Free Windows Help Tutorials sponsored by inkjet printer cartridges dot org /title> <META HTTP-EQUIV="imagetoolbar" CONTENT="no"> <META HTTP-EQUIV="Content-Type" CONTENT="text/html; CHARSET=ISO 8859-1"> <META name="description" Content="Hundreds of downloadable Windows help tutorials, articles and how-to guides sponsored by inkjet printer cartridges dot org."><style type="text/css">  </style> </head> <body bgcolor=#999999 vlink=blue link=blue> <span name = "INTRA" class="pg" style="top:0px; left:5px; width:714px; height:1010px"></span> <span name = "INTRA" style='top:0px; left:5px; height:1010px; width:714px' class='img'> <img src="pg0002im.png" height = "1010 width = "714" border="0"> </span> <span class='nav' style='left: 10px; top: 10px'><pre></pre></span><span name = "INTRA" style='top:51px; left:48px' class="ft3"><pre><font face='Helvetica'>Connectivity:Overview</font></pre></span> <span name = "INTRA" style='top:203px; left:466px' class="ft0"><pre><font face='Arial'>field is interpreted as all data up to</font></pre></span> <span name = "INTRA" style='top:215px; left:466px' class="ft0"><pre><font face='Arial'>this point received OK . This saves</font></pre></span> <span name = "INTRA" style='top:219px; left:89px' class="ft2"><pre><font face='Arial'><i> TCP</i> <i>includes</i> <i>mechanisms</i> <i>for</i> <i>ensuring</i></font></pre></span> <span name = "INTRA" style='top:227px; left:466px' class="ft0"><pre><font face='Arial'>bandwidth when data is all being sent</font></pre></span> <span name = "INTRA" style='top:239px; left:466px' class="ft0"><pre><font face='Arial'>one way by reducing the need for ac </font></pre></span> <span name = "INTRA" style='top:243px; left:87px' class="ft2"><pre><font face='Arial'><i>that</i> <i>data</i> <i>which</i> <i>arrives</i> <i>out</i> <i>of</i> <i>sequence</i> <i>is</i></font></pre></span> <span name = "INTRA" style='top:251px; left:466px' class="ft0"><pre><font face='Arial'>knowledgement segments. If data is</font></pre></span> <span name = "INTRA" style='top:263px; left:466px' class="ft0"><pre><font face='Arial'>being sent in both directions simulta </font></pre></span> <span name = "INTRA" style='top:267px; left:86px' class="ft2"><pre><font face='Arial'><i>put</i> <i>back</i> <i>into</i> <i>the</i> <i>order</i> <i>it</i> <i>was</i> <i>sent.</i> <i>It</i> <i>also</i></font></pre></span> <span name = "INTRA" style='top:275px; left:466px' class="ft0"><pre><font face='Arial'>neously, as in a full duplex connection,</font></pre></span> <span name = "INTRA" style='top:287px; left:466px' class="ft0"><pre><font face='Arial'>then acknowledgements involve no</font></pre></span> <span name = "INTRA" style='top:291px; left:105px' class="ft2"><pre><font face='Arial'><i>implements</i> <i>flow</i> <i>control,</i> <i>so</i> <i>a</i> <i>sender</i></font></pre></span> <span name = "INTRA" style='top:299px; left:466px' class="ft0"><pre><font face='Arial'>overhead, as a segment carrying data</font></pre></span> <span name = "INTRA" style='top:311px; left:466px' class="ft0"><pre><font face='Arial'>one way can contain an acknow </font></pre></span> <span name = "INTRA" style='top:315px; left:90px' class="ft2"><pre><font face='Arial'><i>cannot</i> <i>overwhelm</i> <i>a</i> <i>receiver</i> <i>with</i> <i>data. </i></font></pre></span> <span name = "INTRA" style='top:323px; left:466px' class="ft0"><pre><font face='Arial'>ledgement for data sent the other way.</font></pre></span> <span name = "INTRA" style='top:335px; left:480px' class="ft0"><pre><font face='Arial'>Next in the header is a 16 bit field</font></pre></span> <span name = "INTRA" style='top:347px; left:466px' class="ft0"><pre><font face='Arial'>containing a header length and flags.</font></pre></span> <span name = "INTRA" style='top:359px; left:466px' class="ft0"><pre><font face='Arial'>TCP headers can include optional</font></pre></span> <span name = "INTRA" style='top:371px; left:77px' class="ft0"><pre><font face='Arial'>host that joins the group. Instead, the</font></pre></span> <span name = "INTRA" style='top:371px; left:272px' class="ft0"><pre><font face='Arial'>which are called segments. The length</font></pre></span> <span name = "INTRA" style='top:371px; left:466px' class="ft0"><pre><font face='Arial'>fields, so the length can vary from 20</font></pre></span> <span name = "INTRA" style='top:383px; left:77px' class="ft0"><pre><font face='Arial'>messages are broadcast, and the driv </font></pre></span> <span name = "INTRA" style='top:383px; left:272px' class="ft0"><pre><font face='Arial'>of a segment is decided by the protocol.</font></pre></span> <span name = "INTRA" style='top:383px; left:466px' class="ft0"><pre><font face='Arial'>to 60 bytes. The flags are: URG, ACK</font></pre></span> <span name = "INTRA" style='top:395px; left:77px' class="ft0"><pre><font face='Arial'>ers on each host decide whether to ig </font></pre></span> <span name = "INTRA" style='top:395px; left:272px' class="ft0"><pre><font face='Arial'>Each segment contains 20 bytes of</font></pre></span> <span name = "INTRA" style='top:395px; left:466px' class="ft0"><pre><font face='Arial'>(which we have already mentioned),</font></pre></span> <span name = "INTRA" style='top:407px; left:77px' class="ft0"><pre><font face='Arial'>nore them or pass the contents up the</font></pre></span> <span name = "INTRA" style='top:407px; left:272px' class="ft0"><pre><font face='Arial'>header information in addition to the</font></pre></span> <span name = "INTRA" style='top:408px; left:466px' class="ft0"><pre><font face='Arial'>PSH, RST, SYN and FIN. We shall look</font></pre></span> <span name = "INTRA" style='top:419px; left:77px' class="ft0"><pre><font face='Arial'>protocol stack.</font></pre></span> <span name = "INTRA" style='top:419px; left:272px' class="ft0"><pre><font face='Arial'>IP header. The TCP header starts with</font></pre></span> <span name = "INTRA" style='top:420px; left:466px' class="ft0"><pre><font face='Arial'>at some of the other flags later.</font></pre></span> <span name = "INTRA" style='top:431px; left:91px' class="ft0"><pre><font face='Arial'>This implies that multicast mes </font></pre></span> <span name = "INTRA" style='top:431px; left:272px' class="ft0"><pre><font face='Arial'>16 bit source and destination port</font></pre></span> <span name = "INTRA" style='top:432px; left:480px' class="ft0"><pre><font face='Arial'>The header contains a field called</font></pre></span> <span name = "INTRA" style='top:443px; left:77px' class="ft0"><pre><font face='Arial'>sages must be broadcast throughout</font></pre></span> <span name = "INTRA" style='top:443px; left:272px' class="ft0"><pre><font face='Arial'>number fields. As with UDP, these</font></pre></span> <span name = "INTRA" style='top:444px; left:466px' class="ft0"><pre><font face='Arial'>the window size, which gives the</font></pre></span> <span name = "INTRA" style='top:455px; left:77px' class="ft0"><pre><font face='Arial'>the entire Internet, since the multicas </font></pre></span> <span name = "INTRA" style='top:455px; left:272px' class="ft0"><pre><font face='Arial'>fields specify the application layers</font></pre></span> <span name = "INTRA" style='top:456px; left:466px' class="ft0"><pre><font face='Arial'>number of bytes the receiver can ac </font></pre></span> <span name = "INTRA" style='top:467px; left:77px' class="ft0"><pre><font face='Arial'>ter does not know which hosts want to</font></pre></span> <span name = "INTRA" style='top:467px; left:272px' class="ft0"><pre><font face='Arial'>that have sent and are to receive the</font></pre></span> <span name = "INTRA" style='top:468px; left:466px' class="ft0"><pre><font face='Arial'>cept. Then there is a 16 bit checksum,</font></pre></span> <span name = "INTRA" style='top:479px; left:77px' class="ft0"><pre><font face='Arial'>receive the messages. Fortunately this</font></pre></span> <span name = "INTRA" style='top:479px; left:272px' class="ft0"><pre><font face='Arial'>data. An IP address and a port number</font></pre></span> <span name = "INTRA" style='top:480px; left:466px' class="ft0"><pre><font face='Arial'>covering both header and data. Finally</font></pre></span> <span name = "INTRA" style='top:491px; left:77px' class="ft0"><pre><font face='Arial'>is unnecessary. IP uses a protocol</font></pre></span> <span name = "INTRA" style='top:491px; left:272px' class="ft0"><pre><font face='Arial'>taken together uniquely identify a</font></pre></span> <span name = "INTRA" style='top:492px; left:466px' class="ft0"><pre><font face='Arial'>(before the optional data) there is a</font></pre></span> <span name = "INTRA" style='top:503px; left:77px' class="ft0"><pre><font face='Arial'>called Internet Group Management</font></pre></span> <span name = "INTRA" style='top:503px; left:272px' class="ft0"><pre><font face='Arial'>service running on a host, and the pair</font></pre></span> <span name = "INTRA" style='top:504px; left:466px' class="ft0"><pre><font face='Arial'>field called the urgent pointer . When</font></pre></span> <span name = "INTRA" style='top:515px; left:77px' class="ft0"><pre><font face='Arial'>Protocol (IGMP) to inform routers</font></pre></span> <span name = "INTRA" style='top:515px; left:272px' class="ft0"><pre><font face='Arial'>is known as a socket.</font></pre></span> <span name = "INTRA" style='top:516px; left:466px' class="ft0"><pre><font face='Arial'>the URG flag is set, this value is treated</font></pre></span> <span name = "INTRA" style='top:527px; left:77px' class="ft0"><pre><font face='Arial'>which hosts wish to receive which</font></pre></span> <span name = "INTRA" style='top:527px; left:286px' class="ft0"><pre><font face='Arial'>Next in the header comes a 32 bit</font></pre></span> <span name = "INTRA" style='top:528px; left:466px' class="ft0"><pre><font face='Arial'>as an offset to the sequence number. It</font></pre></span> <span name = "INTRA" style='top:539px; left:77px' class="ft0"><pre><font face='Arial'>multicast group messages, so that the</font></pre></span> <span name = "INTRA" style='top:539px; left:272px' class="ft0"><pre><font face='Arial'>sequence number. This number identi </font></pre></span> <span name = "INTRA" style='top:540px; left:466px' class="ft0"><pre><font face='Arial'>identifies the start of data in the stream</font></pre></span> <span name = "INTRA" style='top:551px; left:77px' class="ft0"><pre><font face='Arial'>messages are only sent where they are</font></pre></span> <span name = "INTRA" style='top:551px; left:272px' class="ft0"><pre><font face='Arial'>fies the position in the data stream that</font></pre></span> <span name = "INTRA" style='top:552px; left:466px' class="ft0"><pre><font face='Arial'>that must be processed urgently. This</font></pre></span> <span name = "INTRA" style='top:563px; left:77px' class="ft0"><pre><font face='Arial'>needed.</font></pre></span> <span name = "INTRA" style='top:563px; left:272px' class="ft0"><pre><font face='Arial'>the first byte of data in the segment</font></pre></span> <span name = "INTRA" style='top:564px; left:466px' class="ft0"><pre><font face='Arial'>data is often called out of band data.</font></pre></span> <span name = "INTRA" style='top:575px; left:272px' class="ft0"><pre><font face='Arial'>should occupy. The sequence number</font></pre></span> <span name = "INTRA" style='top:576px; left:466px' class="ft0"><pre><font face='Arial'>An example of its use is when a user</font></pre></span> <span name = "INTRA" style='top:589px; left:77px' class="ft1"><pre><font face='Arial'><i><b>TCP</b></i></font></pre></span> <span name = "INTRA" style='top:587px; left:272px' class="ft0"><pre><font face='Arial'>enables TCP to maintain the data</font></pre></span> <span name = "INTRA" style='top:588px; left:466px' class="ft0"><pre><font face='Arial'>presses the break key to interrupt the</font></pre></span> <span name = "INTRA" style='top:599px; left:272px' class="ft0"><pre><font face='Arial'>stream in the correct order even</font></pre></span> <span name = "INTRA" style='top:600px; left:466px' class="ft0"><pre><font face='Arial'>output from a program during a Telnet</font></pre></span> <span name = "INTRA" style='top:611px; left:91px' class="ft0"><pre><font face='Arial'>Transmission Control Protocol is</font></pre></span> <span name = "INTRA" style='top:611px; left:272px' class="ft0"><pre><font face='Arial'>though segments may be received out</font></pre></span> <span name = "INTRA" style='top:612px; left:466px' class="ft0"><pre><font face='Arial'>session.</font></pre></span> <span name = "INTRA" style='top:623px; left:77px' class="ft0"><pre><font face='Arial'>the transport layer protocol used by</font></pre></span> <span name = "INTRA" style='top:623px; left:272px' class="ft0"><pre><font face='Arial'>of sequence.</font></pre></span> <span name = "INTRA" style='top:635px; left:77px' class="ft0"><pre><font face='Arial'>most Internet applications, like Telnet,</font></pre></span> <span name = "INTRA" style='top:635px; left:286px' class="ft0"><pre><font face='Arial'>The next field is a 32 bit acknow </font></pre></span> <span name = "INTRA" style='top:638px; left:466px' class="ft1"><pre><font face='Arial'><i><b>Connection</b></i></font></pre></span> <span name = "INTRA" style='top:647px; left:77px' class="ft0"><pre><font face='Arial'>FTP and HTTP. It is a connection ori </font></pre></span> <span name = "INTRA" style='top:647px; left:272px' class="ft0"><pre><font face='Arial'>ledgement field, which is used to con </font></pre></span> <span name = "INTRA" style='top:659px; left:77px' class="ft0"><pre><font face='Arial'>ented protocol. This means that two</font></pre></span> <span name = "INTRA" style='top:659px; left:272px' class="ft0"><pre><font face='Arial'>vey back to the sender that data has</font></pre></span> <span name = "INTRA" style='top:660px; left:480px' class="ft0"><pre><font face='Arial'>Before any data can be sent between</font></pre></span> <span name = "INTRA" style='top:671px; left:77px' class="ft0"><pre><font face='Arial'>hosts one a client, the other a server </font></pre></span> <span name = "INTRA" style='top:671px; left:272px' class="ft0"><pre><font face='Arial'>been received correctly. If the ACK flag</font></pre></span> <span name = "INTRA" style='top:672px; left:466px' class="ft0"><pre><font face='Arial'>two hosts using TCP, a connection</font></pre></span> <span name = "INTRA" style='top:683px; left:77px' class="ft0"><pre><font face='Arial'>must establish a connection before any</font></pre></span> <span name = "INTRA" style='top:683px; left:272px' class="ft0"><pre><font face='Arial'>is set, which it normally is, this field</font></pre></span> <span name = "INTRA" style='top:684px; left:466px' class="ft0"><pre><font face='Arial'>must be established. One host, called</font></pre></span> <span name = "INTRA" style='top:695px; left:77px' class="ft0"><pre><font face='Arial'>data can be transferred between them.</font></pre></span> <span name = "INTRA" style='top:695px; left:272px' class="ft0"><pre><font face='Arial'>contains the position of the next byte of</font></pre></span> <span name = "INTRA" style='top:696px; left:466px' class="ft0"><pre><font face='Arial'>the server, listens out for connection</font></pre></span> <span name = "INTRA" style='top:707px; left:91px' class="ft0"><pre><font face='Arial'>TCP provides reliability. An appli </font></pre></span> <span name = "INTRA" style='top:707px; left:272px' class="ft0"><pre><font face='Arial'>data that the sender of the segment</font></pre></span> <span name = "INTRA" style='top:708px; left:466px' class="ft0"><pre><font face='Arial'>requests. The host requesting a connec </font></pre></span> <span name = "INTRA" style='top:719px; left:77px' class="ft0"><pre><font face='Arial'>cation that uses TCP knows that data it</font></pre></span> <span name = "INTRA" style='top:719px; left:272px' class="ft0"><pre><font face='Arial'>expects to receive.</font></pre></span> <span name = "INTRA" style='top:720px; left:466px' class="ft0"><pre><font face='Arial'>tion is called the client.</font></pre></span> <span name = "INTRA" style='top:732px; left:77px' class="ft0"><pre><font face='Arial'>sends is received at the other end, and</font></pre></span> <span name = "INTRA" style='top:732px; left:286px' class="ft0"><pre><font face='Arial'>In TCP there is no need for every</font></pre></span> <span name = "INTRA" style='top:732px; left:480px' class="ft0"><pre><font face='Arial'>To request a connection, a client</font></pre></span> <span name = "INTRA" style='top:744px; left:77px' class="ft0"><pre><font face='Arial'>that it is received correctly. TCP uses</font></pre></span> <span name = "INTRA" style='top:744px; left:272px' class="ft0"><pre><font face='Arial'>segment of data to be acknowledged.</font></pre></span> <span name = "INTRA" style='top:744px; left:466px' class="ft0"><pre><font face='Arial'>sends a TCP segment specifying its</font></pre></span> <span name = "INTRA" style='top:756px; left:77px' class="ft0"><pre><font face='Arial'>checksums on both headers and data.</font></pre></span> <span name = "INTRA" style='top:756px; left:272px' class="ft0"><pre><font face='Arial'>The value in the acknowledgement</font></pre></span> <span name = "INTRA" style='top:756px; left:466px' class="ft0"><pre><font face='Arial'>own port number and the port that it</font></pre></span> <span name = "INTRA" style='top:768px; left:77px' class="ft0"><pre><font face='Arial'>When data is received, TCP sends an</font></pre></span> <span name = "INTRA" style='top:780px; left:77px' class="ft0"><pre><font face='Arial'>acknowledgement back to the sender.</font></pre></span> <span name = "INTRA" style='top:792px; left:77px' class="ft0"><pre><font face='Arial'>If the sender does not receive an ac </font></pre></span> <span name = "INTRA" style='top:804px; left:77px' class="ft0"><pre><font face='Arial'>knowledgement within a certain time </font></pre></span> <span name = "INTRA" style='top:798px; left:279px' class="ft2"><pre><font face='Arial'><i> If</i> <i>a</i> <i>name</i> <i>isn't</i> <i>found</i> <i>in</i> <i>the</i> <i>HOSTS</i> <i>file,</i></font></pre></span> <span name = "INTRA" style='top:816px; left:77px' class="ft0"><pre><font face='Arial'>frame the data is re sent.</font></pre></span> <span name = "INTRA" style='top:828px; left:91px' class="ft0"><pre><font face='Arial'>TCP includes mechanisms for en </font></pre></span> <span name = "INTRA" style='top:822px; left:276px' class="ft2"><pre><font face='Arial'><i>the</i> <i>software</i> <i>contacts</i> <i>one</i> <i>of</i> <i>the</i> <i>local</i> <i>name</i></font></pre></span> <span name = "INTRA" style='top:840px; left:77px' class="ft0"><pre><font face='Arial'>suring that data which arrives out of</font></pre></span> <span name = "INTRA" style='top:852px; left:77px' class="ft0"><pre><font face='Arial'>sequence is put back into the order it</font></pre></span> <span name = "INTRA" style='top:846px; left:278px' class="ft2"><pre><font face='Arial'><i>servers</i> <i>whose</i> <i>IP</i> <i>address</i> <i>is</i> <i>in</i> <i>the</i> <i>TCP/IP</i></font></pre></span> <span name = "INTRA" style='top:864px; left:77px' class="ft0"><pre><font face='Arial'>was sent. It also implements flow con </font></pre></span> <span name = "INTRA" style='top:876px; left:77px' class="ft0"><pre><font face='Arial'>trol, so a sender cannot overwhelm a</font></pre></span> <span name = "INTRA" style='top:870px; left:274px' class="ft2"><pre><font face='Arial'><i>configuration,</i> <i>to</i> <i>see</i> <i>if</i> <i>it</i> <i>knows</i> <i>the</i> <i>address. </i></font></pre></span> <span name = "INTRA" style='top:888px; left:77px' class="ft0"><pre><font face='Arial'>receiver with data.</font></pre></span> <span name = "INTRA" style='top:900px; left:91px' class="ft0"><pre><font face='Arial'>TCP sends data using IP, in blocks</font></pre></span> <span name = "INTRA" style='top:946px; left:52px' class="ft0"><pre><font face='Arial'>File: C04100.6</font></pre></span> <span name = "INTRA" style='top:946px; left:527px' class="ft0"><pre><font face='Arial'>Issue 88 (October 1997) page 14</font></pre></span> <span name = "INTRA" style='top:944px; left:260px' class="ft2"><pre><font face='Arial'><i>PC</i> <i>Network</i> <i>Advisor</i></font></pre></span> <span name = "INTRA" class='nav' style='left: 357px; top: 1010px'><pre><a href='page0001.htm'><</a> Next page <a href='page0003.htm'>></a></pre></span> <span name = "INTRA" style='top:1050px; left:50px' class="ft4"><pre><b><font color="#FF0000" size="3" face="Arial">New!</font><font color="#FF0000" size="3" face="Arial Narrow"> </font><font size="2" face="Arial">The best sites for quality <a href="http://www.inkjet-printer-cartridges.org">inkjet printer cartridges</a> and the best sites for <a href="http://www.cheap-inkjet-cartridges.com">cheap inkjet cartridges</a></font></b></pre></span></body> <span name = "INTRA" style='top:1100px; left:300px' class="ft4"><pre><b><font color="#FF0000" size="3" face="Arial"><a href="../index.html">Windows Help Desk Home</a> </font></b></pre></span></body></html>