Interface Configuration
7750 SR Interface Configuration Guide Page 51
Multilink Frame Relay
MLFR is a bundling capability allowing users to spray FR frame fragments over multiple T1/E1
links. This allows a dynamic provisioning of additional bandwidth by adding incremental
bandwidth between T1/E1 and DS3/E3. A MLFR bundle increases fault tolerance and improves
QoS characteristics since one single large frame of low priority cannot block a higher priority
frame.
A MLFR supports up to eight (8) member links and a maximum of 128 bundles with up to 336 T1
/ 252 E1 members links can be configured per MDA. NxDS0 circuits or higher speed circuits are
not supported.
The MLFR implementation supports FRF.16.1 bundle link integrity protocol to verify
serviceability of a member link.
MLFR Bundle Data Plane
FRF.16.1 reuses the UNI/NNI fragmentation procedures defined in FRF.12. Frames on all FR
SAP on the MLFR bundle have the UNI/NNI fragmentation header added regardless if they are
fragmented or not. A separate sequence number state machine is used for each FR SAP configured
on the bundle. The fragmentation threshold is configurable in the range 128-512 bytes.
In order to provide priority based scheduling of the FR SAP fragments over the bundle links, the
user configures a FR scheduling class for each FR SAP configured on the bundle. As in MC-
MLPPP, four scheduling classes are supported.
A separate fragmentation context is used by each FR SAP. FR SAPs of the same scheduling class
share the same egress FR scheduling class queue with fragments of each SAP packets stored
contiguously. The fragments from each scheduling class queue are then sprayed over the member
links. Furthermore, the user may select the option to not fragment but spray the FR frames with
the fragmentation header included over the member links.
Received fragments over the member links are re-assembled on a per SAP basis to re-create the
original FR frame.
A user is not allowed to add an FR SAP with FRF.12 e2e fragmentation enabled to an MLFR
bundle. Conversely, the user cannot enable FRF.12 e2e fragmentation on an FR SAP configured
on an MLFR bundle. If an FR frame with the e2e fragmentation header is received on a bundle, it
is forwarded if the FR SAP is part of an Fpipe service. It will be discarded if the FR SAP is part of
any other service.
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