[cisco-voip] Cisco IOS dial-peers AF31 (default) change to CS3

[Anthony Holloway]

Well Scuba Jason,

IOS has always marked control traffic as AF31, as well as SCCP control
traffic for registered media resources.

The two things I have seen recommended and done are:

1. Change the settings per dial-peer / sccp config (technically this is ip
precedence 3, which aligns loosely with cs3, as they share the first 3 bits)
2. Use a match-any for cs3 and af31 in your class maps

>From the QoS SRND:

"The QoS Baseline recommends marking Call-Signaling to CS3. However,
currently most Cisco IP Telephony products mark Call-Signaling to AF31. A
marking migration from AF31 to CS3 is under way within Cisco, but in the
interim it is recommended that both AF31 and CS3 be reserved for
Call-Signaling and that Locally-Defined Mission-Critical Data applications
be marked to a temporary placeholder non-standard DSCP, such as 25. Upon
completion of the migration, the QoS Baseline marking recommendations of
CS3 for Call-Signaling and AF31 for Locally-Defined Mission-Critical Data
applications should be used. These marking recommendations are more in line
with RFC 2474 and RFC 2597."

Source
<https://www.cisco.com/c/en/us/td/docs/solutions/Enterprise/WAN_and_MAN/QoS_SRND/QoS-SRND-Book/QoSIntro.html>

Though, this "transition period" seems to have gone on indefinitely.

FWIW, I have never seen a global command to switch it, and the documentation
<https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/vcr2/vcr2-cr-book/vcr-i1.html#wp3986668457>
doesn't tell us that there is one for dial-peer signaling.  The sccp
command is global.

Stay buoyant!

On Thu, Apr 23, 2020 at 1:55 PM Jason Aarons <scubajasona at gmail.com> wrote:

> CallManager marks control traffic as CS3, but just see that IOS-XE on 4431
> 16.09.05 marks control as AF31 by default.
>
> Is there a global IOS command to change IOS-XE to use CS3 ? Rather then on
> a per dial-peer level?
>
> All my class maps to protect control are based on CS3.
>
> Hope all is well here.  Work changed emails couple times and that created
> challenges! I still read every week, but changed emails so I can actually
> reply again!
>
> -jason
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