Addressing Through the Layers

Data Link Layer Address

Network Layer Address

Data Link Layer Address

Also called MAC address, after Media Access Control (MAC) sublayer

Number uniquely defining a network node Manufacturer-hard codes the address

– Block ID

– Device ID

Network Layer Address

Resides at Network level of OSI Model Follows hierarchical addressing scheme Can be assigned through operating system

software Why would we use BOTH a Network address

AND a MAC address?

Data Link Layer Sublayers

LLC – Upper sublayer– Provides common interface– Supplies reliability and flow control services

MAC– Lower sublayer– Appends the physical address of the destination

computer onto the frame

IEEE Ethernet and Token Ring differ here

Chapter Three

Network

Protocols

Chapter Objectives

Identify the characteristics of TCP/IP, IPX/SPX, NetBIOS, and AppleTalk

Understand the position of network protocols in the OSI Model

Identify the core protocols of each protocol suite and its functions

Understand each protocol’s addressing scheme Install protocols on Windows 95 and Windows

NT clients

Introduction to Protocols

Protocols– Rules a network uses to transfer data

– Protocols that can span more than one LAN segment are routable

Multiprotocol Network– Network using more than one protocol

TCP/IP

Transmission Control Protocol/Internet Protocol (TCP/IP)– Suite of small,

specialized protocols called subprotocols

OSI Model TCP/IP

FIGURE 3-1 TCP/IP compared to the OSI Model

TCP/IP Compared to theOSI Model

Application layer roughly corresponds to Application and Presentation layers

Transport layer roughly corresponds to Session and Transport layers

Internet layer is equivalent to the Network layer Network Interface layer roughly corresponds to

Data Link and Physical layers

Internet Protocol (IP)

Provides information about how and where data should be delivered

Subprotocol enabling TCP/IP to internetwork– Traverse more than one LAN segment and more than

one type of network through a router

– Subnets• The individual networks joined together by routers in an

internetwork

Internet Protocol (IP)

IP Datagram – IP portion of a

TCP/IP frame that acts as an envelope for data

– Contains information necessary for routers to transfer data between subnets

FIGURE 3-2 Components of an IP datagram

TCP

Internet Protocol (IP)

What is a Datagram?– Packaged data sent without establishment of a

communication channel or connection

IP does not guarantee delivery of data– Connectionless

• Allows the protocol to service a request without requesting a verified session and without guaranteeing delivery of data

Transport Control Protocol (TCP)

Provides reliable data delivery services Connection oriented

– Requires the establishment of a connection between communicating nodes before the protocol will transmit data

TCP segment– Holds the TCP data fields

– Becomes encapsulated by the IP datagram

Transport Control Protocol (TCP)

Port– Address on host where an application makes itself

available to incoming data

FIGURE 3-3 A TCP segment

header

TCP/IP Protocols

Telnet, FTP, SMTP, SNMP

TransportUDP,, TCP

Application

InternetIP , ICMP

Network Interface

ARP

Additional Core Protocols of the TCP/IP Suite

User Datagram Protocol (UDP)– A connectionless transport service– Less overhead than TCP

Internet Control Message Protocol (ICMP)– Notifies the sender that something has gone

wrong in the transmission process and that packets were not delivered

– No error control– PING uses this

Additional Core Protocols of the TCP/IP Suite

Address Resolution Protocol (ARP)– Obtains the MAC address of a host or node– Creates a local database mapping the MAC

address to the host’s IP address– Used in conjunction with IP

TCP/IP Application Layer Protocols

Telnet is used to log on to remote hosts using TCP/IP Protocol

File Transfer Protocol (FTP) is used to send and receive files via TCP/IP

Simple Mail Transfer Protocol (SMTP) is responsible for moving messages from one e-mail server to another, using the Internet and other TCP/IP-based networks

Simple Network Management Protocol (SNMP) manages devices on a TCP/IP network

Addressing in TCP/IP

IP Address– Logical address used in TCP/IP networking– Unique 32-bit number

• Divided into four groups of octets (8-bit bytes)

• Separated by periods

Addressing in TCP/IP

How did we get the # of hosts? - 28 , 216 , 224

Though 8 bits have 256 possible combinations, only the numbers 1 through 254 are used to identify networks and hosts

Numbers 0 and 255 are reserved for broadcasts– Transmissions to all stations on a network

TABLE 3-1 Commonly used TCP/IP classes (4 exist)

Addressing in TCP/IP

Loopback address– IP address reserved for communicating from a

node to itself

– Value of the loopback address is always 127.0.0.1

InterNIC– Authority for Internet IP addressing and

domain name registration– Also known as Network Solutions

Addressing in TCP/IP

Firewall– Specialized device

– Selectively filters or blocks traffic between networks

– May be strictly hardware-based or may involve a combination of hardware and software

Host– Computer connected to a network using the

TCP/IP protocol

Addressing in TCP/IP

In IP address 131.127.3.22, to convert the first octet (131) to a binary number:– On Windows 95, click Start, point to Programs,

point to Accessories, then click Calculator– Click View, then click Scientific (make sure Dec

option button is selected)– Type 131, then click Bin option button– The binary number 131, 10000011, appears in the

display window

Addressing in TCP/IP

Static IP address– IP address manually assigned to a device

Dynamic Host Configuration Protocol protocol– Application layer protocol

– Manages the distribution of IP addresses on a network

Viewing IP Information On a Windows 95

workstation connected to a network– Click Start, then click

Run– Type winipcfg

• (ipconfig /all (NT at DOS prompt)

– Click OK– Click More Info

– Click OK to close window

FIGURE 3-4 Example of an IP configuration window

Addresses and Names

In addition to using IP addresses, TCP/IP networks use names for networks and hosts– Each host requires a host name– Each network requires a network name, also

called a domain name• Symbolic name that identifies and Internet domain

IPX/SPX Internetwork Packet

Exchange/Sequenced Packet Exchange (IPX/SPX)– Protocol originally

developed by Xerox– Modified and adopted

by Novell in the 1980s for the NetWare network operating system

NWLink - Microsoft IPX/SPX emulation

FIGURE 3-6 IPX/SPX compared to the OSI Model

IPX/SPX Core Protocols

IPX – Network layer – Connectionless routing

Sequence Packet Exchange (SPX)– Works in tandem with IPX to ensure data are

received (and acknowledged):• Whole

• In sequence

• Error free

IPX/SPX Core Protocols

Service Advertising Protocol (SAP)– Runs directly over IPX– Used by NetWare servers and routers to advertise to

entire network which services they can provide

NetWare Core Protocol (NCP)– Handles requests for services between clients and

servers

Read for yourself

NetBIOS and NetBEUI Network Basic Input Output System

(NetBIOS)– Originally designed by IBM to provide Transport

and Session layer services

– Adopted by Microsoft as its foundation protocol

– Microsoft added Application layer component called NetBIOS Enhanced User Interface (NetBEUI)

NetBEUI

Fast and efficient protocol Consumes few network resources Provides excellent error correction Requires little configuration 254 connection limit removed for later

versions Non routable

AppleTalk

Protocol suite used to interconnect Macintosh computers

Originally designed to support peer-to-peer networking among Macintoshes

Can now be routed between network segments and integrated with NetWare- and Microsoft-based networks

Installing Protocols

After installing protocols, they must be binded Binding

– Process of assigning one network component to work with another