Compound Module AFxyQueue

This is an example queue, that implements one class of the Assured Forwarding PHB group (RFC 2597).

Packets with the same AFx class, but different drop priorities arrive at the afx1In, afx2In, and afx3In gates. The received packets are stored in the same queue. Before the packet is enqueued, a RED dropping algorithm may decide to selectively drop them, based on the average length of the queue and the RED parameters of the drop priority of the packet.

The afxyMinth, afxyMaxth, and afxyMaxp parameters must have values that ensures that packets with lower drop priorities are dropped with lower or equal probability than packets with higher drop priorities.

See also: DiffservQueue

Usage diagram:

The following diagram shows usage relationships between types. Unresolved types are missing from the diagram.

Inheritance diagram:

The following diagram shows inheritance relationships for this type. Unresolved types are missing from the diagram.

Used in compound modules:

Parameters:

Properties:

Gates:

Unassigned submodule parameters:

Source code:

//
// This is an example queue, that implements
// one class of the Assured Forwarding PHB group (RFC 2597).
//
// Packets with the same AFx class, but different drop priorities
// arrive at the afx1In, afx2In, and afx3In gates. The received
// packets are stored in the same queue. Before the packet
// is enqueued, a RED dropping algorithm may decide to selectively
// drop them, based on the average length of the queue and the RED parameters
// of the drop priority of the packet.
//
// The afxyMinth, afxyMaxth, and afxyMaxp parameters must have values that
// ensures that packets with lower drop priorities are dropped with lower
// or equal probability than packets with higher drop priorities.
//
// @see ~DiffservQueue
//
module AFxyQueue
{
    parameters:
        double wq = default(0.002); // smoothing factor, i.e.  the weight of the current queue length in the averaged queue length

        double afx1Minth = default(50);  // minimum queue length thresholds for dropping packets with drop priority 1
        double afx1Maxth = default(100); // maximum queue length thresholds for dropping packets with drop priority 1
        double afx1Maxp = default(0.3);  // maximum probability of drop when the queue length is between thresholds for drop priority 1

        double afx2Minth = default(30); // minimum queue length thresholds for dropping packets with drop priority 2
        double afx2Maxth = default(60); // maximum queue length thresholds for dropping packets with drop priority 2
        double afx2Maxp = default(0.6); // maximum probability of drop when the queue length is between thresholds for drop priority 2

        double afx3Minth = default(10); // minimum queue length thresholds for dropping packets with drop priority 3
        double afx3Maxth = default(40); // maximum queue length thresholds for dropping packets with drop priority 3
        double afx3Maxp = default(0.9); // maximum probability of drop when the queue length is between thresholds for drop priority 3

        @display("i=block/queue;q=l2queue");

    gates:
        input afx1In;
        input afx2In;
        input afx3In;
        output out;
    submodules:
        fifoQueue: FIFOQueue {
            @display("p=251,102");
        }
        redDropper: REDDropper {
            numGates = 3;
            wq = wq;
            minths = string(afx1Minth) + " " + string(afx2Minth) + " " + string(afx3Minth);
            maxths = string(afx1Maxth) + " " + string(afx2Maxth) + " " + string(afx3Maxth);
            maxps = string(afx1Maxp) + " " + string(afx2Maxp) + " " + string(afx3Maxp);
            @display("p=105,102");
        }
    connections:
        afx1In --> { @display("m=w"); } --> redDropper.in[0];
        afx2In --> { @display("m=w"); } --> redDropper.in[1];
        afx3In --> { @display("m=w"); } --> redDropper.in[2];
        redDropper.out[0] --> { @display("m=m,100,20,0,50"); } --> fifoQueue.in++;
        redDropper.out[1] --> { @display("m=m,100,50,0,50"); } --> fifoQueue.in++;
        redDropper.out[2] --> { @display("m=m,100,80,0,50"); } --> fifoQueue.in++;
        fifoQueue.out --> { @display("m=e"); } --> out;
}

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