[conex] Comments on WGLC for draft-ietf-conex-tcp-modifications-06
Nandita Dukkipati <nanditad@google.com> Tue, 25 November 2014 06:17 UTC
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From: Nandita Dukkipati <nanditad@google.com>
To: Mirja Kühlewind <mirja.kuehlewind@tik.ee.ethz.ch>, "Scheffenegger, Richard" <rs@netapp.com>
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Subject: [conex] Comments on WGLC for draft-ietf-conex-tcp-modifications-06
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Mirja and Richard, Thanks! for the draft. Some comments below: * Introduction "First congestion information have to be extracted from loss or ECN feedback in TCP as described in section 3"... ". Remove the extra quotes. * "It is therefore recommend to use the SACK extension when using TCP with ConEx." It is therefore recommended... * " This document describes congestion accounting for both TCP with and without the Selective Acknowledgment (SACK) extension [RFC2018] in section 3.1. ... The detailed mechanism to respectively set the L bit in response to loss- based congestion feedback signal is given in section 4.1." "The congestion accounting for both, with the classic ECN feedback as well as a more accurate ECN feedback are explained in detail in section 3.2 while the setting of the E bit in response to ECN-based congestion feedback is again detailed in section 4.1." This jumps around around describing Section 3.1 -> Section 4.1 -> Section 3.2 -> and back to Section 4.1 Suggestion is to consolidate to keep all the Section 3 material by itself and Section 4 material by itself. Also the last three paragraphs of the Intro. seem disconnected with the rest. The para starting with "Section 2 provides an overview of the needed modifications for TCP senders to implement ConEx..." already laid out the Section contents. * Accounting Congestion Reword the first sentence. A ConEx sender maintains two counters: one that accounts congestion byte-wise based on the congestion information received by loss detection, and a second that accounts for ECN based congestion feedback. * 3.1.1 Without SACK Support The last para of Section 3.1.1: "At this point of time in the transmission, in the worst case, all packets in flight minus three that trigged the dupACks could have been lost. For each retransmission that is sent, the LEG will still be increased but the LEC will also be decreased by the payload size of the retransmission. During the following RTT, LEC should be reduced by SMSS for each ACK that is received. Thus after one RTT the LEC estimates the number of outstanding bytes that should be ConEx L marked. To not further delay this information, now LEG should be increased by LEC. From then on every following retransmission should only reduce the LEC and not increase the LEG until the LEC is zero, as those bytes were already accounted." Have you considered putting the above in a pseudo code: On a retransmission: XXX On receipt of ACK: XXX * 5. Loss of ConEx information "Of course also packets..." -> Packets carrying ConEx can also get lost. 6. Timeliness of the ConEx Signals nodewith -> node with avoiad -> avoid
- [conex] Comments on WGLC for draft-ietf-conex-tcp… Nandita Dukkipati
- Re: [conex] Comments on WGLC for draft-ietf-conex… Mirja Kühlewind