1 CIS 6930: Review on Network Technology Jonathan C.L. Liu, Ph.D. Department of Computer, Information Science and Engineering (CISE), University of Florida

2 Network Hardware Local Area Networks Metropolitan Area Networks Wide Area Networks Wireless Networks Home Networks Inter-networks

3 Local Area Networks

4 Metropolitan Area Networks A metropolitan area network based on cable TV.

5 Wide Area Networks A stream of packets from sender to receiver.

6 Wireless Networks (a) Bluetooth configuration (b) Wireless LAN

7 Network Software Protocol Hierarchies Design Issues for the Layers Connection-Oriented and Connectionless Services Service Primitives The Relationship of Services to Protocols

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9 Connection-Oriented and Connectionless Services Six different types of service.

10 Service Primitives Packets sent in a simple client- server interaction on a connection-oriented network.

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13 Fiber Optic Networks A fiber optic ring with active repeaters.

14 The Electromagnetic Spectrum The electromagnetic spectrum and its uses for communication.

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16 Global Star (a) Relaying in space. (b) Relaying on the ground.

17 Structure of the Telephone System A typical circuit route for a medium- distance call.

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19 Time Division Multiplexing The T1 carrier (1.544 Mbps).

20 Time Division Multiplexing (3) Multiplexing T1 streams into higher carriers.

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23 Packet Switching A comparison of circuit switched and packet- switched networks.

24 Functions of the Data Link Layer Provide service interface to the network layer Dealing with transmission errors Regulating data flow Slow receivers not swamped by fast senders

25 Elementary Data Link Protocols An Unrestricted Simplex Protocol A Simplex Stop-and-Wait Protocol A Simplex Protocol for a Noisy Channel

26 Unrestricted Simplex Protocol

27 Simplex Stop-and- Wait Protocol

28 For a Noisy Channel A positive acknowledgement with retransmission protocol. Continued 

29 For a Noisy Channel (2) A positive acknowledgement with retransmission protocol.

30 Sliding Window Protocols A One-Bit Sliding Window Protocol A Protocol Using Go Back N A Protocol Using Selective Repeat

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33 Dynamic Channel Allocation Station Model. Single Channel Assumption. Collision Assumption. (a) Continuous Time. (b) Slotted Time. (a) Carrier Sense. (b) No Carrier Sense.

34 Pure ALOHA In pure ALOHA, frames are transmitted at completely arbitrary times.

35 Pure ALOHA (2) Vulnerable period for the shaded frame.

36 Pure ALOHA (3) Throughput versus offered traffic for ALOHA systems.

37 Performance Comparison

38 CSMA with Collision Detection CSMA/CD can be in one of three states: contention, transmission, or idle.

39 Ethernet Cabling The most common kinds of Ethernet cabling.

40 Ethernet MAC Sublayer Protocol

41 Ethernet Performance Efficiency of Ethernet at 10 Mbps with 512-bit slot times.

42 Switched Ethernet A simple example of switched Ethernet.

43 Fast Ethernet The original fast Ethernet cabling.

44 Some Wireless Networks 384 Kbps 56 Kbps 54 Mbps 5-11 Mbps 1 Mbps b {a,g} IS-95 CDMA, GSM UMTS/WCDMA, CDMA p-to-p link 2G 3G Indoor 10 – 30m Outdoor 50 – 200m Mid range outdoor 200m – 4km Long range outdoor 5km – 20km

45 Wireless Link Characteristics Differences from a wired link …. decreased signal strength: radio signal attenuates as it propagates through matter (path loss) interference from other sources: standardized wireless network frequencies (e.g., 2.4 GHz) shared by other devices (e.g., phone); devices (motors) interfere as well multipath propagation: radio signal reflects off objects ground, arriving at destination with slightly different times …. make communication across (even a point to point) wireless link much more “difficult”

46 IEEE Wireless LAN b GHz unlicensed radio spectrum up to 11 Mbps direct sequence spread spectrum (DSSS) in physical layer all hosts use same chipping code widely deployed, using base stations a 5-6 GHz range up to 54 Mbps g GHz range up to 54 Mbps All use CSMA/CA for multiple access All have base-station and ad-hoc network versions

47 Hidden-Node Problem (a) The hidden station problem. (b) The exposed station problem.

48 IEEE : multiple access avoid collisions: 2 + nodes transmitting at same time : CSMA - sense before transmitting don’t collide with ongoing transmission by other node : no collision detection! difficult to receive (sense collisions) when transmitting due to weak received signals (fading) can’t sense all collisions in any case: hidden nodes, and/or fading goal: avoid collisions: CSMA/C(ollision)A(voidance)

49 Timing of the protocol The use of virtual channel sensing using CSMA/CA.

50 Avoiding collisions (more) idea: allow sender to “reserve” channel rather than random access of data frames: avoid collisions of long data frames sender first transmits small request-to-send (RTS) packets to BS using CSMA RTS may still collide with each other (but they’re short) BS broadcasts clear-to-send (CTS) in response to RTS RTS heard by all nodes sender transmits data frame other stations defer transmissions Avoid data frame collisions completely using small reservation packets!

51 Collision Avoidance: RTS-CTS exchange AP A B time RTS(A) RTS(B) RTS(A) CTS(A) DATA (A) ACK(A) reservation collision defer

: Channels, association b: 2.4GHz-2.485GHz spectrum divided into 11 channels at different frequencies AP admin chooses frequency for AP interference possible: channel can be same as that chosen by neighboring AP! host: must associate with an AP scans channels, listening for beacon frames containing AP’s name and MAC address selects AP to associate with may perform authentication will typically run DHCP to get IP address in AP’s subnet

53 Broadband Wireless The Protocol Stack The Physical Layer The MAC Sublayer Protocol The Frame Structure

54 The Protocol Stack

55 The Physical Layer The transmission environment.

56 The Physical Layer (2) Frames and time slots for time division duplexing.

MAC Sublayer Protocol Service Classes Constant bit rate service Real-time variable bit rate service Non-real-time variable bit rate service Best efforts service

Frame Structure (a) A generic frame. (b) A bandwidth request frame.

59 Bluetooth Bluetooth Architecture Bluetooth Applications The Bluetooth Protocol Stack The Bluetooth Radio Layer The Bluetooth Baseband Layer The Bluetooth L2CAP Layer The Bluetooth Frame Structure

60 M radius of coverage S S S P P P P M S Master device Slave device Parked device (inactive) P : personal area network less than 10 m diameter replacement for cables (mouse, keyboard, headphones) ad hoc: no infrastructure master/slaves: slaves request permission to send (to master) master grants requests : evolved from Bluetooth specification GHz radio band up to 721 kbps

61 The Bluetooth Protocol Stack The version of the Bluetooth protocol architecture.

62 The Bluetooth Frame Structure A typical Bluetooth data frame.

63 IEEE Overview High data rate WPAN Potential future standard Motivation: The need for higher bandwidths currently supported with Mpbs within 10 meter 400 Mpbs within 5 meter Data, High quality TV, Home cinema

64 IEEE Overview Dynamic topology Mobile devices often join and leave the piconet Short connection times High spatial capacity Multiple Power Management modes Secure Network

65 IEEE Overview Based on piconets Data Devices (DEV) establish peer-to- peer communication Includes also a Piconet Coordinator (PNC)

66 IEEE Topology

67 IEEE Superframe

68 IEEE Beacon Beacon Control information Allocates GTS Synchronization

69 IEEE CAP CAP Allows contention via CSMA/CA Command exchange between DEV and PNC File transfers from DEV without request

70 IEEE CFP CFP Time slot allocation specified in the beacon Reserved bandwidth for DEV MTS: Command, GTS: Data

71 IEEE GTS GTS reservation DEV sends a Channel Time Request (CTR) to PNC Isochronous data: number and duration of slot(s) Asynchronous data: Total amount of data PNC allocates GTSs to DEV via CTA DEV is responsible of utilizing allocated GTSs

72 IEEE GTS Two types of GTSs Dynamic GTS Location within a superframe may change PNC can optimize channel utilization Pseudostatic GTS Only for isochronous data Fixed location within a superframe May be changed, but only after a series of notitications to the DEV

73 IEEE Starting a piconet DEV scans the for the best channel and sends out beacons -> the DEV becomes PNC If no channels available: Establishes a child or neighbor piconet instead Requests a private GTS from parent PNC All communication takes place within assigned GTS

74 IEEE QoS QoS IEEE supports both synchronous and asynchronous data CAP offers only best-effort The PNC will allocate resources in the CFP Through admission control Synchronous data: Based on number of time slots per superframe, duration of slot, priority and GTS type

75 IEEE QoS Asynchronous data: Based on total data and priority After performing admission control, GTSs may be allocated