Alcatel-Lucent 7750 SR OS Interface Configuration Manual page 36

Ports
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A SONET/SDH port/path or a TDM port/channel can be configured with the following
encapsulations depending on the MDA type:
→ Frame Relay
→ PPP
→ cHDLC
ATM
Some MDAs support ATM encapsulation on SONET/SDH and TDM ports. The ATM cell
format and can be configured for either UNI or NNI cell format. The format is
configurable on a SONET/SDH or TDM port/channel path basis. All VCs on a path,
channel or port must use the same cell format. The ATM cell mapping can also be
configured on per-interface basis for either Direct or PLCP on some MDAs (for example
ASAP MDA).
Several Alcatel-Lucent Media Dependent Adapters (MDAs) support channelization down
to the DS-0 level. ATM, Frame Relay, PPP, and cHDLC are supported encapsulations on
channelized ports.
Link Aggregation (LAG) — LAG can be used to group up to 16 ports into one logical
link. The aggregation of multiple physical links allows for load sharing and offers
seamless redundancy. If one of the links fails, traffic will be redistributed over the
remaining links. Up to 16 links can be supported in a single LAG, up to 200 LAGs can be
configured on a node.
Multilink Bundles — A multilink bundle is a collection of channels on channelized ports
that physically reside on the same MDA. Multilink bundles are used by providers who
offer either bandwidth-on-demand services or fractional bandwidth services (fraction of a
DS-3/E-3 for example). Multilink bundles are supported over PPP channels (MLPPP) and
ATM channels (IMA).
APS — Automatic Protection Switching (APS) is a means to provide redundancy on
SONET equipment to guard against linear unidirectional or bidirectional failures. The
network elements (NEs) in a SONET/SDH network constantly monitor the health of the
network. When a failure is detected, the network proceeds through a coordinated
predefined sequence of steps to transfer (or switchover) live traffic to the backup facility
(called protection facility.) This is done very quickly to minimize lost traffic. Traffic
remains on the protection facility until the primary facility (called working facility) fault is
cleared, at which time the traffic may optionally be reverted to the working facility.
Bundle Protection Group (BPGrp) — A BPGrp is a collection of two bundles created on
the APS Group port. Working bundle resides on the working circuit of the APS group,
while protection bundle resides on the protection circuit of the APS group. APS protocol
running on the circuits of the APS Group port monitors the health of the SONET/SDH line
and based on it or administrative action moves user traffic from one bundle to another in
the group as part of an APS switch.
Cross connect adaptor (CCA) — A CCA on a VSM module interconnects the egress
forwarding path on the IOM directly to the ingress forwarding path. This eliminates the
7750 SR OS Interface Configuration Guide