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Chapter 6. Networking Protocols. Introduction. Topics Protocol Basics Protocol Characteristics Transmission Control Protocol/Internet Protocol Network Access Layer Protocols Internet Layer Protocols Transport Layer Protocols Application Layer Protocols. Protocol Basics.

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Chapter 6

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chapter 6

Chapter 6

Networking Protocols

  • Topics
    • Protocol Basics
    • Protocol Characteristics
    • Transmission Control Protocol/Internet Protocol
    • Network Access Layer Protocols
    • Internet Layer Protocols
    • Transport Layer Protocols
    • Application Layer Protocols
protocol basics
Protocol Basics
  • A protocol is a set of rules 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 stacksorprotocol stacks
protocol characteristics
Protocol Characteristics
  • Data packets can be sent over a medium using any one of a number of protocols
  • Protocols can be either standard or proprietary
  • Standard protocols
    • Support universal communication so equipment from different manufacturers can interact
proprietary protocols
Proprietary Protocols
  • Proprietary protocols are vendor specific and are usually protected by patents or other legal stipulations
  • Proprietary protocols include
    • XNS
    • NetBIOS
    • IPX/SPX
    • AppleTalk
    • DECNet
xerox network system xns
Xerox Network System (XNS)
  • XNS is a suite of protocols created by Xerox in the late 1970s for Ethernet networks
  • XNS is rarely used in 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
ipx spx
  • Novell introduced Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX) in the early 80s
  • 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
  • DECnetis 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
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 standard for many LANs, as well as for the Internet
transmission control protocol internet protocol12
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 protocol13
Transmission Control Protocol/Internet Protocol
  • The TCP/IP suite maps the seven layers of the OSI model to a four-layer model
  • The TCP/IP model focuses more on interconnectivity than on functional layers
transmission control protocol internet protocol15
Transmission Control Protocol/Internet Protocol
  • The TCP/IP model is also called the Internet reference model
  • Layers
    • Network Access
    • Internet
    • Transport
    • Application
network access layer protocols
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 framing (DL) and physical delivery of datagrams
network access layer protocols18
Network Access Layer Protocols
  • Access Layer Protocols deliver data to computers and devices on the network
  • These include Serial Line Interface Protocol (SLIP) and Point-to-Point Protocol (PPP)
  • These protocols support serial data transmission over a modem
network access layer protocols19
Network Access Layer Protocols
  • Other Network Access protocols
    • the Address Resolution Protocol (ARP)
    • the Reverse Address Resolution Protocol (RARP)
  • Provide a means of mapping IP addresses to MAC addresses
  • These protocols provide a means for last hop message delivery
internet layer protocols
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
internet layer protocols23
Internet Layer Protocols
  • The Internet Protocol (IP) is responsible addressing and routing of data packets
  • Routing tables created by routing protocols are used to forward messages from one network to another
  • It is a low overhead, best effort delivery protocol
ip message format
IP Message Format
  • IP Packets or datagrams consist of a header, data (payload), and a trailer
  • The header contains routing information
  • Trailers contain a checksum value, which is used to determine if data was corrupted during transmission
packet delivery
Packet Delivery
  • IP compares the destination address in the packet header to router table addresses
  • If the address corresponds to a local network, the datagram is delivered to the appropriate computer
  • If the address corresponds to a remote network, the packet is passed to a router for delivery
routing controls
Routing Controls
  • Time to Live (TTL)
    • prevents packets from circulating on the network forever
    • The TTL value is decremented by one each time the packet traverses a router (each hop)
    • Default value is usually 120
  • Fragmentation – Routers may break oversize packets into fragments, then route the individual fragments, which are reassembled at the destination computer
  • Each subnetwork 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 as a single packet on another network
  • Fragmentation is the process of dividing a packet into smaller pieces
internet control message protocol
Internet Control Message Protocol
  • ICMP
    • Internet layer protocol
    • uses IP to send its messages
    • uses IP as if it was higher-level protocol
    • used as an aid for other protocols
    • used to test for connectivity and search for configuration errors in a network
icmp error messages
ICMP Error Messages
  • Destination Unreachable – message returned to sender if a router cannot forward an IP datagram
  • Buffer Full – message returned until congestion due to full buffer has abated
  • Hops – an IP datagram has passed through its allotted number of routers
  • Ping – ICMP echo messages are returned to sender if destination exists and is reachable
  • Traceroute – ICMP timeouts used to discover path a packet takes as it traverses an internetwork
  • Used to test connectivity
  • uses the ICMP echo function
  • A small packet containing an ICMPecho 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, an echo message is returned to the sender
  • Originally developed for the Unix operating system
  • used to track the path a packet takes from sender to destination
  • Calculates travel time for each hop
  • uses an ICMP echo request packet to determine the path
transport layer protocols
Transport Layer Protocols
  • The protocol layer above the Internet layer
  • provides a reliable communication service so that extended two-way conversations may take place
  • responsible for providing end-to-end data integrity
transport layer protocols36
Transport Layer Protocols
  • Transmits data as a stream of characters
  • initiates and terminates the connections between sender and receiver
  • Two main protocols
    • Transmission Control Protocol (TCP)
    • User Datagram Protocol (UDP)
transmission control protocol tcp
Transmission Control Protocol (TCP)
  • provides connection-oriented data transmission
  • supports multiple data streams
  • provides for flow and error control
  • uses sequence numbers and acknowledgements to guarantee delivery
tcp connections
TCP Connections
  • TCP communications are port to port
  • A socket is an IP address plus a port number
  • Well-defined port numbers have been assigned to common applications
port numbers
Port Numbers
  • Used to communicate with upper layers by keeping track of conversations with different services (applications)
  • Well-Known port numbers define different application locations on the server that hosts the applications
user datagram protocol udp
User Datagram Protocol (UDP)
  • a connectionless protocol
  • Low overhead - does not provide either sequencing or acknowledgements
  • used a lot in telephony traffic and the Remote Procedure Call (RPC)
  • UDP does not provide the reliability that TCP provides
application layer protocols
Application Layer Protocols
  • The top layer in the Internet reference model
  • Provides applications access to network services
application layer protocols46
ApplicationLayer Protocols
  • Telnet – remote client access to resources on a Telnet server
  • FTP – reliable file transport using TCP; requires authentication
  • TFTP – Unreliable file transport using UDP
  • NFS – allows file sharing on different platforms
  • SMTP – delivers mail to a server; use POP or IMAP to retrieve mail
  • LPD – for printer sharing
  • X Window – graphical interface for client/server applications
  • SNMP –Provides network management by polling capable devices
  • DNS –maps host names to IP addresses
  • DHCP – provides IP address configuration to workstations
file transfer and remote access
File Transfer and Remote Access
  • 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
  • Both FTP and Telnet use TCP as their Transport layer protocol
mail and internet
Mail and Internet
  • Simple Mail Transfer Protocol (SMTP) which supports basic message delivery services to mail servers on port 25
  • HyperText Transfer Protocol (HTTP) which is a low-overhead Web browser service protocol that uses port 80
management and news
Management and News
  • 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
address assignment and name mapping
Address Assignment and Name Mapping
  • 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