Yealink SIP-T27P [612/841] Sip qos

Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series IP Phones

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simply based on the DiffServ class. The DSCP value ranges from 0 to 63 with each DSCP

specifying a particular per-hop behavior (PHB) applicable to a packet. A PHB refers to

the packet scheduling, queuing, policing, or shaping behavior of a node on any given

packet.

Four standard PHBs available to construct a DiffServ-enabled network and achieve

QoS:

 Class Selector PHB -- backwards compatible with IP precedence. Class Selector

code points are of the form “xxx000”. The first three bits are the IP precedence bits.

These class selector PHBs retain almost the same forwarding behavior as nodes

that implement IP precedence-based classification and forwarding.

 Expedited Forwarding PHB -- the key ingredient in DiffServ model for providing a

low-loss, low-latency, low-jitter and assured bandwidth service.

 Assured Forwarding PHB -- defines a method by which BAs (Bandwidth Allocations)

can be given different forwarding assurances.

 Default PHB -- specifies that a packet marked with a DSCP value of “000000” gets

the traditional best effort service from a DS-compliant node.

VoIP is extremely bandwidth and delay-sensitive. QoS is a major issue in VoIP

implementations, regarding how to guarantee that packet traffic not be delayed or

dropped due to interference from other lower priority traffic. VoIP can guarantee

high-quality QoS only if the voice and the SIP packets are given priority over other kinds

of network traffic. IP phones support the DiffServ model of QoS.

Voice QoS

In order to make VoIP transmissions intelligible to receivers, voice packets should not be

dropped, excessively delayed, or made to suffer varying delay. DiffServ model can

guarantee high-quality voice transmission when the voice packets are configured to a

higher DSCP value.

SIP QoS

SIP protocol is used for creating, modifying and terminating two-party or multi-party

sessions. To ensure good voice quality, SIP packets emanated from IP phones should be

configured with a high transmission priority.

DSCPs for voice and SIP packets can be specified respectively.

Procedure

QoS can be configured using the configuration files or locally.

Configuration File

<y0000000000xx>.cfg

Configure the DSCPs for

voice packets and SIP

packets.

Parameters: