Atom Vccv Signaling; Selection Of Atom Vccv Switching Types - Cisco ASR 900 Series Manual

Any Transport over MPLS Virtual Circuit Connection Verification

AToM VCCV Signaling

One of the steps involved in Any Transport over Multiprotocol Label Switching (AToM) virtual circuit (VC)
setup is the signaling of VC labels and AToM Virtual Circuit Connection Verification (VCCV) capabilities
between AToM VC endpoints. The device uses an optional parameter, defined in the Internet Draft
draft-ieft-pwe3-vccv-01.txt, to communicate the AToM VCCV disposition capabilities of each endpoint.
The AToM VCCV disposition capabilities are categorized as follows:
• Applications—MPLS LSP Ping and Internet Control Message Protocol (ICMP) Ping are applications
that AToM VCCV supports to send packets inband of an AToM PW for control purposes.
• Switching modes—Type 1 and Type 2 are switching modes that AToM VCCV uses for differentiating
between control and data traffic.
The table below describes AToM VCCV Type 1 and Type 2 switching modes.
Table 6: Type 1 and Type 2 AToM VCCV Switching Modes
Switching Mode
Type 1
Type 2

Selection of AToM VCCV Switching Types

Cisco devices always use Type 1 switching, if available, when they send MPLS LSP Ping packets over an
Any Transport over Multiprotocol Label Switching (AToM) virtual circuit (VC) control channel. Type 2
switching accommodates those VC types and implementations that do not support or interpret the AToM
control word.
The table below shows the AToM Virtual Circuit Connection Verification (VCCV) switching mode advertised
and the switching mode selected by the AToM VC.
Table 7: AToM VCCV Switching Mode Advertised and Selected by AToM Virtual Circuit
Type Advertised
AToM VCCV not supported
Type 1 AToM VCCV switching
Type 2 AToM VCCV switching
Type 1 and Type 2 AToM VCCV switching
MPLS Basic Configuration Guide, Cisco IOS XE Everest 16.5.1 (Cisco ASR 900 Series)
70
MPLS LSP Ping, Traceroute, and AToM VCCV
Description
Uses a Protocol ID (PID) field in the AToM control
word to identify an AToM VCCV packet.
Uses an MPLS Router Alert Label above the VC label
to identify an AToM VCCV packet.
Type Selected
–
Type 1 AToM VCCV switching
Type 2 AToM VCCV switching
Type 1 AToM VCCV switching