The MPLS WG Archive

["Kullberg, Alan" <akullber@netplane.com>]

Yakov,

Now I'm (more) confused.  Could you further clarify what you mean?

Thanks,

Alan

> -----Original Message-----
> From: Yakov Rekhter [mailto:yakov@juniper.net]
> Sent: Tuesday, October 30, 2001 8:45 AM
> To: Kullberg, Alan
> Cc: George Swallow; mpls@UU.NET
> Subject: Re: Simplification for UNNUM draft. 
> 
> 
> Alan,
> 
> > Yakov & George,
> > 
> > I don't like this suggested change.  See reasoning below.
> 
> Actually the change I suggested wasn't exactly what I have in
> mind. What I have in mind is to have the Interface ID being the
> interface identifier assigned to the interface by the LSR specified
> by the router ID. 
> 
> Yakov.
> 
> P.S. Sorry for the confusion...
> 
> > 
> > Alan
> > 
> > > -----Original Message-----
> > > From: Yakov Rekhter [mailto:yakov@juniper.net]
> > > Sent: Monday, October 29, 2001 11:36 AM
> > > To: George Swallow
> > > Cc: mpls@UU.NET
> > > Subject: Re: Simplification for UNNUM draft. 
> > > 
> > > 
> > > George,
> > > 
> > > > draft-ietf-mpls-rsvp-unnum-02.txt allows both the 
> normal HOP and the
> > > > IF_ID Hop object to be used on an unnumbered link.  
> This leads to
> > > > unnecessary cases and extra checking at the incoming interface.
> > 
> > George's reasoning for making the following change is the 
> above sentence.
> > 
> > > > I suggest the following modifications:
> > > > 
> > > > a) mandate that one always use the IF_ID HOP object on 
> an unnumbered
> > > >    link.
> > > > 
> > > > b) pop the unnumbered interface subobject off of the ERO before
> > > >    forwarding the Path message over the unnumbered link (the
> > > >    information is now in the PHOP
> > > 
> > > May I also suggest that we change the semantics of the Unnumbered
> > > Interface ID subobject in the ERO from:
> > > 
> > >    The Interface ID is the outgoing interface identifier with 
> > > respect to
> > >    the LSR specified by the router ID.
> > > 
> > > to
> > > 
> > >    The Interface ID is the incoming interface identifier with 
> > > respect to
> > >    the LSR specified by the router ID.
> > > 
> > > Yakov.
> > 
> > > George replies:
> > >
> > > That would be fine.  In fact in that case, the upstream 
> router would
> > > not have to pop off the subobject, since the next node 
> would receive a
> > > an ero which has a valid first object.
> > >
> > > ...George
> > 
> > By not popping the subobject off, the receiver of the PATH 
> must do some
> > "extra checking at the incoming interface" because the IF_ID must be
> > validated to refer to the same interface.  In this case, 
> the IF_ID is
> from the sender's perspective and the UI.interface_id is from the
> > receiver's perspective, which I think is worse than before 
> for cross-
> > checking.
> > 
> > In addition, Yakov's change affects Explicit Label Control 
> at the Egress
> > node.  Let's say the egress node is node B, and there is an 
> unnumbered
> > interface from B to a node C.  OSPF is not running between B and C,
> > C doesn't have a Router ID, and B doesn't know what C's 
> unnumbered ID
> > is.  This makes it impossible to use the ERO to specify the Explicit
> > Labels between B and C when that interface is unnumbered.
>