Yealink SIP-T48G Administrator's Manual

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Yealink SIP-T48G Administrator's Manual Manual pdf 457 page image

Configuring Advanced Features443bits of the ToS (Type of Service) field. Each router on the network can provide QoSsimply based on the DiffServ class. The DSCP value ranges from 0 to 63 with each DSCPspecifying a particular per-hop behavior (PHB) applicable to a packet. A PHB refers tothe packet scheduling, queuing, policing, or shaping behavior of a node on any givenpacket.Four standard PHBs available to construct a DiffServ-enabled network and achieveQoS: Class Selector PHB -- backwards compatible with IP precedence. Class Selectorcode 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 nodesthat implement IP precedence-based classification and forwarding. Expedited Forwarding PHB -- the key ingredient in DiffServ model for providing alow-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” getsthe traditional best effort service from a DS-compliant node.VoIP is extremely bandwidth and delay-sensitive. QoS is a major issue in VoIPimplementations, regarding how to guarantee that packet traffic not be delayed ordropped due to interference from other lower priority traffic. VoIP can guaranteehigh-quality QoS only if the voice and the SIP packets are given priority over other kindsof network traffic. IP phones support the DiffServ model of QoS.Voice QoSIn order to make VoIP transmissions intelligible to receivers, voice packets should not bedropped, excessively delayed, or made to suffer varying delay. DiffServ model canguarantee high-quality voice transmission when the voice packets are configured to ahigher DSCP value.SIP QoSSIP protocol is used for creating, modifying and terminating two-party or multi-partysessions. To ensure good voice quality, SIP packets emanated from IP phones should beconfigured with a high transmission priority.DSCPs for voice and SIP packets can be specified respectively.ProcedureQoS can be configured using the configuration files or locally.Configuration File .cfgConfigure the DSCPs forvoice packets and SIPpackets.