[Nsi-wg] Topology virtualisation

Thu Jun 24 11:25:34 CDT 2010

Hi John,

See inline:

On Jun 24, 2010, at 10:24 AM, John MacAuley wrote:

> Cees beat me to the punch on the path computation topic.  Whether a GOLE is considered a domain itself, or whether it is a node in a larger domain, I think the key attribute in path computation is the high level of inter-domain connectivity a GOLE node represents.  The concept of “open” versus “closed” is really just a policy on the resources associated with the GOLE node.

Correct. Where and when policy goes in the path computation depends on the algorithm. Do you search for any path or for any path "Cees de Laat" is allowed to use, etc. I do not see a way to think of path computation code that has a statement:

If (I enter a GOLE) then
  I do this
Else
  I do that
Endif

The high connectivity will implicitly present itself as statistically easy to find paths through GOLE's but if it were well connected domains; so what.

> The big advantage I see with the GOLE node is that when path computation is performed, inter-domain connections transiting the domain associated with the GOLE node only ever touch the GOLE node.  Exposing detailed intra-domain topology to external domains so they can find optimal paths transiting the domain is not really required since they would never leave the GOLE node.

This should be true if GOLE's are geographically point like objects. Two possible exceptions:
- multi technology GOLE may have some more internal structure
- distributed GOLE that says "if you connect anywhere to us you can exit anywhere else. I seem to remember CENIC regarded their network that way. Obviously then the whole Administrative ownership delegation and policy structure is then important to precisely define... For sake of discussion I would at this point not want to discuss distributed GOLE's.

Exposing intradomain topology is only needed when part of that topology is used for interdomain links. For example if SURFnet regards the dark fiber AMS-CERN as their domain, then that is intradomain topology (or not?).

Best regards,
Cees.

> 
> John.
> 
> 
> 
> On 10-06-24 10:37 AM, Cees de Laat wrote:
>> There are different ways to look at GOLE's or as the initial name was "Open Exchanges".
>> As many of you remember the first mention of this term that I heard in a discussion between Tom DeFanti and Kees Neggers at the Pittsburgh SC prompted me to think about what they meant with the term "Open". That resulted in a study by Freek Dijkstra an Leon Gommans and some others that resulted in an article dwelling into the notion of exchanges, ownership types and policy. See below for one of the articles and talks about this subject.
>> 
>> What does this mean in my opinion:
>> - technically, device wise, there is no difference between domains and goles. If you come from a far planet and you would look at the switches cables, fibers, etc. you would not be able to tell the difference between a domain and a gole apart from that it seems that at some places many fibers seem to come together.
>> - obviously one of the reasons for the exchanges and gole's is scaling. By going to a gole or exchange you add lots of potential connectivity to your graph as at that gole you can immediately peer with the others at that same exchange.
>> - the real difference is in the policy and operations model. An "open" exchange is supposed to be not involved in the decision for connection two or more of the peers connecting to that exchange (*). That implies legal, economic and administrative ownership roles for the different parties involved as described on the article and talk. Those are different for a GOLE compared to a normal domain. For example in a GOLE to be truly open the administrative ownership of a port should be with the connecting party and not with the owner of the GOLE. That required NRPS systems supporting that, and those are coming around. Path setup requires that both the incoming and outgoing party at a GOLE need to agree that they want to connect before the connectivity in the GOLE can be changed. In a chain of domains one can handle that serially. If that really makes a difference in practical implementations is to be seen and heavily debated between John Vollbrecht and myself ;-).
>> - (*) exception is technical capabilities as a gole could run out of resources or have technical reasons. Another issue is that GOLE's may be placed at locations or financed in such a way that there are restrictions on who can physically connect there (e.g. only not for profit networks NREN's, e.g.).
>> 
>> [2004-c-3] Freek Dijkstra, Cees de Laat, "Optical Exchanges", GRIDNETS conference proceedings, oct 2004, 
>> http://www.broadnets.org/2004/workshop-papers/Gridnets/DijkstraF.pdf
>> .
>> 
>> 13-feb 2005: Internet2 joint techs, Salt Lake City (USA): "What makes an exchange open?".
>>  Sheets (pdf) 
>> http://staff.science.uva.nl/~delaat/talks/cdl-2005-02-13.pdf
>> 
>> 
>> So in path computation or topology description there seems not to be a difference in my opinion. In policy and sequence for lightpath setup yes.
>> 
>> Best regards,
>> Cees.
>> 
>> On Jun 24, 2010, at 8:46 AM, Victor Reijs wrote:
>> 
>>   
>> 
>>> Hello Gigi,
>>> 
>>> Gigi Karmous-Edwards wrote:
>>>     
>>> 
>>>> True, it is a domain. However, if a GOLE has the property of being "open 
>>>> policy"  and its main service is to interconnect paths between GOLEs and 
>>>> domains, then from a "strictly" path computation perspective, and if 
>>>> given a choice between a transient link across a domain w/ policy or 
>>>> through an open policy GOLE, then it seems that the path computation 
>>>> entity will find it simpler to  choose the  the path through the GOLE 
>>>> rather than the domain. What are your thoughts on this particular 
>>>> scenario...
>>>>       
>>>> 
>>> Perhaps I have no full solution to the problem, but IMHO it would be 
>>> great if we can define the properties of a GOLE to any Domain.
>>> So the main question is: are 'GOLE' and 'Domain' different objects, or 
>>> are they the same object (different instances) with different attribute 
>>> values.
>>> I would prefer the last one as it provide a larger flexibility (e.g. a 
>>> 'Domain' can be a 'GOLE'  in context or when time changes)
>>> 
>>>     
>>> 
>>>> I can see a situation  where an end user may choose to go through a 
>>>> particular  domain  if  they are members of a domain and have certain  
>>>> privileges.
>>>>       
>>>> 
>>> This is not only related to policy, might also be QoS, etc.
>>> 
>>> All the best,
>>> 
>>> 
>>> Victor
>>> 
>>> -- 
>>> Victor Reijs, Network Development Manager
>>> HEAnet Limited, Ireland's Education and Research Network
>>> 1st Floor, 5 George's Dock, IFSC, Dublin 1
>>> Registered in Ireland, no 275301
>>> tel: +353-1-660 9040  fax: +353-1-660 3666
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>>> http://www.heanet.ie/
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>>>     
>>> 
>> 
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