internetworking with tcp ip by douglas comer ppt

... of data with each call Thus, the outgoing TCP buffer be- gins with sufficient data for at least one maximum size segment Furthermore, because the application produces data faster than TCP can ... control, TCP allows systems of widely varying speeds to communicate The basic unit of transfer used by TCP is a segment Segments are used to pass data or control information (e.g., to allow TCP software ... round-trip delays Jain [I9861 describes timer- based congestion control in a sliding window environment Borman [April 19891 sum- marizes experiments with high-speed TCP on Cray computers EXERCISES TCP

Ngày tải lên: 04/07/2014, 22:21

... Berkeley distri- buting routed software along with their popular 4BSD UNIX systems Thus, many TCPIIP sites adopted and installed routed, and started using RIP without even consider- ing its technical ... system 16.3 Routing Information Protocol (RIP) 16.3.1 History of RIP One of the most widely used IGPs is the Routing Information Protocol (RIP), also known by the name of a program that implements ... Although TCP/IP architectures continue to evolve, centralized roots are evident in many protocols Without some centralization, each ISP would need to exchange reachability information with all

Ngày tải lên: 04/07/2014, 22:21

... Carefully consider the manipulation of IP addresses in a UDP echo server Under what conditions is it incorrect to create new IP addresses by reversing the source and destina- tion IP addresses? As we ... disks and data files An early implementa- tion of TCP/IP under UNIX also used the open-read-write-close paradigm with a special file name, /dev/tcp The group adding network protocols to BSD UNIX ... file descriptors and socket descriptors is that the operating system binds a file descriptor to a specific file or device when the application calls open, but it can create sockets without binding

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... e-mail server (TCP port 25) The filter also blocks incoming datagrarns destined for FTP (TCP port 21), TELNET (TCP port 23), WHOIS (UDP port 43), TFTP (UDP port 69), or FINGER (TCP port 79) Trang ... circumvent the restric- tions imposed by one firewall by entering the organization's internet through another$ We can summarize: An organization that has multiple e x t e m l connections must install ... Sockets By the mid 1990s when it became evident that security was important for Internet commerce, several groups proposed security mechanisms for use with the Web Although not formally adopted by

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... interconnections among networks are formed by computers called IP routers, or IP gateways, that attach to two or more networks. A router forwards packets between networks by receiving them from one network ... networks. In essence, TCPAP defines an abstraction of "network that hides the details of physical networks; we will learn that such abstractions help make TCPIIP extremely powerful. ... depict each physical network because TCPIIP treats them equally despite their differences. The point is: Sec. 3.8 All Networks Are Equal 59 The TCPLP internet protocols treat all networks

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... lengths Such quantities must be understood by both the senders and re- ceivers The TCP/IP protocols solve the byte-order problem by defining a network standard byte order that all machines must use ... follow the TCPIIP byte-order standards Of course, users who merely invoke applica- tion programs never need to deal with the byte order problem directly The internet standard for byte order specifies ... high-order byte of the in- teger Still others store integers in groups of 16-bit words, with the lowest addresses holding the low-order word, but with bytes swapped Thus, direct copying of bytes

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... can be discarded IP is such a fundamental part of the design that a TCP/IP internet is sometimes called an IP-based technology We begin our consideration of IP in this chapter by looking at the ... and is usually referred to by its initials, IPt IP provides three important definitions First, the IP protocol defines the basic unit of data transfer used throughout a TCPhP internet Thus, it ... fundamental principle of connectionless delivery and discusses how it is provided by the Internet Protocol (IP), which is one of the two major protocols used in internetworking (TCP being the other)

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... header contains IP ad- dresses whereas the frame header contains physical addresses Figure 7.2 shows the general form of a datagram: Figure 7.2 General form of an IP datagram, the TCP/IP analogy to ... shipped across the underlying network in a single frame In addition, because IP represents the offset of the data in multiples of eight octets, the fragment size must be chosen to be a multiple ... corrupted data go undetected Fields SOURCE IP ADDRESS and DESTINATION IP ADDRESS contain the 32-bit IP addresses of the datagram's sender and intended recipient Although the datagram may be routed

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... basic unit of transfer in a TCP/IP internet is the IP da- tagram This chapter adds to the description of connectionless service by describing how routers forward IP datagrams and deliver them ... use it FIRST IP ADDRESS SECOND lP ADDRESS Trang 4specifies a routing path by including a sequence of IP addresses in the option as Figure 7.14 shows IP ADDRESS OF FIRST HOP IP ADDRESS OF ... To understand IP routing completely, we must review the architecture of a TCP/IP internet First, recall that an internet is composed of multiple physical networks inter- connected by computers

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... always specify the IP address of the original source and the IP address of the ultimate destination? When IP executes the routing algorithm, it selects a new IP address, the IP address of the ... an IP datagram has reached its final destination is not quite as trivial as it seems Remember that even a host may have multiple physical connec- tions, each with its own IP address When an IP ... destination We said that the IP address selected by the IP routing algorithm is known as the next hop address because it tells where the datagram must be sent next Where does IP store the next hop address?

Ngày tải lên: 04/07/2014, 22:21

... message mechanism to the TCP/IP protocols The mechanism, known as the Internet Control Message Protocol (ICMP), is considered a required part of IP and must be included in every IP implemen- tation ... ICMP messages are encapsulated and sent using IP, ICMP is not considered a higher level protocol - it is a required part of IP The reason for using IP to deliver ICMP messages is that they may ... Because both the request and reply travel in IP datagrams, successful receipt of a reply verifies that major pieces of the transport system work First, IP software on the source computer must route

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... cycle endlessly As mentioned previously, to prevent datagrams from circling forever in a TCP/IP internet, each IP datagram contains a time-to-live counter, sometimes called a hop count A router decrements ... operate indepen- dently, with each machine maintaining its own notion of the current time Clocks that differ widely can confuse users of distributed systems software The TCPJIP protocol suite includes ... are used by the source to associate replies with requests Remaining fields specify times, given in milliseconds since midnight, Universal Time? The ORIGINATE TIMESTAMP field is filled in by the

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... internet with hundreds of networks and thousands of hosts They did not foresee tens of thousands of small networks of personal computers that would suddenly appear in the decade after TCP/IP was ... have its own IP prefix; hosts attached to it are as- signed addresses as if they connected directly to the WAN The transparent router demultiplexes datagrams that arrive from the WAN by sending ... install mappings obtained through ARP without checking their validity and without maintaining consistency Thus, it may happen that the ARP table maps several IP addresses to the same physical address,

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... layer The realistic diagram in Figure 11.2b shows that the IP software may communicate with multiple high-level protocol modules and with multiple network interfaces Although a diagram of conceptual ... 11.5.1 The TCPAP 5-Layer Reference Model The second major layering model did not arise from a standards committee, but came instead from research that led to the TCPIIP protocol suite With a little ... located in the TCP/IP transport layer uses checksums, acknowledgements, and timeouts to con- trol transmission Thus, unlike the connection-oriented X.25 protocol layering, the TCP/IP software focuses

Ngày tải lên: 04/07/2014, 22:21

... were found, declare a routing error; Figure 10.8 The unified IP routing algorithm. Given an IP datagram and a routing table with masks, this algorithm selects a next hop router to which ... subdivision flexible by allowing one to specify the exact number of bits that correspond to a prefm. To summarize: Classless addressing, which is now used by ISPs, treats IP addresses as arbitrary ... example demonstrates a technique often employed with unnumbered net- works. Rather than leaving the next hop empty, it is filled with one of the IP addresses assigned to the next-hop router...

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... encounter when traversing a TCP/ IP internet. 11.2 The Need For Multiple Protocols We have said that protocols allow one to specify or understand communication without knowing the details ... decided to add subnet addressing to its IP software by allocating a single subnet mask used for all IP network addresses. The vendor modified its standard IP routing software to make the subnet ... hardware ad- dress. The third technique, a TCPnP standard called subnet addressing, allows a site to share a single IP network address among multiple physical networks. All hosts and routers...

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... service offered by a commercial util- ity, while the TCPIIP protocols provide an example of a different layering scheme. In practice, protocol software uses multiplexing and demultiplexing to ... IP module, the IP software extracts the datagram and demulti- plexes further based on the transport protocol. Figure 11.11 demonstrates demultiplex- ing at the Internet layer. A Demultiplexing ... contents. Multiplexing and demultiplexing occur at almost every protocol layer. For exam- ple, after the network interface demultiplexes frames and passes those frames that con- tain IP datagrams...

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... examine the reli- able stream service provided by the TCPIIP Internet protocol suite. The service is de- fined by the Transmission Control Protocol, or TCP. The reliable stream service is so important ... here as part of the TCP/ IP Internet protocol suite, it is an independent, general purpose protocol that can be adapted for use with other delivery systems. For example, because TCP makes very few ... specification for TCP that can be used to build software for a variety of machines. Because TCP assumes little about the underlying communication system, TCP can be used with a variety of...

Ngày tải lên: 04/07/2014, 22:21