Customer Equipment VLAN (CE-VLAN or 802.1p) This CoS ID refers to the CoS
(802.1p) bits in the IEEE 802.1Q tag in a tagged Ethernet service frame. These are
usually referred to as the priority bits. Using this MEF-defined approach, up to eight
classes of service can be provided. A bandwidth profile and performance parameters,
which can be enforced by the Service Provider,16 are associated with each CoS. The
user-defined CE-VLAN value(s) may be mapped by a service provider to its own CoS
and acted on accordingly.
DiffServ Code Points (DSCP)/IP Type of Service (ToS) The DSCP or IP ToS values
in an IP header can be used to determine the CoS. IP ToS provides 8 CoS values,
referred to as IP precedence; this is similar to the 802.1p bits in the VLAN tag of
an Ethernet frame. DSCP, by contrast, specifies 64 different CoS values that correspond
to a much more granular performance definition. In addition, DSCP provides a
more robust capability that defines the performance over multiple hops in the network
(referred to as per-hop behaviors or PHBs) and attempts to provide a QoS.
Types of Bandwidth Profiles There are three types of bandwidth profiles defined
by the MEF; the initial focus has been on the ingress traffic only.
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