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The sentence was: "Let network engineers do their jobs, with
appropriate oversight, and consumers will benefit." I don't
see why that's a problem. To reiterate the essence of my observation: Real-time apps, especially ones with high bandwidth requirements, will always be problematic without QoS on a network in which most flows are governed by TCP. TCP's congestion avoidance behavior creates the need for QoS. RB On 8/14/2010 1:57 PM, Bob Frankston wrote: Bennett's letter is a warning against trusting network management. Layer 2 is not real -- the ISO stack is a model. Just one possible decomposition. I remember a presentation in 1965 -- the speaker had to rush along as the slides started melting after a few seconds. Perhaps it was a hint of things to come. Treating a model as hard reality is a classic newbie error."Layer 3 people are consumers making a buy-or-don't-buy decision" misses the entire point! If the networks are not for people then what are they for? I have to pay for network services but don't make buy decisions? Huh? "Let network engineers do their jobs"? What are their jobs -- just to take orders? As I've said a pedestrian engineer does what he's told. A great engineer also checks back against reality and learns. I could go on but these examples should be enough to make it clear we shouldn't trust network engineers who know they know what the users want even if the users disagree. -----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Richard Bennett Sent: Saturday, August 14, 2010 15:59 To: Lauren Weinstein Cc: George Ou; [email protected]; 'Vint Cerf' Subject: [ NNSquad ] Re: Irish Times: "A modest proposal on internet neutrality" RFC 2475 is an architecture document that was written to explain the thinking behind the standards track RFC 2474, the RFC that defined the use of the DSCP field. Architecture documents are always informational, so there's no knock on it for that. QoS is implemented at Layers 1 and 2; the mechanisms above Layer 2 that relate to QoS tend to deal with means by which the applications specify their desired QoS from Layer 2 rather than with the implementation. QoS for Internet protocols is simply a question of whether IP should utilize the QoS that Layer 2 implements. IP engineers therefore don't need to know much about QoS; IP is essentially a consumer of the network services provided by Layer 2. Having worked in Layer 2 networking since before the Internet was designed, I can tell you that QoS is not a controversial feature in that field, and that there's always been a lot of head-scratching among network engineers about the reluctance of internetwork engineers to use the features that networks provide. The discussion of QoS among internetwork engineers, especially those whose familiarity goes back to the ARPANET days tend to be of a more hand-wavy nature than it is among the people who design, model, and implement the QoS control mechanisms in Layer 2 networks, but it's a different discussion. Layer 2 QoS engineers are solving an engineering problem, while Layer 3 people are consumers making a buy-or-don't-buy decision. Layer 2 deals with issues on a very different time scale than Layer 3 does. Prioritization as a form of QoS is typically managed across congestion periods of less than 1 second. It doesn't address the problem of chronic under provisioning, but it does address TCP's aggressive behavior in terms of constantly seeking to consume all available bandwidth. Regardless of the amount of bandwidth provisioned, when most flows are governed by TCP, the network will oscillate between periods of light use and overload. This is baked-in to the TCP metrics, and DiffServ is simply a means by which real-time applications can succeed in the face of it. Fred Baker tells a story about a network segment that Bell South used to operate. The admins noticed 25% packet loss on the segment, so they upgraded it from OC-3 to OC-12. That's a 4 x increase in bandwidth. What do you suppose happened to the network? Packet loss declined, but not all the way to 0: they still about 5 percent. That's TCP for you, it wants to get all the bandwidth that's available, even though its applications are flexible in terms of their completion time. Internets of the future need to accommodate diverse and heterogeneous applications. Layer 2 networks are constantly tweaked, tuned, and provisioned for the application mix. This isn't evil, it's network engineering. Let network engineers do their jobs, with appropriate oversight, and consumers will benefit. RB On 8/14/2010 9:05 AM, Lauren Weinstein wrote: -- Richard Bennett Senior Research Fellow Information Technology and Innovation Foundation Washington, DC |
- [ NNSquad ] Irish Times: "A modest proposal on i... Lauren Weinstein
- [ NNSquad ] Re: Irish Times: "A modest propo... George Ou
- [ NNSquad ] Re: Irish Times: "A modest p... Vint Cerf
- [ NNSquad ] Re: Irish Times: "A mode... Richard Bennett
- [ NNSquad ] Re: Irish Times: "A mode... George Ou
- [ NNSquad ] Re: Irish Times: "A ... Lauren Weinstein
- [ NNSquad ] Re: Irish Times: &qu... Barry Gold
- [ NNSquad ] Re: Irish Times:... Stefano Quintarelli
- [ NNSquad ] Re: Irish Times: &qu... Richard Bennett
- [ NNSquad ] Re: Irish Times:... Bob Frankston
- [ NNSquad ] Re: Irish Ti... Richard Bennett
- [ NNSquad ] Re: Irish Times: "A ... Adam Rothschild
- [ NNSquad ] Re: Irish Times: &qu... George Ou
