User's Manual

XGS-PON FGW User Manual

Technical Description

Q_PPS_DM_018_V1.3

2.13.2 Upstream QoS

Figure 11: Upstream QoS diagram

In the upstream, Figure 11, for each T-CONT DBA the ingress traffic in the FGW passes by a mapping

block that maps the traffic in one of the eight queues according with the p-bit, (in case the ingress traffic

is untagged a DSCP->p-bit mapping is performed).

These queues have a Strict Priority Scheduler. Packets are stored at the intended T-CONT priority

queue, which is scheduled according to FGW configuration.

The ONT “waits” until the OLT assigns a transmission timeslot for that T-CONT, according to DBA, so

that the most prioritized queues are the ones that transmit first.

In the OLT PON ingress port, traffic is remarked and can be policed per-CoS. The traffic is put into a

Traffic Class according with what is defined in the p-bit/DSCP->queue mapping.

Each of these Traffic Classes has an associated scheduler and policer. Queue management is

performed based on Tail Drop or WRED. Then Traffic Classes to P-bit remarking is done and the traffic

is sent to the uplink, Figure 11.

2.13.3 Dynamic Bandwidth Allocation (DBA)

The DBA (Dynamic Bandwidth Allocation) is available in order to optimize the upstream bandwidth. This

mechanism consists in defining an adequate T-CONT to the service traffic in question. There are five

types of T-CONT, defined by the Fixed, Assured and Maximum Parameters:

• Type 1: Only fixed Bandwidth;

• Type 2: Only Assured Bandwidth;

• Type 3: Assured+Maximum Bandwidth;

• Type 4: Only Maximum Bandwidth (Best Effort);

• Type 5: Fixed+Assured+Maximum Bandwidth.