composed with two parts, one is LDP signalled, and one is RSVP signalled?

Thanks in advance
Ted
Guy Davies <[email-masked]> wrote:
>
> Hi,
> 
> Let's assume that there is already an RSVP signalled LSP from LER1 to LER2
> and, as you've stated, A and B don't speak RSVP (at least on the interfaces
> to LER1 and LER2 respectively).  There are two possibilities.
> 
> 1: You statically configure/LDP signal an LSP right from A to B.  This is
> totally independent of the existing, RSVP signalled LSP from LER1 to LER2
> and (if you use LDP to signal the path) requires LER1, LSR and LER2 to
> understand LDP in addition to RSVP.  In this case, you have two LSPs between
> LER1 and LER2, one of which extends right out to A and B.
> 
> 2: You configure an LSP from A to B using the LSP from LER1 to LER2 to make
> that "hop".  In that case, you require label stacking.  i.e. you push a
> label at A and transmit to LER1, you push a second label at LER1 and
> transmit to LSR, you swap/pop the top label at LSR and transmit to LER2, you
> pop the top label (if it's still there) and swap/pop the bottom label at
> LER2 then transmit to B.  At B, you pop the bottom label (if it's still
> there) and forward the packet using IP.  In this case, you have a single LSP
> from LER1 to LER2.  It just happens to be "carrying" another LSP.  This is
> analogous to an ATM VP.
> 
> In 2, the swap/pop decision is based on whether penultimate hop popping is
> configured.
> 
> Finally, remember that you'll have to configure a reverse path LSP to carry
> the return traffic (B to A) since LSPs are unidirectional.
> 
> Regards,
> 
> Guy
> ---
> Guy Davies              Telindus K-NET Ltd
> IP Architect            Hatchwood Place, Farnham Road, 
> e: [email-masked] Odiham, Hants, RG29 1AB
> t: +44 (0)1256 709285  f: +44 (0)1256 709210  m: +44 (0)7879 434214
> 
> 
> > -----Original Message-----
> > From: Edward Brookhouse [mailto:[email-masked]]
> > Sent: Tuesday, August 01, 2000 9:38 PM
> > To: [email-masked]; [email-masked]
> > Subject: Re: 
> > 
> > 
> > Just making sure I understand the scenario, do you mean that you are
> > stitching the two LSP's together across and LSR?
> > 
> > If not, would this be more like...
> > 
> > A - LIR-TLSR-LER-B
> > 
> >     LIR= Label Ingress Router
> >    TLSR=Transit Label Switch Router
> >     LER=Label Egress Router
> > 
> > Just making sure I caught what you were asking.
> > 
> > Edward Brookhouse
> > Greenwich Technology Partners
> > [email-masked]
> > 
> > 
> > ----- Original Message -----
> > From: <[email-masked]>
> > To: <[email-masked]>
> > Sent: Tuesday, August 01, 2000 2:07 PM
> > 
> > 
> > > Hi,
> > >
> > > I have a question about RSVP LSP:
> > >
> > > if we have a LSP like below:
> > >
> > > A--LER1--LSR--LER2--B
> > >
> > > A,B are none rsvp nodes. LER1, LSR and LER2 are RSVP nodes.
> > > if LSP is setup from A to B, what happened to LER1, LSR and LER2?
> > >
> > > Is there a RSVP LSP established from LER1 to LER2? or they 
> > just forward
> > sessions without another RSVP LSP setup?
> > >
> > >
> > > Thanks in advance
> > > John
> > >
> > > ----------
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