The MPLS WG Archive

[Grenville Armitage <gja@dnrc.bell-labs.com>]

Francois,

Use of "(P)" in second figures of 2.6.3 and 2.6.4:

Francois Le Faucheur wrote:
	[..]
> >#6 Section 2.6.3, 2nd Figure
> >
> >   There's a "(P)" floating to the right of "(outer header)"
> >   that perhaps ought not be there?  (Same for 2nd figure in
> >   section 2.6.4)
> 
> (P) indicates the penultimate LSR in all diagrams. It appears at the
> right location even in the 2nd figures (ie without PHP). It insists
> on the fact that in those cases (P) does a swap (and not a pop) so
> that the "outer header" is there between (P) and (E) to carry some
> Diff-Serv info .

Okay, I now understand the intent. But now I'm not sure the ASCII art
is clear. In the non-PHP examples the "(P)" _appears_ to sit two hops
prior to the "(E)" LSR, which is confusing. (Alternatively, it isn't
clear from the ASCII art how to distinguish LSRs and links and
therefore derive the message you intend about where the egress
hops and penultimate hops exist. I can't figure out if the "(M)"
represent LSRs or links using 'meaningful diffserv info' - my
initial read took them as LSRs.) Perhaps the ASCII art could
be clarified (or we could just assume readers know that non-PHP
means "label swap all the way"?)

cheers,
gja
________________________________________________________________________
Grenville Armitage                    http://members.home.net/garmitage/
Bell Labs Research Silicon Valley