Friday, April 24, 2009

NSDI 2009, Day Three

Today is the last day of NSDI 2009 here in Boston. The conference was great this year, and the community is clearly going strong. My only regret is that, the conference being in Boston, there was no excuse for me to go out cavorting with my colleagues until the wee hours. (Not that this stopped my grad students...)

My favorite talks from today:

Softspeak: Making VoIP Play Well in Existing 802.11 Deployments
Patrick Verkaik, Yuvraj Agarwal, Rajesh Gupta, and Alex C. Snoeren, University of California, San Diego

This paper is about improving the performance of VoIP flows in wireless networks, which can be very negatively impacted by bulk TCP and UDP traffic. I liked how this work looks at something other than bulk throughput as the only performance metric for a wireless network: this paper focuses on the MOS scores for the VoIP calls. The basic idea is to allow the VoIP stations to use a shorter contention window and aggregate downlink traffic across multiple VoIP stations. It's a clever idea and very well evaluated in the paper, although it seems fairly complex and would require substantial changes to the clients and APs to support. I was surprised how many questions were asked after the talk. I raised the question about what happens with multiple TCP bulk flows. Given that a single TCP flow is so badly impacted by VoIP, it seems to me that multiple TCP flows would really hammer the VoIP traffic.

Making Routers Last Longer with ViAggre
Hitesh Ballani, Paul Francis, and Tuan Cao, Cornell University; Jia Wang, AT&T Labs—Research

Cheeky title aside, this paper focuses on the problem of reducing the size of the expensive FIB memory in Internet routers as the routing table sizes increase. The key idea is to partition forwarding responsibility so that each router only maintains routes to a fraction of the IP address space. This can be supported on unmodified routers by using separate "route reflectors" that filter the routing tables on behalf of the routers themselves. Of course, this approach requires encapsulation and tunneling since intermediate routers don't have the complete routing information.

Ironically, the talk just before this (NetReview: Detecting When Interdomain Routing Goes Wrong) dealt with detecting BGP misconfigurations -- the ViAggre approach adds even more complexity and potentially creates a nightmare for someone trying to debug their network (or, at least for Andreas). That said they've thought hard about how to make this deployable in practice.


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