[c-nsp] effect of different packet size? and how to ensure video packet are not lost during other TCP communication

[Bill Wichers]

> What will be the effect if the packet size is changed. like  using FTP
> and video confrencing which uses UDP. If packet size is varied then wt
> are the possible results as the link bandwidth is same transmissino
> rate is same.

Smaller packets will generally result in less effective use of link
bandwidth from either increased overhead due to a higher ratio of packet
overhead to payload, or added CPU load resulting in a router being able to
process fewer packets in a given time interval, or some combination of
both.

Smaller packets have the one advantage of not "plugging up" a link as much
since there is less time to complete sending single packets and thus it
doesn't take as long to get to and send the next packet in the queue. This
can result in lower latency across the link for other small-packet
applications.

You generally want to avoid packet fragmentation on a link though, so you
most likely do *not* want to intentionally set a small MTU to try to keep
packet sizes small.

> And how it can be  ensured that  video packet are not lost during
> other TCP communication like ftp on the link shared for ftp and video
> confrencing...?

Looks at QoS and ACLs. You can prioritize protocols you care about over
those that you don't. You can also reserve bandwidth in some cases, but it
depends what you're running (hardware and software load), and what you
network can support.

     -Bill

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Waveform Technology
UNIX Systems Administrator