Network

Protocols

Introduction to Protocols

Protocol Rules 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

TCP/IP model File Transfer Protocol (FTP) Hypertext Transfer Protocol (HTTP) Simple Mail Transfer Protocol (SMTP) Domain Name System (DNS) Trivial File Transfer Protocol (TFTP)

The common transport layer

protocols include: Transport Control Protocol (TCP) User Datagram Protocol (UDP)

The primary protocol of the

Internet layer is: Internet Protocol (IP)

TCP/IP model

TCP/IP Compared to theOSI Model

Application layer roughly corresponds to Session, Application, and Presentation layers of OSI Model

Transport layer roughly corresponds to Transport and session layers of OSI Model

Internet layer is equivalent to Network layer of OSI Model

Network Interface layer roughly corresponds to Data Link and Physical layers of 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

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

IP header format

IP header format: Version

• 4 bits.• Indicates the version of

IP currently used.– IPv4 : 0100– IPv6 : 0110

• 4 bits.• Indicates the version of

IP currently used.– IPv4 : 0100– IPv6 : 0110

IP header format: Header length

• 4 bits.• IP header length : Indicates the

datagram header length in 32 bit words (4 bits), and thus points to the beginning of the data.

• 4 bits.• IP header length : Indicates the

datagram header length in 32 bit words (4 bits), and thus points to the beginning of the data.

IP header format: Service type

• 8 bits.• Specifies the level of importance

that has been assigned by a particular upper-layer protocol.• Precedence. • Reliability. • Speed.

• 8 bits.• Specifies the level of importance

that has been assigned by a particular upper-layer protocol.• Precedence. • Reliability. • Speed.

IP header format: Total length

• 16 bits.• Specifies the length of the

entire IP packet, including data and header, in bytes.

• 16 bits.• Specifies the length of the

entire IP packet, including data and header, in bytes.

IP header format: Identification

• 16 bits.• Identification contains an integer

that identifies the current datagram.• Assigned by the sender to aid in

assembling the fragments of a datagram.

• 16 bits.• Identification contains an integer

that identifies the current datagram.• Assigned by the sender to aid in

assembling the fragments of a datagram.

IP header format: Flags

• 3 bits.• The second bit specifying whether the

packet can be fragmented .• The last bit specifying whether the packet

is the last fragment in a series of fragmented packets.

• 3 bits.• The second bit specifying whether the

packet can be fragmented .• The last bit specifying whether the packet

is the last fragment in a series of fragmented packets.

IP header format: Fragment offset

• 13 bits.• The field that is used to help piece together

datagram fragments.• The fragment offset is measured in units of

8 octets (64 bits). • The first fragment has offset zero.

• 13 bits.• The field that is used to help piece together

datagram fragments.• The fragment offset is measured in units of

8 octets (64 bits). • The first fragment has offset zero.

IP header format: Time to Live

• 8 bits.• Time-to-Live maintains a counter that

gradually decreases to zero, at which point the datagram is discarded, keeping the packets from looping endlessly.

• 8 bits.• Time-to-Live maintains a counter that

gradually decreases to zero, at which point the datagram is discarded, keeping the packets from looping endlessly.

IP header format: Protocol

• 8 bits.• Indicates which upper-layer protocol receives

incoming packets after IP processing has been completed• 06 : TCP• 17 : UDP

• 8 bits.• Indicates which upper-layer protocol receives

incoming packets after IP processing has been completed• 06 : TCP• 17 : UDP

IP header format: Header checksum

• 16 bits.• A checksum on the header only,

helps ensure IP header integrity.

• 16 bits.• A checksum on the header only,

helps ensure IP header integrity.

IP header format: Addresses

• 32 bits each.• Source IP Address• Destination IP Address

• 32 bits each.• Source IP Address• Destination IP Address

IP header format: Options

• Variable length.• Allows IP to support various options,

such as security, route, error report ...

• Variable length.• Allows IP to support various options,

such as security, route, error report ...

IP header format: Padding

• The header padding is used to ensure that the internet header ends on a 32 bit boundary.

• The header padding is used to ensure that the internet header ends on a 32 bit boundary.

Ethereal Lab (Analyzing the IP Header)

Use Ethereal to capture some frames. Open one of the frames and look at the IP header. Based on what you see, try to answer the following:

What is the IP version? What is the IP header length? What is the type of Service? What is the time to live? What is the protocol? What is the source IP address? What is the destination IP address?

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

Ethereal Lab (Analyzing the TCP Header)

Use Ethereal to capture some frames. Open one of the frames and look at the TCP header. Based on what you see, try to answer the following:

What is the source Port? What is the destination Port? What is the sequence Number? What Is the Acknowledgement Number? What is the header Length?

Additional Core Protocols of the TCP/IP Suite User Datagram Protocol (UDP)

Connectionless transport service Internet Control Message Protocol (ICMP)

Notifies sender of an error in transmission process and that packets were not delivered

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

host’s IP address

ARP Lab

TCP/IP Application Layer Protocols

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

Labs

FTP Lab Telnet Lab

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

Addressing in TCP/IP

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

Number 255 is reserved for broadcasts Broadcast are transmissions to all stations on a network

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 Internet Corporation for Assigned Names and

Numbers (ICANN) 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

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

Viewing Current IP Information

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)

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

NetBIOS Addressing

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

Chapter Summary Protocols define standards for

communication between nodes on a network

Protocols vary in speed, transmission efficiency, utilization of resources, ease of setup, compatibility, and ability to travel between one LAN segments

TCP/IP is the most popular network protocol

Chapter Summary TCP/IP suite of protocols can be divided into

four layers roughly corresponding to seven layers of OSI Model

Operating in Transport or Network layers of OSI Model, TCP/IP core protocols provide communications between hosts on a network

Each IP address is a unique 32-bit number, divided into four groups of octets separated by periods

Chapter Summary Every host on a network must have a unique

number Internetworking Packet Exchange/Sequenced

Packet Exchange (IPX/SPX) is a protocol originally developed by Xerox then modified and adopted by Novell in the 1980s for its NetWare network operating system

Core protocols of IPX/SPX provide services at Transport and Network layers of OSI Model

Chapter Summary Addresses on an IPX/SPX network are called

IPX addresses Network Basic Input Output System

(NetBIOS) was originally developed by IBM to provide Transport and Session layer services

Microsoft adopted NetBIOS as its foundation protocol, then added an Application layer component called NetBIOS Enhanced User Interface (NetBEUI)

Chapter Summary To transmit data between network nodes,

NetBIOS needs to know how to reach each workstation Each workstation must have a NetBIOS name

AppleTalk is the the protocol suite used to interconnect Macintosh computers

An AppleTalk network is separated into logical groups of computers called AppleTalk zones

Chapter Summary Though Apple has improved AppleTalk’s ability

to use different network models and span network segments, it remains unsuited to large LANs or WANs

In addition to zone names, AppleTalk uses node IDs and network numbers to identify computers on a network

Though some protocols (such as NetBIOS) require no configuration after installation, others (such as TCP/IP) do require configuration