1. COMP 421 /CMPET 401 COMMUNICATIONS and NETWORKING CLASS 2

2. OSI Reference Model a Developed by the International Standards Organization (ISO) to facilitate the international standardization of communications protocols a For U.S.: ANSI (American National Standard Institute) - www.ansi.org a OSI is ISO's Basic Reference Model for Open Systems Interconnect (hence: ISO/OSI) a The Reference Model itself is not a Network Architecture (does not specify any protocols or services)

3. The ISO/OSI Reference Model a The model describes computer communications protocols in a general sense to facilitate discussion a No assumptions are made regarding: u Programming language bindings u Operating system bindings u Applications programming interfaces a Development of the model started in the mid-1970’s a Biggest Problems u Very long time to complete the model and protocol standards u Very hard to understand the detailed standards u Difficult (expensive) to get the standards documents

4. OSI MODEL

5. The seven layers divided into two important subnets: 1. Communications Subnet – This is comprised of the lower 3 layers 2. Host Process – This is comprised of the upper three layer The network layer is middle layer and the first end to end layer. It acts as buffer between the two subsets.

6. ISO/OSI Reference Model - Why 7 Layers a One layer for each level of abstraction a Each layer performs (ideally) a limited, well defined function a Functions for each layer are selected with International Standardization as a goal a Layer boundaries are chosen to minimize information crossing the interface a Want to keep the model manageable (5 would have been nice) but not have to jumble together distinct functions

7. Data Unit OSI Model Application Session Transport Network Physical Presentation Data Link Application Session Transport Network Physical Presentation Data Link App Process XApp Process Y Physical Transmission Medium Communication Path BITS Data Unit Application Data AH PH SH TH NH F A CFCS F

8. OSI Layer 1 Layer 1 is the Physical Layer. It handles bit transmission between one node and the next. The functions of this layer include interfacing with the transmission media, encoding the data signal, defining the range of the voltage or current magnitudes, defining the connector sizes, shape, and anything generally associated with the physical transmission of a bit stream.

9. OSI Layer 1 - Physical layer a Primary function is transmitting raw bits over a physical communications channel a Primary design issues include: mechanical, electrical, functional, procedural characteristics u what voltage represents a “1” versus a “0” u How many pins in and the shell shape the connector. u Defines functions between the system and transmission medium u Specifies sequence of events by which bits streams are exchanged across the physical medium a By “raw bits” we mean there is no interpretation of the bits - stream of bits in and bits out

10. OSI Layer 2 - Data Link layer a Primary function is to make Layer 1 into what appears to be a channel free of undetected errors a Deals with data in chunks (typically 100s-1000s of bytes) generally called Frames a This layer must create/recognize frame boundaries u remember - Physical layer does not care u often requires special bit patterns to signal boundaries u may have to deal with possibility of pattern appearing in data

11. OSI Layer 2 In other words it maintains the reliable communications link between adjacent nodes. The DLL inserts addresses in the data frame and provides error control for the data.

12. OSI Layer 2 - Data Link layer a Among the key issues dealt with are: u Error handling (e.g. corrupted frame) u Flow control u Providing various qualities of service a For Broadcast networks, a key issue is controlling access to the channel: u Use a sub-layer called the Media Access Control (MAC) sub-layer

13. OSI Layer 3 - Network layer a Primary function is to control the operation of the layers below a Among the key issues dealt with are: u Routing packets from source to destination through the network (or multiple networks) using static or dynamic routing algorithms u Controlling congestion in the network u Accounting functions (for billing) u Translating between protocols across heterogeneous networks u Concerned with Addressing

14. OSI Layer 3 This layer establishes the path for the traveling data packet

15. OSI Layer 4 - Transport layer a First end-to-end layer a Uses the network to (most often) provide higher layers with a connection oriented, reliable, error free channel that delivers messages (or byte stream) in order a Layer 4 of the OSI Model coordinates communications between systems. a May also perform flow control a Often performs multiplexing of multiple transport connections over one or more network connections a Generally requires Address (or naming)

16. OSI Layer 4 This layer provides reliable delivery of host messages originating at layer 7 the same way as the DLL assures reliable delivery of frames between adjacent nodes. This is the layer responsible for Segmenting long messages in smaller units (packets) and then Reassembling them at the other end.

17. OSI Layer 5 - Session layer a Manages dialog control (e.g. may manage who’s turn it is to talk in a high-level half-duplex protocol) a Manages synchronization of transactions which may need to be able to roll back in case of a crash a Sort of an unwanted layer, this layer is usually very thin and little more than a pass through for most protocols a Key services provided include : a Dialogue discipline a Grouping - data mark as belonging to a special group a Recovery – checkpoint mechanism

18. OSI Layer 5 In other words it establishes and terminates process to process communications Sessions between hosts.

19. OSI Layer 6 - Presentation layer a Rather than being concerned with moving information, the Presentation layer is concerned with the interpretation of information representation a Ensures that the syntax and meaning is the same for each participant in a communication a Provides for standard representation and may provide capabilities for conversion of data

20. OSI Layer 6 Simply put this layer establishes the syntax in which data is exchanged between the two hosts. It provides a data manipulation function rather than a communication function (data compression and data encryption are examples of this layers activities)

21. OSI Layer 7 - Application layer a The layer where end-user applications live a This is the highest level of abstraction and the level which is of primary importance (for most users) a All the rest of the layers exist to support these applications a Layering exists so we can move these around to different machines, and so they can communicate across any platforms - Open Systems Interconnect

22. OSI Layer 7

23. OSI Examples

24. Review - Functions of the OSI Layers a Layer 1 (physical): Transmission of bits a Layer 2 (data link): Transmission of frames on one given link a Layer 3 (network): Routing of packets through the network a Layer 4 (transport): End-to-end delivery of messages

25. Review - Functions of the OSI Layers a Layer 5 (session): Setup and management of end-to- end conversation, synchronization a Layer 6 (presentation): Formatting, encryption, and compression of data a Layer 7 (application): user applications

26. Introduction to TCP/IP

27. What is TCP/IP Transmission Control Protocol/Internet Protocol TCP/IP refers to an entire suite of networking protocols, developed for use on the Internet TCP and IP are certainly two of the most important

28. TCP/IP Protocol Suite n Advanced Research Project Agency (ARPA) of DoD sponsored the development of ARPANET in 1970s. n TCP/IP has been adopted as the ARPANET protocol suite n TCP/IP became popular by the inclusion of this protocol in BSD Unix system (a version of Unix developed by University of California @ Berkley)

29. TCP/IP (cont.) n Transport Layer-TCP (Transmission Control Protocol) Provides fully reliable, connection-oriented serviceProvides fully reliable, connection-oriented service Byte-stream transmissionByte-stream transmission n Network Layer- IP (Internet Protocol) IP provides datagram service (used in packet switching)IP provides datagram service (used in packet switching) It is connectionless unreliable serviceIt is connectionless unreliable service IP handles routingIP handles routing

30. TCP/IP Characteristics TCP/IP provides the services necessary to interconnect computers and to interconnect networks, creating the Internet Independence from underlying network topology, physical network hardware, and OS Unique IP Address Universal connectivity throughout the network Standardize high-level protocols

31. TCP/IP Protocol Architecture Model Application TCP Application TCP IP Network Access IP Network Access Physical SourceTransmitter Trans- Mission System ReceiverDestination Source SystemDestination System Network

32. A Comparison Application Session Transport Network Physical Presentation Data Link IP Network Access Physical Application Transport Hardware Firmware Software User Space Operating System

33. TCP/IP Network Structure hardware interface TCPIPUDP user processor user processor OSI Layer 5-7 OSI Layer 4 OSI Layer 3 OSI Layer 1-2 ARP ICMP RARP UDP: User Datagram Protocol ICMP: Internet Control Message Protocol IP: Internet Protocol ARP: Address Resolution Protocol RARP: Reverse ARP

34. Port Number user proc.A user proc.B user proc.C user proc.D user proc.E user proc.F user proc.G IDPIPSPPPEXTCPUDP Ethernet interface Ethernet interface Ethernet interface Ethernet interface TCP/IP protocol suite XNS protocol suite Ethernet cable 2 Ethernet cable 1

35. Port Assignments Servers are known by ports number FTP 20, TELNET 23, SMTP 25, HTTP 80 Port numbers are generally allocated by 0 --not used 1-255 --Reserved ports for well-known services 256-1023 --Other reserved ports 1024 -65535 --user-defined server ports Unix stores general used ports in /etc/services directory Applications Transport Network access 1 2 3 4 ( ) ( )

36. Hierarchical Addressing Scheme Connection defines the communication link between two processes data UDP header data UDP header IP header UDP header data IP header Ethernet trailer Ethernet header 16-bit UDP source port # 16-bit UDP dest. port # protocol = UDP internet 32-bit source addr internet 32-bit dest. addr frame type = IP Ethernet 48-bit source addr Ethernet 48-bit dest. addr Ethernet frame UDP = User Datagram Protocol

37. TCP/IP Internetworking Token Ring FDDI Private Nets and Internet Router

38. LAN and Devices LANs are designed to : Operate within a limited geographic area Allow multi-access to high-bandwidth media Control the network privately under local administration Provide full-time connectivity to local services Connect physically adjacent devices ATM Switch Ethernet Switch BridgeHubRouter

39. Wide-Area Networks and Devices WANs are designed to : Operate over geography of telecommunications carriers Allow access over serial interfaces operating at lower speeds Control the network subject to regulated public services Provide full-time and part-time connectivity Connect devices separated over wide, even global areas ATM Switch Router Modem CSU/DSU TA/NT1 S X.25 or Frame Relay Switch Comm. Server Multiplexor stat mux

40. TCP/IP Architectural Layers Application Transport Internet Network Physical Network Applications End-to-end Services Routing Transmission Network Interface

41. Layer Hardware Routers, PAD’s, X.25 switches Bridges, LAN switches, ATM switches and terminal servers Transceivers, repeaters, hubs, FDDI concentrators, modems, terminal adapters, DSU’s, CSU’s, MUX and NIC’s Application Transport Internet Network Physical

42. Transceivers A transceiver connects a network device to the network cable A transceiver listens to the bus to determine if it is being used by another station A transceiver determines if the bus is being used by another station A transceiver alerts the connected device when there is a collision during transmission A transceiver may have DIP switches for controlling the exchange of SQE or heartbeat signals with the directly connected device.

43. Transceivers Attachment Interface Unit (AUI): The portion of the Ethernet standard that specifies how a cable is to be connected to an Ethernet card. AUI specifies a coaxial cable connected to a transceiver that plugs into a 15-pin socket on the network interface card (NIC).

44. Repeaters A repeater is used to connect two segments of the same network A repeater receives a signal from one segment, cleans and boosts the signal and sends it to the other segment A repeater is responsible for ensuring that a collision is propagated to all attached segments A repeater may be used to extend the network beyond the limitations of the network’s architecture by increasing segment length Cannot add an infinite number of repeaters as this would adversely affect collision propagation.

45. Hubs A hub often attaches at least four nodes and many hubs include connectors for linking to other hubs A hub provides connectivity by passing incoming signals to connected nodes Hubs may be cascaded together to allow small workgroups with low-intensity applications to be formed Hubs typically have LEDs to indicate the status of each port Hubs may do partitioning to allow isolation of a non- functioning node Hubs allow connection to different physical media.

46. NIC’s A NIC is an internetworking device that is a component part of a much larger host NICs are used to connect the systems to the network NICs will be different for each type of host system and type of network topology (and for each bus type) Remote access is achieved through remote access to the host system When installing a NIC it is important to consider the network topology, cabling and electrical considerations to avoid network disruption.

47. TCP/IP Networking Software TCP/IP protocol suites define a set of universal communication services Services can be implemented in a standardized manner in the networking software, normally bundled with OS TCP/IP Comm. Software Internet TCP/IP Comm. Software

48. TCP/IP and Internet 1957 USSR sputnik, USA established ARPA 1969 ARPA funded ARPANET 1971 Network with 15 nodes 1974 Cerf/Kahn Protocol 1973 Ethernet (Ph.D Dissertation Bob Metcalfe) 1982/83 TCP/IP as a core protocol 1983 4.2 BSD Unix with TCP/IP from UCB (univ. of California @ Berkley)

49. TCP/IP Standards

50. Internet Technical Bodies ISOC - Internet Society. Professional society to promote the use of Internet for research and scholar communication and collaboration IAB - Internet Architecture Board. Technical oversight and coordination, falls under ISOC IETF - Internet Engineering Task force. Current protocols and specifications for standardization. Meets 3 times a year, organized in working groups IRTF - Internet Research Task force. Research oriented for future.

51. Internet Administrations DDN - the USA Defense Data Network is the government organization that has overall responsibilty for administrating the Internet DDN NIC (Network Information Center) assigns unique names and addresses collects and distributes information about TCP/IP protocols IANA Internet Assigned Numbers Authority assigns value for network parameters, name of services, identifiers NOC (Network Operations Center) manages communication links

52. Internet Standards RFC Internet Draft Proposed Standard Draft Standard Official Standard Circulated technical documents call Request For Comments Revision RFC protocol specifications should be stable technically and should have no bugs or holes. at least 2 independent and interoperable implementations that test all specification funcions have had significant field use and clear community interest in production use.

53. Protocol Status Levels TCP/IP protocols have one of the following five status levels: Required Recommended Elective Limited use Not recommended

54. Internet documents RFC number with RFC XXXX, more than 1700 now updated RFCs are published with new RFC numbers not all RFCs describe protocols. not all RFCs are used ftp://ds.internic.net STD (STandDard) official Internet standard FYI (For Your Information) RFC series that do not contain protocol specifications

55. Sample Documents RFC 2030 I D. Mills, "Simple Network Time Protocol (SNTP) Version 4 for IPv4, IPv6 and OSI", 10/30/1996. (Pages=18) (Format=.txt) (Obsoletes RFC1769) 1879 I B. Manning, "Class A Subnet Experiment Results and Recommendations", 01/15/1996. (Pages=6) (Format=.txt) FYI 0023 Guide to Network Resource Tool. EARN Staff. March 1994. (Format:TXT=235112 bytes) (Also RFC1580) 0028 Netiquette Guidelines. S. Hambridge. October 1995. (Format: TXT=46185 bytes) (Also RFC1855)

56. Wireless LANs

57. Why RF? IEEE 802.11 activities RF Technologies - 2.4GHz/5GHz Wireless LAN Topology Basics Customers WLAN requirements Building-to-Building Bridges

58. IEEE802.11

59. IEEE 802.11 The IEEE 802.11 standard defines the protocol for two types of networks; Ad-hoc and client/server networks. An Ad-hoc network is a simple network where communications are established between multiple stations in a given coverage area without the use of an access point or server. The standard specifies the etiquette that each station must observe so that they all have fair access to the wireless media. It provides methods for arbitrating requests to use the media to ensure that throughput is maximized for all of the users in the base service set.

60. IEEE802.11 The IEEE802 standards committee formed the 802.11 Wireless Local Area Networks Standards Working Group in 1990. The 802.11-working group took on the task of developing a global standard for radio equipment and networks operating in the 2.4GHz unlicensed frequency band for data rates of 1 and 2Mbps. The standard does not specify technology or implementation but simply specifications for the physical layer and Media Access Control (MAC) layer. The standard allows for manufacturers of wireless LAN radio equipment to build interoperable network equipment.

61. IEEE802.11 The membership of the committee consists of individuals from a number of companies and universities, who research, manufacture, install and use products in wireless LAN network applications. Manufacturers of semiconductors, computers, radio equipment, WLAN systems solution providers, University research labs and end-users make up the core group. Companies globally represent the working group from the United States, Canada, Europe, Israel and the Pacific Rim.

62. IEEE 802.11 Standard Activities 802.11a - 5GHz- Ratified in 1999 802.11b - 11Mb 2.4GHz- ratified in 1999 802.11d - Additional regulatory domains 802.11e - Quality of Service 802.11f - Inter-Access Point Protocol (IAPP) 802.11g - Higher Datarate (>20mBps) 2.4GHz 802.11h - Dynamic Frequency Selection and Transmit Power Control mechanisms 802.11i - Authentication and security

63. IEEE802.11 Physical Layer Implementation Choices The Physical Layer in any network defines the modulation and signaling characteristics for the transmission of data. At the physical layer, two RF transmission methods and one infrared are defined. Operation of the WLAN in unlicensed RF bands requires the of spread spectrum modulation to meet the requirements for operation in most countries. The RF transmission techniques in the standard are Frequency Hopping (FH) and Direct Sequence (DS) spread spectrum.

64. IEEE802.11 Both architectures are defined for operation in the 2.4GHz (ISM) frequency band. Each occupies 83Mhz of bandwidth ranging from 2.400 GHz to 2.483 GHz. Differential BPSK (DBPSK) and DQPSK is the modulation for the direct sequence. Frequency hopping uses 2-4 level Gaussian FSK as the modulation signaling method. The radiated RF power at the antenna is set by the rules governed by FCC part 15 for operation in the United States. Antenna gain is also limited to 6 dBi maximum.

65. Range of a Radio Link The range of a RF radio link can be calculated by using the following items: Transmitter power Receiver sensitivity (at a given data rate) Path loss in free space (increases as Frequency increases) Antenna system gain (includes cable losses)

66. IEEE802.11 Operating Frequency Ranges Lower Limit Upper Limit Regulatory Range Geography 2.402 GHz 2.480 GHz 2.400-2.4835 GHz North America* 2.402 GHz 2.480 GHz 2.400-2.4835 GHz Europe* 2.473 GHz 2.495 GHz 2.471-2.497 GHz Japan* 2.447 GHz 2.473 GHz 2.445-2.475 GHzSpain* 2.448 GHz2.482 GHz 2.4465-2.4835 GHz France* The radiated power is limited to 1W for the United States, 10mW per 1Mhz in Europe and 10mW for Japan. There are different frequencies approved for use in Japan, United States and Europe and any WLAN product must meet the requirements for the country in which it is sold.

67. IEEE802.11 The MAC Layer The MAC layer specification for 802.11 has similarities to the 802.3 Ethernet wired line standard. The protocol for 802.11 uses a protocol scheme know as carrier-sense, multiple access, collision avoidance (CSMA/CA). This protocol avoids collisions instead of detecting a collision like the algorithm used in 802.3. It is difficult to detect collisions in a RF transmission network and it is for this reason that collision avoidance is used. The MAC layer operates together with the physical layer by sampling the energy over the medium transmitting data.

68. IEEE802.11 The physical layer uses a clear channel assessment (CCA) algorithm to determine if the channel is clear. This is accomplished by measuring the RF energy at the antenna and determining the strength of the received signal. This measured signal is commonly known as RSSI. If the received signal strength is below a specified threshold the channel is declared clear and the MAC layer is given the clear channel status for data transmission. If the RF energy is above the threshold, data transmissions are deferred in accordance with the protocol rules. The standard provides another option for CCA that can be alone or with the RSSI measurement. Carrier sense can be used to determine if the channel is available.

69. IEEE802.11

70. Comparing Radio specs 5Ghz vs. 2.4GHz 2.4Ghz (Cisco 350) 5Ghz (802.11a) TX Power20dBm (11Mbps) (100mW) 12dBm (6Mbps) (16mW) RX Sens.-85dBm ( 11Mbps) -79dBm (6Mbps) Results= 14dBm less for 5Ghz than 2.4 @similar rates. 14dB less > 50% range reduction

71. 5GHz vs.. 2.4GHz 1 3 2 4 5 6 7 2.4GHz Range Range of 5GHz is MUCH MUCH less. About 30%. Overall investment of infrastructure is much higher (more APs)

72. Shared Local Area Network (LAN) Server Ethernet Shared Hub Internet

73. Wireless Local Area Network (WLAN) Access Point Server Ethernet Internet Remember: An Access Point is a SHARED device and has similar performance to a SHARED Ethernet HUB.

74. Typical Single Cell Configuration LAN Backbone Wireless Clients Wireless Cell Wireless Cell

75. Typical Multi-cell Configuration Access Point LAN Backbone Wireless Cell Wireless Cell Channel 1 Channel 6 Wireless Clients Wireless Cell Wireless Cell

76. Typical Multi-cell Configuration Access Point LAN Backbone Wireless Cell Wireless Cell Channel 1 Channel 6 Wireless Clients Wireless Cell Wireless Cell

77. Wireless Repeater Channel 1 Access Point Wireless Clients LAN Backbone Wireless Repeater Cell Wireless Repeater Cell

78. Standard Office Application Use three non- overlapping channels Rotate channels to fill in

79. Reduce Cell size Reduce Antenna gain or Transmitter power to create smaller cell size Enable Load Balancing

80. Mixed Antenna Example Maximum Coverage Autorate Negotiation Wireless for Students DiPole Indoor, Patch Outdoor Class 1Class 3 Hallway 1000’ 850’ Class 4Class 2 Class 8Class 10Class 11Class 9 BuildingCourtyard 1000’ Channel 1 Channel 11 Channel 6

81. END Class 2