Subject: [alto] Question on draft-penno-alto-protocol-03

From: Antonio Fusco <[email-masked]>
Date: Wed, 15 Jul 2009 18:12:35 +0200

Hi folks,

I found a new version of draft-penno-alto-protocol
(draft-penno-alto-protocol-03.txt) and I have a question about it.
Since an ALTO Server presents to ALTO clients its "my--Internet View",
it may be reasonable for this view to be accurate in describing "near"
Network Locations and being less and less accurate when we move away
from them. So my question is: is there a way to represent "the rest of
the world"?
It seems, reading section 6.3.2.2, that every endpoint is mapped to a
PID (since there's nothing like a 404 "No PID for the endpoint" response
available), so we may group all the "far" networks we have few
information about ("the rest of the world") within a PID. The problem
with this approach would be how to answer to a Reverse PID Property
Lookup on such a PID (enumerating all network maps of far networks?).
Have you already addressed this issue?

Regards,
Antonio Fusco

PS: I found in appendix C.2 a Reverse PID Property Lookup response with
three PID, the third one mapped on a 0.0.0.0/0 mask: is it intended to
represent "the rest of the world" (and so PIDs in the response have to
be processed sequentially)?

--
_________________________________________________
Telecom Italia
Antonio Fusco
Control, Service Layer & Applications
Service Layer & Messaging Innovation & Engineering
Via Reiss Romoli, 274 10148 Torino
+39 011 228 5124
+39 3316001359

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---

From: Richard Alimi <[email-masked]>
Date: Wed, 15 Jul 2009 13:04:36 -0400

Hi Antonio,

> Have you already addressed this issue?

When mapping from IP addresses into PIDs, an ALTO Client can use longest-
prefix matching.  This will be stated explicitly in the next revision of the 
document.

Thus, the "rest of the world" can be represented simply as the 0/0 IP prefix. 
The prefix can be assigned to either an existing PID (along with other 
prefixes), or allocated to its own PID. This is indeed what we have done in 
the P4P tests.

For example, the ALTO Server's reply from Reverse PID Property Lookup can 
including the following mappings:

PID1: 128.36.0.0/16 130.132.0.0/16
...
PIDDEFAULT: 0.0.0.0/0

-- 
Richard Alimi
Department of Computer Science
Yale University

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From: sy ding <[email-masked]>
Date: Thu, 16 Jul 2009 11:57:27 +0800

Hi all:

    I am wondering if we need hierarchical PID structure to facilitate
P2P tracker to organize its peers. As I know in some current P2P
applications, they organize the peers into a hierarchical structure
according to its location.

   Best
   China Telecom Guangzhou Institute
   Syon Ding

2009/7/16 Richard Alimi <[email-masked]>:
> _______________________________________________
> alto mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/alto
>

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From: "Y. Richard Yang" <[email-masked]>
Date: Thu, 16 Jul 2009 01:10:29 -0400

Hi Syon,

It is great that you started this discussion thread. Yes. There are 
multiple implementations (e.g., P4P Location Alg. using two levels of 
hierarchy, and Kontiki using traceroute trees) using topological 
hierarchy to implement preferential (localized) peer selection.

During the revision process, introduction of hierarchical PID was 
discussed multiple times. In terms of supporting hierarchical peer 
selection, we added a sentence (top of page 28) in the current draft 
(http://tools.ietf.org/html/draft-penno-alto-protocol-03): "Note that it 
is possible that a tracker may use only the Network Map to implement 
hierarchical peer selection by preferring peers within the same PID and 
ISP." The IETF meeting is a good place to discuss more about this issue, 
which can benefit greatly from a "high-bandwidth" setting.

Richard

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From: "Y. Richard Yang" <[email-masked]>
Date: Thu, 16 Jul 2009 01:16:52 -0400

Dear Syon,

It is great that you bring this issue up. Yes. There are multiple 
systems using location hierarchy to achieve preferential (localized) 
peer selection. Two examples I know of are Kontiki (traceroute trees) 
and P4P Location Algorithms (two level hierarchy).

During the revision process, we discussed multiple times the possibility 
of introducing hierarchical location. In the current draft 
(http://tools.ietf.org/html/draft-penno-alto-protocol-03), we added a 
sentence (at the  top of page 28): 

  Note that it is possible that a tracker may use only
  the Network Map to implement hierarchical peer selection by
  preferring peers within the same PID and ISP.

Clearly, this topic can benefit from a "high-bw-low-delay" discussion 
setting during this IETF meeting.

Best,

Richard