Don't know how to respond via 'SIP/2.0/TCP'

Who can tell me the meaning of this warning: (and how to stop it)

[Jan 8 14:19:15] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:17] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:20] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:26] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:28] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:31] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:33] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:39] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:42] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:44] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:47] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:52] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:55] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:19:58] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:20:00] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:20:06] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:20:09] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:20:11] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:20:14] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:20:20] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:20:22] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’
[Jan 8 14:20:25] WARNING[3675]: chan_sip.c:9010 check_via: Don’t know how to respond via ‘SIP/2.0/TCP’

It looks like a client (phone or softphone) is trying to register with your Asterisk server using TCP, and SIP 2.0.

Check your clients and see if they can be “downgraded” to use earlier versions of SIP and UDP (not TCP).

Hello,
You client is using SIP over TCP which asterisk does not support. You need to either tell your client to use SIP over UDP or use some software that will change the transport to UDP for asterisk to use.

Thanks
-TheLostPacket