EthernetCsmaMac¶

simple module EthernetCsmaMac

Implements the Ethernet CSMA/CD MAC protocol. It supports building both Ethernet CSMA/CD and Ethernet PLCA network interfaces.

Implements the exponential backoff algorithm, sends jam signal when a collision is detected, and maintains IFG between signals on the channel. It expects complete Ethernet MAC protocol frames containing an Ethernet MAC header and an Ethernet FCS.

The lower layer must be connected to a module implementing the ~IEthernetCsmaPhy C++ interface. There are two such modules: EthernetCsmaPhy and EthernetPlca. The former can be used to build an Ethernet CSMA/CD network interface, the latter can be used to build an Ethernet PLCA network interface.

Usage diagram¶

Inheritance diagram¶

Used in compound modules¶

Name	Type	Description
EthernetPlcaInterface	compound module	Implements a network interface that is suitable for use in Ethernet 10BASE-T1S multidrop links. Such a multidrop link uses the Ethernet Phyisical Layer Collision Avoidance (PLCA) protocol. The protocol is defined in the IEEE 802.3cg-2019 standard. This network interface can be used in any network node module (e.g. StandardHost) that allows replacing its network interfaces. All network interfaces on the same multidrop link must use this module.

Extends¶

Name	Type	Description
MacProtocolBase	simple module	Module base for different MAC protocols.

Parameters¶

Name	Type	Default value	Description
displayStringTextFormat	string	“{fsmState}”	Determines the text that is written on top of the submodule, supports displaying pars, watches, and module-specific information
interfaceTableModule	string
promiscuous	bool	false	if true, all packets are received, otherwise only the
mtu	int	1500B	ones with matching destination MAC address
fcsMode	string

Properties¶

Name	Value	Description
class	EthernetCsmaMac
display	i=block/rxtx

Gates¶

Name	Direction	Size	Description
upperLayerIn	input
upperLayerOut	output
lowerLayerIn	input
lowerLayerOut	output

Signals¶

Name	Type	Description
carrierSenseChanged	int	emitted when the incoming carrier sense signal changes, the value is 1 or 0
collisionChanged	int	emitted when the incoming collision signal changes, the value is 1 or 0
packetDropped	cPacket
packetReceivedFromLower	cPacket
packetReceivedFromUpper	cPacket
packetSentToLower	cPacket
packetSentToUpper	cPacket
stateChanged	int	emitted when the state of the state machine changes, the value is one of IDLE, WAIT_IFG, TRANSMITTING, JAMMING, BACKOFF, RECEIVING

Statistics¶

Name	Title	Source	Record	Interpolation Mode	Description
carrierSense	carrier sense	carrierSenseChanged	count,vector	sample-hold	the time evolution of the incoming carrier sense signal
collision	collision	collisionChanged	count,vector	sample-hold	the time evolution of the incoming collision signal
state	state	stateChanged	count,vector	sample-hold	the time evolution of the state of the state machine

Source code¶

//
// Implements the Ethernet CSMA/CD MAC protocol. It supports building
// both Ethernet CSMA/CD and Ethernet PLCA network interfaces.
//
// Implements the exponential backoff algorithm, sends jam signal
// when a collision is detected, and maintains IFG between signals on the channel.
// It expects complete Ethernet MAC protocol frames containing an Ethernet MAC
// header and an Ethernet FCS.
//
// The lower layer must be connected to a module implementing the ~IEthernetCsmaPhy
// C++ interface. There are two such modules: ~EthernetCsmaPhy and ~EthernetPlca.
// The former can be used to build an Ethernet CSMA/CD network interface, the
// latter can be used to build an Ethernet PLCA network interface.
//
// @see ~EthernetCsmaPhy, ~EthernetPlca, ~EthernetPlcaInterface
//
simple EthernetCsmaMac extends MacProtocolBase
{
    parameters:
        bool promiscuous = default(false);  // if true, all packets are received, otherwise only the
                                            // ones with matching destination MAC address
        int mtu @unit(B) = default(1500B);
        string fcsMode @enum("declared","computed");
        @class(EthernetCsmaMac);
        displayStringTextFormat = default("{fsmState}");
        // emitted when the incoming carrier sense signal changes, the value is 1 or 0
        @signal[carrierSenseChanged](type=int);
        // emitted when the incoming collision signal changes, the value is 1 or 0
        @signal[collisionChanged](type=int);
        // emitted when the state of the state machine changes, the value is one of IDLE, WAIT_IFG, TRANSMITTING, JAMMING, BACKOFF, RECEIVING
        @signal[stateChanged](type=int);
        // the time evolution of the incoming carrier sense signal
        @statistic[carrierSense](title="carrier sense"; type=int; source=carrierSenseChanged; record=count,vector; interpolationmode=sample-hold);
        // the time evolution of the incoming collision signal
        @statistic[collision](title="collision"; type=int; source=collisionChanged; record=count,vector; interpolationmode=sample-hold);
        // the time evolution of the state of the state machine
        @statistic[state](title="state"; type=enum; enum=IDLE, WAIT_IFG, TRANSMITTING, JAMMING, BACKOFF, RECEIVING; source=stateChanged; record=count,vector; interpolationmode=sample-hold);
}

File: src/inet/linklayer/ethernet/basic/EthernetCsmaMac.ned