North American Network Operators Group
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Re: Jumbo frames

  • From: Stephen Sprunk
  • Date: Fri Mar 30 12:37:47 2007

Thus spake "Andy Davidson" <[email protected]>
The original poster was talking about a streaming application - increasing the frame size can cause it take longer for frames to fill a packet and then hit the wire increasing actual latency in your application.

Probably doesn't matter when the stream is text, but as voice and video get pushed around via IP more and more, this will matter.

It's a serious issue for voice due to the (relatively) low bandwidth, which is why most voice products only put 10-30ms of data in each packet.

Video, OTOH, requires sufficient bandwidth that packetization time is almost irrelevant. With a highly compressed 1Mbit/s stream you're looking at 12ms to fill a 1500B packet vs 82ms to fill a 10kB packet. It's longer, yes, but you need jitter buffers of 100-200ms to do real-time media across the Internet, so that and speed-of-light issues are the dominant factors in application latency. And, as bandwidth inevitably grows (e.g. ATSC 1080i or 720p take up to 19Mbit/s), packetization time quickly fades into the background noise.

Now, if we were talking about greater-than-64kB jumbograms, that might be another story, but most folks today use "jumbo" to mean packets of 8kB to 10kB, and "baby jumbos" to mean 2kB to 3kB.

S

Stephen Sprunk "Those people who think they know everything
CCIE #3723 are a great annoyance to those of us who do."
K5SSS --Isaac Asimov