A basic Layer 3 unit of transmission.
A Path Vector Algorithm is a particular type of dynamic routing protocol used by BGP. In this protocol, each destination route is accompanied not by a single metric indicating the cost of this path, but by a detailed list of all Autonomous Systems that the path includes.
Protocol Data Unit. A logical grouping of information.
Per-Hop Behavior in QoS scheme.
Protocol Independent Multicast. This dynamic routing protocol is used with multicast networking.
Protocol Independent Multicast Dense Mode. A particular flavor of the PIM protocol in which all routers in an Autonomous System are assumed to care about all multicast groups.
Protocol Independent Multicast Sparse Mode. A particular flavor of the PIM protocol in which only some routers in an Autonomous System are assumed to care about all multicast groups. This is generally much more difficult to handle in than Dense Mode.
An application used to send ICMP echo- request packets to specified destination IP addresses and watch for the ICMP echo response. One often loosely refers to the ICMP echo request and response as ping packets, although this term is rather imprecise.
Private Network to Network Interface. In ATM networks, there are actually a few different ways to handle the communication between switches. PNNI is one method that is particularly useful in isolated private ATM network.
When network congestion is encountered, dropping the excess packets is often necessary, particularly if their flow rate has exceeded the amount subscribed to. This process of discarding excess packets is called policing.
Point-to-Point Protocol. A general Layer 2 protocol that is frequently used over point-to-point links such as serial connections.
Point-to-Point Protocol over Ethernet. A special adaptation of PPP that allows the emulation of a point-to-point link on an Ethernet connection. A PPP connection can then run through this virtual link. This is a popular way of implementing DSL-based Internet connections.
A device that is able to listen to and decode all of the traffic on a LAN segment. One of the most popular commercial protocol analyzers is called the Sniffer by Network Associates. Frequently, one hears protocol analyzers generically (and incorrectly) referred to as "sniffers."
See PDU.
When an appropriately configured router receives an ARP request for a device that it knows (from its routing table) is on a different segment, it will respond to the ARP request on behalf on this device. It can then route the packet normally. This routing generally happens when the device sending the ARP request does not have an appropriate default gateway configured.
Permanent Virtual Circuit. In many packet-switching networks, such as ATM and Frame Relay, logical connections called Virtual Circuits are set up between end point devices. If this Virtual Circuit is permanently configured through the network, it is called a PVC.