[asterisk-users] QOS for outgoing SIP calls

[Roger Marquis]

Chris Mason wrote:
> QOS can only be on outgoing, you can't set the priority of a packet
> after you receive it. The only other solution would be the cooperation
> of the ISP to provide QOS upstream of you. Good luck.

QOS is probably not the most precise term as it's normally associated with
RSVP, MPLS, packet headers, etc.  But you can, in Netscreens at least,
define a Guaranteed Bandwidth.

We do this for SIP/IAX IPs, in both outgoing and incoming policies, and it
works both ways.  Audio quality is good and there are no "chan_sip.c: Peer
is now (UNREACHABLE|Lagged)" messages even during long DVD or Bitorrent
xfers.

The reason it works outbound is a no-brainer, but inbound bandwidth is also
effectively guaranteed.  Sure there's no way to control external devices
that ignore ICMP source-quench or break TCP congestion control but those
flows are typically limited to nefarious sources which would not be
responsive to other types of QOS anyhow (BGP being one potential exception).

Roger Marquis