Yealink VC Series Administrator's Manual

Also see for VC Series: Quick start guide

Contents

Administrator‘s Guide for Yealink Video Conferencing Systems60The Best-Effort service is the default QoS model in the IP networks. It provides noguarantees for data delivery, which means delay, jitter, packet loss and bandwidthallocation are unpredictable. Differentiated Services (DiffServ or DS) is the most widelyused QoS model. It provides a simple and scalable mechanism for classifying andmanaging network traffic and providing QoS on modern IP networks. DifferentiatedServices Code Point (DSCP) is used to define DiffServ classes and is stored in the first sixbits 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, , with regard to guaranteeing how that packet traffic is not delayed ordropped due to interference from other lower priority traffic. VoIP can guaranteehigh-quality QoS only if the voice, video and data packets are given priority over otherkinds of network traffic. Yealink video conferencing systems support the DiffServ modelof QoS. DSCPs for voice, video and data packets that can be specified respectively.Voice QoSTo 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.Video QoSTo ensure acceptable visual quality for video, video packets emanated from the systemshould be configured with a high transmission priority.