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RE: [PWE3] PWE3 question
Shahram,
Please see some comments inline.
Hopefully they clarify my point.
With best regards,
Sasha Vainshtein
email: sasha@axerra.com <mailto:sasha@axerra.com>
tel: +972-3-7659993 (office)
+972-8-9254948 (res.)
+972-58-674833 (cell.)
> -----Original Message-----
> From: Shahram Davari [mailto:Shahram_Davari@pmc-sierra.com]
> Sent: Wednesday, May 15, 2002 4:38 PM
> To: 'Sasha Vainshtein'; 'Rutemiller, John'; 'pwe3@ietf.org'
> Subject: RE: [PWE3] PWE3 question
>
>
> Sasha,
>
>
>
> > -----Original Message-----
> > From: Sasha Vainshtein [mailto:Sasha@axerra.com]
> > Sent: Wednesday, May 15, 2002 11:14 AM
> > To: 'Rutemiller, John'; 'pwe3@ietf.org'
> > Subject: RE: [PWE3] PWE3 question
> >
> >
> > John,
> > Thank you for a prompt response.
> > Please see some more comments inline.
> > Hopefully they will be useful.
> >
> > With best regards,
> > Sasha Vainshtein
> > email: sasha@axerra.com <mailto:sasha@axerra.com>
> > tel: +972-3-7659993 (office)
> > +972-8-9254948 (res.)
> > +972-58-674833 (cell.)
> >
> >
> >
> > > -----Original Message-----
> > > From: Rutemiller, John [mailto:John.Rutemiller@marconi.com]
> > > Sent: Wednesday, May 15, 2002 3:58 PM
> > > To: 'pwe3@ietf.org'
> > > Subject: RE: [PWE3] PWE3 question
> > >
> > >
> > > There are many ways to build a network.
> > >
> > > The virtual "network" you describe is one way, in which case
> > > the tunnel is not created explicitly for PW transport. But
> > > others may choose to create a tunnel explicitly for PW transport.
> > >
> > No problem with that. But, IMHO, there is a difference between
> > creating a tunnel to b used by a (still unknown) group of PWs
> > and creating a tunnel per PW.
> > In the 1st case, there is no casual connection between creation
> > of any specific PW and the state of P routers; in the 2nd one,
> > there would be.
>
> OK, how about this: I have my PSN and don't have any PW yet, but I
> expect to have N*PW (N is small) between to PEs. I could create
> N*LSP between the two PEs. Now After I receive a PW request, I choose
> one of the LSPs that best fits that PW.
>
> If no suitable LSP is found, then I either will change the attributes
> of that LSP (by signaling) or create a new LSP. This last part is no
> different in tunneled or non-tunneled solution, because even in case
> of tunneled solution, if the tunnel is not suitable you need to take
> exactly the same actions.
>
> > >
> > > In the later case, the tunnel is closely tied to the PW. No, the
> > > tunnel is not created in direct response to any PW stream.
> > >
> > IMHO this means that setup/teardown of PWs do not exert any
> > control over the state of P routers, so it's OK.
>
> What if all PWs are tear downed, do you still keep the tunnel?
> if so why?
>
Probably I do - because I may use it for other traffic including other
PWs that have not been set up yet.
>
> > >
> > > But it is still created directly for the PW service.
> > >
> > My English may be faulty, but I would say that the tunnel is
> > created to be used by the (multiple and currently
> non-existing) PWs,
> > not "for the (specific) PW service". If I install new
> > interface cards in
> > my
> > P routers and connect them over a new fiber with the intent to
> > use new capacity thus created for (yet non-existent) PWs,
> > these PWs still do not exert any control over my PSN!
>
> But PWs can't use those links either, unless you modify the
> FIBs on those routers.
>
The FIBs will be modified as the result of installation of interface
cards, regardless of the PWs.
>
> -Shahram
>
> > >
> > > Same goes with the choice of whether to use an E-LSP. Network
> > > design decision.
> > >
> > > Clearly, using a common LSP for all traffic between two nodes
> > > and using E-LSPs has certain scaling and restoration advantages
> > > (fewer restore faster for the entire network).
> > >
> > > But, some carriers may want to seperate the fate of the different
> > > traffic. For example, the carrier may want to restore PW services
> > > before voice services because the PW users pay more for the
> > bandwidth.
> > >
> > > John
> > >
> > >
> > >
> > > > -----Original Message-----
> > > > From: Sasha Vainshtein [mailto:Sasha@AXERRA.com]
> > > > Sent: Wednesday, May 15, 2002 10:11 AM
> > > > To: 'Rutemiller, John'
> > > > Cc: 'pwe3@ietf.org'
> > > > Subject: RE: [PWE3] PWE3 question
> > > >
> > > >
> > > > John,
> > > > Please see some comments/responses inline.
> > > > Hopefully they will clarify my position.
> > > > With best regards,
> > > > Sasha Vainshtein
> > > > email: sasha@axerra.com <mailto:sasha@axerra.com>
> > > > tel: +972-3-7659993 (office)
> > > > +972-8-9254948 (res.)
> > > > +972-58-674833 (cell.)
> > > >
> > > >
> > > >
> > > > > -----Original Message-----
> > > > > From: Rutemiller, John [mailto:John.Rutemiller@marconi.com]
> > > > > Sent: Wednesday, May 15, 2002 12:12 PM
> > > > > To: 'pwe3@ietf.org'
> > > > > Subject: RE: [PWE3] PWE3 question
> > > > >
> > > > >
> > > > >
> > > > >
> > > > > > -----Original Message-----
> > > > > > From: Sasha Vainshtein [mailto:Sasha@AXERRA.com]
> > > > > > Sent: Friday, May 10, 2002 2:57 AM
> > > > > > To: 'Shahram Davari'
> > > > > > Cc: 'pwe3@ietf.org'; Danny McPherson (E-mail); 'Andrew G.
> > > > > > Malis'; Neil.
> > > > > > 2. Harrison (E-mail)
> > > > > > Subject: RE: [PWE3] PWE3 question
> > > > > >
> > > > > >
> > > > > > Shahram and all.
> > > > > > Please see a brief comment inline.
> > > > > >
> > > > > [SNIP]
> > > > > >
> > > > > > I would suggest a very simple criterion regarding
> exertion or
> > > > > > non-exertion of control over PSN: if setup/teradown of a PW
> > > > > > requires modification of the FIB in at least one PSN
> > node that
> > > > > > does not act as the PE for this PW, it means that
> > control over
> > > > > > this router has been exerted.
> > > > > >
> > > > > > This criterion does not depend on the protocol being used
> > > > > > (static,LDP, RSVP or else).
> > > > > >
> > > > > > The single-label model requires allocation of a new
> > label per PW
> > > > > > in each interior node on the path fromingress to
> > > egress, and hence
> > > > > > means exertion of control over the PSN unless the
> the pair of
> > > > > > PEs are adjacent (the "single hop" case mentioned by Neil).
> > > > > >
> > > > > > Can we agree on that?
> > > > > >
> > > > >
> > > > >
> > > > > Creation of a Pseudo wire requires a tunnel label.
> > > > >
> > > > Correct. You must associate every direction of a PW
> > > > over an MPLS network with an LSP leading from the
> > > > ingress PE (for this direction) to egress PE.
> > > > >
> > > > >The creation of this tunnel must be configured.
> > > > >
> > > > It can be created regardless of any specific PW that
> would use it.
> > > > And it could be created in many ways, including hop-by-hop
> > > forwarding
> > > > provided by the vanilla LDP.
> > > > Once created, such a tunnel can be used by - and, for
> scalability
> > > > reasons, SHOULD be used - by more than one PW between the
> > > > same pair of PEs.
> > > >
> > > > And it could be created in many ways, including "vanilla" LDP
> > > > in DU mode.
> > > > >
> > > > >The establishment of the tunnel will affect the FIB if the P
> > > > routers.
> > > > >
> > > > Correct. However, as I said above, creation of the tunnel
> > > (to be used
> > > > by multiple PWs) is not caused by creation of the PWs. Creation
> > > > of PWs using an already existing tunnel would not affect
> > FIB in the
> > > > P routers, only in PEs.
> > > > >
> > > > >Furthermore, the tunnel must be created with a
> forwarding class
> > > > >that is sufficient to carry the desired pseudo wire traffic.
> > > > >
> > > > There are many ways to associate a certain forwarding behavior
> > > > with the EXP bits across an LSP. E.g., one can use
> > > > Preconfigured EXP<-->PHB Mapping in LSPs that have been
> > > > created by LDP in DU mode.
> > > >
> > > > Such an method cannot be used if reservation of resources
> > > > must be associated with an LSP. But even then nothing
> > > > prevents creation of a "planned" network of DiffServ-enabled
> > > > LSPs with BW reservation beforehand regardless of any
> > > > specific PW, and then creation of PWs that use available
> > > > capaity on this "network".
> > > > >
> > > > > If traffic classes are to be separated (e.g, ATM CBR
> gets EF and
> > > > > ATM UBR gets best effort), then multiple tunnels must
> be created
> > > > > across the network.
> > > > >
> > > > Not necessarily. A single E-LSP will may support up to
> 8 different
> > > > traffic classes. And this can be done by using preconfigured
> > > > EXP<-->PHB mappings, too.
> > > > >
> > > > >
> > > > > Therefore, the PW has in some way exerted control over
> > > the P routers
> > > > > even with the tunnel creation.
> > > > >
> > > > This would only happen if you apply the "One PW = One
> > Tunnel" model
> > > > that originated this thread. And that is exactly why I said
> > > > that, IMHO,
> > > > this model is beyound the chartered PWE3 scope. The model that
> > > > separates creation of transport tunnels from creation of PWs is
> > > > within this scope.
> > > > >
> > > > > John
> > > > >
> > > > > _______________________________________________
> > > > > pwe3 mailing list
> > > > > pwe3@ietf.org
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> > > > >
> > > >
> > >
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> >
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>
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