LBE Implementation On GÉANT

The Less than Best Effort service can be characterised as: “a very small percentage of network capacity is allocated to LBE so that, under congestion, the BE traffic and any higher priority traffic classes are protected from LBE traffic”. The configuration applied on the routers therefore has to be engineered in order to support this.

The Weighted Round Robin scheduling algorithms implemented on the Juniper router are used to service the LBE queue and the higher priority queues enabled on a given output interface. A very small bandwidth share is assigned to the LBE queue. If another class of traffic is not using its allocated bandwidth, the LBE traffic will get it.

If the LBE service is not deployed within a network, the LBE traffic will be carried as Best Effort (better service than LBE). The network must not change the LBE tagging value.

The DSCP used for LBE is the same DSCP as used for Scavenger on Internet2, namely binary 001000 (decimal 8). Usage of LBE may be voluntary, or a matter of site policy. It is expected that LBE marking will be performed in the end host system voluntarily, or at site border routers by enforced policy. Under the definition of the LBE service, DSCP 8 is used to mark packets can be given a lesser priority than regular Best Effort (BE) traffic.

Any congestion produced at a given interface by LBE traffic is completely transparent to packets belonging to higher-priority classes like Premium IP and BE. Congestion is produced by LBE traffic if the output capacity of the interface is exceeded because of the injection of LBE packets, but both the instantaneous and average BE traffic rate can be handled by the interface without introducing BE packet loss. Performance of packets belonging to higher-priority classes cannot be protected against congestion if the amount of traffic belonging to that class or to higher-priority classes at a given output interface is sufficient to produce either short or long-term congestion, regardless of the presence of LBE packets. Protection of higher priority classes from LBE traffic is supported both with and without congestion. Protection requires that packet loss, one-way delay, instantaneous packet delay variation and throughput of streams belonging to higher-priority traffic classes are not too affected by the presence of LBE traffic, either with or without LBE congestion.