6.2 Connectors

Connectors, unlink classifiers, only generate data for one recipient; either the packet is delivered to the target_ neighbor, or it is sent to he drop-target_.

A connector will receive a packet, perform some function, and deliver the packet to its neighbor, or drop the packet. There are a number of different types of connectors in ns. Each connector performs a different function.

networkinterface labels packets with incoming interface identifier--it is used by some multicast routing protocols. The class variable ``Simulator NumberInterfaces_ 1'' tells ns to add these interfaces, and then, it is added to either end of the simplex link. Multicast routing protocols are discussed in a separate chapterChapterchap:multicast.
DynaLink Object that gates traffic depending on whether the link is up or down. It expects to be at the head of the link, and is inserted on the link just prior to simulation start. It's status
variable control whether the link is up or down. The description of how the DynaLink object is used is in a separate chapterChapterchap:net-dynamics.
DelayLink Object that models the link's delay and bandwidth characteristics. If the link is not dynamic, then this object simply schedules receive events for the downstream object for each packet it receives at the appropriate time for that packet. However, if the link is dynamic, then it queues the packets internally, and schedules one receives event for itself for the next packet that must be delivered. Thus, if the link goes down at some point, this object's []reset method../ns-2/delay.ccDelayLink::reset is invoked, and the object will drop all packets in transit at the instant of link failure. We discuss the specifics of this class in another chapterChapterchap:delays.
Queues model the output buffers attached to a link in a ``real'' router in a network. In ns, they are attached to, and are considered as part of the link. We discuss the details of queues and different types of queues in ns in another chapterChapterchap:qmgmt.
TTLChecker will decrement the ttl in each packet that it receives. If that ttl then has a positive value, the packet is forwarded to the next element on the link. In the simple links, TTLCheckers are automatically added, and are placed as the last element on the link, between the delay element, and the entry for the next node.

Tom Henderson 2011-11-05