Có 120+ tài liệu thuộc chủ đề "tiêu chuẩn mạng không dây"
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The protocol software needs to detect such failures and recover from them if possible.. The protocol software needs to ar- range ways that a congested machine can suppress further traffic.. The protocol software needs to learn about failures or adapt to long delays.. Protocol software needs to detect and recover from such errors.. The protocol software needs to reorder packets...
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11.7.1 Layering in a TCPnP lnternet Environment. Our statement of the layering principle is somewhat vague, and the illustration in Figure 11.6 skims over an important issue because it fails to distinguish between transfers from source to ultimate destination and transfers across multiple networks.. Figure 11.7 illustrates the distinction, showing the path of a message sent from an appli- cation...
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198 User Datagram Protocol (UDP) Chap. Once the data arrives, the operating system passes the data to the process and restarts it. To communicate with a foreign port, a sender needs to know both the IF' address of the destination machine and the protocol port number of the destination within that machine. Each message must carry the number of the...
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Reliable Stream Transport Service (TCP). 13.1 Introduction. Although TCP is presented 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. 13.2 The Need For Stream Delivery. 210 Reliable Stream Transport Service (TCP) Chap. At the highest level, application programs often need to send...
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It might seem strange that two connections can use the TCP port 53 on machine simultaneously, but there is no ambiguity. 13.8 Passive And Active Opens. That is, before TCP traffic can pass across an internet, application programs at both ends of the connection must agree that the connection is desired. At that time, the operating system assigns a TCP...
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13.1 7 Accurate Measurement Of Round Trip Samples. In theory, measuring a round trip sample is trivial - it consists of subtracting the time at which the segment is sent from the time at which the acknowledgement arrives.. Should TCP assume acknowledgements belong with the earliest (i.e., original) transmission or the latest (i.e., the most recent retransmission)? Surprisingly, neither as-...
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Figure 13.13 The sequence of messages in a three-way handshake. The first segment of a handshake can be identified because it has the SYNt bit set in the code field. The three-way handshake is both necessary and sufficient for correct synchroniza- tion between the two ends of the connection. A three-way handshake (plus the rule that TCP ignores additional requests...
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More irnpor- tant, TCP cannot know whether to wait because it cannot know whether the application will generate more data in the near future. On the other hand, if TCP does not wait long enough, segments will be small and throughput will be low.. Be- cause TCP is designed to be general, however, it can be used by a diverse...
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14.5 Core Routers 259. To avoid the inefficiencies default routes cause, Internet designers arranged for all core routers to exchange routing information so that each would have complete informa- tion about optimal routes to all possible destinations. In essence, the core design avoided inefficiency by eliminating default routes.. Figure 14.3 depicts the conceptual basis of a core routing architecture. Outlying...
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Routing: Exterior Gate way Protocols And Autonomous Systems (BGP). 15.1 Introduction. It discusses the concept of autonomous sys- tems, and shows a protocol that a group of networks and routers operating under one administrative authority uses to propagate routing information about its networks to oth- er groups.. 15.2 Adding Complexity To The Architectural Model. Consequently, part of the motivation for...
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Finally, the 1-octet TYPE field contains one of the four values for the message type listed in Figure 15.5.. In the initial message, the marker consists of all 1s. To understand why synchronization is necessary, recall that all BGP messages are exchanged across a stream transport (i.e., TCP), which does not identify the boundary between one message and the next....
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Figure 15.15 The meaning of the ERR SUBCODE field in a BGP NOTIFI- CATION message.. 290 Routing: Exterior Gateway Protocols And Autonomous Systems (BGP) Chap. The connected Internet is composed of a set of autonomous systems, where each autonomous system consists of routers and networks under one administrative au- thority. An autonomous system uses an Exterior Gateway Protocol to advertise...
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16.3 Routing Infomation Protocol (RIP) 299. As Figure 16.4a shows, router R, has a direct connection to network I, so there is a route in its table with distance 1 , which will be included in its periodic broadcasts.. In the next broadcast, R, will re- port the higher cost route. Figure 16.4b depicts the result. In the next round...
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16.9 The Open SPF Protocol (OSPF) 309. We described the algorithm using a point-to-point graph and said that each router running SPF would periodically broadcast link status messages about each reachable neighbor. Consequently, OSPF allows every multi-access network to have a designated gateway (i.e., a designated router) that sends link status messages on behalf of all routers at- tached to...
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17.1 Introduction. This chapter explores an additional feature of the IP addressing scheme that permits efficient multipoint delivery of datagram. We begin with a brief review of the underlying hardware support. 17.2 ~Qrdware Broadcast. On networks composed of switches with point-to-point comec- tions, software must implement broadcasting by forwarding copies of the packet across individual connections until all switches have...
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send general IGMP queries to the all hosts address, hosts send some IGMP messages to the all routers address, and both hosts and routers send IGMP messages that are specific to a group to the group's address. Third, if multiple multicast routers attach to the same network, they quickly and efficiently choose a single router to poll host membership. Thus,...
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As a consequence, routers at- tached to leaf networks can decide whether to forward over the leaf network - if a leaf network contains no members for a given group, the router connecting that network to the rest of the internet does not forward on the network. In addition to taking local ac- tion, the leaf router infornls the next...
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Analo- gous to the error-correcting codes used with audio CDs, the scheme requires a sender to incorporate error-correction infomlation into each datagram in a data stream. Argue that IP multicast addresses should use only 23 of the 28 possible bits. The standard says that IP software must arrange to deliver a copy of any outgoing multi- cast datagram to application...
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18.8 ATM Adaptation Layers. ADAPTATION LAYER. Figure 18.6 The conceptual organization of ATM interface hardware and the flow of data through it. Both ends of the connection must agree on the choice, and the adaptation layer cannot be changed once the connection has been established. Although ATM hardware uses small, jixed-size cells to transport data, a higher layer protocol called...
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18.18 Using ATMARP Packets To Determine An Address 369. 18.18 Using ATMARP Packets To Determine An Address. 18.1 8.1 Permanent Virtual Circuits. In particular, a host begins operation with PVCs in place, and does not receive any information from the hardware about the address of the remote endpoint.. Thus, unless address information has been configured into the hosts (e.g., stored...