Point-to-point protocol is ...

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<h2>Point-to-point protocol</h2><div class="wp-caption alignright" style="width: 310px"><a href="http://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/PPPPhaseDiagram.svg/450px-PPPPhaseDiagram.svg.png" target="_blank"><img title="Point-to-point protocol" alt="Point-to-point protocol" src="http://upload.wikimedia.org/wikipedia/commons/thumb/0/0f/PPPPhaseDiagram.svg/450px-PPPPhaseDiagram.svg.png" width="300" height="270" /></a> </div><div class="wp-caption alignright" style="width: 310px"><a href="http://www.thenetworkencyclopedia.com/imagens/M19.jpg" target="_blank"><img title="Point-to-point protocol" alt="Point-to-point protocol" src="http://www.thenetworkencyclopedia.com/imagens/M19.jpg" width="150" height="135" /></a> </div><div class="wp-caption alignright" style="width: 310px"><a href="http://www.freepatentsonline.com/7062568-0-large.jpg" target="_blank"><img title="Point-to-point protocol" alt="Point-to-point protocol" src="http://www.freepatentsonline.com/7062568-0-large.jpg" width="150" height="135" /></a> </div>
<p>In networking, the Point-to-Point Protocol is a data link protocol commonly used in establishing a direct connection between two networking nodes. It can provide connection authentication, transmission encryption (using ECP, RFC 1968), and compression.</p>
<p>PPP is used over many types of physical networks including serial cable, phone line, trunk line, cellular telephone, specialized radio links, and fiber optic links such as SONET. PPP is also used over Internet access connections. Internet service providers (ISPs) have used PPP for customer dial-up access to the Internet, since IP packets cannot be transmitted over a modem line on their own, without some data link protocol. Two derivatives of PPP, Point-to-Point Protocol over Ethernet (PPPoE) and Point-to-Point Protocol over ATM (PPPoA), are used most commonly by Internet Service Providers (ISPs) to establish a Digital Subscriber Line (DSL) Internet service connection with customers.</p>
<p>PPP is commonly used as a data link layer protocol for connection over synchronous and asynchronous circuits, where it has largely superseded the older Serial Line Internet Protocol and telephone company mandated standards (such as Link Access Protocol, Balanced (LAPB) in the X.25 protocol suite). PPP was designed to work with numerous network layer protocols, including Internet Protocol (IP), TRILL, Novell's Internetwork Packet Exchange (IPX), NBF and AppleTalk.</p>
<p>PPP was designed somewhat after the original HDLC specifications. The designers of PPP included many additional features that had been seen only in proprietary data-link protocols up to that time.</p>
<p>RFC 2516 describes Point-to-Point Protocol over Ethernet as a method for transmitting PPP over Ethernet that is sometimes used with DSL. RFC 2364 describes Point-to-Point Protocol over ATM (PPPoA) as a method for transmitting PPP over ATM Adaptation Layer 5 (AAL5), which is also a common alternative to PPPoE used with DSL.</p>
<p>PPP is specified in RFC 1661.</p>
<p>RFC 1994 describes Challenge-handshake authentication protocol, which is preferred for establishing dial-up connections with ISPs. Although deprecated, Password authentication protocol (PAP) is still sometimes used.</p>
<p>Another option for authentication over PPP is Extensible Authentication Protocol described in RFC 2284.</p>
<p>After the link has been established, additional network configuration may take place. Most commonly, the Internet Protocol Control Protocol (IPCP) is used, although Internetwork Packet Exchange Control Protocol (IPXCP) and AppleTalk Control Protocol (ATCP) were once very popular. Internet Protocol Version 6 Control Protocol (IPv6CP) will see extended use in the future, when IPv6 replaces IPv4's position as the dominant layer-3 protocol.</p>
<p>PPP permits multiple network layer protocols to operate on the same communication link. For every network layer protocol used, a separate Network Control Protocol is provided in order to encapsulate and negotiate options for the multiple network layer protocols. It negotiates network-layer information, e.g. network address or compression options, after the connection has been established.</p>
<p>For example, Internet Protocol uses the IP Control Protocol (IPCP), and Internetwork Packet Exchange (IPX) uses the Novell IPX Control Protocol (IPX/SPX). NCPs include fields containing standardized codes to indicate the network layer protocol type that the PPP connection encapsulates.</p>
<p>PPP detects looped links using a feature involving magic numbers. When the node sends PPP LCP messages, these messages may include a magic number. If a line is looped, the node receives an LCP message with its own magic number, instead of getting a message with the peer's magic number.</p>
<p>The Protocol field indicates the type of payload packet.</p>
<p>The Information field contains the PPP payload; it has a variable length with a negotiated maximum called the Maximum Transmission Unit. By default, the maximum is 1500 octets. It might be padded on transmission; if the information for a particular protocol can be padded, that protocol must allow information to be distinguished from padding.</p>
<p>PPP frames are encapsulated in a lower-layer protocol that provides framing and may provide other functions such as a checksum to detect transmission errors. PPP on serial links is usually encapsulated in a framing similar to HDLC, described by IETF RFC 1662.</p>
<p>The Flag field is present when PPP with HDLC-like framing is used.</p>
<p>The Address and Control fields always have the value hex FF and hex 03 (for "unnumbered information"), and can be omitted whenever PPP LCP Address-and-Control-Field-Compression (ACFC) is negotiated.</p>
<p>The Frame Check Sequence field is used for determining whether an individual frame has an error. It contains a checksum computed over the frame to provide basic protection against errors in transmission. This is a CRC code similar to the one used for other layer two protocol error protection schemes such as the one used in Ethernet. According to RFC 1662, it can be either 16 bits (2 bytes) or 32 bits (4 bytes) in size (default is 16 bits - Polynomial x16 + x12 + x5 + 1).</p>
<p>The FCS is calculated over the Address, Control, Protocol, Information and Padding fields after the message has been encapsulated.</p>
<p>Multilink PPP provides a method for spreading traffic across multiple distinct PPP connections. It is defined in RFC 1990. It can be used, for example, to connect a home computer to an Internet Service Provider using two traditional 56k modems, or to connect a company through two leased lines.</p>
<p>On a single PPP line frames cannot arrive out of order, but this is possible when the frames are divided among multiple PPP connections. Therefore Multilink PPP must number the fragments so they can be put in the right order again when they arrive.</p>
<p>Multilink PPP is an example of a link aggregation technology. Cisco IOS Release 11.1 and later supports Multilink PPP.</p>
<p>With PPP, one cannot establish several simultaneous distinct PPP connections over a single link.</p>
<p>That's not possible with Multilink PPP either. Multilink PPP uses contiguous numbers for all the fragments of a packet, and as a consequence it isn't possible to suspend the sending of a sequence of fragments of one packet in order to send another packet. This prevents from running Multilink PPP multiple times on the same links.</p>
<h3>Related Sites for Point-to-point protocol</h3>
<ul><li>What is PPP (<strong>Point-to-Point Protocol</strong>)? - Definition from WhatIs.com <a href="http://searchnetworking.techtarget.com/definition/PPP" target="_blank">read Point-to-point protocol</a></li>
<li><strong>Point-to-Point Protocol</strong> - Wikipedia <a href="http://it.wikipedia.org/wiki/Point-to-Point_Protocol" target="_blank">read Point-to-point protocol</a></li>
<li><strong>Point-to-Point Protocol</strong> â€" Wikipédia, a… <a href="http://pt.wikipedia.org/wiki/Point-to-Point_Protocol" target="_blank">read Point-to-point protocol</a></li>
<li><strong>Point-to-Point Protocol</strong> â€" Wikipedia <a href="http://de.wikipedia.org/wiki/Point-to-Point_Protocol" target="_blank">read Point-to-point protocol</a></li></ul>




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tags: Point-to-point, protocol, Point-to-point protocol, ppp, protocol, over, used

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