Cisco Cisco IOS Software Release 12.0(13)S7

Accepting frames from the Q.922 data link layer for transmission on the bundle interface

Operating frame fragmentation procedures

Scheduling frames for transmission on individual bundle links

Reassembling received frame fragments for forwarding to the Q.922 data link layer

6PE is a PE router running dual-stack IPv4 and IPv6. 6PE enables transport of IPv6 traffic over an MPLS 
IPv4 network. The Border Gateway Protocol (BGP) is used as the label distribution protocol while 
MPLS is used as the forwarding mechanism inside the MPLS cloud. 

In using Frame Relay over IPv6, only PE routers need to support IPv6. The IPv6 traffic received from 
the IPv6 network is transported to the destination IPv6 network using the MPLS infrastructure in the 
core (in the MPLS core, all control protocols, including label distribution and interior gateway protocols, 
remain IPv4). 

Multiprotocol BGP is used between 6PEs to exchange IPv6 reachability information. An ingress 6PE 
knows the IPv6 address of the remote egress 6PE (that is, a BGP next-hop address) needed to reach a 
destination IPv6 subnet. This IPv6 address for the BGP next hop contains an embedded IPv4 address 
that is the IPv4 address of the BGP speaker.

BGP is used to bind a label to each advertised destination IPv6 prefix. Multiprotocol BGP uses two 
labels in the MPLS header, the IPv4 label (which is the top label) and aggregate IPv6 label (which is the 
lower label) for the destination IPv6 prefix. The aggregate IPv6 label is allocated by the egress 6PE to 
form a local pool of 16 labels (a pool of 16 labels used for all IPv6 prefixes). 

The term “QoS service model” is used in this document to define a specific combination of QoS features 
and functionality deployed by SPs. The QoS nC/nD and 1c/1D models are supported in the 12.0(33)S 
release. 

In the nC/nD model, there are a number (n) of DLCIs configured under a single physical interface. Each 
DLCI supports a single customer and is attached to a logical subinterface. The customer-specific 
modular quality of service (QoS) command-line interface (CLI) (MQC) configuration is also attached to 
the subinterface. Typically the customer buys an aggregate service, which is then divided into different 
classes. This model is generally applied to point-to-point rather point-to-multipoint subinterfaces.

In the 1c/1D model, a single customer is provisioned on the main interface with a single DLCI. The MQC 
configuration is attached on the main interface.

IPv6 Frame Relay supports the QoS 1C/nD model.