lesson 1: local area network (lan) technologies lan encapsulations ethernet token ring fddi ieee...

Lesson 1: Local Area Network (LAN) Technologies LAN encapsulations Ethernet Token Ring FDDI IEEE 802.11

LAN Encapsulations

Delimitation Protocol identification Addressing Bit-level integrity check

Ethernet

Ethernet II IEEE 802.3 IEEE 802.3 SNAP

Destination AddressSource Address

Payload ...

EtherType

Frame Check Sequence

Preamble

46 - 1,500 bytes

Ethernet II

The Maximum Extent Ethernet Network

Repeater

2500 meters

A B

Slot time = 57.6 s

IEEE 802.3 Frame Format

Destination AddressSource Address

DSAPSSAP

Control

Payload

Length

Frame Check Sequence

Preamble

IEEE 802.2 LLC Header

Start Delimiter

. . .

IEEE 802.3 Header

IEEE 802.3 Trailer

IEEE 802.3 SNAP Frame Format

Destination AddressSource Address

DSAPSSAP

Control

IP Datagram

Length

Frame Check Sequence

Preamble

IEEE 802.2 LLC Header

Start Delimiter

. . .

IEEE 802.3 Header

IEEE 802.3 Trailer

Organization CodeEtherType

= 0x00-00-00

= 0x08-00

SNAPHeader

38-1,492 bytes

= 0xAA

= 0xAA

= 0x03

Special Bits on Ethernet MAC Addresses

Destination Address

Source Address

0 - Individual1 - Group

0 - Universal Admin1 - Local Admin

0 - No Routing1 - Routing Present

0 - Universal Admin1 - Local Admin

IEEE 802.5 Frame Format

DSAPSSAP

Control

IEEE 802.2 LLC Header

. . .

IEEE 802.5 Header

IEEE 802.5 Trailer

Start DelimiterAccess ControlFrame Control

Destination AddressSource Address

Frame Check Sequence

End DelimiterFrame Status

Payload

IEEE 802.5 SNAP Frame Format

IEEE 802.5 Header

IEEE 802.5 Trailer

Start DelimiterAccess ControlFrame Control

Destination AddressSource Address

Frame Check Sequence

End DelimiterFrame Status

DSAPSSAP

Control

IP Datagram

IEEE 802.2 LLC Header

. . .

Organization CodeEtherType

= 0x00-00-00

= 0x08-00

SNAPHeader

= 0xAA

= 0xAA

= 0x03

Special Bits on Token Ring MAC Addresses

Destination Address

0 - Individual1 - Group

0 - Universal Admin1 - Local Admin

0 - No Routing1 - Routing Present

0 - Universal Admin1 - Local Admin

Source Address

0 - Functional1 - Nonfunctional

FDDI Frame Format

DSAPSSAP

Control

IEEE 802.2 LLC Header

. . .

FDDI Header

FDDI Trailer

PreambleStart DelimiterFrame Control

Destination AddressSource Address

Frame Check Sequence

End DelimiterFrame Status

Payload

FDDI SNAP Frame Format

FDDIHeader

FDDI Trailer

PreambleStart DelimiterFrame Control

Destination AddressSource Address

Frame Check Sequence

End DelimiterFrame Status

DSAPSSAP

Control

IP Datagram

IEEE 802.2 LLC Header

. . .

Organization CodeEtherType

= 0x00-00-00

= 0x08-00

SNAPHeader

= 0xAA

= 0xAA

= 0x03

Up to 4,352 bytes

IEEE 802.11 Frame Format

Address 1Address 2

DSAPSSAP

Control

Payload

Address 3

Frame Check Sequence

Frame Control

IEEE 802.2 LLC Header

Duration/ID

. . .

IEEE 802.11 Header

IEEE 802.11 Trailer

Sequence ControlAddress 4

Protocol VersionType

SubtypeTo DS

From DSMore Fragments

RetryPower Management

More DataWEP

Order

The Frame Control Field

IEEE 802.11 SNAP Frame Format

Address 1Address 2

DSAPSSAP

Control

IP Datagram

Address 3

Frame Check Sequence

Frame Control

IEEE 802.2 LLC Header

Duration/ID

. . .

IEEE 802.11 Header

IEEE 802.11 Trailer

Sequence Control

Organization CodeEtherType

= 0x00-00-00

= 0x08-00 SNAPHeader

= 0xAA

= 0xAA

= 0x03

Lesson 2: Wide Area Network (WAN) Technologies WAN encapsulations Point-to-Point Protocol Frame relay

WAN Encapsulations

Delimitation Protocol identification Addressing Bit-level integrity check

Point-to-Point Protocol (PPP)

Data Link Layer encapsulation method Link Control Protocol (LCP) Network Control Protocols (NCPs)

PPP Encapsulation Using HDLC Framing

FlagAddressControl

Protocol

IP Datagram

Frame Check SequenceFlag

= 0x7E

= 0xFF

= 0x03

= 0x00-21

= 0x7E

. . .

Typical PPP Framing

Flag

Protocol

IP Datagram

Frame Check SequenceFlag

= 0x7E

= 0x21

= 0x7E

. . .

Multilink Protocol Long Sequence Number Format

Flag

Protocol

Beginning Fragment BitEnding Fragment Bit

ReservedSequence Number

Multilink Fragment

Frame Check SequenceFlag

= 0x7E

= 0x3D

= 0x7E

. . .

Multilink Protocol Short Sequence Number Format

Flag

Protocol

Beginning Fragment BitEnding Fragment Bit

ReservedSequence Number

Multilink Fragment

Frame Check SequenceFlag

= 0x7E

= 0x3D

= 0x7E

. . .

Frame Relay Encapsulation for IP Datagrams

FlagAddressControl

= 0x7E

. . .

Frame Check SequenceFlag

IP Datagram

= 0x7E

NLPID = 0xCC

= 0x03

Frame Relay Two-Byte Address Field

DLCIC/REA

DLCIFECNBECN

DEEA

= 0

= 1

= 0 First byte

Second byte

Lesson 3: Address Resolution Protocol (ARP)

Overview of ARP ARP frame structure ARP in Windows Server 2008 and

Windows Vista Inverse ARP Proxy ARP

Overview of ARP Resolves the next-hop IP address of a node to

its corresponding media access control (MAC) addressFor direct deliveries, ARP resolves the datagram’s

destination IP address For indirect deliveries, ARP resolves the IP address

of a neighboring router ARP message exchange

Broadcast ARP RequestUnicast ARP Reply

The ARP or Neighbor Cache

Table of resolved IP addresses and their corresponding MAC addresses

Checked before sending ARP Request messageNetwork black holes

ARP Frame Structure

Hardware Type

Protocol Type

Hardware Address Length

Protocol Address Length

Operation

Sender Hardware Address

Sender Protocol Address

Target Hardware Address

Target Protocol Address

= 0x0800

= 6

= 4

ARP in Windows Server 2008 and Windows Vista

Works in the same way as Neighbor Discovery in IP version 6 (IPv6)

Neighbor Discovery processesAddress resolutionDuplicate address detectionNeighbor unreachability detection

Address Resolution

ARP RequestSHA: 00-60-08-52-F9-D8SPA: 10.0.0.99THA: 00-00-00-00-00-00TPA: 10.0.0.1

ARP ReplySHA: 00-10-54-CA-E1-40SPA: 10.0.0.1THA: 00-60-08-52-F9-D8TPA: 10.0.0.99

Node 1IP Address: 10.0.0.99

MAC Address: 00-60-08-52-F9-D8

Node 2IP Address: 10.0.0.1

MAC Address: 00-10-54-CA-E1-40

Duplicate Address Detection

ARP Request for one’s own addressReply received: Duplicate IP addressNo reply received: Unique IP address for the

network segment Duplicate address ARP exchange

Broadcast ARP Request sent by offending nodeUnicast ARP Reply sent by defending node

Neighbor Unreachability Detection

Reachable if IP packets sent to the neighboring node were received and processed by the neighboring node Exchange of ARP Request and ARP Reply

messages Indications from Transmission Control

Protocol (TCP) that sent data is being acknowledged

Neighbor Cache Entry States

INCOMPLETE REACHABLE STALE DELAY PROBE

Inverse ARP Used for non-broadcast multiple access

(NBMA) technologies (frame relay) MAC-level address is known, but IP

address of node at the other end of the connection is not

Inverse ARP message exchange InARP Request InARP Reply

Proxy ARP

Proxy ARP Device

Node 1

Node 2

SingleSubnet

A Windows Server 2008 Remote Access Server and Proxy ARP

Remote Access ClientAssigned address: 10.1.1.201

Windows Server 2008Remote Access Server

10.1.1.0/24

10.1.1.50

10.1.1.8

Configured range:10.1.1.200-10.1.1.254

Lesson 4: Point-to-Point Protocol (PPP)

PPP overview PPP connection process Link Control Protocol (LCP) PPP authentication protocols Network Control Protocols (NCPs) PPP over Ethernet (PPPoE)

PPP Overview

A Data Link Layer encapsulation method LCP for negotiating the Data Link Layer

characteristics NCPs for negotiating Network Layer

protocols over the point-to-point connection

PPP Connection Process

1. PPP configuration using LCP

2. Authentication

3. Callback

4. Protocol configuration using NCPs

LCP Frame StructureFlag

AddressControl

Protocol

CodeIdentifier

LengthData

Frame Check SequenceFlag

= 0x7E

= 0xFF

= 0x03

= 0xC0-21

= 0x7E

. . .

LCPFrame

LCP Options

Protocol

CodeIdentifier

Length

TypeLength

Option Data

= 0xC0-21

. . .

LCPOption

LCP Negotiations LCP messages

Configure-RequestConfigure-NakConfigure-RejectConfigure-Ack

For Peer A and Peer BPeer A initiates an LCP negotiation for the data to

be sent by Peer BPeer B initiates a separate LCP negotiation for the

data to be sent by Peer A

PPP Authentication Protocols Password Authentication Protocol (PAP) Challenge Handshake Authentication

Protocol (CHAP) Microsoft-CHAP version 2 (MS-CHAP v2) Extensible Authentication Protocol (EAP)

PAP Simple, plaintext authentication protocol PAP authentication process:

1. Connection-initiating PPP peer (the calling peer) sends a PAP Authenticate-Request message to the authenticating PPP peer (the answering peer)

2. The answering peer validates the user name and password and sends either a PAP Authenticate-Ack or PAP Authenticate-Nak message

PAP Authentication Request Message

Protocol

CodeIdentifier

LengthPeer ID Length

Peer IDPassword Length

Password

= 0xC0-23

. . .

= 1

. . .

PAP Authenticate-Ack and Authenticate-Nak Messages

Protocol

CodeIdentifier

LengthMessage Length

Message

= 0xC0-23

. . .

= 2 or 3

CHAP More secure authentication protocol

Provides proof of knowledge of password without sending the password

CHAP authentication process1. The answering peer sends a CHAP Challenge

message that contains a challenge string2. The calling peer sends a CHAP Response message

that contains a Message Digest-5 (MD5) hash of the CHAP session ID, the challenge string, and the user’s password

3. The answering peer verifies hash and sends a CHAP Success or CHAP Failure message

CHAP Challenge or Response Messages

Protocol

CodeIdentifier

LengthValue Size

ValueName

= 0xC2-23

. . .

. . .

CHAP Success or Failure Messages

Protocol

CodeIdentifier

LengthMessage

= 0xC2-23

. . .

MS-CHAP v2 Microsoft authentication protocol

MS-CHAP with mutual authentication

MS-CHAP v2 authentication process1. The answering peer sends a CHAP Challenge

message that contains a challenge string

2. The calling peer sends an MS-CHAP v2 Response message that contains an encrypted response and a challenge for the answering peer

3. The answering peer verifies the response and sends a CHAP Success message with an encrypted response based on the calling peer’s challenge

4. The calling peer verifies the answering peer’s response

MS-CHAP v2 Response MessageProtocol

CodeIdentifier

LengthValue Size

Peer ChallengeReserved

Windows NT ResponseFlagsName

= 0xC2-23

. . .

. . .

. . .

(16 bytes)

(8 bytes)

. . . (24 bytes)

= 49

EAP

An extension to PPP to allow for more extensibility and flexibility for authentication methods for PPP connections

EAP messages:EAP-RequestEAP-ResponseEAP-SuccessEAP-Failure

EAP Request or Response Messages

Protocol

CodeIdentifier

LengthType

Type-specific data

= 0xC2-27

. . .

= 1 or 2

EAP Success or Failure Messages

Protocol

CodeIdentifier

Length

= 0xC2-27

= 3 or 4

= 4

EAP Authentication Types

EAP-Transport Layer Security (TLS) Protected EAP (PEAP)

EAP-MS-CHAP v2 EAP-TLS

NCPs IP Control Protocol (IPCP)

IP Compression Protocol IP Address Primary Domain Name System (DNS) Server Address Primary NetBIOS Name Server (NBNS) Server Secondary DNS Server Address Secondary NBNS Server

Compression Control Protocol (CCP) Microsoft Point-to-Point Compression (MPPC) Microsoft Point-to-Point Encryption (MPPE)

Encryption Control Protocol (ECP)

PPP over Ethernet (PPPoE)

Method of encapsulating PPP frames so that they can be sent over an Ethernet network

PPPoE connection phases:1. Discovery phase

Presence of an access concentrator (AC) Determine a PPPoE session ID

2. PPP session phase A PPP connection is established and used for data

transfer

Destination AddressSource Address

PPPoE payload ...

EtherType

Frame Check Sequence

Preamble

40 - 1,494 bytes

VersionTypeCode

Session IDLength

= 1

= 1

PPPoE Frame Format

Destination AddressSource Address

PPP ProtocolPPP payload ...

EtherType

Frame Check Sequence

Preamble

38 - 1,492 bytes

VersionTypeCode

Session IDLength

= 0

= 1

= 1

= 0x88-64

PPPoE Frame Format for PPP Frames