Subject: [alto] Initial comments on draft-dulinski-alto-inter-problem-statement-02

From: "Y. Richard Yang" <[email-masked]>
Date: Sun, 19 Jul 2015 00:48:31 +0800

Dear Piotr, all,

I am reading up on draft-dulinski-alto-inter-problem-statement-02, and here
is some initial comment.

My high-level feedback is that this is a very valuable piece of work. In
particular, Section 2 gives a good starting point to discuss related basic
concepts; Figure 1 starts to show the basic structure; and the core section
(Section 3) gives good examples to motivate the benefit for inter-ALTO
communications.

Personally, I see inter-ALTO as a natural direction for ALTO extension
(e.g., a potential for a WG work item), and this document can be a good
base. At a high level, to form such a base, I see some additions to this
document where the following issues are discussed:

-  Additional analysis on why existing mechanisms are not sufficient. For
example, do the authors conclude that RFC7285 does not provide enough
capabilities to support inter-ALTO? If so, which features are missing,
according to the use cases? Have the authors evaluated other candidate
mechanisms (e.g., applying BGP would be a first consideration)?

- It may help if the framework provides some discussions on information
aggregation. For example, BGP uses import and export to implement policy
routing. I see that similar mechanisms may be needed in inter-ALTO as
well--the draft discussed about polices already, and what I am asking for
is more elaboration.

More details:
- The partitioned use case is a bit terse. It helps to elaborate more.

Minors:
- The draft has "Due to various reasons" at multiple places. At some
places, examples are given and at others no. It helps to be specific.

- Abstract: "ALTO servers are limited by the fact that it may not be
possible for an ALTO server to compute costs for source/destination pairs
correctly if a source and/or a destination is outside ..." The word correct
is strong. Correct implies there is an objective value, and in some
context, the cost can be "subjective". Hence, a weaker word can be helpful
here.

- Introduction: "Topology- and policy-related information may be supplied
through ALTO in a proactive or in a reactive way." I found this usage of
proactive and reactive quite interesting.

- Section 3: "It can be shown that without additional information on ..."
Can you give an example to support it can be shown?

- Section 3.1: "Moreover, there is a significant disproportion between
availability of information on upstream and downstream paths." How about
giving definitions on upstream vs downstream, as some readers may not be
familiar with the terms?

- Section 3.1: "To mitigate this situation, the inter-ALTO communication
framework may be used to exchange information on downstream paths between
two interested parties. " My understanding is that this may require a
recursive process, all the way to the final local administrative domain,
right?

Cheers,

Richard