Re: Fwd: Re: SE style in optical neyworks

[Zhi-Wei Lin <zwlin@lucent.com>]

Hi Suresh,

Sorry. Wasn't picking on terminology, anyway, some more comments below...

Suresh Katukam wrote:

>
>>
>> Tom and all,
>>
>> I think everyone seemed to pick on my terminology or misinterpreted
>> what I said.
>>
>> Here is an example:
>>
>>          1+1                        1+1
>> A ----------------B --------- C ------------D
>>                      \          /
>>                        \       /
>>                           E
>>
>>
>> A - B & C - D 1+1 line protected
>> B - C, C - E, B - E are all unprotected links.
>
So this network you drew assumes a single point of interconnect at B and 
C...that's fine

>>
>> Say, one wants to create a protected LSP from A to D.
>> then, you would create one primary LSP from A to D via
>> A - B - C - D, and then you would create another LSP
>> from A to D using SE style ( to indicate that this is an
>> alternate path for same Tunnel ) via A - B - E - C - D.
>> This way B - C is protected by B - E - C. 
>
By creating a new LSP A-B-E-C-D, this circuit is completely separate 
from the original A-B-C-D circuit. There is no sharing at all. It is 
just incidental that they carry the same traffic (i.e., you just happen 
to have set up the A-B-E-C-D to carry the same traffic as in A-B-C-D). 
Again this is not merging (as represented by SE), unless you are 
re-defining what SE means...

>>
>>
>> B - C - E is not configured as a UPSR. All unprotected links.
>> Virtual UPSR can be created such a way that B has a bridge
>> and C has a selector. Ofcourse, for bidirectional LSP, you need
>> the same thing in the opposite direction too.
>
Yes, just as the two LSPs making up the 1+1 from A-B are both 
unprotected LSPs, but taken together provide the 1+1 service. As such, 
if B-E-C is carrying the same traffic as B-C *all the time*, then it's 
still 1+1, but more specifically, it is a 1+1 SNC (sub-network 
connection). 1+1 doesn't necessary only apply to 1+1 path (when you say 
path, I think you mean trail? -- G.805 terminology).

However, if B-E-C is not carrying the same traffic, but may be used to 
support *extra traffic*, then this is a 1:1 type protection.

And if B-E-C LSP is actually supporting multiple LSPs going over B-C, 
then it's 1:N protection. However, note that even in this case it is 
still NOT SE, since the B-E-C LSP at any given time is only ever 
carrying one single traffic.

Hope this clarifies.

Zhi

>>
>> Now, what do you call this kind of protection? Protected LSP?
>> But not 1+1 path protected  - since it is not end-to-end path
>> protected.
>>
>> To clarify again, this is when you would use SE style.
>>
>> Thanks
>> Suresh
>>
>>
>> At 01:17 PM 4/12/2002 -0400, Thomas D. Nadeau wrote:
>>
>>
>>>> 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.
>>>
>>>
>>>         You do not share the bandwidth across 1+1 circuits. You
>>> double-book the bandwidth because the same packets are
>>> sent twice: once over each LSP.  You only share bandwidth
>>> with 1:N.
>>>
>>>         --Tom
>>>
>>>
>>>> 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.
>>>>
>>>
>>>
>>>
>>> ------------------------------------------------------------------------ 
>>>
>>> Mathematics is the supreme nostalgia of our time.
>>
>
>