MLPPP in subscriber management context is supported only over Ethernet transport (MLPPPoX). Native MLPPP over PPP/HDLC links is supported outside of the subscriber management context on the ASAP MDA.
MLPPPoX is supported only on LNS.
Interleaving is supported only on MLPPPoX bundles with a single member link. If more than one link is present in an MLPPPoX bundle, the interleaving is automatically disabled and a SNMP trap is generated. The MIB for this even is defined as tmnxMlpppBundleIndicatorsChange.
If MLPPPoX is enabled on LNS, the load balancing mode between the BB-ISAs within the group should be set to per tunnel. This ensures that all sessions of the same MLPPPoX bundle are terminated on the same BB-ISA. On the LAC, sessions of the same bundle are setup in the same tunnel.
Virtual schedulers are not supported on MLPPPoX tunnels on LNS. However, aggregate-rate-limit is supported.
The aggregate-rate-limit on LNS is automatically adjusted to the minimum value of:
configured aggregate-rate-limit
minimum last mile rate (obtained by LUDB, RADIUS, or PPPoE tags) multiplied by the number of links in the bundle.
The aggregate-rate-limit on the LAC is not adjusted automatically. Therefore, if configured it should be set to a high value and therefore the traffic treatment should rely on QoS performed on the LNS.
The rate (rate-down information) of the member links within the bundle must be the same. Otherwise the lowest rate is selected and applied to all member links.
A single CoA for a rate change (Alc-Access-Loop-Rate-Down) of an individual link in an MLPPPoX bundle modifies rates of all links in the bundle. This is applicable on LNS only.
The range of supported last mile rate (rate-down information) for the member links on an MLPPPoX session is 1 kb/s to 100 Mb/s. On the LNS, obtain the last mile rate:
From the LAC by Tx-Connect-Speed AVP or by standard L2TP encoding as described in the RFC 5515, Layer 2 Tunneling Protocol (L2TP) Access Line Information Attribute Value Pair (AVP) Extensions.
From the LAC by LUDB or RADIUS
Directly on the LNS by LUDB or RADIUS.
The session fails to come up if the obtained rate-down information is outside of the allowable range (1 kb/s to 100 Mb/s).
A session within the MLPPPoX bundle is terminated if the rate-down information for the session is out of bounds (1 kb/s to 100 Mb/s).
If a member link in the last mile fails, traffic is blackholed until the LNS is notified of this failure. The failure detection in the LNS relies on PPP keepalives.
Shaping is performed per MLPPPoX bundle and not individually per member links.
If encapsulation overhead associated with fragmentation is too large in comparison to payload, the fragments are sized based on the encapsulation overhead (to increase link efficiency) instead of on maximum transmission delay.
There can be only a single MLPPPoX bundle per subscriber.
MLPPPoX bundles and non-MLPPPoX (plain L2TP PPPoE) sessions cannot coexist under the same subscriber.
Filters and mirrors (LI) are not supported on MLPPPoX bundles on LAC.
ip-only type mirrors are supported on MLPPPoX bundles.
In MLPPP scenario, downstream traffic is traversing Carrier IOM and BB-ISA twice. This is referred to as dual-pass and effectively cuts the throughput for MLPPP in half (for example, 5Gb/s of MLPPP traffic on a 10Gb/s capable BB-ISA).