Re: Pool Handle Translation in draft-ietf-rserpool-enrp-06.txt

Hi, Thomas,

To add a "more data" flag to NAME_RESOLUTION_RESPONSE will add
complexity to the implementation and add significant delay to ENRP query
responses when the flag is used. To allow the use of "an appropriate
subset of PEs" will raise the question (and ambiguity) of "what is the
appropriate subset of PEs", and will break the load sharing mechanism,
and may potentially cause inter-op problems. IMO, either change above
would need a very strong justification to make.

Let's do a little calculation to see how big the problem you mentioned
is.

With 16 bit length field, you are allowed to have a 64k byte size
response msg.

a) if each PE in the pool is of SCTP type with dual-homed IPv6
interfaces, a PE param TLV would take 72 bytes, and you would be able to
comfortably fit about 900 PEs in a response;

b) if each PE is of SCTP type with triple-homed IPv6, a PE TLV would
take 92 bytes and you would be able to have >700 PEs.

For IPv4 or transport type other than SCTP, you could easily get >1000
PEs in a single response message. 

We talked about RSERPOOL scalability issues a long time ago and I
remember our consensus was to be able to support pool size in the range
of no more than 150~200 PEs as our requirement.

So I am not convinced that the message size limit here is causing a
problem for us.

regards,
-Qiaobing

Thomas Dreibholz wrote:
> 
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> Hi all,
> 
> a comment on section 4.5 of the ENRP draft:
> "In the response message, the ENRP server MUST list all the PEs currently
> registered in this pool, in a list of PE parameters."
> 
> It is not a good idea to list all PEs currently registered in the pool: The
> NAME_RESOLUTION_RESPONSE message as defined in 2.2.6 of the ASAP draft
> version 07 has no "More Data" flag or something like this. Since the length
> field is limited to 16 bits, the amount of PEs in a pool would be limited by
> the size of the resulting NAME_RESOLUTION_RESPONSE message.
> 
> What about replacing the sentence in section 4.5 by "In the response message,
> the ENRP server MUST list an appropriate subset of the PEs currently
> registered in this pool, in a list of PE parameters."
> 
> Best regards
> - --
> =======================================================================
>  Dipl.-Inform. Thomas Dreibholz
> 
>  University of Essen,                            Room ES210
>  Inst. for Experimental Mathematics              Ellernstraße 29
>  Computer Networking Technology Group            D-45326 Essen/Germany
> - -----------------------------------------------------------------------
>  E-Mail:     [email protected]
>  Homepage:   http://www.exp-math.uni-essen.de/~dreibh
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