Post on 15-Jan-2016
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 Brief Protocol Prospectus
• A proprietary protocol is usually protected by patents or other legal stipulation
• Proprietary protocols include – XNS– NetBIOS – IPX/SPX – AppleTalk – DECNet
A Brief Protocol Prospectus
• 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
A Brief Protocol Prospectus
• 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
A Brief Protocol Prospectus
• 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
A Brief Protocol Prospectus
• 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
A Brief Protocol Prospectus
• 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
Transmission Control Protocol/Internet Protocol
• 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)
Transmission Control Protocol/Internet Protocol
• 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
Transmission Control Protocol/Internet Protocol
• 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
TCP/IP Network Access Layer Protocols
• 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
TCP/IP Network Access Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Internet Layer Protocols
• 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
TCP/IP Transport Layer Protocols
• 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/IP Transport Layer Protocols
• 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
TCP/IP Transport Layer Protocols
• 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
TCP/IP Transport Layer Protocols
• 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.
TCP/IP Application Layer Protocols
• 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
TCP/IP Application Layer Protocols
• 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
TCP/IP Application Layer Protocols
• 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
TCP/IP Application Layer Protocols
• 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