Lucent Technologies CBX 3500 Configuration Manual page 309

Beta Draft Confidential
As
header. In an ATM-UNI cell header, the top 2 bits of the Generic Flow Control (GFC)
field are used. In an ATM-NNI cell header, the top 2 bits of the VPI field are used. The
ATM interface of the MPLS router uses this QoS information along with the Trunk ID
to map the ATM cell to a QoS-based RSVP-TE tunnel.
QoS
3
Figure 8-5.
To map cells to MPLS tunnels and provide appropriate QoS treatment, the ATM
interface of the MPLS router implements 4 queues per Lucent Trunk VPN, reading the
top 2 bits in the cell header to queue packets on ingress. On egress, the ATM interface
of the MPLS router rewrites the Trunk ID portion of the cell header before
transmitting the cell to the Lucent ATM switch, and implements scheduling of the 4
queues based on the bandwidth information for the QoS classes that is configured on
the Lucent Trunk VPN.
The Lucent Trunk VPN solution is based on a two-layer MPLS stack as follows:
•
•
The MPLS LSPs or MPLS tunnels work on a node-to-node basis, and carry traffic
from multiple Lucent Trunk VPNs between the two nodes. Each LSP is unidirectional,
and if the MPLS switch supports bidirectional LSPs, this enables reduction of the
number of LSPs that need to be configured and managed.
Note – Tetsing by Lucent and Juniper Networks has identified certain engineering
rules to be followed for maximum line rate performance. For more information see the
CBX 3500 Multiservice Edge Switch Software Release Notice for this release.
ATM Services Configuration Guide for CBX 3500, CBX 500, GX 550, and B-STDX 9000
Figure 8-5 shows, QoS information is embedded in the top 2 bits of the ATM cell
UNI Header
Trunk ID
2 1 0 7 6 5 4
GFC VPI Field
UNI and NNI Cell Header Formats Between Lucent ATM
and MPLS LER Interfaces
The outer label, known as the tunnel label, carries traffic from the ingress MPLS
LER to the egress MPLS LER.
The inner label, known as the VPN label, is used to indicate the trunk to which the
traffic belongs. There is one VPN label per Lucent Trunk VPN.
Configuring ATM Over MPLS Trunks
Path Index QoS
3 2 1 0 11 10
About ATMoMPLS Trunks
NNI Header
Trunk ID Path Index
9 8 7 6 5 4 3 2
VPI Field
1/19/058-11
1 0