sime

Class Link

java.lang.Object

sime.NetworkElement

sime.Link

public class Link
extends NetworkElement

A full-duplex communication link that connects two network nodes. Packets that are fed on one end will come out at the other end of the link, after appropriate delays. The link has associated transmission and propagation times.

Author:

Ivan Marsic

See Also:

NetworkElement

Field Summary

Fields

Modifier and Type	Field and Description
protected double	lastTimeProcessCalledMode1 Parameters that override NetworkElement.lastTimeProcessCalled because Link has different modes of processing.
protected double	lastTimeProcessCalledMode2
protected NetworkElement	node1 Nodes node1 and node2 connected by this link.
protected NetworkElement	node2
protected double[]	packetDelaysN1toN2 Delay times for packets stored in the list packetsFromN1toN2, in simulation-clock ticks.
protected double[]	packetDelaysN2toN1 Similar to packetDelaysN1toN2.
protected java.util.ArrayList<Packet>	packetsFromN1toN2 Container for packets in transit from node1 to node2. We never check whether this array overflows, because we hope there will be never more than 100 packets in flight on a link?!?
protected java.util.ArrayList<Packet>	packetsFromN2toN1 Container for packets in transit from node2 to node1. Similar to packetsFromN1toN2.
protected double	propagationTime Propagation time for this communication link.
protected double	transmissionTime Transmission time for this communication link (per packet, assuming all packets are of the same size!).

Fields inherited from class sime.NetworkElement

lastTimeProcessCalled, name, simulator

Constructor Summary

Constructors

Constructor and Description
Link(Simulator simulator_, java.lang.String name_, NetworkElement node1_, NetworkElement node2_) Constructor.
Link(Simulator simulator_, java.lang.String name_, NetworkElement node1_, NetworkElement node2_, double transmissionTime_, double propagationTime_) Constructor.

Method Summary

Methods

Modifier and Type	Method and Description
protected void	deliverArrivedPackets(java.util.ArrayList<Packet> packets_, double[] packetDelays_, NetworkElement node_, double lastTimeProcessCalled_) Helper method to deliver the packets that propagated through the link and arrived to the other end, if any. Note that we assume that the packets are enqueued on the first-come-first-served basis, so their delays are sorted in an ascending order.
protected void	enqueueNewPacket(java.util.ArrayList<Packet> packets_, double[] packetDelays_, Packet packet_) Helper method to enqueue a new packet into one of the lists and calculate its delay on the link.
double	getPropagationTime() Parameter getter.
double	getTransmissionTime() Parameter getter.
void	handle(NetworkElement dummySource_, Packet dummyPacket_) Link does not "handle" incoming packets, so this method does nothing.
void	process(int mode_) This method should be called to signal the passage of time.
void	send(NetworkElement source_, Packet packet_) The link just accepts any new packets given to it and enqueues the new packet behind any existing packets.
void	setPropagationTime(double propagationTime_) Parameter setter.
void	setTransmissionTime(double transmissionTime_) Parameter setter.

Methods inherited from class sime.NetworkElement

getName, getSimulator

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Field Detail

lastTimeProcessCalledMode1

protected double lastTimeProcessCalledMode1

Parameters that override NetworkElement.lastTimeProcessCalled because Link has different modes of processing.

lastTimeProcessCalledMode2

protected double lastTimeProcessCalledMode2

node1

protected NetworkElement node1

Nodes node1 and node2 connected by this link.

node2

protected NetworkElement node2

packetDelaysN1toN2

protected double[] packetDelaysN1toN2

Delay times for packets stored in the list packetsFromN1toN2, in simulation-clock ticks. The delay for each packet is calculated when the packet is received in send(NetworkElement, Packet) and the delay is decremented in process(int) until it reaches zero. At this time, the packet is delivered to node2.

packetDelaysN2toN1

protected double[] packetDelaysN2toN1

Similar to packetDelaysN1toN2.

packetsFromN1toN2

protected java.util.ArrayList<Packet> packetsFromN1toN2

Container for packets in transit from node1 to node2.
We never check whether this array overflows, because we hope there will be never more than 100 packets in flight on a link?!?

packetsFromN2toN1

protected java.util.ArrayList<Packet> packetsFromN2toN1

Container for packets in transit from node2 to node1.
Similar to packetsFromN1toN2.

propagationTime

protected double propagationTime

Propagation time for this communication link. Measured in ticks of the simulator clock.

transmissionTime

protected double transmissionTime

Transmission time for this communication link (per packet, assuming all packets are of the same size!). The time is measured in ticks of the simulator clock.

Constructor Detail

Link

public Link(Simulator simulator_,
    java.lang.String name_,
    NetworkElement node1_,
    NetworkElement node2_)

Constructor.

Parameters:

simulator_ - the runtime environment

name_ - the name given to this link

node1_ - one node to be connected with this link

node2_ - the other node to be connected with this link

Link

public Link(Simulator simulator_,
    java.lang.String name_,
    NetworkElement node1_,
    NetworkElement node2_,
    double transmissionTime_,
    double propagationTime_)

Constructor.

Parameters:

simulator_ - the runtime environment

name_ - the name given to this link

node1_ - one node to be connected with this link

node2_ - the other node to be connected with this link

transmissionTime_ - the transmission time associated with this link (measured in clock ticks)

propagationTime_ - the propagation time associated with this link (measured in clock ticks)

Method Detail

deliverArrivedPackets

protected void deliverArrivedPackets(java.util.ArrayList<Packet> packets_,
                         double[] packetDelays_,
                         NetworkElement node_,
                         double lastTimeProcessCalled_)

Helper method to deliver the packets that propagated through the link and arrived to the other end, if any.
Note that we assume that the packets are enqueued on the first-come-first-served basis, so their delays are sorted in an ascending order.

Parameters:

packets_ - the list of packets

packetDelays_ - the array of delays associated with packets

node_ - the node to which the arrived packets will be delivered

lastTimeProcessCalled_ -

enqueueNewPacket

protected void enqueueNewPacket(java.util.ArrayList<Packet> packets_,
                    double[] packetDelays_,
                    Packet packet_)

Helper method to enqueue a new packet into one of the lists and calculate its delay on the link.

Parameters:

packets_ - the list of packets

packetDelays_ - the array of delays associated with packets

packet_ - the new packet to enqueue

getPropagationTime

public double getPropagationTime()

Parameter getter.

Returns:

the propagation time (in simulator clock ticks)

getTransmissionTime

public double getTransmissionTime()

Parameter getter.

Returns:

the transmission time (in simulator clock ticks)

handle

public void handle(NetworkElement dummySource_,
          Packet dummyPacket_)

Link does not "handle" incoming packets, so this method does nothing.

Specified by:

handle in class NetworkElement

Parameters:

dummySource_ - this dummy parameter is ignored

dummyPacket_ - this dummy parameter is ignored

See Also:

NetworkElement.handle(NetworkElement, sime.Packet)

process

public void process(int mode_)

This method should be called to signal the passage of time. The link will deliver appropriate number of packets, if any, at the other end (opposite from where the packet was received).

Specified by:

process in class NetworkElement

Parameters:

mode_ - the transmission mode for this link; value "0" means both-way transmission, value "1" means one-way transmission from node1 to node2, and value "2" means one-way transmission from node2 to node1

See Also:

NetworkElement.process(int)

send

public void send(NetworkElement source_,
        Packet packet_)

The link just accepts any new packets given to it and enqueues the new packet behind any existing packets. These packets in transit/flight will be delivered on the other end of the link after appropriate delays, when method process(int) is called.
Parameter source_ is used to distinguish the nodes connected to the link's ends.

At the time when a packet is enqueued, its delay is also calculated and stored in the corresponding array (packetDelaysN1toN2 or packetDelaysN2toN1).

Note: In the current implementation when calculating the packet delay, we do not check the packet length. The transmission time transmissionTime is assumed to be the same for all packets. Of course, this is not true because TCP acknowledgment-only segments are much shorter than TCP segments carrying data. this is a TODO item.

Specified by:

send in class NetworkElement

Parameters:

source_ - the source of the packet

packet_ - the new packet in flight on this link

See Also:

NetworkElement.send(NetworkElement, Packet)

setPropagationTime

public void setPropagationTime(double propagationTime_)

Parameter setter.

Parameters:

propagationTime_ - the propagation time to set (in simulator clock ticks)

setTransmissionTime

public void setTransmissionTime(double transmissionTime_)

Parameter setter.

Parameters:

transmissionTime_ - the transmission time to set (in simulator clock ticks)