[Nrg-l] NRG Next Wednesday

abhishek at bu.edu abhishek at bu.edu
Sun Oct 3 23:49:42 EDT 2004


Dear all,
Is it possible for the NRG to meet at 4 pm instead of 3 pm on Wednesdays as 
well? I have a class till 4 pm on Monday and Wednesday.
regards,
abhishek
Quoting Georgios Smaragdakis <gsmaragd at cs.bu.edu>:

> As there is no Colloquium next week, NRG will take
> place on Wednesday. I will present the paper "Sizing 
> Router Buffers" that appears in SIGCOMM 2004 and lead
> the discussion of possible extensions.
> 
> 
> Date: Wednesday October 6
> Time: 3:00pm
> Place: Grad Lounge
> 
> 
> paper info:
> -----------
> 
> link:
> http://www.acm.org/sigs/sigcomm/sigcomm2004/papers/p277-appenzeller1.pdf
> 
> "Sizing Router Buffers"
> by Guido Appenzeller, Isaac Keslassy, Nick McKeown 
> Stanford University
> 
> Abstract:
> 	
> All Internet routers contain buffers to hold packets during times
> of
> congestion. Today, the size of the buffers is determined by the
> dynamics
> of TCP's congestion control algorithm. In particular, the goal is to
> make
> sure that when a link is congested, it is busy 100% of the time;
> which is
> equivalent to making sure its buffer never goes empty. A widely
> used
> rule-of-thumb states that each link needs a buffer of size B = RTT X
> C,
> where RTT is the average round-trip time of a flow passing across
> the
> link, and C is the data rate of the link. For example, a 10Gb/s
> router
> linecard needs approximately 250ms X 10Gb/s = 2.5Gbits of buffers;
> and the
> amount of buffering grows linearly with the line-rate. Such large
> buffers
> are challenging for router manufacturers, who must use large, slow,
> off-chip DRAMs. And queueing delays can be long, have high variance,
> and
> may destabilize the congestion control algorithms.
> 
> In this paper we argue that the rule-of-thumb B = RTT X C is now
> outdated
> and incorrect for backbone routers. This is because of the large
> number of
> flows (TCP connections) multiplexed together on a single backbone
> link. Using theory, simulation and experiments on a network of real
> routers, we show that a link with n flows requires no more than B
> =(RTT X
> C) / sqrt{n}, for long-lived or short-lived TCP flows. The
> consequences on
> router design are enormous: A 2.5Gb/s link carrying 10,000 flows
> could
> reduce its buffers by 99% with negligible difference in throughput;
> and a
> 10Gb/s link carrying 50,000 flows requires only 10Mbits of
> buffering,
> which can easily be implemented using fast, on-chip SRAM.
> 
> 
> _______________________________________________
> Nrg-l mailing list
> Nrg-l at cs.bu.edu
> http://cs-mailman.bu.edu/mailman/listinfo/nrg-l
> 


More information about the Nrg-l mailing list