Re: SE style in optical neyworks

[John Ellson <ellson@lucent.com>]

[ post by non-subscriber ]

Sudheer Dharanikota wrote:
> Hi Gentelmen:
> 
> I changed this list to camp, as it is more appropriate
> for this discussion.
> 
> I would like to understand the following..
> 
> Assumptions:
> 
> - Segments of network are inherantly made protected.
>   For example, as suresh said, span/UPSR/BLSR etc protected.
> 
> - PAth request contains requirements to set up a path
>   of *certain* protection guarantees without knowing the
>  topoogy and its capability
> 
> Now ...
> 
> If i want to set up an end-to-end *backup* path, it is the network
> (intermediate nodes) which has to decide if a *backup*
> link or a segment need to be overloaded. Don't you think in this
> case SE may make sense.



I the circuit world, if you obtain a second circuit for use as backup
you don't need to tell the network about it.  Its just going to
give you a dedicated circuit, with whatever reliability guarantees
you have in your service contract, and with an expectation of being
paid for the circuit wether or not the end-system chooses to
put bits on it.

In the packet world its different.  I suppose you could obtain
a second circuit with a service contract that allowed the network
to stat-mux the bandwidth with other traffic.   I still don't
know why you would tell the network what you wanted it for.

BTW. If you used such a circuit for protection it would have to be
1:1, not 1+1, because the sharing on the standby channel clearly
means that you can't duplicate the working channel data.

John





> Thanks for your input.
> 
> sudheer
> 
> John Ellson wrote:
> 
> 
>>Suresh Katukam wrote:
>>
>>>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..
>>
>>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
>