The GBN protocol allows the sender to potentially "fill the pipeline" in Pipelined Reliable Data Transfer Protocols Figure 2 with packets, therefore avoiding the channel utilization problems we noted with stop-and-wait protocols. There are, on the other hand, scenarios in which
In a Go-Back-N (GBN) protocol, the sender is allowed to transmit several packets (when available) without waiting for an acknowledgment, but is constrained to have no more than some maximum allowable number, N, of unacknowledged packets in the pipeline. We describe the
Protocol rdt3.0 is a functionally correct protocol, but it is doubtful that anyone would be happy with its performance, especially in todays high-speed networks. At the heart of rdt.3.0s performance problem is the fact that it is a stop-and-wait protocol.
We first examine the simplest case, in which the underlying channel is completely reliable. The protocol itself, which we'll call rdt1.0, is trivial. The finite-state machine (FSM) definitions for the rdt1.0 sender and receiver are shown in Figure 1. The FSM in Figure 1(a) defines the
In this section, we look at the problem of reliable data transfer in a general context. This is appropriate since the problem of implementing reliable data transfer takes place not only at the transport layer, but also at the link layer and the application layer as well. The common
The application data shown in Figure 1 occupies the data field of the UDP segment. For instance, for DNS, the data field includes either a query message or a response message. For a streaming audio application, audio samples fill the data field. The UDP header has only four
In this section, we'll examine UDP, how it works, and what it does. We encourage you to refer back to Principles of Network Applications, which contains an overview of the UDP service model, and to Socket Programming with UDP, which discusses socket programming using
To understand TCP demultiplexing, we have to study TCP sockets and TCP connection establishment. One slight difference between a TCP socket and a UDP socket is that a TCP socket is identified by a four-tuple: (source IP address, source port number, destination IP address,
In this section we discuss transport-layer multiplexing and demultiplexing, that is, extending the host-to-host delivery service provided by the network layer to a process-to-process delivery service for applications running on the hosts. In order to keep the discussion concrete, we'll
Recollect that the internet, and more commonly a TCP/IP network, makes available two distinct transport-layer protocols to the application layer. One of these protocols is UDP (User Datagram Protocol), which provides an unreliable, connectionless service to the invoking