Presentation is loading. Please wait.

Presentation is loading. Please wait.

Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com PPP Last Update 2011.06.01 1.4.0 1.

Published byAmice Shepherd Modified over 8 years ago

Similar presentations

Presentation on theme: "Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com PPP Last Update 2011.06.01 1.4.0 1."— Presentation transcript:

1 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com PPP Last Update 2011.06.01 1.4.0 1

2 Objective Learn what PPP is Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 2

3 3 What is PPP PPP – Point-to-Point protocol is a layer 2 protocol that is used on either asynchronous, in other words dialup, or synchronous data lines as a simple way to transport packets between two peers Its purpose is to get layer 3 packets across a serial point-to-point link that is full duplex PPP was developed to replace SLIP – Serial Line Internet Protocol

4 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 4 What is PPP SLIP does not –Support any layer 3 protocol but TCP/IP –Allow dynamic IP address assignment –Support authentication or encryption –Operate at high speeds PPP also extends on HDLC as described elsewhere, but part of which is used in PPP itself The main extension is the use of NCP

5 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 5 Operation It is often said that PPP defines activity at both the physical and data link layers of the OSI model In practice the only definition that PPP does concerning the physical layer is to say that there must be one, which is somewhat obvious, and to say that it must be a serial point-to-point link

6 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 6 Operation This makes PPP primarily a layer 2 protocol At layer 2, PPP defines three sublayers

7 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 7 PPP Layers Layer 3 NCP LCP HDLC Layer 1

8 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 8 PPP Layered Architecture

9 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 9 PPP at Layer 1 As stated, the physical layer for PPP is specified to be a serial communication method including –EIA/TIA-232 –EIA/TIA-422 –V.35 The only requirement for this serial link is that circuit must be full duplex and asynchronous

10 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 10 PPP at Layer 2 At layer 2 PPP begins to do its work To do this work of carrying data from one end of a point-to-point serial link to the other, PPP must transition between several states

11 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 11 PPP at Layer 2 Idle Establishing Authenticating Networking Terminating

12 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 12 Establishing a PPP Session

13 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 13 PPP Configuration Options

14 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 14 PPP Operation

15 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 15 Transition States In the idle state the link is not being used There is no active carrier on the line In the establishing state the two end points have started communication If any of the PPP options are to be used, they are negotiated here During authentication, which is optional, the end points exchange information to establish they are who they say they are

16 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 16 Transition States When the networking state is reached the real transfer of data begins The connection remains in this state until communication is terminated In the termination state one side closes the link

17 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 17 PPP Frame Format To do its work PPP uses several different frames The major PPP frame looks like this

18 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 18 PPP Frame Format Flag Address Control Protocol Data and Padding FCS Flag

19 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 19 PPP Frame Format These fields do the following –Flag 1 byte This field marks the start of the frame The value is always 0111110 –Address 1 byte No purpose as PPP does not support addressing The address is always 11111111, which is the HDLC broadcast address

20 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 20 PPP Frame Format Control –1 byte –This is used to indicate that transmission of the data will not be sequenced and is to be sent over a connectionless link –The value is always 00000011 Protocol –2 bytes –This field is used to direct whatever is in the data field to its proper location –It identifies the encapsulated protocol

21 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 21 PPP Frame Format Data Field –Variable size, but 1500 bytes is the default –Larger sizes can be used, if both sides agree –This field contains the important stuff FCS –2 bytes, but can be 4 bytes –The FCS – Frame Check Sequence is the CRC used to ensure everything arrived intact

22 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 22 PPP Frame Format –Flag 1 byte This field marks the end of the frame The value is always 0111110

23 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 23 Protocol Field The value in the protocol field is typically expressed as a hexadecimal number Common codes include –IP – 0021 –IPX – 002b

24 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 24 HDLC in PPP Although HDLC is discussed elsewhere as an alternative to PPP as a way to send data over a serial link, a form of HDLC is used to encapsulate the datagrams to be sent over the serial link

25 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 25 Link Control Protocol The LCP - Link Control Protocol is a part of the PPP specification LCP is used to establish, configure, maintain, and terminate links LCP information is carried in the data field of the PPP frame

26 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 26 Link Control Protocol The way a the device knows this data relates to LCP instead of data to be passed up the stack is by looking in the protocol field LCP data is indicated by C021, a hexadecimal number, in that field The LCP looks like this

27 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 27 Link Control Protocol Format Code Identifier Length Information

28 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 28 Link Control Protocol Format The fields in this packet do the following –Code 1 byte The code defines the type of LCP packet this is –Identifier 1 byte This field is used to match a request to a reply One end point places a value in this field This value will be copied to the reply

29 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 29 Link Control Protocol Format –Length 2 bytes –Information Variable in length This field holds the extra information that is required by some types of LCP packets, such as whether authentication will be required

30 PPP Capture File Let’s look at some PPP frames Download –PPP with RIP.cap Open it in Wireshark by double-clicking it Select frame 1 This is a LCP PPP frame In frame 13 we see a PPP ACK Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 30

31 PPP Capture File Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 31

32 PPP Capture File In frame 15 some IP traffic appears Then in frame 16 some CDP traffic Notice in frame 15 that an IP address appears as the links begin to come up Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 32

33 PPP Capture File Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 33

34 PPP Capture File Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 34

35 PPP Capture File In frames 23 and 28 RIP begins to talk at both ends of the link Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 35

36 PPP Capture File Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 36

37 PPP Capture File The RIP responses are in frames 31 and 35 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 37

38 PPP Capture File Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 38

39 PPP Capture File Beginning with frame 50 a series of ping requests and responses go back and forth all carried at layer 2 by PPP Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 39

40 PPP Capture File Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 40

41 PPP Capture File So we see here PPP hard at work carrying all types of information Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 41

42 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 42 Authentication Authentication was an important addition to PPP compared to SLIP Authentication is not needed in a point-to- point link over a T1 line, but it is needed for a dialup connection You want to know who you are talking to whenever you cannot control both ends of the connection

43 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 43 Authentication PPP can use either of two protocols for authentication –PAP –CHAP

44 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 44 PPP Authentication Protocols

45 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 45 PAP

46 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 46 PAP PAP – Password Authentication Protocol is very simple and basically useless It works this way –The user wanting access to an end point sends an authentication request that includes the username and password –The end point either accepts or rejects the request

47 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 47 PAP The problem is the password is sent in clear text PAP packets can be identified by the code C023 in the protocol field

48 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 48 PPP Authentication Protocols

49 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 49 CHAP CHAP provides protection against playback attack through the use of a variable challenge value that is unique and unpredictable

50 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 50 CHAP CHAP – Challenge Handshake Authentication Protocol improves on PAP by keeping the password secret CHAP will also recheck the authentication on a periodic basis CHAP is indicated by C223 in the protocol field

51 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 51 Encapsulation Authentication

52 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 52 CHAP Authentication Process

53 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 53 Configuring PPP Authentication

54 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 54 PAP Configuration

55 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 55 CHAP Configuration

56 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 56 Compression In addition to authentication, compression is another optional service offered by PPP Compression does not have to be used, but it is very useful for dial-up connections

57 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 57 PPP from Layer 2 to 3 At the top of PPP is the NCP – Network Control Protocol NCP is used once LCP has established the connection and any authentication has taken place At this stage NCP connects PPP to the higher level protocols that begin their work at layer 3

58 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 58 PPP from Layer 2 to 3 More specifically it encapsulates the IP, IPX, or whatever other traffic comes down into a form PPP can deal with at layer 2 For example, IPCP – Internetwork Protocol Control Protocol is used by NCP to create and then terminate a connection that will send TCP/IP packets The protocol field 8021 indicates this

59 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 59 Network Control Protocol

60 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 60 Using PPP Using PPP is quite easy on most devices For example to use PPP encapsulation on a Cisco router, just type –encapsulation ppp At the configure interface level

61 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 61 Configuring PPP

62 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 62 PPP Configuration Commands

63 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 63 Verifying PPP

64 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 64 Troubleshooting PPP The first thing to do when a problem arises on a link that uses PPP is to check the physical connection Also check the configuration of physical layer devices, such as the CSU/DSU This is by far the most common source of the trouble

65 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 65 Troubleshooting PPP The next thing to check is the configuration of PPP in the router for a direct link or access server if a dial-up connection is being made The most common error is when authentication is being used for the link The username setting causes the most errors in this case

66 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 66 Troubleshooting PPP When configuring the username on a router, it is the hostname of the router at the other end of the connection Consult the Oppenheimer and Bardwell text for more details on this issue

67 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 67 Debug PPP Authentication

68 For More Information T1: A Survival Guide –Matthew S. Gast –ISBN 0-596-00127-4 Troubleshooting Campus Networks –Priscilla Oppenheimer and Joseph Bardwell –ISBN 0471210137 Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com 68

Download ppt "Copyright 2005-2011 Kenneth M. Chipps Ph.D. www.chipps.com PPP Last Update 2011.06.01 1.4.0 1."

Similar presentations

PPPoE Last Update 2011.07.21 1.4.0 Copyright 2000-2011 Kenneth M. Chipps Ph.D. www.chipps.com 1.

PPPoE Last Update Copyright Kenneth M. Chipps Ph.D. 1.
McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Chapter 12 Point-to-Point Access: PPP.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2004 Chapter 12 Point-to-Point Access: PPP.
Rick Graziani PPP authentication protocols 1. Link establishment - (LCPs) 2. Authentication - Optional (LCPs) 3. Link quality determination.

Rick Graziani PPP authentication protocols 1. Link establishment - (LCPs) 2. Authentication - Optional (LCPs) 3. Link quality determination.
Point-to-Point Protocol (PPP) ผศ. ดร. อนันต์ ผลเพิ่ม Asst.Prof.Anan Phonphoem, Ph.D. Computer Engineering.

Point-to-Point Protocol (PPP) ผศ. ดร. อนันต์ ผลเพิ่ม Asst.Prof.Anan Phonphoem, Ph.D. Computer Engineering.
S4C4 PPP. Protocols Point to Point Protocol Link Control Protocol Network Control Program Password Authentication Protocol Challenge Handshake Authentication.

S4C4 PPP. Protocols Point to Point Protocol Link Control Protocol Network Control Program Password Authentication Protocol Challenge Handshake Authentication.
1 Data Link Protocols Relates to Lab 2. This module covers data link layer issues, such as local area networks (LANs) and point-to-point links, Ethernet,

1 Data Link Protocols Relates to Lab 2. This module covers data link layer issues, such as local area networks (LANs) and point-to-point links, Ethernet,
Point-to-Point Protocol

Point-to-Point Protocol
Gursharan Singh Tatla SLIP and PPP 27-Mar-2011 1

Gursharan Singh Tatla SLIP and PPP 27-Mar
© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—5-1 Establishing Serial Point-To-Point Connections Configuring Serial Point-To-Point Encapsulation.

© 2006 Cisco Systems, Inc. All rights reserved. ICND v2.3—5-1 Establishing Serial Point-To-Point Connections Configuring Serial Point-To-Point Encapsulation.
1 Data Communications Point-to-Point Protocol (PPP)

1 Data Communications Point-to-Point Protocol (PPP)
11-6 HDLC High-level Data Link Control (HDLC) is a bit-oriented protocol for communication over point-to-point and multipoint links. It implements the.

11-6 HDLC High-level Data Link Control (HDLC) is a bit-oriented protocol for communication over point-to-point and multipoint links. It implements the.
11-6 HDLC High-level Data Link Control (HDLC) is a bit-oriented protocol for communication over point-to-point and multipoint links. It implements the.

11-6 HDLC High-level Data Link Control (HDLC) is a bit-oriented protocol for communication over point-to-point and multipoint links. It implements the.
Semester 4 - Chapter 4 – PPP WAN connections are controlled by protocols In a LAN environment, in order to move data between any two nodes or routers two.

Semester 4 - Chapter 4 – PPP WAN connections are controlled by protocols In a LAN environment, in order to move data between any two nodes or routers two.
Point to Point Protocol Operation. Point to Point Protocol Protocol Layers of PPP –Physical Layer –Data Link Layer – HDLC derivative –Other protocols.

Point to Point Protocol Operation. Point to Point Protocol Protocol Layers of PPP –Physical Layer –Data Link Layer – HDLC derivative –Other protocols.
PPP (Point to Point protocol).  On WAN connection, the protocol depends on the WAN technology and communicating equipment:  Examples:  HDLC –  The.

PPP (Point to Point protocol).  On WAN connection, the protocol depends on the WAN technology and communicating equipment:  Examples:  HDLC –  The.
K. Salah 1 Chapter 12 Point-to-Point Access: PPP.

K. Salah 1 Chapter 12 Point-to-Point Access: PPP.
1 CCNA 4 v3.1 Module 3. 2 CCNA 4 v3.0 Module 3 PPP.

1 CCNA 4 v3.1 Module 3. 2 CCNA 4 v3.0 Module 3 PPP.
Example Data Link Protocols 16-10-2012. Quick review Reference Models? Layers? Flow Control? Bit stuffing? Connection Oriented? Synchronous transmission?

Example Data Link Protocols Quick review Reference Models? Layers? Flow Control? Bit stuffing? Connection Oriented? Synchronous transmission?
Point-to-Point Access: PPP. In a network, two devices can be connected by a dedicated link or a shared link. In the first case, the link can be used by.

Point-to-Point Access: PPP. In a network, two devices can be connected by a dedicated link or a shared link. In the first case, the link can be used by.
© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE I Chapter 6 1 Point-to-Point Protocol (PPP) Accessing the WAN – Chapter 2.

© 2006 Cisco Systems, Inc. All rights reserved.Cisco PublicITE I Chapter 6 1 Point-to-Point Protocol (PPP) Accessing the WAN – Chapter 2.

Similar presentations

Ads by Google