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<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Good Evening <o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">I have seen Optus and Telstra in certain areas with very low MTU below 1200 bytes so causes issues with UDP traffic because no fragmentation. We try to keep the headers below 1000 bytes or recommend
TCP for SIP signalling for Mobile customers. A work around might be to strip not required information from the headers to get the MTU down<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US">Thanks Steve<o:p></o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="mso-fareast-language:EN-US"><o:p> </o:p></span></p>
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<font style="font-family:Calibri;font-size:12pt;font-weight:normal;">Steven Waite</font><br>
<font style="font-family:Calibri;font-size:12pt;font-weight:normal;">Pre-Sales Engineer</font><br>
<font style="font-family:Calibri;font-size:12pt;">Comtel Pty Ltd</font></td>
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<font style="font-family:Calibri;font-size:11pt;color:#000000;"><font style="font-family:Calibri;font-size:11pt;color:#000000;">Tel:
</font>+61 (7) 37154818<font style="font-family:Calibri;font-size:11pt;color:#000000;"><br>
</font><font style="font-family:Calibri;font-size:11pt;color:#000000;">Email: </font>
Steven.Waite@comtel.com.au<font style="font-family:Calibri;font-size:11pt;color:#000000;"><br>
</font><font style="font-family:Calibri;font-size:11pt;color:#000000;">Website: </font>
www.comtel.com.au</font></td>
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<p class="MsoNormal"><b><span lang="EN-US">From:</span></b><span lang="EN-US"> AusNOG <ausnog-bounces@lists.ausnog.net>
<b>On Behalf Of </b>Andras Toth<br>
<b>Sent:</b> Wednesday, 5 January 2022 5:33 PM<br>
<b>To:</b> Matthew H <Matthew@marrold.co.uk><br>
<b>Cc:</b> ausnog@ausnog.net <ausnog@lists.ausnog.net><br>
<b>Subject:</b> Re: [AusNOG] Telstra Mobile NAT64 Gateway dropping UDP?<o:p></o:p></span></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Hi Matthew,<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">As long as you use a DNS hostname instead of an IPv4 literal address, things should work fine for both local apps or tethered/hotspot access because Telstra's DNS servers can do DNS64. Locally on the iPhone you can use a literal IPv4 too
because iOS will do local address translation (CLAT), but it can't translate IPv4 literals to IPv6 for connections via the hotspot.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I don't have any problems with UDP on Telstra IPv6-only connection, I just tried and I can send and receive UDP packets via the Telstra NAT64 gateway when visiting <a href="https://h2o.examp1e.net/">https://h2o.examp1e.net/</a> in a browser
that supports QUIC (because that uses UDP) and since that hostname does not have an IPv6 address, Telstra converts it to IPv6 via DNS64. You can see from the packet capture below that both src and dst addresses are Telstra (one is mine, other side is the DNS64
gateway).<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">18:25:12.424022 IP6 (flowlabel 0xd0300, hlim 64, next-header UDP (17) payload length: 1238) 2001:8004:c81:6820:f5b6:b0a:c39c:7cf.58910 > 2001:8004:11d0:4e2a::84e2:18c.443: [udp sum ok] UDP, length 1230<o:p></o:p></p>
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<p class="MsoNormal">18:25:12.666177 IP6 (hlim 45, next-header UDP (17) payload length: 1288) 2001:8004:11d0:4e2a::84e2:18c.443 > 2001:8004:c81:6820:f5b6:b0a:c39c:7cf.58910: [udp sum ok] UDP, length 1280<br>
18:25:12.667703 IP6 (flowlabel 0xd0300, hlim 64, next-header UDP (17) payload length: 1238) 2001:8004:c81:6820:f5b6:b0a:c39c:7cf.58910 > 2001:8004:11d0:4e2a::84e2:18c.443: [udp sum ok] UDP, length 1230<br>
18:25:12.668868 IP6 (hlim 45, next-header UDP (17) payload length: 1288) 2001:8004:11d0:4e2a::84e2:18c.443 > 2001:8004:c81:6820:f5b6:b0a:c39c:7cf.58910: [udp sum ok] UDP, length 1280<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">I would suggest trying to replicate the issue and gathering a packet capture to see what packets go through and what gets lost. It might be MTU related issues if too large packets can't go through but I can send 1410 bytes packets via the
cellular connection successfully.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">Regards,<o:p></o:p></p>
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<p class="MsoNormal">Andras<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">On Tue, Jan 4, 2022 at 9:34 PM Matthew H <<a href="mailto:Matthew@marrold.co.uk">Matthew@marrold.co.uk</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Hi,<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">The app works fine on other IPv6 only networks with NAT64 in place which appears to satisfy Apple's requirements.<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">We are looking into adding proxies with IPv6 support, however it's likely to take some time and it would be good if we can find a fix / workaround in the meantime<o:p></o:p></p>
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<p class="MsoNormal">Thanks<o:p></o:p></p>
</div>
<p class="MsoNormal"><o:p> </o:p></p>
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<div>
<p class="MsoNormal">On Tue, Jan 4, 2022 at 10:10 AM Troy <<a href="mailto:troy@troykelly.com" target="_blank">troy@troykelly.com</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Apologies for a non answer, but any app (at least with Apple) is required to support IPv6 only networks.<br>
<br>
<a href="https://developer.apple.com/support/ipv6/" target="_blank">https://developer.apple.com/support/ipv6/</a><br>
<br>
Rather than work on a 6 to 4 fix, why not put some energy into supporting IPv6?<o:p></o:p></p>
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<p class="MsoNormal"><b>Regards, Troy</b><o:p></o:p></p>
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<p class="MsoNormal">Brevity is the elixir of life.<o:p></o:p></p>
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<p class="MsoNormal"><span style="font-size:7.5pt">Father Hector McGrath, Pixie 2020</span><o:p></o:p></p>
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<p class="MsoNormal"><br>
<br>
<br>
<br>
-------- Original Message --------<br>
On 4 Jan 2022, 9:03 pm, Matthew H < <a href="mailto:Matthew@marrold.co.uk" target="_blank">
Matthew@marrold.co.uk</a>> wrote:<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Hi,<o:p></o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">We are developing a WebRTC mobile app that sets up a media session via Web Socket and then sends the media via RTP over UDP. It's working on most networks but we've had users report issues with the app when
their iPhone is connected to the Telstra Mobile network.<o:p></o:p></p>
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<p class="MsoNormal">Unfortunately our network only supports IPv4, and after examining the available logs it appears their iPhone only gets an IPv6 address. The Web Socket communication is able to reach us so I assume a NAT64 gateway is in use, but we don't
see any RTP / UDP arrive at our network edge.<o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal">We found a couple of posts that suggest users have had similar issues with UDP being dropped:<br>
<br>
<a href="https://crowdsupport.telstra.com.au/t5/network-roaming/unable-to-stream-video-over-udp-on-ipv6-only-connection/td-p/933472" target="_blank">https://crowdsupport.telstra.com.au/t5/network-roaming/unable-to-stream-video-over-udp-on-ipv6-only-connection/td-p/933472</a><br>
<a href="https://crowdsupport.telstra.com.au/t5/network-roaming/ios-and-ipv6/td-p/931449" target="_blank">https://crowdsupport.telstra.com.au/t5/network-roaming/ios-and-ipv6/td-p/931449</a><o:p></o:p></p>
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<p class="MsoNormal"><a href="https://crowdsupport.telstra.com.au/t5/apple-ios/nordvpn-won-t-connect-on-4g-ios/td-p/932511" target="_blank">https://crowdsupport.telstra.com.au/t5/apple-ios/nordvpn-won-t-connect-on-4g-ios/td-p/932511</a><o:p></o:p></p>
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<p class="MsoNormal"><o:p> </o:p></p>
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<p class="MsoNormal" style="margin-bottom:12.0pt">Is anyone aware of Telstra's NAT64 gateway dropping UDP?
<o:p></o:p></p>
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<p class="MsoNormal">Thanks<o:p></o:p></p>
</div>
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<p class="MsoNormal">Matthew<o:p></o:p></p>
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<p class="MsoNormal">_______________________________________________<br>
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