RE: [PWE3] Proposed change to 5..4.1 of PWE3 architecture

[Sasha Vainshtein <Sasha at AXERRA.com>]

Yaakov and all,
Please see inline.
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: Yaakov Stein [mailto:yaakov_s@rad.com]
> Sent: Monday, March 22, 2004 6:11 PM
> To: stbryant@cisco.com; Sasha Vainshtein
> Cc: pwe3@ietf.org
> Subject: RE: [PWE3] Proposed change to 5..4.1 of PWE3 architecture
> 
> 
> Sasha,
> 
> As conventional, my remarks are in-lined. 
> 
> <snip>
> > Let's start from a simple point: if PW label over an IP PSN 
> > is an MPLS label, what protocol number must be set in the IP 
> > header of the corresponding packets?
> > 
> > I see two options:
> > 
> > 1) It is MPLS-in-IP protocol number (still to be assigned by IANA).
> >    If this is the case, then MPLS-in-IP encapsulation mechanism
> >    as described in draft-ietf-mpls-in-ip-or-gre-07 fully applies.
> >    Of course in this case the demultiplexor is an MPLS label, and,
> >    IMO, this is the only way to use an MPLS label as a demultiplexer
> >    for PWs over an IP PSN.
> > 
> > 2) It is some new, not yet specified protocol (let's call it
> >    PW-in-IP). If this is the case, you may use any 32-bit 
> >    demultiplexer (a.k.a PW label) you wish but, IMHO, you 
> >    MUST NOT call this demultiplexer an MPLS label.
> >    (Of course, it would be also nice to specify such a protocol
> >    and to provide justification for adding it to the 
> >    set of already existing tunneling mechanisms.:-)
> 
> This is the same debate we had regarding Ethertypes
> in another forum ...
> 
> It seems obvious to me that when using UDP/IP the IP protocol type 
> is set to obviously 11H, signifying UDP. Then the UDP destination
> port MUST be set to an application identifier assigned
> by IANA to the PW type being used. As you know,
> IANA has assigned 085EH to TDMoIP for this purpose.
> We should request port numbers for the various PW types.
> 
> If you choose NOT to use UDP, rather L2TP,
> then the protocol is set to 73H. 
> Similarly, if use use MPLS-in-IP, then you use 
> whatever IANA decides.
>
Sorry, but I do not follow you. The ORIGINAL question
(AFAIK) has been usage of an MPLS label as  a demultiplexer
(a.k.a. PW label) in PWs over an IP PSN. I have suggested 
that the (only, IMO) correct way to do that is by using 
MPLS-in-IP (with all the implications). How is your explanation
above related to that?
> 
> The question arises - where is the PW label 
> for the UDP case? Well, this is the function of the UDP
> port, but that has already been taken, so the only sensible
> thing to do is to use the UDP source port.
>
This is a different question that has not been even asked 
in the architecture document. I suggest to discuss it in another 
thread. As you know, I keep different opinion wrt to what
does and what does not makes sense here. 
>
... snipped ...
> > > Does it rule out non-LDP control protocols for PW setup?
> > >
> > IMO, no. You can always use manual PW setup. 
> 
> Yes, of course. But I was asking whether alternative
> control PROTOCOLS are ruled out. 
> 
> Although UDP/IP has been with us in PWE from the beginning,
> we have tacitly assumed MPLS in almost everything we have done.
> In particular, the control protocol is LDP based.
> 
> Of course, there is nothing wrong with using targetted LDP
> in a pure IP network for this purpose. But perhaps we may want
> to do something else (I intend writing a draft before the next
> meeting on this subject).
>
I'd say that the control protocol for distribution of PW labels
depends on the nature of these labels. E.g., LDP is one of
the native choices for distributing MPLS labels serving as a
PW label; and L2TPv3 uses its own way of distributing Session IDs.
In both cases the point is not inventing a new protocol.
IMO, if you want to use UDP as the demultiplexing layer, and
define correctly which UDP port is used as the demultiplexer, you
can reuse some suitable protocol as well.
> 
> Y(J)S
> 

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