Subject: [P2PSIP] P2PSIP diagnostics: PING discussion

From: Song Haibin <[email-masked]>
Date: Tue, 11 Nov 2008 16:53:12 +0800

Dear all,

In P2PSIP base protocol, Ping is used to test connectivity along a path.
However, connectivity quality can not be measured well without some useful
information, such as the timestamp and HopCounter. In p2psip diagnostics
draft version 03 http://tools.ietf.org/id/draft-zheng-p2psip-diagnose-03.txt
we extend the Ping message payloads with a few kinds of useful information
for connectivity quality check purposes. 

The initiator node receiving the Ping response should compute the overlay
hops to the destination peer for the statistics of connectivity quality from
the perspective of overlay hops.

About the Timestamp, we are not sure if the NTP time is a good candidate for
it, or we have other ways to describe it, or we don't need the timestamp at
all. But if NTP time is used in the overlay, then it is a good choice,
because every peer along the message path will know when the message is
generated, and it is easy for the peer along the path to calculate the
message latency. However many overlays may not be synchronized with the NTP
time. Any comments?

Best Regards,
Song Haibin
Email: [email-masked]
Skype: alexsonghw

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From: "Bruce Lowekamp" <[email-masked]>
Date: Wed, 12 Nov 2008 14:16:44 -0500

I don't think it's a good idea to have Ping extensible by multiple
drafts.  Implementing that would require much more complex encoding
and parsing to deal with the combination of extensions supported by a
particular implementation.  The overlay methods are extensible, but
only by whichever overlay algorithm is currently being used, so there
is exactly one encoding.

With that said, the ttl response might be a reasonable addition to the
base Ping response.  I don't understand the purpose of UnderlayTTL,
however.

Bruce

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From: Song Haibin <[email-masked]>
Date: Thu, 13 Nov 2008 11:59:01 +0800

Bruce,

See inline.

>-----Original Message-----
>From: Bruce Lowekamp [mailto:[email-masked]]
>Sent: Thursday, November 13, 2008 3:17 AM
>To: Song Haibin
>Cc: [email-masked]
>Subject: Re: [P2PSIP] P2PSIP diagnostics: PING discussion
>

I am not quite sure here.

>base Ping response.  

I have the same thought.

>I don't understand the purpose of UnderlayTTL,
>however.

There may be the requirement that one may want to limit each hop underlay
TTL from the initiator to the destination, if the underlay TTL expires
somewhere, one may think that the link there is not of good quality. It is
an optional function, because you can clear the value so that the
intermediate peer will ignore it. I don't know if this is often be used, if
many guys think this parameter is of no use, I will delete it for the next
revision.

BR
Song

>> draft version 03
>http://tools.ietf.org/id/draft-zheng-p2psip-diagnose-03.txt

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From: "Bruce Lowekamp" <[email-masked]>
Date: Thu, 13 Nov 2008 11:17:34 -0500

> many guys think this parameter is of no use, I will delete it for the next

So the thought is to set a max value for the IP TTL header in the
outgoing packet?  Cool idea.  I have no idea how many platforms it's
possible to implement that on from user level, though.  Strikes me as
something very interesting for diagnostics, but I'm not sure I would
want to see it specified in the base Ping.  Could be done as a
ForwardingOption, however.

Bruce

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From: Song Haibin <[email-masked]>
Date: Mon, 17 Nov 2008 15:24:53 +0800

Bruce,

>Sent: Friday, November 14, 2008 12:18 AM
>To: Song Haibin
>Cc: [email-masked]

Thanks for your comments. We would like to add more clarification text for
the UnderlayTTL parameter in the diagnostic draft. We propose to extend Ping
(although the structure of Ping in the base draft is not extendable at
present) for the additional functions of connectivity check in the
diagnostics draft, and we also define additional Error response codes to the
connectivity check. I think it is reasonable to do that. If many people
think that is not reasonable, maybe we would define a new method.

BR
Song Haibin