[Iccrg] Looking for reviewer for draft-ietf-ledbat-congestion-06

[Lisong Xu]

Hi Michael,

Below are my comments after reading the draft.
Thanks
Lisong


**** Section 3.1 ****
First sentence: "a loss occurs [RFC5681], which, in the absence of any 
Active Queue Management (AQM) in the network, occurs only when the queue 
at the bottleneck link on the end-to-end path overflows "

Since a loss may occur due to link errors, such as fiber errors and 
wireless errors, we may change the first sentence to
"... (AQM) and link errors in the network,...."

**** Section 3.3 ****
The data type of each variable is not specified. Since some variables 
must be signed variables, it is important to specify the type of each 
variable in order to correctly implement the algorithm.

For example, tcp_time_stamp is an unsigned int, so local_timestamp and 
remote_timestamp are also unsigned int.  But variable 
acknowledgement.delay should be a signed int, since 
local_timestamp-remote_timestamp may be negative.

**** Section 3.4.2 ****
"a LEDBAT sender stores BASE_HISTORY+1 separate minima- one each for the 
last BASE_HISTORY minutes, and one for the running current minute."

But the update_current_delay(delay) code maintains only BASE_HISTORY 
minima. So the above sentence should be changed to
"a LEDBAT sender stores BASE_HISTORY separate minima- one each for the 
last BASE_HISTORY-1 minutes, and one for the running current minute."

**** Section 3.5 ****
"we recommend that the sender SHOULD use at least 4 samples in each RTT. 
Thus, CURRENT_FILTER SHOULD be at least 4, and limited such that no 
samples in list are older than an RTT in the
past."

But what if cwnd is less than 4? In this case, there are less than 4 
samples in each RTT.


**** General *****

It is not clear what the relation between cwnd and flightsize is. Is 
flightsize always the same as cwnd, or could be less than cwnd? When is 
flightsize less than cwnd?


On 6/5/2011 12:38 AM, Michael Welzl wrote:
> Hi,
>
> We're urgently looking for a volunteer to review
> draft-ietf-ledbat-congestion-06:
> http://tools.ietf.org/html/draft-ietf-ledbat-congestion-06
> which is currently in Last Call, ending in less than two weeks (15 June).
>
> If anyone here is willing to do a review, please drop Murari and me a
> note ASAP!
>
> Thanks,
> Michael
>
>
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>

-- 
Lisong Xu, Associate Professor
Computer Science & Engineering
University of Nebraska-Lincoln
http://cse.unl.edu/~xu