Ethernet Wire Service; L2Vpn And Ethernet Services Configuration Guide For Cisco Asr 9000 Series Routers, Ios Xr Release 6.3; Igmp Snooping - Cisco ASR 9000 Series Configuration Manuallines

Implementing Point to Point Layer 2 Services
Note Pseudowire grouping is disabled by default.
Network convergence for pseudowires can take longer than the usual two seconds in events such as:
• Manual reload of an active working router
• Interface or controller shutdown
• Reload or shutdown or power disable of a line card on an enabled protect router
• Router Processor fail-over (RPFO) on an enabled protect router
• Simultaneous failure of two controllers or Shared Port Adapters (SPAs)
• Two Automatic Protection Switching (APS) group switchovers

Ethernet Wire Service

An Ethernet Wire Service is a service that emulates a point-to-point Ethernet segment. This is similar to
Ethernet private line (EPL), a Layer 1 point-to-point service, except the provider edge operates at Layer 2 and
typically runs over a Layer 2 network. The EWS encapsulates all frames that are received on a particular UNI
and transports these frames to a single-egress UNI without reference to the contents contained within the
frame. The operation of this service means that an EWS can be used with VLAN-tagged frames. The VLAN
tags are transparent to the EWS (bridge protocol data units [BPDUs])—with some exceptions. These exceptions
include IEEE 802.1x, IEEE 802.2ad, and IEEE 802.3x, because these frames have local significance and it
benefits both the customer and the Service Provider to terminate them locally.
Since the service provider simply accepts frames on an interface and transmits these without reference to the
actual frame (other than verifying that the format and length are legal for the particular interface) the EWS is
indifferent to VLAN tags that may be present within the customer Ethernet frames.
EWS subscribes to the concept of all-to-one bundling. That is, an EWS maps a port on one end to a
point-to-point circuit and to a port on another end. EWS is a port-to-port service. Therefore, if a customer
needs to connect a switch or router to n switches or routers it will need n ports and n pseudowires or logical
circuits.
One important point to consider is that, although the EWS broadly emulates an Ethernet Layer 1 connection,
the service is provided across a shared infrastructure, and therefore it is unlikely that the full interface bandwidth
will be, or needs to be, available at all times. EWS will typically be a sub-line rate service, where many users
share a circuit somewhere in their transmission path. As a result, the cost will most likely be less than that of
EPL. Unlike a Layer 1 EPL, the SP will need to implement QoS and traffic engineering to meet the specific
objectives of a particular contract. However, if the customer's application requires a true wire rate transparent
service, then an EPL service—delivered using optical transmission devices such as DWDM (dense wavelength
division multiplexing), CDWM (coarse wavelength division multiplexing), or SONET/SDH—should be
considered.

IGMP Snooping

IGMP snooping provides a way to constrain multicast traffic at Layer 2. By snooping the IGMP membership
reports sent by hosts in the bridge domain, the IGMP snooping application can set up Layer 2 multicast
forwarding tables to deliver traffic only to ports with at least one interested member, significantly reducing
the volume of multicast traffic.
L2VPN and Ethernet Services Configuration Guide for Cisco ASR 9000 Series Routers, IOS XR Release 6.3.x
Ethernet Wire Service
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