Ancp Over Multi-Chassis Link Aggregation - Cisco ASR 9000 Series Service Configuration Manual

Configuring Access Node Control Protocol on Cisco ASR 9000 Series Routers

ANCP over Multi-Chassis Link Aggregation

Multi Chassis Link Aggregation
Multi Chassis Link Aggregation (MC-LAG) provides a simple redundancy mechanism for a Digital
Subscriber Line Access Multiplier (DSLAM) to Cisco ASR 9000 Series Routers connection. The
redundancy is achieved by allowing a dual-homed connection to two routers. There is no added software
complexity on the DSLAM, because the DSLAM views the dual-homed connection as a single LAG.
The DSLAM is known as a dual-homed device (DHD), and each router is known as a point of attachment
(PoA) in MC-LAG terminology. For more detailed information about MC-LAG, see the Cisco ASR 9000
Series Aggregation Services Router L2VPN and Ethernet Services Configuration Guide.
Figure 1
DHD
(DSLAM)
ANCP over MC-LAG
Access Node Control Protocol (ANCP) is required to support a network topology that includes MC-LAG
connections to DSLAMs. CPE circuits connect to DSLAMs and adjust line speeds based on signal
quality with Rate Adaptive DS. Uplinks connect DSLAMs to routers. If the line speed of a circuit
adjusts to a lower data rate than the uplink, subscriber data can be lost on the DSLAM. To prevent data
loss, a DSLAM notifies the router of the new DSL rate with ANCP, and downstream shaping is
dynamically applied on the router such that the data rate of the uplink does not exceed the CPE circuit
data rate.
ANCP applies DSLAM subscriber circuit DSL rate data it learns, to MC-LAG VLAN subinterfaces that
are mapped to the subscriber circuit. The rates are applied to QoS shapers. The DSL rates that ANCP
has applied to the MC-LAG VLAN subinterfaces are distributed by the ANCP application running on
the active PoA for the MC-LAG to the ANCP application that is running on the standby PoA for the
OL-23108-02
MC-LAG connects DSLAM to ASR 9000 Series Routers
ICCP Group
Standby PoA
(ASR 9000)
MC-LAG
Active PoA
(ASR 9000)
DHD: Dual-Homed Device
PoA: Point of Attachment
ICCP: Inter-Chassis Communication Protocol
MC-LAG: Multi-Chassis Link Aggregation Group
Cisco ASR 9000 Series Aggregation Services Router Modular Quality of Service Configuration Guide
Information About Configuring ANCP on Cisco ASR 9000 Series Routers
ICCP
QC-93