Subject: Re: SE style in optical neyworks

From: Suresh Katukam <[email-masked]>
Date: Fri, 12 Apr 2002 09:22:08 -0700

This can be used to set up Protected circuits which may contain
1+1 lines and 1+1 path protected segments. So on 1+1 line
protected segments, you Share the bandwidth among primary
and alternate paths. Setting up protected circuits is not considered
in detail so far. Hopefully, P&R design team will consider this..

Thanks,
Suresh

At 04:32 PM 4/12/2002 +0530, Khuzema Pithewan wrote:
>Hi,
>
>How does SE style of RSVP signalling fits in the optical nature of network
>i.e. in wavelength, TDM switching etc.
>
>  In other words, How two lsp can share resource in optical networks??
>
>Regards,
>Khuzema.

---

From: John Ellson <[email-masked]>
Date: Fri, 12 Apr 2002 12:50:08 -0400

I'm a lurker on this list, but I do know something about protection
in circuit networks, so I feel a need to comment on this.

Perhaps a terminology confusion, but if you have an end-system
which can share bandwidth across two connections, why do
you want 1+1 protection?

1:1 and 1:N architectures (as opposed to 1+1) can provide an
"extra-traffic" feature for carrying "low-priority" traffic on
the protection connection when it is not being used to protect
a working channel.  However, if you share bandwidth across a
working and an extra-traffic connection, at the time of a fault
not only will you see your bandwidth drop by half, but you will
also incur a traffic hit from the switching operation on the
remaining half of your bandwidth.

1+1 systems duplicate the traffic on working and protection,
they don't share it.

It seems to me that bandwidth sharing is an alternative survivabilty
strategy to protection switching, not in addition too.

John Ellson

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From: Zhi-Wei Lin <[email-masked]>
Date: Fri, 12 Apr 2002 12:56:57 -0400

Hi Suresh,

I may be wrong, but I think the way 1+1 works is not quite what SE 
specifies...

1+1 is the same traffic at the head-end been carried by two separate 
LSPs, while SE is sort of the converse of that...

Zhi

---

From: Suresh Katukam <[email-masked]>
Date: Fri, 12 Apr 2002 10:05:33 -0700

Zhi,

You are correct about 1+1 path protected...

But if you have a LSP that is protected by some 1+1 links and some
UPSRs, BLSRs etc.. then this LSP contains mixed protection schemes
(I am not sure what you call this LSP - 1+1 protected, just Protected circuit).
In this case, SE style can be used..

-- Suresh

At 12:56 PM 4/12/2002 -0400, Zhi-Wei Lin wrote:
>1+1 is the same traffic at the head-end been carried by two separate LSPs, 
>while SE is sort of the converse of that...
>
>Zhi
>
>
>Suresh Katukam wrote:
>
>>

---

From: Sudheer Dharanikota <[email-masked]>
Date: Fri, 12 Apr 2002 10:16:24 -0700

My opinion...

SE is more for M:N. Also we have to be careful in devising these
extensions. We need to consider

- Reservation with/without pre-established backup paths (these
are typical in transport networks - to reduce the switchover time).

- Reservations with/wothout extra traffic (typical again to transport
network to better use the backup resources)

- sudheer

---

From: Sudheer Dharanikota <[email-masked]>
Date: Fri, 12 Apr 2002 10:19:41 -0700

Hi Suresh:

> In this case, SE style can be used..

I think we should not call this 1+1.

In this specific case recovery is segment by segment.

- sudheer

---

From: Zhi-Wei Lin <[email-masked]>
Date: Fri, 12 Apr 2002 13:28:58 -0400

Hi Suresh,

Your example is the case of nested protections. So clarifying your 
example, I'm interpreting it to say:

A --- B --- C --- D
  \     \ /     /
   \     E     /
    \------F--/

Ring A-B-C-D-F is a UPSR ring, running over a B-C-E BLSR ring (possibly 
with B-C as dual-node interconnect or simply as points of interconnect).

Even in such case the LSP of interest is still only carrying a single 
traffic, not merged traffic. Even in the case of 1:1 (John Ellson's 
email) where you may have extra traffic, that LSP is also carrying 
single traffic at any instance not merged traffic (either-or, not and)

I think SE style is something that a circuit network doesn't really 
handle. The circuit itself may be carrying traffic that is aggregated 
from, e.g., an IP router (where merging may occur), but the circuit 
itself (which is of interest) does not really merge...so from a circuit 
world perspective merging is an "upper layer" or application layer 
capability...

Zhi

---

From: John Ellson <[email-masked]>
Date: Fri, 12 Apr 2002 13:29:23 -0400

> In this case, SE style can be used..

If you're talking about nodes other than the nodes that are
at the the ends of the protection span, then I suggest that you just refer
to it as a "reliable segment".  It shouldn't matter
to the end-systems how that segment reliability is achieved.

Protection is only interesting to nodes that have to take part in it,
otherwise its just a segment of a connection with a greater or
lesser propensity to failure.

John Ellson