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Administrator’s Guide for SIP-T2 Series/T19(P) E2/T4 Series/T5 Series/CP860 IP Phones114low-loss, low-latency, low-jitter and assured bandwidth service. Assured Forwarding PHB -- defines a method by which BAs (Bandwidth Allocations) canbe given different forwarding assurances. Default PHB -- specifies that a packet marked with a DSCP value of “000000” gets thetraditional 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 interferencefrom other lower priority traffic. VoIP can guarantee high-quality QoS only if the voice and theSIP packets are given priority over other kinds of network traffic. IP phones support the DiffServmodel 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 can guaranteehigh-quality voice transmission when the voice packets are configured to a higher DSCP value.SIP QoSSIP 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 witha high transmission priority.DSCPs for voice and SIP packets can be specified respectively.NoteProcedureQoS can be configured using the following methods.Central Provisioning(Configuration File).cfgConfigure the DSCPs for voicepackets and SIP packets.Parameters:static.network.qos.rtptosstatic.network.qos.signaltosWeb User InterfaceConfigure the DSCPs for voicepackets and SIP packets.Navigate to:http:///servlet?p=network-adv&q=loadFor voice and SIP packets, the IP phone obtains DSCP info from the network policy if LLDPfeature is enabled, which takes precedence over manual settings. For more information on LLDP,refer to LLDP on page 72.
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