On Mon, Jan 10, 2011 at 5:44 PM, Marc Petit-Huguenin <[email protected]> wrote:
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> Thanks for your responses. see below for more comments.
>
> On 01/07/2011 02:24 PM, Bruce Lowekamp wrote:
>> inline
>>
>> On Mon, Nov 22, 2010 at 2:32 PM, Marc Petit-Huguenin <[email protected]> 
>> wrote:
>> More questions, comments and nits:
>>
>
> [...]
>
>>
>> - A.10. It seems that this version of RELOAD lacks the support of virtual
>> servers (see draft-harjula-p2psip-loadbalancing-survey), more precisely a 
>> way to
>> share connections between two virtual servers on the same physical server 
>> (see
>> Frank Dabek, M. Frans Kaashoek, David Karger, Robert Morris, Ion Stoica,
>> Wide-area cooperative storage with CFS: "Use of virtual servers could
>> potentially increase the number of hops in a Chord lookup.  CFS avoids this
>> expense by allowing virtual servers on the same physical server to examine 
>> each
>> others' tables: the fact that these virtual servers can take short-cuts 
>> through
>> each others' routing table exactly compensates for the increases number of
>> servers.").  Because the certificates contains a list of Node-IDs, it is not
>> possible to know on a hop by hop basis what are the source and destination
>> NodeIds of a specific message.  Section 3 of
>> draft-rosenberg-dispatch-vipr-reload-usage seems to acknowledge that by 
>> adding a
>> PeerID Shim to exchange the source and destination peerIDs (aka Node-IDs).
>>
>> Because of this, it is probably a good idea to add in p2psip-base the
>> possibility to know the source Node-ID and destination Node-ID of a message.
>> One way to do that would have be to have the sender of a message add its own
>> Node-ID in the via_list, and the Node-ID of the destination in the
>> destination_list before sending a message (similar to what SIP is doing), 
>> but I
>> guess that it is too late for such a modification.
>>
>>
>>> I totally agree that vnodes should share routing state.  But it's not
>>> clear to me what benefit would be obtained by making that sort of a
>>> protocol change.
>>
>>> * on request routing, a message should normally have exactly one
>>> destination node-id.  The only reason to have more would be that the
>>> request sender has some particular reason to want to source-route the
>>> request.
>>> * on response sending, with recursive response you simply want to
>>> reverse the initial request routing.  If there was an advantage to
>>> "short-cutting" between v-nodes, it would have been done on the
>>> request routing.   If you're not doing recursive response routing,
>>> then this case is the same as request routing.
>
> Let's forget for now the solution I proposed.  Do you agree that Section 3 of
> draft-rosenberg-dispatch-vipr-reload-usage exposes a problem that would be 
> worth
> been solved in p2psip-base?

I think we're merging two separate issues here:

- how do you differentiate the sender of an end-to-end-message
- how do you identify the multiple Node-IDs of an adjacent node

For the first, I think SignerIdentity is the logical place.  Using
hash_alg, certificate_hash, and Node-ID would be sufficient.

For adjacent nodes, I would rather encode it using an IceExtension in
the Attach sequence that's already flowing than use a shim approach,
particularly because it avoids issues with datagram protocols.

I have mixed feelings on whether either of these should be in the base
protocol.  I really think that SignerIdentity should handle that case.
 But I think the support for multiple NodeIDs over a connection adds a
lot of complexity and might be better as an extension.

Bruce
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