PPPPPP

Point to Point ProtocolPoint to Point Protocol

By Bill Reed

PPPPPP•Point to Point Protocol is an Point to Point Protocol is an encapsulation encapsulation standard.standard.

•Major standard for modem based Major standard for modem based communication.communication.

•PPP is in reality a suite of protocols not PPP is in reality a suite of protocols not a a single entity.single entity.

•PPP resides at layer 2 of the OSI model.PPP resides at layer 2 of the OSI model.

By Bill Reed

By Bill Reed

PPPPPP

Point to Point Protocol suite includes:Point to Point Protocol suite includes:

LCP – Link Control ProtocolLCP – Link Control ProtocolNCP – Network Control ProtocolNCP – Network Control Protocol

PAP – Password Authentication ProtocolPAP – Password Authentication Protocol

CHAP – Challenge Handshake CHAP – Challenge Handshake Authentication ProtocolAuthentication Protocol

By Bill Reed

PPPPPP

Point to Point Protocol supports;Point to Point Protocol supports;

Multiplexing of multiple upper layer protocolsMultiplexing of multiple upper layer protocols

Error detection (FCS)Error detection (FCS)

Tunnelling using (L2TP or PPTP)Tunnelling using (L2TP or PPTP)

A range of layer 1&2 technologiesA range of layer 1&2 technologies

(X.25, ATM, Frame relay & serial)(X.25, ATM, Frame relay & serial)

Bandwidth Allocation Protocol (BAP)Bandwidth Allocation Protocol (BAP)

Dynamic assignment of IP addressesDynamic assignment of IP addresses

By Bill Reed

PPPPPPBy Bill Reed

PPP uses HDLC (High level Data Link Control) as the basis for data encapsulation over point to point links.

PPP uses LCP (Link Control Protocol) for the establishment, configuration and testing of connections.

PPP uses multiple NCPs to allow simultaneous use of multiple network layer protocols ( IPCP for IP & IPXCP for IPX ).

PPPPPPBy Bill Reed

Session Establishment;

1. Link is setup

2. Link is tested (optional phase)

3. Negotiation, configuration

4. Termination

PPPPPPBy Bill Reed

1. Link Establishment

Establishing node sends a series of LCP frames which are used to configure and establish the data link.

2. Link Quality Determination (Optional)

Testing takes place to determine if the link is of sufficient quality to support network layer protocols.

3. Network layer protocol negotiation

Originator sends NCP frames to choose network protocols and configure the protocols chosen.

4. Termination of the link

The link remains open until LCP or NCP frames close the link, or an external event forces the termination of the connection.

PPPPPPBy Bill Reed

Authentication

Authentication is optional

If used authentication occurs between phases 2 and 3 of the link establishment process

PPP supports either PAP or CHAP authentication

PAP authentication

Two way handshake

Password sent in plain text

Susceptible to playback attacks

CHAP authentication

Three way handshake

Uses variable challenge value to guard against playback attacks

PPPPPPBy Bill Reed

Authentication configuration

Router(config)#username name password secret

Name indicates the hostname of the remote router it is case sensitive.

Secret when using Cisco equipment the Secret password must be the same on both ends of the connection.

Router(config-if)# encapsulation ppp

Router(config-if)# ppp authentication option

Option can be chap, pap chap, chap pap, pap

Router(config-if)# ppp pap sent-username username password password

Router(config-if)# ppp chap hostname hostnameRouter(config-if)# ppp chap password secret