© 2009 Pearson Education, Inc. Publishing as Prentice Hall Network Standards Chapter 2 Updated January 2009 Raymond Panko’s Business Data Networks and Telecommunications, 7th edition May only be used by adopters of the book

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 1.2 Five components of data communication 1.Message 2.Sender 3.Receiver 4.Medium 5.Protocol Introduction

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 1.3 Data flow (simplex, half-duplex, and full-duplex)

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 1.4 DATA FLOW/ Transmission Modes Simplex mode:The communication is unidirectional, as on one way street. Only one of the two devices on a link can transmit. For Example, Television Half-Duplex mode: Each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. Full-Duplex mode: In full-duplex mode, both stations can transmit and receive simultaneously. For Example, Telephone Network

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Network Standards Network Standards (Protocols) –Network standards govern the exchange of messages between different host computers, including message order, semantics, syntax, reliability, and connection orientation –Computers are not intelligent, so standards must be very rigid 2-5 Message

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 1. Message Standards (Protocols) Message syntax Message semantics Message order

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Network Standards Network Standards Govern –Message Syntax (organization) Like human grammar Header, data field, and trailer (Figure 2-2) –Message semantics (meaning) HTTP request message: “Please give me this file” HTTP response message: Here is the file. (Or, I could not comply for the following reason) –Message order Turn taking, order of messages in a complex transaction, who must initiate communication, etc.

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : General Message Organization General Message Syntax (Organization) –Primary parts of messages Data Field (content to be delivered) Header (everything before the data field) Trailer (everything after the data field) –The header and trailer act like a delivery envelope for the data field HeaderData FieldTrailer

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : General Message Organization General Message Syntax (Organization) –Header and trailer are further divided into fields TrailerData FieldHeader Destination Address Field is Used by Switches and Routers Like the Address on an Envelope Message with all three parts

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : General Message Organization Data FieldHeader Other Header Field Destination Address Field Message without a trailer

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : General Message Organization Header Other Header Field Destination Address Field Message with only a header e.g. TCP supervisory messages are pure headers (there is no data field content to deliver)

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 2. Reliability Error Detection and Correction

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 2-3: Reliable Transmission Control Protocol (TCP) Session TCP enables two hosts to establish a connection and exchange streams of data. –Provides guarantee that packets delivered –Provide two-way (full duplex) communication 2-13

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Reliable Transmission Control Protocol (TCP) Session The Transmission Control Protocol (TCP) is an important standard in Internet transmission TCP –Receiver acknowledges each correctly-received TCP message (called a TCP segment) –If an acknowledgments is not received by the sender, the sender retransmits the TCP segment –This gives reliability: error detection AND error correction 2

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 15 TCP SourceDestination Can I talk to you? OK. Can I talk to you? OK. Here’s a packet. Got it. Here’s a packet. Here’s a resent packet. Got it. Establish connection. { { { Send packet with acknowledgment. Resend packet if no (or delayed) acknowledgment.

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Reliable TCP Session Client PC TCP Process Webserver TCP Process 4. Data = HTTP Request 5. ACK (4) 6. Data = HTTP Response 7. ACK (6) Carry HTTP Req & Resp (4) Request-Response Cycle for Data Transfer TCP Segment (Message) 4 Carries an HTTP Request Segment 5 Acknowledges It There Is No Need to Resend 1

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Reliable TCP Session Client PC TCP Process Webserver TCP Process Carry HTTP Req & Resp (4) 8. Data = HTTP Request (Error) 8. Data = Retransmits HTTP Request because No ACK was received 9. ACK (8) Error Handling 3 No receipt, so so no ACK

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Unreliable Protocols HTTP is an unreliable protocol –If an HTTP message is lost, there is no retransmission Some protocols detect errors, dropping incorrect messages –There is no retransmission, so these protocols are unreliable –There must be both error detection and error correction for a protocol to be reliable 2-18 Message

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 3. Connection-Oriented and Connectionless Protocols

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Connection-Oriented and Connectionless Protocols Client PC TCP Process Webserver TCP Process Connection-Opening Messages Time Connection-Closing Messages Messages During the Connection In TCP Connection-oriented protocols have formal openings and closings, like human telephone calls

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Connection-Oriented and Connectionless Protocols Message (No Sequence Number) Connectionless Protocol AB Message with Sequence Number A1 Message with Sequence Number A2 Close Connection Connection-Oriented Protocol Open Connection AB Message with Sequence Number B1 Connectionless protocols, like HTTP simply send messages without prior connection openings and without subsequent connection closings Connection-oriented protocols give each message a unique sequence number 4

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 4. The Hybrid TCP/IP-OSI Standards Architecture

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 2-23 Standards Architecture The dominant architecture today is the hybrid TCP/IP-OSI standards architecture shown in the next slide

© 2009 Pearson Education, Inc. Publishing as Prentice Hall2-24 Figure 2-8: Hybrid TCP/IP-OSI Architecture General Purpose (Core Layer) LayerSpecific Layer Purpose Application-application communication Application (5)Application-application interworking Transmission of a packet across an internet Transport (4)Host-host communication Internet (3)Packet delivery across an internet Transmission of a frame across a single network (switched or wireless LAN or WAN) Data Link (2)Frame delivery across a network Physical (1)Device-device connection

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Physical and Data Link Layer Standards in a Switched or Wireless Network A physical link is a connection between two devices: A-X1 (host-switch), X1-X2 (switch-switch), X2-R1 (switch-router) 1 A data link is a frame’s path though a single switched or wireless network: A-R1 (host-router)

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Physical and Data Link Layer Standards in a Switched or Wireless Network –Physical layer standards govern transmission between adjacent devices connected by a transmission medium Switch X1 Physical Link A-X1 Host A Physical Layer

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 2-7: Physical and Data Link Layer Standards in a Switched or Wireless Network Data Link Layer –Data link layer standards govern the transmission of frames across a single network—typically by sending them through several switches along the data link Switch X1 Host A Switch X2 Host B Data Link A-B Frame

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Internet Layer –Internet layer standards govern the transmission of packets across an internet—typically by sending them through several routers along the route : Internet and Data Link Layers in a Routed Network

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Internet and Data Link Layers in a Routed Network Host B Host A Network X Network Y Network Z R1 R2 Data Link A-R1 Data Link R3-B Data Link R1-R2 Route A-B 3 Data Links: One per Network 3 1 Route through the internet

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Internet and Data Link Layers in a Routed Network Host A Mobile Client Station Server Station Switch X2 Switch X1 Switch Data Link A-R1 Router R1 Packet Frame X Network X Route A-B In Network X: Two destination addresses: Packet: Host B (destination host) Frame: Router R1

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Internet and Data Link Layers in a Routed Network Router R1 Router R2 Packet Frame Y To Network X To Network Z Network Y Data Link R1-R2 Route A-B In Network Y: Two destination addresses: Packet: Host B (destination host) Frame: Router R2

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Internet and Data Link Layers in a Routed Network Host B Mobile Client Stations Switch Z1 Switch X2 Switch Z2 Packet Frame Z Network Z Router R2 Router Data Link R2-B

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 2-33 Transport Layer –Transport layer standards govern aspects of end- to-end communication between two end hosts that are not handled by the data link layer –These standards also allow hosts to work together even if the two computers are from different vendors and have different internal designs 2-9: Internet and Transport Layers Standards

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Internet and Transport Layers Standards The internet layer carries packets on the route between the two hosts, across a series of routers. There will be many hops across pairs of routers, so internet layer protocols are kept very simple to reduce cost The transport layer adds functionality for the two hosts to talk with each other to fix errors and do other things 1

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Internet and Transport Layers Standards The internet layer carries packets on the route between the two hosts, across a series of routers. There will be many hops across pairs of routers, so internet layer protocols are kept very simple to reduce cost The transport layer adds functionality for the two hosts to talk with each other to fix errors and do other things 1 Transport Layer End-to-End (Host-to-Host) TCP is reliable and connection-oriented UDP is unreliable and connectionless Internet Layer Hop-by-Hop (Router to Router) IP is connectionless and unreliable

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Application Layer Standards Application Layer Standards –Govern how two applications work with each other, even if they are from different vendors There are many application layer standards because there are many applications –World Wide Web (HTTP) – (SMTP, POP, etc.) –FTP (FTP) –Database (ODBC) –etc.

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 2-37 Standards Layers: Recap Application (5) Transport (4) Internet (3) Data Link (2) Physical (1)

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 6. Reliability Options at the Transport Layer TCP versus UDP

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : TCP and UDP at the Transport Layer Reliability Is Expensive Not all applications need reliability –Voice over IP cannot wait for lost or damaged packets to be retransmitted –Network management protocols need to place as low a burden on the network as possible Both types of applications use the simpler User Datagram Protocol (UDP) instead of TCP

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : TCP and UDP at the Transport Layer ComparisonTCPUDP LayerTransport* Connection-orientation?Connection- oriented Connectionless Reliable?ReliableUnreliable Burden on the two hostsHighLow Traffic burden on the networkHighLow *Note: TCP and UDP are the only transport-layer protocols

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 7. Vertical Communication Between Layer Processes on the Same Host

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered Communication on the Source Host

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered Communication on the Source Host Application Process HTTP Message Transport Process Passes Message Down to Transport Process The process begins when a browser creates an HTTP request message 2 HTTP Message Fragment 1 If the application message is long, the transport process will first fragment it into fragments small enough to fit into single packets HTTP Message Fragment 2 HTTP Message Fragment 3

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Application Process HTTP Message Transport Process HTTP Message TCP Hdr Encapsulation of HTTP Message in Data Field of TCP Segment by adding a TCP header Passes Message Down to Transport Process The process begins when a browser creates an HTTP request message 2-15: Layered Communication on the Source Host

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered Communication on the Source Host When a layer process (N) creates a message, it passes it down to the next-lower-layer process (N-1) immediately The receiving process (N-1) will encapsulate the Layer N message, that is, place it in the data field of its own (N-1) message

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered Communication on the Source Host Transport Process HTTP Message Internet Process TCP Hdr HTTP Message TCP Hdr 1 The transport process then passes the message down to the internet layer process IP Hdr The internet layer process encapsulates The TCP segment in the data field of an IP Packet

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered Communication on the Source Host Internet Process HTTP Message TCP Hdr IP Hdr Data Link Process HTTP Message TCP Hdr IP Hdr Eth Hdr Eth Trlr Encapsulation of IP Packet in Data Field of Ethernet Frame 1

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered Communication on the Source Host Data Link Process HTTP Message TCP Hdr IP Hdr Eth Hdr Eth Trlr Physical Process Physical Layer converts the bits of the frame into signals. There are no messages at the physical layer, so there is no encapsulation at the physical layer The data link process passes the frame down to the physical layer 1

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered Communication on the Source Host Recap

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered Communication on the Source Host The following is the final frame for an HTTP message on an Ethernet LAN HTTP Message TCP Hdr IP Hdr Eth Hdr Eth Trlr L5L4L3L2 Notice the Pattern: From Right to Left: L2, L3, L4, L5, maybe L2 Start with the highest-layer message (in this case, 5) Add headers for each lower layer (L4, L3, and L2, in this case) Don’t forget the possible trailing L2 trailer 4

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Decapsulation on the Destination Host

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Layered End-to-End Communication Encapsulation and decapsulation also occurs on each switch and router along the way In switches, the highest layer is the data link layer, so switches are called Layer 2 devices On routers, the highest layer is the internet layer, So routers are called Layer 3 devices

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 2-53 Figure 2-18: Layered Message Exchange Initiated at the Internet Layer The application layer process does not always initiate communication In ICMP, the internet layer initiates the communication and so is the highest layer

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Combining Horizontal and Vertical Communication Horizontal communication using protocols lets processes talk to their peers on other hosts, switches, or routers Vertical communication links processes on the same device Horizontal and vertical communication work together to provide message delivery

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 8. OSI, TCP/IP, and Other Standards Architectures

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 2-20: The Hybrid TCP/IP-OSI Architecture TCP/IPOSIHybrid TCP/IP-OSIBroad Purpose Application Presentation Session Application (Layer 5) Communication between applications Transport Internet Transport Network Transport (Layer 4) Internet (Layer 3) Internetworking Network Interface Layer Data Link Physical Data Link (Layer 2) Physical (Layer 1) Transmission within a single LAN or WAN

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Physical layer Physical connections between adjacent devices Devices: cables, connectors, etc…

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 58 Data link layer The data link layer is responsible for moving frames in a single switched network. Devices: switches, bridges, NIC’s

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Network layer It is responsible for the delivery of packet inside the network. Devices: routers, firewalls

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Transport layer Controls delivery of data between hosts Connection management, error control,

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 61 Session layer This layer establishes, maintains, and terminates sessions between applications

© 2009 Pearson Education, Inc. Publishing as Prentice Hall 62 Presentation layer Data formatting, conversion, encryption, and compression

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Application layer Provides communication services to applications

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Examples LayerExample 7.) ApplicationHTTP, FTP, SMTP 6.) PresentationASCII, JPEG, PGP 5.) SessionNetBIOS, DHCP, DNS 4.) TransportTCP, UDP 3.) NetworkIP 2.) Data LinkEthernet 1.) PhysicalBits

© 2009 Pearson Education, Inc. Publishing as Prentice Hall PDU’s And the OSI Model LayerPDU Name 7.) ApplicationData 6.) PresentationData 5.) SessionData 4.) TransportSegment 3.) NetworkPacket 2.) Data LinkFrame 1.) PhysicalBits Protocol Data Unit (PDU).

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Characteristics of Protocols Discussed in the Chapter LayerProtocolConnection- Oriented /Connectionless Reliable/ Unreliable 5 (Application)HTTPConnectionlessUnreliable 4 (Transport)TCP Connection- oriented Reliable 3 (Internet)IPConnectionlessUnreliable 2 (Data Link)EthernetConnectionlessUnreliable Note: Only TCP is connection-oriented and reliable 4 (Transport)UDPConnectionlessUnreliable

© 2009 Pearson Education, Inc. Publishing as Prentice Hall Summary of layers

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : OSI and TCP/IP Notes: –Do not confuse OSI (the architecture) with ISO (the organization) –Standards Agency or Agencies OSI : ISO (International Organization for Standardization) ITU-T (International Telecommunications Union– Telecommunications Standards Sector) TCP/IP: IETF (Internet Engineering Task Force)

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : OSI Layers Layer Number OSI NamePurposeUse 1PhysicalPhysical connections between adjacent devices Nearly 100% dominant 2Data LinkEnd-to-end transmission in a single switched network. Frame organization. Switch operation Nearly 100% dominant 3NetworkGenerally equivalent to the TCP/IP internet layer. However, OSI network layer standards are not compatible with TCP/IP internet layer standards Rarely used 4TransportGenerally equivalent to the TCP/IP transport layer. However, OSI transport layer standards are not compatible with TCP/IP transport layer standards Rarely used

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : OSI Layers Layer Number OSI NamePurposeUse 5SessionInitiates and maintains a connection between application programs on different computers If a session is broken, only have to go back to the last rollback point Brilliant idea, but few applications need it and those that do have their own methods for managing sessions Rarely used 6PresentationDesigned to handle data formatting differences, data compression, and data encryption In practice, a category for general file format standards used in multiple applications Rarely used as a layer. However, many file format standards are assigned to this layer. 7ApplicationGoverns remaining application-specific matters Some OSI applications are used

© 2009 Pearson Education, Inc. Publishing as Prentice Hall : Other Major Standards Architectures IPX/SPX –Used by older Novell NetWare file servers for file and print service –Sometimes used in newer Novell NetWare file servers for consistency with older NetWare servers SNA (Systems Network Architecture) –Used by older IBM mainframe computers AppleTalk –Used by Apple Macintosh desktops and notebooks to talk to Macintosh servers