Implements the Address Resolution Protocol for IPv4 and IEEE 802 6-byte MAC addresses.

ARP packets are represented by the ArpPacket class.

Communication Between ARP and IPv4 modules: IPv4 module call the ARP::getMACAddressFor(ipv4Address) method for get the MACAddress of next hop. If this method could not resolve an IPv4 address to MAC address, then IPv4 uses the Arp::startAddressResolution() method. ARP emit a arpResolutionCompleted signal, when added/modified an entry in ARP table. ARP emit a arpResolutionFailed signal when an ARP request failed (ARP request sent retryCount times and retryTimeout elapsed).

ARP resolution is used over broadcast interfaces only, that is, over interfaces that have the isBroadcast() flag set in InterfaceEntry (see InterfaceTable). Since routing files (.irt or .mrt files, given as parameter to Ipv4RoutingTable) may modify the default interface configuration, you must take care that these files don't contain the word BROADCAST e.g. for PPP interfaces.

Inheritance diagram

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

Parameters

Name	Type	Default value	Description
interfaceTableModule	string		The path to the InterfaceTable module
routingTableModule	string
retryTimeout	double	1s	number seconds ARP waits between retries to resolve an IPv4 address
retryCount	int	3	number of times ARP will attempt to resolve an IPv4 address
cacheTimeout	double	120s	number seconds unused entries in the cache will time out
proxyArpInterfaces	string	"*"	list of interfaces that proxy ARP is enabled (all interfaces by default)

Properties

Name	Value	Description
display	i=block/layer

Gates

Name	Direction	Size	Description
netwIn	input		incoming ARP requests and replies
netwOut	output		outgoing ARP requests/replies, and datagrams with resolved next hop
ifIn	input
ifOut	output

Signals

Name	Type	Unit
arpReplySent	inet::Packet
arpResolutionInitiated	inet::IArp::Notification
arpResolutionFailed	inet::IArp::Notification
arpRequestSent	inet::Packet
arpResolutionCompleted	inet::IArp::Notification

Statistics

Name	Title	Source	Record	Unit	Interpolation Mode
arpReplySent	ARP replies sent	arpReplySent	count, sum(packetBytes), vector(packetBytes)
arpResolutionInitiated	ARP initiated resolutions		count
arpResolutionFailed	ARP failed resolutions		count
arpRequestSent	ARP request sent	arpRequestSent	count, sum(packetBytes), vector(packetBytes)
arpResolutionCompleted	ARP completed resolutions		count

Source code

//
// Implements the Address Resolution Protocol for IPv4 and IEEE 802 6-byte
// MAC addresses.
//
// ARP packets are represented by the ~ArpPacket class.
//
// Communication Between ARP and IPv4 modules:
// IPv4 module call the ARP::getMACAddressFor(ipv4Address) method for get the MACAddress
// of next hop. If this method could not resolve an IPv4 address to MAC address, then IPv4
// uses the Arp::startAddressResolution() method.
// ARP emit a arpResolutionCompleted signal, when added/modified an entry in ARP table.
// ARP emit a arpResolutionFailed signal when an ARP request failed (ARP request sent
// retryCount times and retryTimeout elapsed).
//
// ARP resolution is used over <i>broadcast</i> interfaces only,
// that is, over interfaces that have the <tt>isBroadcast()</tt> flag set in
// <tt>InterfaceEntry</tt> (see ~InterfaceTable). Since routing files
// (<tt>.irt</tt> or <tt>.mrt</tt> files, given as parameter to ~Ipv4RoutingTable)
// may modify the default interface configuration, you must take care that
// these files don't contain the word <tt>BROADCAST</tt> e.g. for PPP
// interfaces.
//
simple Arp like IArp
{
    parameters:
        string interfaceTableModule;   // The path to the InterfaceTable module
        string routingTableModule;
        double retryTimeout @unit(s) = default(1s);   // number seconds ARP waits between retries to resolve an IPv4 address
        int retryCount = default(3);                  // number of times ARP will attempt to resolve an IPv4 address
        double cacheTimeout @unit(s) = default(120s); // number seconds unused entries in the cache will time out
        string proxyArpInterfaces = default("*");     // list of interfaces that proxy ARP is enabled (all interfaces by default)
        @display("i=block/layer");
        @signal[arpRequestSent](type=inet::Packet);
        @signal[arpReplySent](type=inet::Packet);
        @signal[arpResolutionInitiated](type=inet::IArp::Notification);
        @signal[arpResolutionCompleted](type=inet::IArp::Notification);
        @signal[arpResolutionFailed](type=inet::IArp::Notification);
        @statistic[arpRequestSent](title="ARP request sent"; source=arpRequestSent; record=count,"sum(packetBytes)","vector(packetBytes)");
        @statistic[arpReplySent](title="ARP replies sent"; source=arpReplySent; record=count,"sum(packetBytes)","vector(packetBytes)");
        @statistic[arpResolutionInitiated](title="ARP initiated resolutions"; record=count);
        @statistic[arpResolutionCompleted](title="ARP completed resolutions"; record=count);
        @statistic[arpResolutionFailed](title="ARP failed resolutions"; record=count);
    gates:
        input netwIn @labels(ArpPacket+Ieee802Ctrl); // incoming ARP requests and replies
        output netwOut @labels(ArpPacket+Ieee802Ctrl,Ipv4Header+Ieee802Ctrl);  // outgoing ARP requests/replies, and datagrams with resolved next hop
        input ifIn @labels(ArpPacket,Ieee802Ctrl);
        output ifOut @labels(ArpPacket,Ieee802Ctrl);
}

File: src/inet/networklayer/arp/ipv4/Arp.ned

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