Appendix B - Defining Service Profiles For Generic Voip Gateways; Introduction - Nera WILINK I System Manual

Appendix B - Defining Service Profiles for Generic VoIP Gateways

B.1

Introduction

This section describes the method used for defining the pre-configured Service
Profiles for Generic (3
The same principles can be used for modifying the pre-configured profiles or
creating new ones for VoIP services that have different characteristics.
B.1.1 Priority Marking
We distinguish between two types of Service Profiles for Generic VoIP devices:
Marking is not used : This scenario is applicable when the VoIP device behind
the SU does not support either DSCP or 802.1p marking to distinguish
between different VoIP related traffic types, or when such marking is not used
for any reason. The implication is that a single Continuous Grant connection
should be used for all VoIP traffic.
Marking is used : This scenario is applicable when the VoIP device is capable
of marking the different VoIP related traffic types. The assumption is that 3
different priority marks are used: One for RTP traffic, the second for RTCP and
VoIP Signaling, and a third one for Data (Device Management).
B.1.2 General Assumptions
Protocol Header : 18 bytes for Ethernet L2 header (including 4 bytes for
VLAN), plus 40 bytes of IP/UDP/RTP headers. A total of 58 bytes.
RTCP bandwidth : RFC 3556, Session Description Protocol (SDP) Bandwidth
Modifiers for RTP Control Protocol (RTCP) Bandwidth, states that normally,
the amount of bandwidth allocated to RTCP in an RTP session is 5% of the
session bandwidth. To be on the safe side allocate 10% of the RTP bandwidth
to RTCP.
VoIP Signaling : Cisco states that its IP Phones generate approximately
150 bps signaling traffic (without L2 overhead). To be on the safe side assume
2 Kbps of VoIP Signaling traffic for each POTS interface.
Fax : Fax services are assumed to be based on T.38 Fax Relay. Protocol
Header is assumed to be 58 bytes (same as for RTP).
Data : Data traffic may include ARP, DHCP, TFTP, SNMP, HTTP and other
management protocols. The recommended default bandwidth value is up to
64 Kbps if a Best Effort connection is used for this traffic. If a Continuous
Grant service is used for all VoIP related traffic, a lower bandwidth will be
186
rd party) VoIP devices that do not use the DRAP protocol.
WILINK I MODULAR BASE STATION SYSTEM MANUAL