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Chapter Three
Network
Protocols
Introduction to Protocols
Protocol


Rules network uses to transfer data
Protocols that can span more than one LAN
segment are routable
SNA & DLC becoming outdated due to nonroutability
Multiprotocol network

Network using more than one protocol
TCP/IP
OSI Model
TCP/IP
Transmission
Control
Protocol/Internet
Protocol (TCP/IP)

Suite of small,
specialized
protocols called
subprotocols
Figure 3-1: TCP/IP compared to the OSI Model
The TCP/IP Core Protocols
Certain subprotocols of TCP/IP suite


Operate in Transport or Network layers of OSI
Model
Provide basic services to protocols in other
layers of TCP/IP
TCP and IP are most significant core
protocols in TCP/IP suite
Internet Protocol (IP)
Provides information about how and where
data should be delivered
Subprotocol that enables TCP/IP to
internetwork


To internetwork is to traverse more than one
LAN segment and more than one type of
network through a router
In an internetwork, the individual networks that
are joined together are called subnetworks (or
subnets)
Internet Protocol (IP)
IP datagram


IP portion of
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
Internet Protocol (IP)
Version


IPv4 – current version used for 20 years
IPv6 – in process
Time to live (TTL) – max time, in seconds,
that a datagram can remain on the
network before it is discarded

Also corresponds to # of router hops
Internet Protocol (IP)
IP is an unreliable, connectionless
protocol, which means it does not
guarantee delivery of data

Connectionless
Allows protocol to service a request without
requesting verified session and without
guaranteeing delivery of data
Transport Control Protocol (TCP)
TCP

Provides reliable data delivery services

Connection-oriented subprotocol
Requires establishment of connection between
communicating nodes before protocol will transmit
data
TCP segment


Holds TCP data fields
Becomes encapsulated by IP datagram
Transport Control Protocol (TCP)
Port

Address on host where application makes itself available to
incoming data
Figure 3-3:
A TCP
segment
Additional Core Protocols of the
TCP/IP Suite
User Datagram Protocol (UDP)


Connectionless transport service
Lack of sophistication makes it more efficient than TCP
Live audio/video transmissions over the Internet
Internet Control Message Protocol (ICMP)


Notifies sender of an error in transmission process and that
packets were not delivered
Sits between IP & TCP in Internet layer of TCP/IP model
Used by PING diagnostic tool
Address Resolution Protocol (ARP)


Obtains MAC address of host or node
Creates local database mapping MAC address to host’s IP
address
TCP/IP Application Layer
Protocols
These protocols work over TCP (or UDP) and IP:
Telnet

Used to log on to remote hosts using TCP/IP protocol suite
File Transfer Protocol (FTP)

Used to send and receive files via TCP/IP
Simple Mail Transfer Protocol (SMTP)

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)
that are separated by periods


IP addresses are assigned and used
according to very specific parameters
Example: 144.92.43.178
Addressing in TCP/IP
Table 3-1: Commonly used TCP/IP classes
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

Broadcast are transmissions to all stations on a network
Addressing in TCP/IP
Group A



Only 126 available – used/reserved for large
corporations or governments
Share the first octet (1-126)
i.e. 23.78.110.109, 23.164.32.97
Group B


Share the first two octets (128-191)
i.e. 168.34.88.29, 168.34.55.41
Group C


Share the first three octets (192-223)
i.e 204.139.118.7, 204.139.118.14
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 (try it)
Internet Corporation for Assigned Names and
Numbers (ICANN) – formerly InterNIC

Non-profit organization currently designated by
U.S. government to maintain and assign IP
addresses
Addressing in TCP/IP
Firewall



Specialized device (typically a router)
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
IP address data are sent across the network
in binary form
In IP address 131.127.3.22, to convert the
first octet (131) to a binary number:



On Windows 2000, 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 equivalent of 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
(DHCP)


Application layer protocol
Manages dynamic distribution of IP addresses
on a network
Viewing Current IP Information
Figure 3-4:
Example of an IP
configuration
window
Viewing Current IP Information
Figure 3-5:
IP address
information
on a
Windows
2000
workstation
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
Together, host name and domain name
constitute the fully qualified domain name
(FQDN)
IPX/SPX
Internetwork Packet
Exchange/Sequence
d Packet Exchange
(IPX/SPX)


Protocol originally
developed by Xerox
Modified and adopted
by Novell in the
1980s for the
NetWare network
operating system
Figure 3-6: IPX/SPX compared
to the OSI Model
IPX/SPX Core Protocols
Internetwork Packet Exchange (IPX)




Operates at Network layer of OSI Model
Provides routing and internetworking services
Similar to IP in TCP/IP suite
Socket – logical address assigned to a specific process
Figure 3-7:
Components
of an IPX
datagram
IPX/SPX Core Protocols
Sequenced Packet Exchange (SPX)


Belongs to Transport layer of OSI Model
Works in tandem with IPX to ensure data are
received:
Whole
In sequence
Error free
Similar to TCP
IPX/SPX Core Protocols
Figure 3-8: SPX packet encapsulated by an IPX datagram
IPX/SPX Core Protocols
Service Advertising Protocol (SAP)



Works in Application, Presentation, Session,
and Transport layers of OSI Model
Runs directly over IPX
Used by NetWare servers and routers to
advertise to entire network which services
they can provide
Can lead to unnecessary network traffic
IPX/SPX Core Protocols
NetWare Core Protocol (NCP)



Works within Presentation and Sessions
layers of OSI Model
Works over IPX
Handles requests for services between clients
and servers
Addressing in IPX/SPX
IPX address


Address assigned to a device on an IPX/SPX
network
Contains two parts:
Network address (external network number)

Established Network Admin when network is installed
Node address

NIC MAC address
Example (8.12):

000008A2:0060973E97F3
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 NetBEUI
NetBIOS and NetBEUI
NetBIOS Enhanced User Interface







Fast and efficient protocol
Consumes few network resources
Provides excellent error correction
Requires little configuration
Can handle only 254 connections
Does not allow for good security
By itself, it is not routable
NetBIOS and NetBEUI Compared
to the OSI Model
Figure 3-9: NetBIOS/NetBEUI compared to the OSI Model
NetBIOS Addressing
Figure 3-10:
Identification
tab in Network
properties
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 Microsoftbased networks
AppleTalk networks are separated into logical
groups of computers called AppleTalk zones
Apple has begun supporting TCP/IP
AppleTalk and OSI Model
Figure 3-11: AppleTalk protocol compared to OSI Model
Addressing in AppleTalk
AppleTalk node ID

Unique 8-bit or 16-bit number identifying a
computer on an AppleTalk network
AppleTalk network number

Unique 16-bit number identifying the network
to which a node is connected
Installing Protocols
After installing protocols, they must be
binded to NICs and services they run on or
with

Binding
Process of assigning one network component to
work with another