/* * ** Network and Service Differentiation Extensions to GridSim 3.0 ** * * Gokul Poduval & Chen-Khong Tham * Computer Communication Networks (CCN) Lab * Dept of Electrical & Computer Engineering * National University of Singapore * August 2004 * * Licence: GPL - http://www.gnu.org/copyleft/gpl.html * * Link.java - Abstract class as a template for a Network Link * */package gridsim.net;import eduni.simjava.*;import gridsim.*;import java.util.*;/** * This class provides a template for a Link which can connect two entities like * routers, GridResources or any other new component that needs to use the * network facilities in Gridsim. * <p> * In the network model used here, the links only * introduce propogation delays. Routers are resposible for queueing and * transmission delays. Also, links do not check whether the packets being sent * through are of size smaller than the MTU. It is the responsibility of the * upstream sender to check the size of the packet. The baud rate and the MTU * attributes are stored in the links to facilitate routers and other entities * that send data through a link. * * @invariant $none * @since GridSim Toolkit 3.1 * @author Gokul Poduval & Chen-Khong Tham, National University of Singapore */public abstract class Link extends Sim_entity{    /** Propagation delay of this link in millisecond */    protected double delay_;    /** Baud rate of this link in bits/s */    protected double baudRate_;    /** Maximum Transmission Unit (MTU) of this link in bytes */    protected int MTU_;     // packet size    /** Default baud rate of a link in bits/sec */    public static final int DEFAULT_BAUD_RATE = 9600;    /** Default propagation delay of a link in millisecond */    public static final int DEFAULT_PROP_DELAY = 5;    /** Default Maximum Transmission Unit (MTU) of a link in bytes */    public static final int DEFAULT_MTU = 1500;    /** A constant represents 1 second in milliseconds */    protected final int MILLI_SEC = 1000;         /**     * Constructs a Link which simulates a physical link between two entities.     *     * @param name      Name of this Link     * @param baudRate  baud rate of this link (bits/s)     * @param propDelay Propogation delay of the Link in milli seconds     * @param MTU       Maximum Transmission Unit of the Link in bytes.     *                  Packets which are larger than the MTU should be split     *                  up into MTU size units. <br>     *                  For e.g. a 1024 byte packet trying to cross a 576 byte     *                  MTU link should get split into 2 packets of 576 bytes     *                  and 448 bytes.     * @throws NullPointerException This happens when name is null or empty     * @throws ParameterException   This happens for the following conditions:     *      <ul>     *          <li> name is null     *          <li> baudRate <= 0     *          <li> propDelay <= 0     *          <li> MTU <= 0     *      </ul>     *     * @pre name != null     * @pre baudRate > 0     * @pre propDelay > 0     * @pre MTU > 0     * @post $none     */    public Link(String name, double baudRate, double propDelay, int MTU)                throws ParameterException, NullPointerException    {        super(name);        String msg = name + "(): Error - ";        if (baudRate <= 0) {            throw new ParameterException(msg + "baud rate must be > 0.");        }        else if (propDelay <= 0) {            throw new ParameterException(msg+"propagation delay mut be < 0.");        }        else if (MTU <= 0) {            throw new ParameterException(msg + "MTU must be > 0.");        }        this.baudRate_ = baudRate;        this.delay_ = propDelay;        this.MTU_ = MTU;    }    /**     * Connects two entities using this link. Any data sent through one end of     * this link will be sent out through the other.     *     * @param end1 Entity attached to one end of the Link     * @param end2 Entity attached to the other end of the Link     * @pre end1 != null     * @pre end2 != null     * @post $none     */    public abstract void attach(Sim_entity end1, Sim_entity end2);    /**     * Connects two entities using this link. Any data sent through one end of     * this link will be sent out through the other.     *     * @param end1 Entity attached to one end of the Link     * @param end2 Entity attached to the other end of the Link     * @pre end1 != null     * @pre end2 != null     * @post $none     */    public abstract void attach(String end1, String end2);    /**     * Returns the baud rate of the link in bits/s.     *     * @return the baud rate (bits/s)     * @pre $none     * @post $none     */    public double getBaudRate() {        return this.baudRate_;    }    /**     * Returns the tramssion delay that this link introduces.     *     * @return tranmission delay in milliseconds     * @pre $none     * @post $none     */    public double getDelay() {        return this.delay_;    }    /**     * Returns the Maximum Transmission Unit of this Link     *     * @return MTU in bytes     * @pre $none     * @post $none     */    public int getMTU() {        return this.MTU_;    }} // end class