User's Manual

hwc_vnsconfiguration.fm
Virtual Network configuration
Defining priority level and service class for VNS traffic
A31003-W1050-U100-2-7619,
March 2008
HiPath Wireless Controller, Access Points and Convergence Software V5 R1 , C20/C2400 User Guide 219
6.13 Defining priority level and service class for VNS traffic
Voice over Internet Protocol (VoIP) using 802.11 wireless local area networks are
enabling the integration of internet telephony technology on wireless networks.
Various issues including Quality-of-Service (QoS), call control, network capacity,
and network architecture are factors in VoIP over 802.11 WLANs.
Wireless voice data requires a constant transmission rate and must be delivered
within a time limit. This type of data is called isochronous data. This requirement
for isochronous data is in contradiction to the concepts in the 802.11 standard that
allow for data packets to wait their turn, in order to avoid data collisions. Regular
traffic on a wireless network is an asynchronous process in which data streams
are broken up by random intervals.
To reconcile the needs of isochronous data, mechanisms are added to the
network that give voice data traffic or another traffic type priority over all other
traffic, and allow for continuous transmission of data.
In order to provide better network traffic flow, the Controller, Access Points and
Convergence Software provides advanced Quality of Service (QoS)
management. These management techniques include:
• WMM (Wi-Fi Multimedia) – Enabled on individual VNSs, the standard
provides multimedia enhancements that improve the user experience for
audio, video, and voice applications. WMM is part of the 802.11e standard for
QoS.
• IP ToS (Type of Service) or DSCP (Diffserv Codepoint) – The ToS/DSCP
field in the IP header of a frame is used to indicate the priority and Quality of
Service for each frame. The IP TOS and/or DSCP is maintained within CTP
(CAPWAP Tunneling Protocol) by copying the user IP QoS information to the
CTP header—this is referred to as Adaptive QoS.
6.13.1 Defining the service class for the VNS
Service class is determined by the combination of the following operations:
• The class of treatment given to a packet. For example, queuing or per hop
behavior (PHB).
• The packet marking of the output packets (user traffic and/or transport).
Service class name (number) Priority level
Network Control (7) 7 (highest priority)
Premium (Voice) (6) 6
Platinum (video) (5) 5
Gold (4) 4