Polycom H340 - Manual (Page 21)

21
© 2010 Polycom, Inc. All rights reserved. POLYCOM ® , the Polycom “Triangles” logo and the names and marks associated with Polycom’s products are trademarks and/or service marks of Polycom, Inc.
and are registered and/or common law marks in the United States and various other countries. All other trademarks are property of their respective owners. No portion hereof may be reproduced or
transmitted in any form or by any means for any purpose other than the recipient’s personal use without the express written permission of Polycom
Deploying SpectraLink e340, h340 and i640 Wireless Telephones BEST PRACTICES GUIDE
October 2010
handset are aware of all SVP Servers even if the Registration SVP Server identified by DHCP option 151 goes down,
the handset will still find another SVP Server to use. This is the SVP self-healing concept in action.
Any new or replacement wireless telephones may fail to Check-In if the SVP Server identified by DHCP option 151 is
down. The new handset has not yet learned the list of all SVP Servers and does not get a response to its Check-In
Request. In this case, check the SVP Server identified by DHCP option 151 for operational status.
Note that it is not possible to create an IP array of the SVP Servers in the DHCP option as the handset would not
understand this and would instead display “No SVP Response” on the screen. DHCP option 151 is required for the
handset when it is operating with an IP protocol but is not required when the handset is working in an Telephony
Gateway environment.
When wireless telephones do the first SRP Check-In Request with the registration SVP Server, the registration SVP
will load balance the handsets across all available SVP Servers. It will tell the wireless telephone to Check-In with
another SVP Server based on a load balancing algorithm. This algorithm does not guarantee an even distribution of
handset across all SVP Servers. The wireless telephone will do an SRP Check-In with this designated SVP Server.
Once connected to the SVP Server the handset will establish its connection to the call server or PBX, then will
become operational and be ready to make or receive calls.
4.1.4 DSCP for SVP Deployments
Quality of Service on the wired network must also be taken into consideration. With any VoIP system there is a need
for QoS to be configured from end-to-end in order to effectively ensure good audio quality and performance. Even
systems that are implemented with only voice and no data clients there is still a need for QoS to ensure background
services do not interfere with the audio.
The SVP Server is responsible for providing packet prioritization and timed release for specific time slot deliveries to
all wireless phones. Additionally, the SVP Server must have its QoS tagging configured to use DSCP (Differentiated
Services Code Point) tags that will be properly recognized by the wired and wireless network in order to provide for
low latency packet transport. There are six different DSCP tags that can be configured in the SVP Server. It is best to
always refer to the network manufacturer’s documentation to see what DSCP tags are supported natively and which
will need to be configured to give high priority to all the of handset’s traffic. By default all SVP Server DSCP tags are
set to a value of zero or four. A valid DSCP tag range is from 0 to 63.
The SVP Server has the following packet types to set with DSCP tags:
 Administration – Network administration services such as telnet and FTP
 In Call – All traffic from the SVP Server to handset during an active call
 Standby – All traffic from the SVP to handset during standby
 RTP – All in-call audio traffic from the SVP Server to call server or PBX
 PBX – All control traffic from the SVP Server to the call server or PBX
 Inter-SVPII – All traffic sent to other SVP Servers
The recommended values for these traffic types should be determined by your network infrastructure manufacturer
and/or call server or PBX manufacturer. However, in most environments specific DSCP tag values are considered to
be the expected or default DSCP values.
The recommended DSCP tag values for the defined traffic types are:
 Administration – Default or 0
 In Call – 46
 Standby – 26 (If using PTT the DSCP tag should be changed to 46)
 RTP – 46
 PBX – 24
 Inter-SVPII – 46