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 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