Tfrc for voice the voip variant
Download
1 / 9

TFRC for Voice: the VoIP Variant - PowerPoint PPT Presentation


  • 90 Views
  • Uploaded on
  • Presentation posted in: General

TFRC for Voice: the VoIP Variant. Sally Floyd, Eddie Kohler. November 2005 draft-ietf-dccp-tfrc-voip-02.txt Slides: http://www.icir.org/floyd/talks.html Graphics: http://www.icir.org/floyd/papers/voipimages.pdf. VoIP: fairness in Bps.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha

Download Presentation

TFRC for Voice: the VoIP Variant

An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -

Presentation Transcript


TFRC for Voice: the VoIP Variant

Sally Floyd, Eddie Kohler.

November 2005

draft-ietf-dccp-tfrc-voip-02.txt

Slides: http://www.icir.org/floyd/talks.html

Graphics:

http://www.icir.org/floyd/papers/voipimages.pdf


VoIP: fairness in Bps.

  • In the TCP throughput equation, use the measured loss event rate and a packet size of 1460 bytes.

  • Reduce the allowed transmit rate to account for the fraction of the VoIP bandwidth that would be used by 40-byte headers:

  • Enforce a Min Interval between packets of 10 ms.

  • For short loss intervals (at most two RTTs), count the actual packet loss rate (but don’t increase the number of loss intervals).


Report from the last IETF: Issues remaining

  • The problem:

    • VoIP TFRC, with small packets, can see different packet drops that it would have with larger packets. When is this a problem?

  • For simulations with configured byte drop rates (where small packets are less likely to be dropped than large packets):

    • When compared with 1460-byte TCP,even standard TFRC with small packets can get much more than its share of the bandwidth in times of high congestion.


The current status for TFRC using small packets:

  • Configured *packet* drop rates:

    • Standard TFRC with small packets doesn’t do well;

    • VoIP TFRC with small packets achieves reasonable fairness with large-packet TCP.

  • Configured *byte* drop rates:

    • With byte drop rates, TCP sometimes does better with smaller packets.

    • Standard TFRC with small packets achieves reasonable fairness with TCP using the optimal packet size for that level of congestion.

    • VoIP TFRC with small packets achieves more bandwidth than TCP using optimal packet sizes.


Configured *packet* drop rates, with 200-byte TFRC segments, 1460-byte TCP segments:


Configured *byte* drop rates, with 14-byte TFRC segments, 1460-byte TCP segments:


Configured *byte* drop rates, with 14-byte TFRC segments, different TCP segment sizes:


Question from last time:

  • Is it ok to have congestion control for small-packet flows that lets small-packet flows receive more bandwidth than large-packet TCP flows in environments where small packets are less likely to be dropped than large ones?

  • Answer: I think so, as an Experimental CCID. It seems that for many paths in the Internet, small packets don’t receive favorable treatment.


Drop rates with different packet sizes:

Downloads from web servers, from Alberto Medina.

Annotation: total # of drops / total # of packets


ad
  • Login