Subject: [TICTOC] Port vs. LSR 1588-awareness

From: Ron Cohen <[email-masked]>
Date: Wed, 19 Jan 2011 22:35:16 +0200

Hi,

The 01 version of 1588overMPLS draft defines a 1588-aware node capability
advertised by OSPF. The issue raised in the conference is the need to
support LSRs that do not support PTP on all ports. For example, assume the
LSR is build out of a chassis with 2 switching cards and 8 networking cards.
If all cards are upgraded to support PTP timestamping, the LSR can advertise
itself as a 1588-aware node. However, there isn't any real need to upgrade
all cards in order to support PTP LSPs. For example, upgrading the 2
switching cards and 2 of the network cards should still suffice to support
TC functionality for any LSP whose ingress port and egress port reside on
the upgraded cards. However, if we can only advertise 1588-awareness
capability on the node level, we would either not be able to support such
LSRs, or advertise false information (i.e. advertise 1588-awareness also on
non-1588-aware ports).

A similar approach is taken in Synchronous Ethernet (SyncE). Not all
Ethernet ports on a node need to support SyncE in order for the node to be
part of the SyncE synchronization chain.

In the example described previously, The LSR TC implementation supports LSP
whose ingress port is on the 1588-aware network card A and whose egress port
is on the 1588-aware card-B because either both cards have access to the
same time reference and can pass the ingress timestamp across the fabric, or
if TC functionality is implemented on the switching cards as well, or in
another ingenious way. However, I do not think that we should mandate that
TC LSR implementation must be able to support cross-card (i.e. any port to
any port) TC functionality, rather we should be able to use TC
implementations that support also only intra-card TC implementations.

It shouldn't be too difficult to accommodate for the above. Instead of
per-node 1588-awareness capability, the capability should be a per-port. In
addition we can introduce a concept of a TC-port-group. A TC that can
implement TC functionality between every 1588-aware port will associate all
ports with one TC-port-group. A TC that can support TC functionality only
between subsets of ports will associate each such subset of ports to a
different TC group. Each 1588-aware port will therefore advertise its
awareness capability and the TC-port-group it belongs to. The PTP LSP will
be setup (e.g. by RSVP-TE) through ports in LSR that are 1588-aware, and
where the ingress and egress ports within each LSR belong to the same
TC-port-group.

Comments are welcome.

Best,
Ron

The proposal is to advertise 1588-awareness capability on a port level.
There are two

There are several options here in terms of how to do that

That is, advertise 1588-awareness only thro