Best Practices - Avaya Application Solutions Deployment Manual

Best practices

To consistently ensure the highest quality voice, Avaya highly recommends consideration of the
following industry best practices when implementing IP Telephony. Note that these suggestions
are options, and might not fit individual business needs in all cases.
QoS/CoS. QoS for voice packets is obtained only after a Class of Service (CoS)
mechanism tags voice packets as having priority over data packets. Networks with periods
of congestion can still provide excellent voice quality when using a QoS/CoS policy. The
recommendation for switched networks is to use IEEE 802.1p/Q. The recommendation for
routed networks is to use DiffServ Code Points (DSCP). The recommendation for mixed
networks is to use both. Port priority can also be used to enhance DiffServ and IEEE
802.1p/Q. Even networks with plentiful bandwidth should implement CoS/QoS to protect
voice communications from periods of unusual congestion, such as a computer virus might
cause. See
information.
Switched network. A fully switched LAN network is a network that allows full duplex and
full endpoint bandwidth for every endpoint that exists on that LAN. Although IP Telephony
systems can work in a shared or hub-based LAN, Avaya recommends the consistently
high results that a switched network lends to IP Telephony.
Network assessment. A Basic Network Readiness Assessment Offer from Avaya is vital
to a successful implementation of IP Telephony products and solutions. Contact an Avaya
representative or authorized dealer to review or certify your network.
offer explains the options that are available with this offer.
VLANs. Placing voice packets on a separate VLAN or subnetwork from data packets is a
generally accepted practice to reduce broadcast traffic. When data is on a shared LAN,
this practice also reduces contention for the same bandwidth as voice. Note that Avaya IP
Telephones provide excellent broadcast storm protection. Other benefits become available
when using VLANs, but there can be a substantial cost with initial administration and
maintenance. Section 3.2.1.2 Using VLANs explains this concept further.
Implementing Communication Manager on a data network
Best practices
for more
Network assessment
Issue 3.4.1 June 2005 281