Authentication: why is it important?

What are the 2 protocols?

Which is most common?

For user verification over dial-up links.

PAP and CHAP.

PAP is most common.

C021₁₆ (C021 hexa) in the protocol field means ?

This frame is carrying an LCP packet.

C023₁₆ in the protocol field means ?

This frame is carrying an PAP packet.

C223₁₆ in the protocol field means ?

This frame is carrying an CHAP packet.

Can link termination be requested from either end?

Yes.

CHAP =

Challenge handshake authentication protocol.

Config packets come in 4 types which are ---

Config-request: asking for 0+ options.

Config-ack: if all options are accepted.

Config-nak: if all options are recognised but 1+ option unacceptable.

Config-reject: if 1+ option unrecognised.

Configuration packets are used to ---

Negotiate the options between 2 ends.

Describe the 2 steps of PAP.

Authenticate-request sends id + pwd.

Authenticate-ack or –nak.

How many layers does PPP have?

They are ---

2.

Physical: no protocol is defined for the physical, so it uses whatever’s available.

Datalink: PPP uses a variation of HDLC

If CHAP doesn’t relay passwords, how does it authenticate users?

System sends the user a challenge packet with a value. User applies predefined formula, sends result. System uses same formula and same value to create a result. If both results the same, user is let in.

Is an LCP packet encapsulated?

If so, in what?

Yes.

In a PPP frame.

LCP =

Is responsible for ---

Link control protocol.

Estab, maintain, config, terminate links.

Link termination packets: the 2 are ---

Terminate-request

Terminate-ack

PAP =

Password authentic protocol.

PAP packets are encapsulated in a --- frame.

PPP.

PPP = ---

Its task is to ---

Point to point link protocol.

Control and manage data transfer.

SLIP =

Serial line internet protocol.

SLIP has 3 deficiencies which --- doesn’t.

SLIP doesn’t

1. support ---

2. allow the IP address to be ---

3. support user ---

PPP.

Any other protocols except IP.

Assigned dynamically.

Authentication.

Syntax within a syntax. Give an example.

When the payload field in a PPP frame contains an LCP packet.

T/False?  All LCP packets are carried in the payload field of the PPP frame.

T

The 4 CHAP packets are ---

Challenge, response, success, failure.

The boundary flags for a PPP frame are set to ---

01111110

0021₁₆ in the protocol field means ?

This frame is carrying an IP data packet.

8021₁₆ in the protocol field means ?

This frame is carrying an IPCP packet.

IPCP =

Internetwork protocol control protocol.

NCP allows for the --- of data from ---

Encapsulation

Network layer protocols (eg IP) in the PPP frame.

Overall, there are 4 phases in a data transfer. They are ---

-Establish link (= config-request, then PAP authentication, then config-ack).

-Authenticate user (= authent-request, then authentic-ack).

-Network (= config-req, then config-ack, send data, then terminate-req, then terminate-ack).  

-Terminate (= user sends term-req, gets term-ack, then terminates the PPP connection).