Link monitoring and debugging packets: These are used to monitor and debug the links. For example: terminate-request, terminate-ack, are some link termination packets.ģ. Link termination packets: These are used to disconnect the link between two end points. For example: configure-request, configure-ack, configure-nak, configure-reject are some configuration packets.Ģ. Configuration packet: These are used to negotiate options between the two ends. There are eleven different type of LCP packets.Information: Contains extra information required for some LCP packet. Length: 2 byte-specifies the length of entire LCP packet.Ĥ. I D: 1 byte-holds a value used to match a request with the reply.ģ. Code: 1 byte-specifies the type of LCP packet.Ģ. The various fields present in LCP packet are:ġ.The presence of a value C021 16 in the protocol field of PPP frame indicates that LCP packet is present in the data field.
All LCP packets are carried in the data field of the PPP frame.It provides negotiation mechanism to set options between two endpoints.It is responsible for establishing, maintaining, configuring and terminating the link.
PPP uses several other protocols to establish link, authenticate users and to carry the network layer data.ģ. Terminate: In this phase connection is terminated. The connection remains in this phase until one of the endpoints wants to end the connection.Ħ. Open: In this phase, data transfer takes place. If a node is running multiple protocols simultaneously at the network layer, the receiving node needs to know which protocol will receive the data.ĥ. This is because PPP supports several protocols at network layer. PPP specifies that two nodes establish a network layer agreement before data at the network layer can be exchanged. Network: In network phase, negotiation for the network layer protocols takes place. If the result is successful, the connection goes to the networking phase otherwise, it goes to the termination phase.Ĥ. However if they decide to proceed with authentication, they send several authentication packets. The two nodes may decide during the establishment phase, not to skip this phase. If negotiation is successful, the system goes into authentication phase or directly to networking phase. In this phase, two parties negotiate the options. Establish: Connection goes into this phase when one of the nodes start communication. There is no active carrier and the line is quiet.Ģ. Dead: In dead phase the link is not used. The PPP connection goes through different states as shown in fig.ġ. It carries user data or other information.Ħ. If the length is not negotiated using LCP during line set up, a default length of 1500 bytes is used. Protocol field: This field specifies the kind of packet in the data field i.e. The value is always 00000011 to show that the frame does not contain any sequence numbers and there is no flow control or error control.Ĥ. This field uses the format of the U-frame (unnumbered) in HDLC.
Control field: This field is also of 1 byte. This address is the broadcast address i.e. Address field: This field is of 1 byte and is always 11111111. Flag field: Flag field marks the beginning and end of the PPP frame. The frame format of PPP resembles HDLC frame. We’ll be covering the following topics in this tutorial:
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