Owner's Manual

782
Chapter 30. vMAN (PBN) 8800 Chassis Switch
In Figure 97, the switch accepts all tagged (C-tag) and untagged VLAN frames on vMAN
access ports 1.1 and 1.2. The switch then adds the S-tag to the frames and switches the
frames to network ports 2.1 and 2.2. When the 802.1ad frames reach the PB egress port, the
egress switch removes the S-tag, and the VLAN traffic exits the egress access port in its
original form.
When the switch in Figure 97 acts as the egress switch for a vMAN, vMAN frames arrive on
network ports 2.1 and 2.2. The switch accepts only those frames with the correct S-tag,
removes the S-tags, and switches those frames to access ports 1.1 and 1.2. Unless special
configuration options are applied, the egress frames are identical to ingress frames of the
vMAN. (Configuration options are described in
vMAN Configuration Options and Features on
page 782.)
Figure 98 shows that the S-tags and C-tags used in vMAN frames contain more than just
customer and service VLAN tags.
Figure 98. S-tag and C-tag Components
Each S-tag and C-tag contains an ethertype, a Class of Service (COS), and a VLAN ID. The
ethertype is described in
Secondary Ethertype Support on page 783, and the COS is
described in QoS Support on page 784. The service VLAN ID (SVID) is the VLAN tag you
assign to a vMAN when you create it (configure vman <vman-name> tag <tag>). The
customer VLAN ID (CVID) represents the customer VLAN tag for tagged VLAN traffic.
The service provider configures the vMAN to support the customer traffic. The vMAN service
provider does not need to know anything about the VLAN traffic in the vMAN. The service
provider simply manages the vMAN, and the ingress VLAN traffic is managed by the
customer or another service provider. This separation of VLAN and vMAN management
reduces the dependence of the separate management teams on each other, and allows both
management teams to make changes independent of the other.
vMAN Configuration Options and Features
This section describes the following vMAN (PBN) configuration options and features:
MAC DA (48b)
MAC SA (48b)
vMAN tag or S-tag (32b, optional)
VLAN tag or C-tag (32b, optional)
L2 PDU: if IP packet, it may include
TOS / Diffserv-Codepoint field
S-ethertype (16b)
C-ethertype (16b)
S-COS (4b)
C-COS (4b)
SVID (12b)
CVID (12b)
EX_vman_0036