Routing:
[Gen][CCNA][CCNP Route][CCNP Remote][CCDA][MPLS][EEM][Add][Juniper][ACL][Host]
Switching: [CCNP Switch] [Switch Add] [Intro] [VLANs] [MLS] [STP] [QoS] [Availability] Security: [CCNP Security] [CCNA Security] [CCNP ISCW][PIX] [Adv PIX/ASA] [Net Sec1] [Net Sec2] Wireless: [Wireless] [Wireless Chall] [CCNA Wireless] [Wireless Theory] Voice: [Voice/QoS] [CCNA Voice] [CCVP Gateway] [CCVP Voice] Topics: [Dot1q][Dot1x][BGP][BRI][DHCP][IGRP][IGMP][OSPF][PPP][QoS][RADIUS][RIP][Subnet][SNMP][VLAN] Point-to-Point Protocol (PPP)The Serial Line Internet Protocol (SLIP) was one of the first standard protocols which allows access to remote servers. It is typically used with UNIX remote access servers. The Point-to-Point Protocol (PPP) has many enhancements over SLIP, and has been defined as a set of protocols which allow remote access to different types of computer systems, and operating systems (Figure 1). It is typically used in dial-up connections, and also allows a remote access server to receive calls from users. PPP permits several different types of authentication, and data compression and encryption. As the complete login service can be automated, it can be used in applications where remote data requires to be sent, without the requirement for user intervention. CCNA Challenges
CCNP Remote Access
PIX/ASA
CCNP ISCW
CCNP ONT
CCVP (Voice)
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Outline
The Serial Line Internet Protocol (SLIP) was one of the first standard protocols which allows access to remote servers. It is typically used with UNIX remote access servers. The standards which relate to SLIP include:
- RFC1144 Compressing TCP/IP Headers for Low-Speed Serial Links
- RFC1055 A Nonstandard for Transmission of IP Datagrams Over Serial Lines: SLIP
The Point-to Point Protocol (PPP) has many enhancements over SLIP, and has been defined as a set of protocols which allow remote access to different types of computer systems, and operating systems (Figure 1). It is typically used in dial-up connections, and also allows a remote access server to receive calls from users. PPP permits several different types of authentication, and data compression and encryption. As the complete login service can be automated, it can be used in applications where remote data requires to be sent, without the requirement for user intervention.
PPP is now one of the most widely used WAN protocols, as it supports:
- Data link setup.
- Dynamic assignment of IP addresses.
- Error detection.
- Link configuration and link quality testing.
- Negotiation options for capabilities such as network-layer address negotiation and data compression negotiations
- Network protocol multiplexing.
Figure 1: PPP/SLIP
PPP provides router-to-router and host-to-network connections over both synchro-nous and asynchronous circuits. It also supports multiple networking protocols, includ-ing TCP/IP, NetBEUI and IPX. Along with PPP, Point-to-Point Tunneling Protocol (PPTP) and Layer 2 Tunneling Protocol (L2TP) can be used to set up Virtual Private Networks (VPN). A VPN is a logical extension to private networks and involves encapsulating, encrypting, and authenticated connections over shared or public networks. VPN connections can provide remote access and routed connections to private networks over the Internet.
PPTP enables remote users to access corporate networks in a secure way over the Internet or from a dial-up connection provided through an Internet service provider (ISP). It tunnels, or encapsulates, IP, IPX, AppleTalk, DECNet or NetBEUI traffic into IP packets (Figure 2). Thus, users can run remote applications using the required network protocol. The L2TP differs from PPTP in that it does not require IP connectivity between the client and the server. In L2TP, only the tunnel mechanism provide packet-oriented point-to-point connectivity. It can thus be used over main different types of networks, such as ATM, Frame Relay, and X.25.
The main PPP specifications are defined in the following RFC’s:
- RFC1331 PPP
- RFC1332 PPP Internet Protocol Control Protocol (IPCP)
- RFC1334 PPP Authentication Protocols
- RFC1549 PPP in HDLC Framing
- RFC1552 PPP Internetwork Packet Exchange Control Protocol (IPXCP)
- RFC1570 PPP LCP Extensions
- RFC1661 Link Control Protocol (LCP)
- RFC1962 The PPP Compression Control Protocol (CCP)
- RFC1990 PPP Multilink Protocol
- RFC2097 PPP NetBIOS Frames Control Protocol (NBFCP)
- RFC2125 PPP Bandwidth Allocation Protocol (BAP), The PPP Bandwidth Allocation Control Protocol (BACP)
- RFC2284 PPP Extensible Authentication Protocol (EAP)
Figure 2: PPTP
PPP uses a layered architecture, as shown in the Figure. With its lower-level functions, PPP can use:
PPP has been designed to encapsulate many of the widely available network layer pro-tocols, such as IP, IPX and AppleTalk. These are supported with NCPs, as illustrated in Figure 3. Examples include:
These are functional fields containing standardized codes to indicate the network-layer protocol type that PPP encapsulates. Figure 4 shows an example window from a Dial-up connection on a Windows-based computer. It can be seen that this connection can support both PPP and SLIP. PPP is normally supported by more remote access systems, and allows for advanced authen-tication and for the support of more network protocols.
Figure 3: PPP protocol stack
Figure 4: PPP or SLIP protocol selection for a dial-up connection