User's Manual

Chapter 15 VoIP
B222s User’s Guide
141
DiffServ
DiffServ is a class of service ( CoS) m odel that m arks packets so t hat t hey receive specific per- hop
treat m ent at DiffServ- com pliant network devices along the rout e based on t he applicat ion t ypes
and t raffic flow. Packet s are m arked with DiffServ Code Point s ( DSCP) indicating t he level of service
desired. This allows t he int erm ediary DiffServ- com pliant net work devices t o handle t he packet s
different ly depending on t he code points wit hout t he need t o negot iat e pat hs or rem em ber st at e
inform ation for every flow. I n addition, applicat ions do not have t o request a part icular service or
give advanced not ice of where the t raffic is going.
3
DSCP and Per-Hop Behavior
DiffServ defines a new DS ( Differentiat ed Services) field to replace the Type of Service (TOS) field
in the I P header. The DS field cont ains a 2- bit unused field and a 6- bit DSCP field w hich can define
up t o 64 service levels. The following figure illust rat es the DS field.
DSCP is backward com patible wit h t he t hree precedence bit s in t he ToS oct et so that non- DiffServ
com pliant , ToS-enabled net work device w ill not conflict wit h t he DSCP m apping.
Figure 79 DiffServ: Differentiat ed Service Field
The DSCP value determ ines t he forwarding behavior, t he PHB ( Per- Hop Behavior) , t hat each packet
get s across t he DiffServ net work. Based on t he m arking rule, different kinds of t raffic can be
m ar ked for different priorit ies of forwarding. Resources can t hen be allocated according t o t he DSCP
values and t he configured policies.
15.8.4 Phone Services Overview
Supplem ent ar y services such as call hold, call waiting, and call t ransfer. are generally available from
your VoI P service provider. The LTE Device support s the following services:
• Call Hold
• Call Wait ing
• Making a Second Call
• Call Transfer
• Three-Way Conference
• I nt ernal Calls
• Do not Dist urb
Note: To t ake full advant age of t he supplem ent ary phone services available t hrough t he
LTE Device's phone port s, you m ay need to subscribe t o t he services from your VoI P
service provider.
3. The LTE Device does not support DiffServ at the time of writing.
DSCP
( 6- bit )
Unused
(2-bit)