Hi,
On 2009-12-26 17:42, wei zhang wrote:
> Hi, Brian and Xiaohu
>
> My response to your comments inline.
>
> 2009/12/26 Xu Xiaohu <x...@huawei.com>:
>>
>>> -----邮件原件-----
>>> 发件人: rrg-boun...@irtf.org [mailto:rrg-boun...@irtf.org] 代表 Brian E
>>> Carpenter
>>> 发送时间: 2009年12月26日 3:32
>>> 收件人: wei zhang
>>> 抄送: rrg@irtf.org
>>> 主题: [rrg] Aggregatable EIDs
>>>
>>> On 2009-12-26 05:52, wei zhang wrote:
>>> ...
>>>> A good answer is that the EID should also be aggregateable,
>>> I may be missing what you mean, because it seems to me that
>>> any set of bit strings (even of variable length) is aggregatable
>>> to an arbitrary extent. Just build a binary tree and chop it
>>> off at whatever level you want (/N if you want 2^N aggregates).
> Here the EID aggregation is based on the same mapping information,
> e.g. if 2 neighboring /16 EIDs map to different RLocs, there needs at
> least 2 entries in the mapping system for this discrimination.
> Therefore they are not "aggregateable" if concerned by scalable
> mapping.
That seems to describe EIDs that have topological significance, and I don't
understand how that works.
>> Agree. Even the EID is a flat label, the corresponding ID->Locator mapping
>> system could scale well by using some methods, e.g., DHT.
>>
> DHT also builds fine hierarchies within its scheme, or to say a flat
> label can be organized in a logic hierarchical structure. Indeed
> hierarchical structure helps to alleviate scalability problems, but it
> might be prudent to say it scales "better" (than flat label) instead
> of "well" if we are facing an already massive mess. IMHO, to make EID
> organized/assigned in an "aggregateable" way beforehand can be easier
> than to find any aftermath remedies.
>
>> IMO, a major reason that the EID should be hierarchical is as follows:
>>
>> The resolution infrastructure for flat names has no "pay-for-your-own”
>> model, as the flat names are stored at essentially random nodes. In
>> contrast, the resolution infrastructure for the hierarchical host
>> identifiers has reasonable business models and clear trust boundaries. Since
>> the hierarchical host identifiers have clear organization affiliation, the
>> identifier resources and the corresponding mappings can be managed by
>> different bodies with clear administrative boundaries.
>>
> I agree. Hierarchically organized EID with some constraints on its
> assignment(clear organization affiliation) guarantees scalable
> mapping, since theoretically the information entropy reduced.
I don't understand. There's no reason in physics or economics why
customers that happen to be adjacent in an ISP's address allocation
scheme should be adjacent in any scheme of organisational affiliation.
This argument fails for exactly the same reason that geographically
based BGP aggregation fails.
I'm not saying there is zero correlation. Obviously, two customers
in the same city are more likely to use the same ISP than two customers
in different countries. But can you point to studies that show that
the observed correlation is enough to significantly affect aggregation?
Significantly means: this would scale a lot better than BGP aggregation
scales today, otherwise we have gained nothing from the loc/ID split.
I'm puzzled how this could be, since if there is such a correlation,
it would also help BGP aggregation.
My understanding of the value of the loc/ID split is not that it
benefits from aggregation in the ID space, but rather that the
cost of non-aggregation is acceptable in the ID-to-loc map
because it is not subject to the performance constraints of
a routing protocol.
Brian
> However, before anyone enforces these constraints in the Internet, we
> need to define the hierarchy with corresponding range of effects which
> is my intention of designing "aggregateable" EID on behalf of ID/Loc
> mapping scalability.
_______________________________________________
rrg mailing list
rrg@irtf.org
http://www.irtf.org/mailman/listinfo/rrg
