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Cisco MGX 8850 Multiservice Switch Installation and Configuration
Release 1.1.31, Part Number 78-11223-03 Rev. B0, May 2005
Chapter 2 Module and Service Descriptions
Frame Relay Service Modules
Figure 2-13 BPX 8600 Series Network with SIW Connections
In Figure 2-13, an MGX 8850 node on the right has three-Frame Relay SIW connections terminating on
an FRSM. Three far-end terminations for these connections appear in other parts of Figure 2-13
• ATM FUNI (framed UNI) port on an FRSM
• ATM UNI port on an RPM
• ATM UNI port on a BPX 8600 series BXM card
In addition to frame-to-cell and DLCI-to-VPI/VCI conversion, SIW maps cell loss priority and
congestion data between the Frame Relay and ATM formats and is FRF.8-compliant. It provides full
support for routed and bridged PDUs, transparent and translation modes, and VP translation.
Cell Loss Priority
In addition to frame-to-cell and DLCI-to-VPI/VCI conversion, the SIW feature maps cell loss priority
(CLP) and congestion information from Frame Relay-to-ATM formats and is FRF.8-compliant. It
provides full support for routed and bridged PDUs, transparent and translation modes, and VP
translation. The CLP and congestion parameters can be modified for individual connections with the
cnfchanmap command.
Frame Relay–to–ATM Direction
Each Frame Relay- to-ATM service interworking connection can be configured as one of the following
Discard Eligibility (DE) to cell loss priority (CLP) schemes:
• DE bit in the Frame Relay frame is mapped to the CLP bit of every ATM cell generated by the
segmentation process of the frame.
• CLP is always 0.
• CLP is always 1.
ATM–to–Frame Relay Direction
Each Frame Relay-to-ATM service interworking connection can be configured as one of the following
CLP to DE mapping schemes:
• If one or more ATM cells belonging to a frame has its CLP set, the DE field of the Frame Relay
frame will be set.
FRSM
FRSM
RPM
FR UNI
CPE
T1 or E1
T1 or E1
ATM FUNI CPE
ATM UNI CPE
MGX 8850
MGX 8850
BPX 8620 network
PVCs
17909
BPX 8620
B
X
M
T3, E3, OC3
ATM-UNI CPE