Chapter 6 Networking Protocols

Chapter 6

Networking Protocols

Introduction

• Look at:– Protocol Basics(6.1)– A Brief Protocol Prospectus(6.2)– Transmission Control Protocol/Internet

Protocol (TCP/IP)(6.3)– TCP/IP Network Access Layer

Protocols(6.4)

Introduction

• Look at:– TCP/IP Internet Layer Protocols(6.5)– TCP/IP Transport Layer Protocols(6.6)– TCP/IP Application Layer Protocols(6.7)

Protocol Basics

• A protocol is a set of rules and conventions that determines how computers exchange information over a network medium

• A wide variety of communication protocols exist, and many of them rely on others for operation

• Groups of related protocols are often called stacks or protocol stacks

A Brief Protocol Prospectus

• Data packets can be sent over the medium using any one of a number of protocols

• Protocols can be either standard or proprietary

• A standard protocol is one where users can purchase equipment from any manufacturer because it is programmed to communicate universally


• A proprietary protocol is usually protected by patents or other legal stipulation

• Proprietary protocols include – XNS– NetBIOS – IPX/SPX – AppleTalk – DECNet


• XNS stands for the Xerox Network Systems

• This is a suite of protocols created by Xerox in the late 1970s and early 1980s for use in Ethernet networks

• XNS is used in very few new networks today


• The Network Basic Input/Output System (NetBIOS) interface was developed in 1983 for IBM

• The intention was to allow applications on different computers to communicate within a local area network

• NetBIOS was not designed for large networks


• In the early 1980s, Novell introduced its own network protocol stack called Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX)

• This stack was based on the XNS network protocol family

• IPX is the Network layer protocol • SPX is the Transport layer protocol


• AppleTalk is Macintosh’s networking protocol • It is designed to be a flexible, simple, and

inexpensive network means for connecting computers, peripherals, and servers

• Newer versions of Macintosh operating systems use TCP/IP and SMB as default protocols rather than AppleTalk

• AppleTalk is a protocol and LocalTalk is a media type


• DECnet is a proprietary network protocol designed by Digital Equipment Corporation

• Currently two versions of DECnet are in use:– DECnet Phase IV which is based on the

Phase IV Digital Network Architecture (DNA)

– DECnet/OSI also called DECnet Phase V is a layered model

Transmission Control Protocol/Internet Protocol

• TCP/IP is considered the language of the Internet

• It is the most widely used protocol today• It is a suite, or stack, of small, specialized

protocols• Because of its routing ability, TCP/IP has

become the protocol of choice for many LANs, as well as the basis for the Internet, making it the standard


• In the early 1970s, the Department of Defense funded ARPA to design a new set of computer communication protocols that would allow multiple networks to be interconnected in a flexible and dynamic way

• The protocol developed was originally called Network Control Protocol

• This success led to the implementation of the two main Internet protocols

• These are Transmission Control Protocol and Internet Protocol (TCP/IP)


• TCP/IP’s implementation of the OSI model makes functionality simpler

• It maps the same seven layers of the OSI model to a four-layer TCP/IP model instead

• The TCP/IP model focuses more on delivering interconnectivity than on functional layers


• Since TCP/IP is the language of the Internet, you may also hear this model referred to as the Internet reference model

• The Layers are:– Network Access– Internet– Transport– Application

TCP/IP Network Access Layer Protocols

• The Network Access layer is the lowest layer in the model

• It Maps to Layers 1 (Physical) and 2 (Data Link) of the OSI model

• It is responsible for the delivery of datagrams by creating a frame for the network type and then sending the data to the wire


• This layer contains the protocols that are used to deliver data to computers and devices on the network

• These include Serial Line Interface Protocol (SLIP) and Point-to-Point Protocol (PPP)

• These are communication protocols for serial data transmission by which IP packets can be sent over a modem


• Other protocols that are used at this layer include a means to relate different types of addresses to each other:– the Address Resolution Protocol (ARP)– the Reverse Address Resolution Protocol

(RARP)• This layer defines the logical network layout

so routers can determine where to forward packets

TCP/IP Internet Layer Protocols

• The layer above the Network Access layer is called the Internet layer

• It manages the routing of packets that are to be forwarded on to different networks

• It relies on routable protocols for delivery


• The Internet Protocol (IP) is responsible for making data packets routable

• It is a forwarding protocol that uses routing tables that are created by routing protocols

• It is a simple, connectionless internetworking protocol

• The basis of IP is how it uses routing tables to make decisions about routing an IP packet


• Every host on the network needs an IP address

• TCP/IP uses a 32-bit Layer 3 address in the format xxx.xxx.xxx.xxx to identify the network and the host compute

• Each set of xxx is called an octet


• There are five classes of IP addresses their corresponding numbers are:– Class A: Has a first octet number between

1 and 126 and can support a network with 16,777,216 hosts.

– Class B: Has a first octet number between 128 and 191 and can support 65,536 hosts


• There are five classes of IP addresses their corresponding numbers are:– Class C: Has a first octet number between

192 and 223 and can support 254 hosts per network

– Class D: Begins at 224 and ends at 239. This address class is reserved for sending multicast messages


• A There are five classes of IP addresses their corresponding numbers are:– Class E: Begins with 240 and ends at 255.

This address class is reserved for experimental use

– The IP address 127.0.0.1 is used as the loopback address


• A datagram is the packet format defined by IP • Datagrams are packets that consist of a

header, data, and a trailer • The header contains information that the

network needs to route the datagram • Trailers typically contain a checksum value,

which is used to ensure that the data is not modified in transit


• IP delivers the datagram by checking the destination address in the header

• When IP checks the destination address in the header, if it is the address of a host on the local network, the datagram is delivered directly to the destination

• If it is not on the local network, the datagram is passed on for delivery


• Each router that a datagram passes through is considered a hop

• A system transmits IP datagrams as fast as it can generate them

• IP has two features that can affect throughput– the IP Time to Live (TTL) – IP Fragmentation


• By interconnecting multiple switches with redundant paths, you overcome problems with faulty cables or port failures

• Another less well-known side effect of a loop is the corruption of the forwarding tables on all the switches

• It would take very little time before Layer 2 broadcast loops completely destroy the functionality of a network


• The Spanning Tree Protocol (STP) prevents bridging loops by identifying a preferred path through a series of looped bridges

• Administrators can provide redundancy and fault-tolerance by wiring a loop, and then using STP turn off ports that would cause loops to occur

• If a primary link fails, STP will reactivate the back-up port allowing normal operation of the network to continue


• The TTL field is actually the number of hops the datagram has made

• IP places a limit on how long a datagram may live in the network

• Specifications for higher-layer protocols usually assume that the maximum time a datagram can live in the network is only two minutes


• Each type of network has a maximum transmission unit (MTU), which is the largest packet it can transfer

• A datagram received from one network may be too large to be transmitted in a single packet on another network

• It may be necessary to divide the datagram into smaller pieces

• This division process is called fragmentation


• Internet Control Message Protocol (ICMP) is part of the Internet layer and uses IP datagram delivery to send its messages

• ICMP uses the basic support of IP as if it was higher-level protocol, but it is actually an integrated part of IP

• ICMP is a protocol meant to be used as an aid for other protocols

• It is used to test for connectivity and search for configuration errors in a network


• PING uses the ICMP echo function • A small packet containing an ICMP echo

message is sent through the network to a particular IP address

• The computer that sent the packet then waits for a return packet

• If the connections are good and the target computer is up, the echo message return packet will be received


• PING is one of the most useful network tools available because it tests the most basic function of an IP network

• Traceroute was originally developed for the Unix operating system but is used for many operating systems and most routers

• It is used to track the path a packet takes to get to its destination

• It measures how long it takes to travel through each hop to get to its target


• Traceroute uses an ICMP echo request packet to find the path

• Besides assisting in troubleshooting functions such as PING and Traceroute, ICMP capabilities include:– Announcing network errors– Congestion– Timeout notification

TCP/IP Transport Layer Protocols

• The protocol layer above the Internet layer is the Transport layer

• It is responsible for providing end-to-end data integrity

• It also provides a reliable communication service so that an extended two-way conversation may take place


• This layer accepts and returns information to be transmitted as a stream of characters

• It uses open and close commands to initiate and terminate the connection

• It consists of two protocols:– Transmission Control Protocol (TCP) – User Datagram Protocol (UDP)


• TCP provides connection-oriented data transmission

• It can support multiple data streams

• It provides for flow and error control

• It uses sequence numbers and acknowledgements to guarantee delivery


• Sockets make up a TCP connection

• The two most typical network applications that use TCP are:– File Transfer Protocol (FTP) – Telnet

• Telnet uses port 23

• FTP uses port 21


• UDP does not provide either sequencing or acknowledgements

• It is a connectionless protocol

• It is used a lot in telephony traffic and the Remote Procedure Call (RPC)

• The major difference between TCP and UDP is reliability

TCP/IP Application Layer Protocols

• The top layer in the Internet reference model is the Application layer

• This is how applications and certain services access the network

• It provides the services that applications use to communicate over the network

• It serves as a service provider for workstations and applications.


• The most widely known and implemented TCP/IP Application layer services are:– File Transfer Protocol (FTP) which allows

files to be uploaded and downloaded on port 21

– Telnet which uses terminal emulation for access to remote hosts using port 23


• The most widely known and implemented TCP/IP Application layer services are:– Simple Mail Transfer Protocol (SMTP)

which supports basic message delivery services between mail servers on port 25

– HyperText Transfer Protocol (HTTP) which is a low-overhead Web browser service protocol that uses port 80


• The most widely known and implemented TCP/IP Application layer services are:– Simple Network Management Protocol

(SNMP) which uses UDP port 161 to collect information from network devices.

– Network News Transfer Protocol (NNTP): handles distribution and posting of news articles using port 119


• The most widely known and implemented TCP/IP Application layer services are:– Dynamic Host Configuration Protocol

(DHCP) allows for automatic IP addressing– Domain Name Service (DNS) uses UDP

port 53 for resolving domain names to IP addresses

Chapter 6 Networking Protocols

Documents

protocol basicsa protocol

network protocol stack

proprietary network

protocol basics6

protocol of choice

protocol todayit

brief protocol prospectus6

brief protocol prospectusxns