We studied in the previous section that when two processes communicate over TCP, it is as if there were a pipe between the two processes. This pipe remains in place until one of the two processes closes it. When one of the processes wants to send some bytes to the other process,
In order to to explain socket programming for both TCP and UDP, we use the following simple client-server application:
As we have considered many important network applications, let's discover how network application programs are actually written. In this section we'll write application programs that use TCP; in the following section we'll write programs that use UDP.
Skype is an immensely popular P2P application, often with seven or eight million users connected to it at any one time. Besides providing PC-to-PC Internet telephony service, Skype offers PC-to-phone telephony service, phone-to-PC telephony service, and PC-to-PC video
To deal with this problem of scale. let's now look at organizing the peers into a circle. In this circular arrangement, each peer only keeps track of its immediate successor (modulo 2n). An instance of such a circle is shown in Figure 1(a). In this instance, n is again 4 and there are
An important element of many P2P applications and other distributed applications is an index (that is, a simple database), supporting search and update operations. When this database is distributed, the peers may carry out content caching and complicated routing of queries among
BitTorrent is a popular P2P protocol for file distribution [BitTorrent 2009]. In BitTorrent lingo, the collection of all peers participating in the distribution of a specific file is called a torrent. Peers in a torrent download equal-size chunks of the file from
The applications explained in this section so far - including the Web, e-mail, and DNS - all employ client-server architectures with significant reliance on always-on infrastructure servers. Recall from Network Application Architectures that with a P2P architecture, there is minimal (or
The discussion in the last article focused on how records are retrieved from the DNS database. You might be wondering how records get into the database in the first place. Let's see how this is done in the context of a particular example. Assume you have just created an exciting
The DNS servers that collectively implement the DNS distributed database store resource records (RRs), including RRs that provide hostname-to-IP address mappings. Each DNS reply message carries one or more resource records. In this and the following subsection, we