practice

Doi: 10.1145/2076450.2076464

Article development led by queue.acm.org

A discussion with Vint Cerf, Van Jacobson,
Nick Weaver, and Jim Gettys.
BufferBloat:
What’s Wrong
with the
internet?

internet DeLaYS nOw are as common as they are maddening. But that means they end up affecting system engineers just like all the rest of us. And when system engineers get irritated, they often go looking for what’s at the root of the problem. Take Jim Gettys, for example. His slow home network had repeatedly proved to be the source of considerable frustration, so he set out to determine what was wrong, and he even coined a term for what he found: bufferbloat.

Bufferbloat refers to excess buffering inside a network, resulting in high latency and reduced throughput. Some buffering is needed; it provides space to queue packets waiting for transmission, thus minimizing data loss. In the past, the high cost of memory kept buffers fairly small, so they filled quickly and packets began to drop shortly after the link became saturated, signaling to the communications

protocol the presence of congestion and thus the need for compensating adjustments.

Because memory now is significantly cheaper than it used to be, buffering has been overdone in all manner of network devices, without consideration for the consequences. Manufacturers have reflexively acted to prevent any and all packet loss and, by doing so, have inadvertently defeated a critical TCP con-gestion-detection mechanism, with the result being worsened congestion and increased latency.

Now that the problem has been diagnosed, people are working feverishly to fix it. This case study considers the extent of the bufferbloat problem and its potential implications. Working to steer the discussion is Vint Cerf, popularly known as one of the “fathers of the Internet.” As the co-designer of the TCP/IP protocols, Cerf did indeed play a key role in developing the Internet and related packet data and security technologies while at Stanford University from 1972−1976 and with the U.S. Department of Defense’s Advanced Research Projects Agency (DARPA) from 1976−1982. He currently serves as Google’s chief Internet evangelist.

Van Jacobson, presently a research fellow at PARC where he leads the networking research program, is also central to this discussion. Considered one of the world’s leading authorities on TCP, he helped develop the random early detection (RED) queue management algorithm that has been widely credited with allowing the Internet to grow and meet ever-increasing throughput demands over the years. Prior to joining PARC, Jacobson was a chief scientist at Cisco Systems and later Packet Design Networks.

Also participating is Nick Weaver, a researcher at the International Computer Science Institute (ICSI) in Berkeley, where he was part of the team that developed Netalyzr, a tool that analyzes network connections, and has been instrumental in detecting bufferbloat and measuring its impact across the Internet.