RE: [Seamoby] Comment on CTP-09

[Nakhjiri Madjid-MNAKHJI1 <[e-mail]>]

I don't think implementing CTP over ICMP should be a MUST.
 None of the transport protocols were supposed to MUSTs.

Madjid

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Subject: [Seamoby] Comment on CTP-09


Hello

As the final reviewed period is ongoing, I would like to provide following comments to the CTP spec.
The CTP draft states about the MN-AR transport the following:

Comment 1:

"3.2 MN-AR Transport

The MN-AR interface MUST implement and SHOULD use ICMP for transport of the CTAR and CTAA messages. 
  :
  :
Because ICMP contains no provisions for retransmitting packets if signaling is lost, the CARD protocol incorporates 
provisions for improving transport performance on the MN-AR interface...."

It is unclear to the reader why CARD protocol is referenced at this point?  Is the intention to imply piggybacking of CTP and CARD over this interface? Plane provision of retransmission doesn't seem to be the motivation since the CTP draft contains already similar retransmission enhancement to CARD:
 
" CTAR messages for which a response is requested which fail to elicit a response are retransmitted.  The initial retransmission
   occurs after a CTP_REQUEST_RETRY wait period. Retransmissions MUST be made with exponentially increasing wait intervals (doubling the
   wait each time).  CTAR messages should be retransmitted until ether a response (which might be an error) has been obtained, or
   for CTP_RETRY_MAX seconds occurs."

In  the CARD draft, section 4.4, there is identical method provided. Hardly the intention is to run double retransmission scheme. So, it appears that the CTP is self-contained regarding to the retransmission and doesn't require any implementation of CARD to be functional. Right?

Suggestion:

- either to remove the reference to CARD, or add wording to explain what is meant by the CARD reference.  

Comment 2 (minor/editorial) to section 2.5.1

The MN MUST sent the sequence number to the same value for the message sent on both pAR and nAR so pAR can determine whether to use a cached message.

change to 
=> The MN MUST set the sequence number  ....


Regards Hannu

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