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76 4600 Series IP Telephone Release 2.2 LAN Administrator Guide
With DiffServ, the default DSCP is all zeroes, and represents “no special handling.” RFC 2474
also defines eight “Class Selector Codepoints,” which are the eight DSCP encodings that can
be represented by xxx000, where “x” represents one bit. These Code Selector Codepoints are
considered prioritized, with the larger numeric values having a higher relative order.
DSCP-compliant routers should give the associated packets of larger-valued DSCPs a
“probability of timely forwarding” greater than a packet with a lower-valued DSCP. In addition to
the eight Class Selector Codepoints, a network can define its own DSCPs by defining
encodings that do not terminate in 000. The specific treatment intended by these custom
DSCPs will not necessarily be carried out by routers outside the customer’s own network.
The 4600 Series IP Telephone Installation Guide describes the Local Administrative Option for
QoS. This option allows you to specify Diffserv values for Layer 3 audio (“L3QAUD”) and
signaling traffic (“L3QSIG”) on a phone-by-phone basis.
The Avaya IP Telephones’ DiffServ values change to the values administered on the media
server as soon as the phone registers. For more information, see the document titled
Administration for Network Connectivity (555-233-504). Unless there is a specific need in your
enterprise LAN, we do not recommend you change the default values.
UDP Port Selection
Some data networks include equipment that can perform UDP port selection. This is a
mechanism that gives packets with port numbers in a given range priority over packets with port
numbers outside that range.
To support UDP port selection, the 4600 Series IP Telephones can be administered from the
Avaya Communication Manager Network Region form. Locate specific implementation details
for local administration of MCPORT in the 4600 Series IP Telephone Installation Guide. For
Avaya Communication Manager administration, find implementation details in Administration for
Network Connectivity for Avaya Communication Manager Software. In summary, the system
value MCPORT represents the port on the TN2302AP board. Use this port number to
administer routers, etc. supporting UDP port selection, to maximize priority of voice packets
being exchanged between the PBX and the telephone.
The default value for MCPORT is 1719. Administer the switch to use a port within the proper
range for the specific LAN, and the IP telephone(s) will copy that port. A related parameter is
PORTAUD, which is the RTP port used by the switch. If no UDP port range is administered on
the switch, the IP telephone uses an even-numbered port, randomly selected from the interval
4000 to 10000.