Re: [OSPF] OSPF Topology Transparent Zone (TTZ) Next Steps

Peter Psenak <ppsenak@cisco.com> Thu, 11 July 2013 19:27 UTC

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Date: Thu, 11 Jul 2013 21:27:25 +0200
From: Peter Psenak <ppsenak@cisco.com>
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To: Huaimo Chen <huaimo.chen@huawei.com>
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Cc: OSPF List <ospf@ietf.org>
Subject: Re: [OSPF] OSPF Topology Transparent Zone (TTZ) Next Steps
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Hi Huaimo,

please see inline:

On 7/11/13 8:22 PM, Huaimo Chen wrote:
> Hi Peter,
>
>      Thanks much for your comments!
>      My responses are inline below.
>
> Best Regards,
> Huaimo
> -----Original Message-----
> From: Peter Psenak [mailto:ppsenak@cisco.com]
> Sent: Tuesday, July 09, 2013 4:22 PM
> To: Huaimo Chen
> Cc: OSPF List
> Subject: Re: [OSPF] OSPF Topology Transparent Zone (TTZ) Next Steps
>
> Huaimo,
>
> OSPF has the concept of areas, which allows you to scale if needed. ABR part is also the most complex part of the OSPF protocol and TTZ is of the same if not higher complexity.
>
> I do not believe current area architecture has reached its scaling limits which would require an introduction of the new protocol mechanism.
>
> In short, you need to find some other applicability of the TTZ, scaling is simply not the relevant one.
>
> [Huaimo] Using TTZ to avoid splitting one area into multiple areas may have some advantages in some cases such as: TTZ may make TE easier. For a network having one area with multiple TTZs, an operator configures a TE LSP crossing multiple TTZs just like s/he configures the LSP in one area. S/he just needs give a source, a destination, and maybe some constraints for the LSP. If one area in divided into multiple areas, configuring a TE LSP crossing multiple areas are complex.

even if it's easier to do TE with TTZ then with multiple areas, which 
I'm not convinced about, it still does not look like a sufficient reason 
to add TTZ extension to a protocol.

thanks,
Peter

>
>
> my 2c,
> Peter
>
> On 9.7.2013 21:33, Huaimo Chen wrote:
>> Hi Hannes,
>>
>>       Thanks for your comments!
>>       See my responses in line below.
>>
>> Best Regards,
>> Huaimo
>> -----Original Message-----
>> From: ospf-bounces@ietf.org [mailto:ospf-bounces@ietf.org] On Behalf
>> Of Hannes Gredler
>> Sent: Tuesday, July 09, 2013 1:21 PM
>> To: Acee Lindem
>> Cc: OSPF List
>> Subject: Re: [OSPF] OSPF Topology Transparent Zone (TTZ) Next Steps
>>
>> scaling a link-state protocols route-calculation path (SPF and RIB-Walk) to support 1000s of nodes is an already solved problem.
>> solving it again, (just different this time) is of limited use ...
>>
>> [Huaimo] How about 10,000s or 100,000s of nodes?
>>
>>
>> quite contrary - i fail to see how *hiding* information (i.e. nodes and links along with their TE attributes) does not break some of the TE eco-system that has been built around link-state IGPs. i am particularly interested how  TE use-cases requiring admission-control and pre-emption play with TTZ.
>>
>> [Huaimo] Regarding to TE, we are working on it and have some solutions.
>>
>>
>> /hannes
>>
>> On Jul 6, 2013, at 9:09 PM, Acee Lindem wrote:
>>
>>> As WG chair, I'd like to initiate a discussion on this technology. We've had it presented at the last couple IETFs and there are varying opinions on its usefulness.
>>> For reference:
>>>
>>>    Base Document: http://www.ietf.org/id/draft-chen-ospf-ttz-05.txt
>>>    Applicability:
>>> http://www.ietf.org/id/draft-chen-ospf-ttz-app-03.txt
>>
>>
>>
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