--- 1/draft-ietf-tsvwg-byte-pkt-congest-06.txt 2012-02-20 19:13:58.494671989 +0100 +++ 2/draft-ietf-tsvwg-byte-pkt-congest-07.txt 2012-02-20 19:13:58.578671223 +0100 @@ -1,19 +1,19 @@ Transport Area Working Group B. Briscoe Internet-Draft BT Updates: 2309 (if approved) J. Manner Intended status: BCP Aalto University Expires: August 23, 2012 February 20, 2012 Byte and Packet Congestion Notification - draft-ietf-tsvwg-byte-pkt-congest-06 + draft-ietf-tsvwg-byte-pkt-congest-07 Abstract This memo concerns dropping or marking packets using active queue management (AQM) such as random early detection (RED) or pre- congestion notification (PCN). We give three strong recommendations: (1) packet size should be taken into account when transports read and respond to congestion indications, (2) packet size should not be taken into account when network equipment creates congestion signals (marking, dropping), and therefore (3) the byte-mode packet drop @@ -372,21 +372,21 @@ on the size of the packet in question. As the example in Section 1.2 illustrates, to drop any bit with probability 0.1% it is only necessary to drop every packet with probability 0.1% without regard to the size of each packet. This approach ensures the network layer offers sufficient congestion information for all known and future transport protocols and also ensures no perverse incentives are created that would encourage transports to use inappropriately small packet sizes. - What this advice means for the case of TCP: + What this advice means for the case of RED: 1. AQM algorithms such as RED SHOULD NOT use byte-mode drop, which deflates RED's drop probability for smaller packet sizes. RED's byte-mode drop has no enduring advantages. It is more complex, it creates the perverse incentive to fragment segments into tiny pieces and it reopens the vulnerability to floods of small- packets that drop-tail queues suffered from and AQM was designed to remove. 2. If a vendor has implemented byte-mode drop, and an operator has @@ -422,21 +422,21 @@ packet. Therefore, the IETF transport area should continue its programme of; o updating host-based congestion control protocols to take account of packet size o making transports less sensitive to losing control packets like SYNs and pure ACKs. - Corollaries: + What this advice means for the case of TCP: 1. If two TCP flows with different packet sizes are required to run at equal bit rates under the same path conditions, this should be done by altering TCP (Section 4.2.2), not network equipment (the latter affects other transports besides TCP). 2. If it is desired to improve TCP performance by reducing the chance that a SYN or a pure ACK will be dropped, this should be done by modifying TCP (Section 4.2.3), not network equipment. @@ -1273,25 +1273,25 @@ www.statslab.cam.ac.uk/~frank/ evol.html>. [I-D.ietf-avtcore-ecn-for-rtp] Westerlund, M., Johansson, I., Perkins, C., O'Hanlon, P., and K. Carlberg, "Explicit Congestion Notification (ECN) for RTP over UDP", draft-ietf-avtcore-ecn-for-rtp-06 (work in progress), February 2012. - [I-D.ietf-conex-concepts-uses] Briscoe, B., Woundy, R., Moncaster, - T., and J. Leslie, "ConEx Concepts - and Use Cases", - draft-ietf-conex-concepts-uses-00 - (work in progress), November 2010. + [I-D.ietf-conex-concepts-uses] Briscoe, B., Woundy, R., and A. + Cooper, "ConEx Concepts and Use + Cases", + draft-ietf-conex-concepts-uses-03 + (work in progress), October 2011. [IOSArch] Bollapragada, V., White, R., and C. Murphy, "Inside Cisco IOS Software Architecture", Cisco Press: CCIE Professional Development ISBN13: 978- 1-57870-181-0, July 2000. [PktSizeEquCC] Vasallo, P., "Variable Packet Size Equation-Based Congestion Control", @@ -1748,20 +1748,25 @@ across different size flows [Rate_fair_Dis]. Appendix D. Changes from Previous Versions To be removed by the RFC Editor on publication. Full incremental diffs between each version are available at (courtesy of the rfcdiff tool): + From -06 to -07: + + * A mix-up with the corollaries and their naming in 2.1 to 2.3 + fixed. + From -05 to -06: * Primarily editorial fixes. From -04 to -05: * Changed from Informational to BCP and highlighted non-normative sections and appendices * Removed language about consensus