Guide to Networking Essentials Fifth Edition Chapter 6 Network - - PowerPoint PPT Presentation

Guide to Networking Essentials Fifth Edition

Chapter 6 Network Communications and Protocols

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Objectives

• Explain the function of protocols in a network
• Describe common protocol suites

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Protocols

• Strictly speaking, protocols are the rules and

procedures for communicating

– For two computers to communicate, they must speak the same language and agree on the rules of communication

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The Function of Protocols

• As protocols serve their functions in the OSI

model, they might work at one or many layers

• When a set of protocols works cooperatively, it’s

called a protocol stack or protocol suite

– The most common protocol stack is TCP/ IP, the Internet protocol suite – IPX/ SPX, used in older versions of Novell NetWare, is disappearing as companies upgrade to newer versions of NetWare – Levels of a protocol stack map to their functions in the OSI model

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Connectionless Versus Connection- Oriented Protocols

• Protocols that use connectionless delivery place

data on the network and assume it will get through

– Connectionless protocols aren’t entirely reliable – Are fast: little overhead, don’t waste time establishing/ managing/ tearing down connections

• Connection- oriented protocols are more reliable

and, consequently, slower

– Two computers establish a connection before data transfer begins

• In a connection, data is sent in an orderly fashion

– Ensures that all data is received and is accurate, or that suitable error messages are generated

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Routable Versus Nonroutable Protocols

• The network layer (OSI) is responsible for moving

data across multiple networks

– Routers are responsible for routing process

• Protocol suites that function at Network layer are

routable or routed protocols; otherwise, they are called nonroutable

– TCP/ IP and IPX/ SPX are routable protocols – An older and nearly obsolete protocol, NetBEUI, is a nonroutable protocol that works well in small networks, but its performance drops considerably as a network grows

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Protocols in a Layered Architecture

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Protocols in a Layered Architecture (continued)

• Some authors consider

session- layer protocols to belong in the Transport layer

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Network Protocols

• Some popular network protocols include:

– Internet Protocol version 4 (IPv4 or simply IP)

• Provides addressing and routing information

– Internetwork Packet Exchange (IPX)

• Novell’s protocol for packet routing and forwarding
• Belongs to the IPX/ SPX protocol suite
• Serves many of the same functions as TCP/ IP’s IP

– Internet Protocol version 6 (IPv6)

• A new version of IP that’s being implemented on many

current networking devices and operating systems – Addresses some weaknesses of IPv4

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Transport Protocols

• Transport protocols can be connection- oriented (reliable)
• r connectionless (best- effort) delivery

– Transmission Control Protocol (TCP)

• Responsible for reliable data delivery in TCP/ IP

– Sequential Packet Exchange (SPX)

• Novell’s connection- oriented protocol used to guarantee

data delivery – NetBIOS/NetBEUI

• NetBIOS establishes/ manages communications between

computers and provides naming services

• NetBEUI provides data transport services for these

communications

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Application Protocols

• Application protocols provide services to client

applications

– Simple Mail Transport Protocol (SMTP) in TCP/IP – File Transfer Protocol (FTP) in TCP/IP – Simple Network Management Protocol (SNMP)

• Manages and monitors network devices (TCP/ IP)

– NetWare Core Protocol (NCP)

• Novell’s client shells and redirectors

– AppleTalk File Protocol (AFP)

• Apple’s remote file- management protocol

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Common Protocol Suites

• Because most protocols contain a combination of

components, these components are usually bundled as a protocol suite

– TCP/ IP

• Dominates the networking arena to the point of

making most of the other suites nearly obsolete

– IPX/ SPX – NetBIOS/ NetBEUI – AppleTalk

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Transmission Control Protocol/ Internet Protocol (TCP/ IP)

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TCP/ IP Network Layer Protocols

• Internet Protocol version 4 (IPv4) is a Network

layer protocol that provides source and destination addressing and routing for the TCP/ IP suite

– Connectionless protocol; fast but unreliable

• Internet Control Message Protocol (ICMP) is a

Network layer protocol used to send error and control messages between systems or devices

– The Ping utility uses ICMP to request a response from a remote host to verify availability

• Address Resolution Protocol (ARP) resolves

logical (IP) addresses to physical (MAC) addresses

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IP, ICMP, and ARP in Action

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IP, ICMP, and ARP in Action (continued)

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TCP/ IP: Transport Layer Protocols

• Transmission Control Protocol (TCP) is the

primary Internet transport protocol

– Connection oriented using a three- way handshake – Message fragmentation and reassembly

• "Byte- oriented" means that messages are reassembled

in correct order

– Uses acknowledgements to ensure that all data was received and to provide flow control

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TCP/ IP: Transport Layer Protocols

• User Datagram Protocol (UDP) is connectionless

– Generally faster, although less reliable, than TCP

• Doesn’t segment data or resequence packets
• Doesn’t use acknowledgements for reliability
• Used by NFS and DNS
• Stream Control Transmission Protocol (SCTP) is

a newer protocol

– More flexibility than TCP – "Transaction" (stream) oriented – Originally intended for telephony over IP

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TCP/ IP Application Layer Protocols

• Domain Name System (DNS)

– Session layer name- to- address resolution protocol

• Hypertext Transport Protocol (HTTP)

– To transfer Web pages from Web server to browser

• File Transfer Protocol (FTP)

– For file transfer and directory and file manipulation

• Telnet

– Remote terminal emulation; operates at layers 7- 5

• Simple Mail Transport Protocol (SMTP)

– Operates at layers 7- 5; provides messaging services

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IP Addressing

• Logical addresses are 32 bits (4 bytes) long

– Each byte is represented as an octet (decimal number from 0 to 255) – Usually represented in dotted decimal notation

• E.g., 172.24.208.192

– Address has two parts: network and host ID

• E.g. 172.24.208.192 (172.24.0.0 and 208.192)

– Categorized into ranges referred to as classes

• Class system provides basis for determining which

part of address is the network and which is the host ID

• The first octet of an address denotes its class

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IP Addressing (continued)

• Classes

– Class A: first octet between 1- 126

• 16,777,214 hosts per network address

– Class B: first octet between 128- 191

• 65,534 hosts per network address

– Class C: first octet between 192- 223

• 254 hosts per network address

– Class D: first octet between 224- 239

• Reserved for multicasting

– Class E: first octet between 240- 255

• Reserved for experimental use

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IP Addressing (continued)

• 127.0.0.0 network is called the loopback address

– localhost always corresponds to address 127.0.0.1

• IETF reserved addresses for private networks

– Class A addresses beginning with 10 – Class B addresses from 172.16 to 172.31 – Class C addresses from 192.168.0 to 192.168.255 – These addresses can’t be routed across the Internet – To access the Internet, NAT is needed – IPv6 eliminates need for private addressing; provides a 128- bit address (vs. IPv4’s 32 bits)

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IP Network Address Classes

• Class A:

1.0.0.0/ 8 .. 126.0.0.0/ 8 (0000 0001 / 8 .. 01111110 / 8)

– reserved/private: 10.0.0.0/ 8 , or just 10/ 8 (0000 1010 / 8)

• Loopback: 127.0.0.0/ 8 (01111111 / 8)
• Class B:

128.0.0.0 / 16 .. 191.255.0.0 / 16 (1000 0000 . 00000000 / 16 .. 10111111 . 11111111 / 16)

– reserved/private: 172.16.0.0 / 16 .. 172.31.0.0 / 16 ,

• r just 172.16/ 12

(1010 1100 . 0001 0000 / 12 .. 1010 1100 . 0001 1111 / 12)

• Class C:

192.0.0.0 / 24 .. 223.255.255.0 / 24 (11000000 . 00000000 . 00000000 / 24 .. 1101 1111 . 11111111 . 1111 1111 / 24)

– reserved/private: 192.168.0.0 / 24 .. 192.168.255.0 / 24 , or just 192.168/ 16 (1100 0000 . 1010 1000 . 0000 0000 / 16 .. 1100 0000 . 1010 1000 . 1111 1111 / 16)

• Class D (Multicast):

224.0.0.1 .. 239.255.255.254 ( 1110 0000 . 0000 0000 . 00000000 . 00000001 .. 1110 1111 . 11111111 . 11111111 . 11111110 )

• Class E (Experimental):

240.0.0.0 .. 255.255.255.255 ( 1111 0000 . 0000 0000 . 00000000 . 00000000 .. 1111 1111 . 11111111 . 11111111 . 11111111 )

• Classless InterDomain

Routing (CIDR) supersedes Classes A, B, and C.

• Classes D and E

(Multicast, Experimental) are not part of CIDR.

• Loopback isn't affected

by CIDR

• Classless InterDomain

Routing (CIDR) supersedes Classes A, B, and C.

• Classes D and E

(Multicast, Experimental) are not part of CIDR.

• Loopback isn't affected

by CIDR

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Classless InterDomain Routing (CIDR)

• Addressing by class has been superseded by a

more flexible addressing method

– Classless InterDomain Routing (CIDR) – The network and host demarcation can be made with any number of bits from beginning of address – E.g., a Class C address’s network section is 24 bits

• Using CIDR, an address registry can assign an address

with a network section of 26 bits – 192.203.187.0/ 26

– Subnetting divides network address in two or more subnetwork addresses (with fewer host IDs for each)

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Why Subnet?

• Subnetting

– Makes more efficient use of available IP addresses – Enables dividing networks into logical groups – Can make network communication more efficient

• Broadcast frames are sent to all computers on the

same IP network

– Hubs and switches forward broadcast frames; routers do not – Broadcast domain: extent to which a broadcast frame is forwarded without going through a router – Subnetting reduces broadcast traffic

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Subnet Masks

• Subnet mask determines which part of address

denotes network portion and which denotes host

– 32- bit number – A binary 1 signifies that the corresponding bit in the IP address belongs to the network portion; a 0 signifies that bit in address belongs to host portion – Default subnet mask uses a 255 in each octet in address that corresponds to the network portion

• Class A: 255.0.0.0
• Class B: 255.255.0.0
• Class C: 255.255.255.0

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Some Simple Binary Arithmetic

• Four kinds of binary calculations:

– Converting between binary and decimal – Converting between decimal and binary – Understanding how setting high- order bits to the value of 1 in 8- bit binary numbers corresponds to specific decimal numbers – Recognizing the decimal values for numbers that correspond to low- order bits when set to 1

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Converting Decimal to Binary

• 125 is converted to binary as follows:

– 125 divided by 2 equals 62, remainder 1 – 62 divided by 2 equals 31, remainder 0 – 31 divided by 2 equals 15, remainder 1 – 15 divided by 2 equals 7, remainder 1 – 7 divided by 2 equals 3, remainder 1 – 3 divided by 2 equals 1, remainder 1 – 1 divided by 2 equals 0, remainder 1

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Converting Binary to Decimal

• To convert 11010011 to decimal:
• 1. Count the total number of digits in the number (8)
• 2. Subtract one from the total (8 - 1 = 7)
• 3. That number (7) is the power of 2 to associate with

the highest exponent for two in the number

• 4. Convert to exponential notation, using all the

digits as multipliers

• 5. 11010011, therefore, converts to:

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Bit Patterns

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Calculating a Subnet Mask

• To decide how to build a subnet mask:
• 1. Decide how many subnets you need
• 2. Decide how many bits you need to meet or exceed

the number of required subnets

• Use the formula 2n, with n representing the number
• f bits you must add to the starting subnet mask
• 3. Borrow bits from the top of the host portion of the

address down

• 4. Ensure that you have enough host bits available to

assign to computers on each subnet (2n- 2)

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Calculating a Subnet Mask (continued)

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Calculating a Subnet Mask (continued)

Setting Up the Subnets

• Network address: 172.31.0.0/ 16

– "/ 16" means 16 bits for network address – Class B, like BloomU's 148.137.0.0/ 16

• Four subnets:

– 4 = 22, so 2 bits for "subnet address"

• Subnet mask – identifies address bits that are

used for network- and- subnet address

– 16 + 4 = 18 bits for a complete network- and- subnet address – 1111 1111

1111 1111 1111

1111 11 1100

– 255. 255.

• 255. 255. ??? . 0

Subnet Hosts

• How many bits for host addresses?

– 32 total – 18 network = 14 bits for host addresses – 214 = 16,384 – the first and last addresses (network, broadcast) –

• Subnet- A address?

– 1010 1010

1100 0001

1111 0000

• First, last host in subnet A?

– 1010

00

0000 0000

0001 - - - 172.31.0.1 – 1010

11

1111 1111

1110 - - - 172.31.63.254

• Broadcast address for subnet A?

– 1010

11

111 111

1111 - - - 172.31.63.255

Subnets Hosts - continued

• Subnet- B/ C/ D addresses?

– 1010 1010

1100 0001

1111 0100

– 1010 1010

1100 0001

1111 1000

– 1010 1010

1100 0001

1111 1100

– dotted- decimal forms?

• First, last host in subnets B, C, D?

– binary, dotted- decimal forms…

• Broadcast address for subnets B, C, D?

– binary, dotted- decimal forms…

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Calculating Supernets

• Supernetting “borrows” bits from network portion
• f an IP address to “lend” those bits to host

portion

– Permits consecutive IP network addresses to be combined and viewed in a single logical network

• Combining two or more small networks into one

larger network is only one reason to supernet

– Supernetting can combine multiple routing table entries into a single entry, which can drastically decrease the table’s size on Internet routers – This reduction in routing table size increases the speed and efficiency of Internet routers

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Network Address Translation (NAT)

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Dynamic Host Configuration Protocol (DHCP)

• Detailed configuration of devices, keeping track of

assigned addresses and to which machine they were assigned, etc., is difficult in large networks

– DHCP was developed to make this process easier – DHCP server must be configured with a block of available IP addresses and their subnet masks – Clients must be configured to use DHCP

• Broadcast request message is sent on boot

– Client leases the address the server assigns to it – If no answer is received, in an APIPA- enabled OS, the

computer assigns itself an address (169.254.x.x)

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Internet Protocol Version 6 (IPv6)

• IPv6 solves several IPv4 problems

– Limiting 32- bit address space

• An IPv6 address is 128 bits long

– Lack of built- in security

• IPSec provides authentication and encryption

– A sometimes complicated setup

• IPv6 is autoconfiguring (stateless or stateful)

– Lack of built- in QoS

• QoS headers in IPv6 packets can identify packets that

require special or priority handling, making applications such as streaming audio and video much easier to implement

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IPv6 Addresses

• IPv6 addresses are specified in hexadecimal

format in 16- bit sections separated by a colon

– Longhand notation: 2001:260:0:0:0:2ed3:340:ab – Shorthand notation: 2001:260::2ed3:340:ab

• If one of the 16- bit numbers doesn’t require four

hexadecimal digits, the leading 0s are omitted

– Addresses have a three- part addressing hierarchy

• A public topology (first three 16- bit sections)
• A site topology (next 16 bits)
• An interface identifier (last 64 bits)

– Derived from the MAC address on the host’s NIC

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Other Protocol Suites

• Other protocol suites are sometimes used on older

networks, where the need to change to TCP/ IP is not warranted, or in environments suited to the suite’s features

– NetBIOS/ NetBEUI

• Used primarily on older Windows networks

– IPX/ SPX

• Designed for use on NetWare networks

– AppleTalk

• Used almost exclusively on Macintosh networks

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NetBIOS and NetBEUI

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IPX/ SPX

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AppleTalk

• Although the AppleTalk standard defines physical

transport in Apple Macintosh networks, it also establishes a suite of protocols those computers use to communicate

• Apple created AppleTalk Phase II to allow

connectivity outside the Macintosh world

• AppleTalk divides computers into zones

– Allow a network administrator to logically group computers and other resources that have frequent communication, in a manner similar to subnetting

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Implementing and Removing Protocols

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Summary

• Many protocols are available for network

communications, each with its strengths/ weaknesses

• The TCP/ IP protocol suite dominates network

communication in part due to its use on the Internet

• IP addressing involves several concepts, including

address classes, subnetting, and supernetting

• IPv6 will eventually replace IPv4 because it offers

several advantages: 128- bit address space, autoconfiguration, built- in security, and QoS