Rsvp And Rtcp; Vlan Considerations - Avaya 4600 Series Administrator's Manual

RSVP and RTCP

Avaya IP Telephones implement the Resource ReSerVation Protocol (RSVP) to support WAN bandwidth
management. RSVP is administered from the media server. Avaya IP Telephones implement the RTP
Control Protocol (RTCP) so that Avaya's Voice over IP (VoIP) Monitoring Manager (VMON) software
can provide real-time monitoring and historical data of the audio quality of VoIP calls.
Resource ReSerVation Protocol (RSVP) is an IETF-standard protocol used by hosts to request resource
reservations throughout a network. RSVP-compliant hosts send messages through a network to receivers,
which respond with messages requesting a type of service and an amount of resources (e.g., bandwidth)
to carry out that service. The host is responsible for admitting (approving) or rejecting (denying) the
request. In a QoS context, RSVP is used to try to reserve bandwidth in the network for voice calls, on a
call-by-call basis. If insufficient bandwidth is available for the target voice quality, a request to use
network bandwidth for a voice call will be rejected.
RTP Control Protocol (RTCP), as its name implies, is a protocol that provides control functions for Real-
time Transport Protocol (RTP). RTP provides end-to-end network services for real-time data (such as
Voice over IP), but does not provide a reservation function, nor does it guarantee any level of QoS. RTCP
supplements RTP by monitoring the quality of the RTP services and can provide real-time information to
users of an RTP service. In a QoS context, RTCP is valuable for identifying information such as packet
loss, 1-way delay (how long a packet has to go from source A to destination B), jitter, etc. RTCP itself
does not improve QoS, but it provides information to help identify where problem areas might be.
You cannot change the telephone's RSVP or RTCP parameters directly on the telephone or via TFTP or
DHCP administration. The only way to change these parameters is by appropriate administration of the
switch. See your Avaya media server administration material for more detail.

VLAN Considerations

If your LAN environment does not include Virtual LANs (VLANs), ignore this section. Otherwise, this
section contains information on how to administer 4600 Series IP Telephones to minimize registration
time and maximize performance in a VLAN environment.
The system value L2QVLAN (initially set to "0"), identifies the 802.1Q VLAN IDentifier. This default
value indicates "priority tagging" as defined in IEEE 802.IQ Section 9.3.2.3, which specifies that the
Ethernet switch in your network closet should automatically insert the default VLAN for the switch port
without changing the user priority of the frame (cf. IEEE 802.1D and 802.1Q).
However, you might not want the default VLAN to be used for voice traffic; for example, you may have
administered a VLAN specifically for IP telephony. In this case, you need to ensure the switch is
configured to allow frames tagged by the 4600 Series IP Telephone through without overwriting or
removing them. In addition, you will want to set the system value L2QVLAN to the VLAN ID
appropriate for your voice LAN.
Another system value you can administer as of Release 1.8 software, is VLANTEST, which stands for
the number of seconds the 4600 IP Series Telephone waits for a DHCPOFFER message when using a
non-zero VLAN ID (the default is "60" seconds). Using this value insures the telephone can return to the
default VLAN if an invalid VLAN ID is administered or if the phone is moved to a port where the value
in L2QVLAN is invalid. The default value is fairly long, to allow for the scenario that a major power
interruption is causing the 4600 Series IP Telephones to restart, but time should be allowed for network
4600 Series IP Telephone Release 2.1 LAN Administrator's Guide
July 2004
Server Administration
VLAN Considerations
65