Re: [PLUG] Are DNS requests with bad checksums dropped?

[Fred Stluka via plug <plug@lists.phillylinux.org>]

Michael,

UDP is better for video (and for audio) because it tolerates
dropped packets better than TCP which insists on an ACK
and retries till it gets one.  TCP is better for complete data,
but UDP is better for audio and video where a little data
dropout doesn't matter.  It's better to have missing bits
in audio and video than to have it slowed down due to
retries.

No one minds a little static, but listening to someone talk
in slow-motion is really annoying to the human ear.

--Fred
------------------------------------------------------------------------
Fred Stluka -- http://bristle.com -- Glad to be of service!
------------------------------------------------------------------------

On 8/15/22 6:32 PM, Michael Lazin via plug wrote:
>      localhost.46633 > localhost.domain: [bad udp cksum 0xfe90 -> 0x1013!] 32170+ [1au] A?rr2---sn-bvvbax-2iae.googlevideo.com  <http://rr2---sn-bvvbax-2iae.googlevideo.com>. ar: . OPT UDPsize=1200 (65)
>      localhost.domain > localhost.46633: [bad udp cksum 0xfe90 -> 0x64b5!] 32170 ServFail* q: A?rr2---sn-bvvbax-2iae.googlevideo.com  <http://rr2---sn-bvvbax-2iae.googlevideo.com>. 0/0/1 ar: . OPT UDPsize=65494 (65)
>      localhost.46633 > localhost.domain: [bad udp cksum 0xfe90 -> 0x76f4!] 5806+ [1au] AAAA?rr2---sn-bvvbax-2iae.googlevideo.com  <http://rr2---sn-bvvbax-2iae.googlevideo.com>. ar: . OPT UDPsize=1200 (65)
>      localhost.domain > localhost.46633: [bad udp cksum 0xfe90 -> 0xcb96!] 5806 ServFail* q: AAAA?rr2---sn-bvvbax-2iae.googlevideo.com  <http://rr2---sn-bvvbax-2iae.googlevideo.com>. 0/0/1 ar: . OPT UDPsize=65494 (65)
>      localhost.44911 > localhost.domain: [bad udp cksum 0xfe90 -> 0x3214!] 25187+ [1au] A?rr2---sn-bvvbax-2iae.googlevideo.com  <http://rr2---sn-bvvbax-2iae.googlevideo.com>. ar: . OPT UDPsize=1200 (65)
>
> I had a discussion with a friend of mine about unusual UDP traffic I have seen, and my friend argues that UDP is standard for streaming video today, but when I watch Youtube and run tcpdump, you can see that there are bad packets.
> I want to know why UDP is superior for streaming video, because my understanding is that bad packets like this are dropped if they are UDP.  Is this not the case?  Can someone please clarify this?  I got this output from running
> "tcpdump -vvfA" while watching Youtube on an Ubuntu 22.04 laptop.
>
> Thank you,
>
> Michael Lazin
>
>
> Michael Lazin
>
> .. τὸ γὰραὐτὸ νοεῖν ἐστίν τε καὶ εἶναι.
>
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