nanog mailing list archives
Re: The Qos PipeDream [Was: RE: Two Tiered Internet]
From: "Stephen Sprunk" <stephen () sprunk org>
Date: Fri, 16 Dec 2005 10:15:16 -0600
Thus spake "Mikael Abrahamsson" <swmike () swm pp se>
On Fri, 16 Dec 2005, Christopher L. Morrow wrote:ah-ha! and here I thought they wanted buzzword compliance :) From what sales/customers say it seems like they have a perception that 'qos will let me use MORE of my too-small pipe' (or not spend as fast on more pipe) more than anything else.When you're running voip over a T1/E1, you really want to LLQ the VOIP packets because VOIP doesn't like delay (not so much a problem) nor jitter (big problem), nor packetloss (not so much a problem if it's less than a 0.1 percent or so).
There's two problems, actually. The first is serialization delay, and afflicts any link under about 3Mb/s regardless of utilization. Access speeds are finally climbing past this, but for links where they haven't you need something like MLPPP for fragmentation and interleaving.
The second is queueing delay, and that tends to only matter when average utilization passes 58% (someone with a stat background explained why, but my math isn't good enough to explain it). LLQ and WRED solve this well enough for end systems to cope with the result.
So combining voip and data traffic on a link that sometimes (more often now when windows machine have a decent TCP window) go full, evenjust in a fraction of a second, means you either go QoS or do what Skype does, crank up the jitter buffer when there is high-jitter, which means latency for the call goes up.
Adaptive jitter buffers are old technology; Skype is hardly the first company to use them. Most phones and softphones have them; it's the gateways at the other end that are usually stuck with static ones.
S Stephen Sprunk "God does not play dice." --Albert Einstein CCIE #3723 "God is an inveterate gambler, and He throws theK5SSS dice at every possible opportunity." --Stephen Hawking
Current thread:
- RE: The Qos PipeDream [Was: RE: Two Tiered Internet], (continued)
- RE: The Qos PipeDream [Was: RE: Two Tiered Internet] Sean Donelan (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] John Kristoff (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Christopher L. Morrow (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] John Kristoff (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Christopher L. Morrow (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Randy Bush (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Christopher L. Morrow (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Randy Bush (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Christopher L. Morrow (Dec 15)
- RE: The Qos PipeDream [Was: RE: Two Tiered Internet] Sean Donelan (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Mikael Abrahamsson (Dec 16)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Stephen Sprunk (Dec 16)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Mikael Abrahamsson (Dec 16)
- Message not available
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] David Meyer (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Marshall Eubanks (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Christopher L. Morrow (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] David Meyer (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Christopher L. Morrow (Dec 15)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Mark Smith (Dec 16)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Michael . Dillon (Dec 16)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Chris Woodfield (Dec 18)
- Re: The Qos PipeDream [Was: RE: Two Tiered Internet] Joe Maimon (Dec 18)