Đang chuẩn bị liên kết để tải về tài liệu:
Ebook Computer network - A systems approach (3rd edition): Part 2

(BQ) Part 2 book "Computer network - A systems approach" has contents: Simple demultiplexer, remote procedure call, reliable byte stream, performance, issues in resource allocation, queuing disciplines, TCP congestion control, congestion avoidance mechanisms,.and other contents. | End-to-End Protocols Victory is the beautiful, bright coloured flower. Transport is the stem without which it could never have blossomed. —Winston Churchill T he previous three chapters have described various technologies that can be used to connect together a collection of computers: direct links (including LAN technologies like Ethernet and token ring), packet-switched networks (including cell-based networks like ATM), and internetworks. The next problem is to turn this host-to-host packet delivery service into a process-to-process communication channel. This is the role played by the transport level of the network archiP R O B L E M tecture, which, because it supports communication between the end Getting Processes to application programs, is sometimes Communicate called the end-to-end protocol. Two forces shape the end-to-end protocol. From above, the application-level processes that use its services have certain requirements. The following list itemizes some of the common properties that a transport protocol can be expected to provide: ■ guarantees message delivery ■ delivers messages in the same order they are sent ■ delivers at most one copy of each message ■ supports arbitrarily large messages ■ supports synchronization between the sender and the receiver ■ allows the receiver to apply flow control to the sender ■ supports multiple application processes on each host Note that this list does not include all the functionality that application processes might want from the network. For example, it does not include security, which is typically provided by protocols that sit above the transport level. From below, the underlying network upon which the transport protocol operates has certain limitations in the level of service it can provide. Some of the more typical limitations of the network are that it may ■ drop messages ■ reorder messages ■ deliver duplicate copies of a given message ■ limit messages to some finite size ■ deliver messages after an .