From: Ali Moin Afshari (parspara@parsonline.net)
Date: Fri May 12 2006 - 22:09:40 ART
Hi,
If you are using MQC, define an LLQ policy (i.e. WFQ with a Priority quque):
policy-map VoIP
class Voice
priority 128
class class-default
bandwidth 256
You can have as many other classes for other types of application traffic
you might have in your network, since IP Precedence bit settings 6 and 7 are
reserved for network control information such as routing updates.
As for the classification, I personally prefere DSCP (Differentiated
Services Code Point) marking. For voice, Cisco recommends EF (Expediated
Forwarding = 10111000) classification. You can pickup the RTP packets as
already discussed in recent posts and mark them in a class-map using "set
dscp ef" command, or in older IOSes "set ip dscp ef" command, if memory
serves.
You can, however, use any one of ToS values that does not interfear with
other network operations.
RFC 1349 states ToS byte as:
MSB<-------------------->LSB
P2 P1 P0 T3 T2 T1 T0 CU
P0~P2: IP Precedence
T0~T3: Type of Service
CU: Currently Unused.
The ToS byte is renamed the DS byte with the standardization of the DSCP
field. DSCP is downward compatible with IP Precedence, therefore DSCP EF
maps to IP Precedence 101 or Precedence 5, or Critical. So, you can
actually only mark IP Precedence, if not using DSCP, which is the first
three most significant bits.
If you use DSCP the first three MSBs are Class bits and the next three are
Drop Precedence bits. The Drop Precedence bits give you four Drop classes
with each class having three drop precedences (low, medium, and high), and
is named DSCP AF (Assured Forwarding), which is not recommended for marking
voice packets.
Hope this helps,
Ali
----- Original Message -----
From: "Radioactive Frog" <pbhatkoti@gmail.com>
To: "ccielab" <ccielab@groupstudy.com>
Sent: Saturday, May 13, 2006 3:32 AM
Subject: TOS for Voice traffic priority
> HI Group,
> What is the best way to implement TOS priority for voice traffic?
>
> thanks
> frog
>
> _______________________________________________________________________
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