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- Match the ppp frame field to the description serial#
- Match the ppp frame field to the description verification#
- Match the ppp frame field to the description password#
- Match the ppp frame field to the description plus#
Match the ppp frame field to the description password#
The device at the other end of PPP link compares the password with its own password and if the password is correct, sends back an acknowledgement. With PAP, the device to be authenticated starts the message exchange by sending a clear text pasword, claiming to be legitimate. Both protocols involve exchanges of messages between the two PPP speaking devices, but there are differences in detail. PPP defines two authentication protocols: Password Authentication Protocol (PAP) and Channel Handshake Authentication Protocol (CHAP). PPP is used over both synchronous leased lines and asynchronous dial lines, and configuration of authentication remains the same for both cases.
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This scenario is where R1 is authenticating R2, or in other words, asking R2 to prove its identity.
Match the ppp frame field to the description serial#
For example, if R1 and R2 are to form a serial link using PPP, R1 may want R2 to somewhow prove that it really is R2.
Match the ppp frame field to the description verification#
This identity verification is needed to confirm that the other device is legitimate and not some one only appearing to be an authentic device in order to cause damage or steal information. In the field of networking, authentication is a mechanism used to verify the identity of another device. Multiple parallel PPP links are bundled together to expand available bandwidth by load balancing traffic over those links. Table 12-2 Functions of Link Control Protocol (LCP) LCP Featureĭisables the router interface if a looped link is detected so that rerouting takes place over a working route.ĭisables a router interface that exceeds certain error percentage threshold, andallows rerouting over better routes.Įxchanges names and passwords so that each device can verify the identity of the device at the other end of the link.
Match the ppp frame field to the description plus#
For example, a PPP link that uses IPv4, IPv6, and Cisco Discovery Protocol (CDP) will use one instance of LCP plus IPCP for IPv4, IPv6CP for IPv6, and CDPCP for CDP. PPP uses a single instance of LCP for a PPP link while one NCP instance is used for each Layer 3 protocol defined on the link. All functions specific to a Layer 3 protocol are performed by the Network Control Protocol (NCP) specific to the related protocl, such as IP Control Protocol (IPCP) for the Internet Protocol (IP). The Link Control Protocol (LCP) implements all those control functions that work regardless of the Layer 3 protocol encapsulated by PPP. Key Concept PPP has two components: LCP that is responsible establishing, configuring, maintaining, and terminating the connection, and NCP which is specific to the Layer 3 protocol encapsulated by PPP. Each protocol performs functions specific to its related Layer 3 protocol. Network Control Protocol (NCP): There is one protocol of this caregory for each network layer protocol.Link Control Protocol (LCP): It has several functions related to the data link itself ignoring the Layer 3 protocol encapsulated by PPP.These control protocols of PPP are separated into two caregories: PPP has control protocols for each higher-layer protocol supported by PPP, allowing easier integration and support for those protocols.Įven though PPP framing is pretty similar to HDLC, PPP defines a set of Layer 2 control protocols that perform various link control functions.
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PPP also supports authentication and two mechanisms are available for this purpose: Password Authentication Porotocol (PAP) and Challenge Handshake Authentication Protocol (CHAP). The protocol Type filed in the header allows multiple Layer 3 protocols to be carried over the same PPP link. PPP is a varsatile protocol and supports both synchronous and asynchronous links. Figure 12-5 shows a PPP frame which is identical to the HDLC frame presented in Figure 12-5 earlier in the chapter. However, in practice only packets for the two versions of IP (IPv4 and IPv6) are encountered. This field allows packets from many different Layer 3 protocols to pass over a single link. But the PPP standard does define a protocol field to identify the type of packet inside the frame. The standard version of HDLC does not have a protocol field to identify the Layer 3 protocol encapsulated by HDLC. We will introduce you to the most important PPP concepts and proceed to do some real PPP configuration as well. However PPP is has more advanced features when compared with HDLC which is quite primitive. Point-to-Point Protocol (PPP) is also data link protocol used on serial links just like HDLC.