P-2302HW/HWL-P1 Series User’s Guide

9.1.10 MWI (Message Waiting Indication)

Enable Message Waiting Indication (MWI) enables your phone to give you a message–waiting (beeping) dial tone when you have one or more voice messages. Your VoIP service provider must have a messaging system that sends message-waiting-status SIP packets as defined in RFC 3842.

9.1.11 Quality of Service (QoS)

Quality of Service (QoS) refers to both a network's ability to deliver data with minimum delay and the networking methods used to provide bandwidth for real-time multimedia applications.

9.1.11.1 Type of Service (ToS)

Network traffic can be classified by setting the ToS (Type Of Service) values at the data source (for example, at the ZyXEL Device) so a server can decide the best method of delivery, that is the least cost, fastest route and so on.

9.1.11.2 DiffServ

DiffServ is a class of service (CoS) model that marks packets so that they receive specific per- hop treatment at DiffServ-compliant network devices along the route based on the application types and traffic flow. Packets are marked with DiffServ Code Points (DSCPs) indicating the level of service desired. This allows the intermediary DiffServ-compliant network devices to handle the packets differently depending on the code points without the need to negotiate paths or remember state information for every flow. In addition, applications do not have to request a particular service or give advanced notice of where the traffic is going.1

9.1.11.3 DSCP and Per-Hop Behavior

DiffServ defines a new DS (Differentiated Services) field to replace the Type of Service (TOS) field in the IP header. The DS field contains a 2-bit unused field and a 6-bit DSCP field which can define up to 64 service levels. The following figure illustrates the DS field.

Figure 75 DiffServ: Differentiated Service Field

DSCPUnused

(6-bit)(2-bit)

DSCP is backward compatible with the three precedence bits in the ToS octet so that non- DiffServ compliant, ToS-enabled network device will not conflict with the DSCP mapping.

1.The ZyXEL Device does not support DiffServ at the time of writing.

Chapter 9 SIP

145