[dccp] The TFRC implementation in ns-2.28: variable size packets support

["Arne Lie" <arne.lie at item.ntnu.no>]

Hi,

As I am writing an ns-2 interface between a rate adaptive version of Evalvid
and DCCP, I have started to work in with the TFRC module in ns-2
($NS_HOME/tcp/tfrc.cc). I know that the TFRC algorithm works best on fixed
packet sized streams. However, this is bandwidth waste for e.g. VBR video,
as many others also have stated. 

Can anybody confirm the following finding in ns-2: the send queue in tfrc.cc
consist only on *number* of packets, assuming ALL packets have equal size =
"size_"!!?? 

If this is true, does anybody have any comments on this issue before I
implement a queue also holding packet sizes? E.g. should  I not do it,
because DCCP/TFRC is not supposed to support this?

A last question: Is it correct to assume 12 + 4 byte of TFRC header (12 byte
generic, 4 byte data packet specific header) in addition to 20 byte IPv4
header?

Best regards

Arne Lie
NTNU Dept. of Telematics
Trondheim, NORWAY