Juniper JUNOSE SOFTWARE FOR E SERIES 11.0.X - BGP AND MPLS CONFIGURATION GUIDE 2009-12-30 Configuration Manual page 553

Selective removal of only the service-delimiting tag when layer 2 frames were
received from the CE devices to be sent to the pseudowire
Selective insertion of only the service-delimiting tag when layer 2 frames were
received from the pseudowire to be sent to the CE device
In this release, you can configure an S-VLAN subinterface to enable the provider edge
(PE) device to strip the S-VLAN tag from all packets that enter the MPLS pseudowires
or Martini circuits. This functionality is also referred to as operation of Martini circuits
or MPLS shim interfaces in raw mode. An Ethernet pseudowire can operate in either
tagged mode or raw mode.
In tagged mode, each frame must contain at least one 802.1Q VLAN tag, and
the tag value is processed based on a predefined rule or algorithm at the two
pseudowire end points. This mode is not supported on E Series routers.
In raw mode, if a frame contains an 802.1Q VLAN tag and the tag is not suitable
to be processed at the two pseudowire end points, it passes transparently through
them. The raw mode operation comprises the following tasks:
Identifying the outermost VLAN tag of the layer 2 frame received from the
attachment circuit as a service-delimiting tag, stripping this tag, and then
inserting the resulting frame into the pseudowire connection
Inserting the specified service-delimiting tag on the layer 2 frame received
from the pseudowire connection and then transmitting the resulting frame
to the attachment circuit
You can enable the raw mode configuration only for MPLS shim interfaces stacked
on S-VLAN interfaces. Unified ISSU and high availablity are supported when the router
is configured in either of these ways:
To strip the S-VLAN tags from all packets that enter Martini circuits
When raw mode encapsulation is configured on the VLAN interface stacked
below the MPLS shim interface
When a pseudowire operates in raw mode, service-delimiting tags, if present in the
frame received from the PE device, are stripped from the frame before being sent
to the next processing point in the circuit. The Ethernet frame is encapsulated
according to the algorithm defined for raw mode. If the local PE device detects a
failure on the Ethernet input port, or if the port is disabled, the PE device sends an
appropriate pseudowire status notification message to the remote PE device. In raw
mode, all Ethernet frames received on the local PE device are transmitted to the
remote PE device on a single pseudowire. The raw-mode attribute of the Martini
circuit is sent to the forwarding controller (FC) on the supported line modules and
the Label Distribution Protocol (LDP) is notified of the correct pseudowire type to be
used in the signaling messages.
S-VLAN Subinterface with an Untagged C-VLAN ID Overview on page 518
Related Topics
mpls-relay
route interface
Ethernet Raw Mode Encapsulation for Martini Layer 2 Transport Overview
Chapter 6: Layer 2 Services over MPLS Overview
517