The MPLS WG Archive

["Brijesh Kumar" <bkumar@ennovatenetworks.com>]

> -----Original Message-----
> In message <393F9EB0.D17E15AA@lucent.com>, Yangguang Xu writes:
> >
> > For example, at least QoS has to be guaranteed to differentiate
> > protection switching messages from other traffic.
>
> The granularity for MPLS protection is the LSP while the granularity
> for SONET is the link itself.  It is therefore much easier to put
> higher priority trraffic on different LSPs from lower priority
traffic
> and provide local-protect for the former and require the latter to
> reroute from the ingress.

I would like to add a bit to Curtis's message.

I don't see a point in comparing essentially two altogether dis-joint
technologies. Moreover, it is meaningless to talk about QoS in the
context of APS in SONET as all services are being shifted on the
alternate path (including all MPLS LSPs). MPLS over SONET
automatically inherits all the virtues of SONET reliability.

MPLS local protection mechanisms (over non-SONET network) are purely
software "possibilities" at this point, but I hope some day techniques
imagined above will indeed be available. But we have to go from MPLS
(1) to MPLS with Diffserv (2) to MPLS with Diffserv with local-protect
(3). That sounds lot of coding work for lot of s/w persons;-).

SONET APS is available now, and there is more to SONET APS such as a
number of options can be considered in the deployment of SONET
architectures, including:

1) What is being protected: SONET has mechanisms to protect at either
the line or path level.

2) Which direction the signals flow in a ring: Signals can all route
in the same direction (unidirectional) or in opposite directions
(bidirectional).

3) How many fibers are being used in each link: Either one- or
two-pair (two- or four-fiber) configurations are selected.

The number of combinations in which these options can be employed
leads to a variety of SONET protection schemes. Some of the more
frequently used abbreviations of the SONET protection architectures
are Bidirectional line-switched ring (BLSR), Bidirectional
path-switched ring (BPSR), Unidirectional line-switched ring (ULSR),
Unidirectional path-switched ring (UPSR).

Whether MPLS can emulate such a wide variety of Protection options
over other networks can't be definitively answered yet. There is a
long way to go, before we reach there.

Cheers,

--brijesh
Ennovate Networks Inc.