Special Course in Computer Science: Local Networks. Lecture

Transcription

1 Special Course in Computer Science: Local Networks Lecture

2 Roadmap of the Course So far Basic telecom concepts General study of LANs Local Networks Ethernet Token bus Token ring ATM LAN Wi-Fi LAN performance, connecting LANs, LAN management Networks-on-Chip (NoC) Åbo Akademi s local network Jan Wennström Today Efficiency in ÅA s network, Bluetooth Next time Sensor networks

3 Efficiency Issues in a Switched LAN M. M. Hassan Åbo Akademi, Finland, 2009

4 Starting point LAN technologies widespread Size grew CAN: campus area networks Issues Fault tolerance, availability Aggregation of switched traffic flow to core Proper design of switched network

5 Efficiency issues Appear when Network deployed Network extended Arbitrary growth Not enough planning Design overlooking Replacement of devices/links How efficient a network is? Case study: ÅA Ethernet

6 Early Ethernet

7 Bridging Bridges SAT Learning Logic Forwarding Logic

8 Ethernet Switch Multiport bridge Hardware based logic Forwarding logic Learning logic No collision domain One broadcast domain

9 Switched Ethernet

10 Hierarchical design: Switch blocks

11 Hierarchical design

12 Access layer Connectivity to end devices DLL Medium access to end user Separation of broadcast domains: VLANs Features Large number of network interfaces to support large number of clients Bigger uplinks to connect to distribution layers

13 Distribution layer Aggregates treffic coming from access layer Features Routing between VLANs defined at access layer High rate of packet forwarding on network layer to support huge traffic volumes coming from access layer Policies to filter/route/re-route traffic Connectivity and translation between media to connect different access layers

14 Core layer Heart of the network Aggregation of entire traffic Should be highly efficient Highly available (virtually no downtime) No policy or network layer processing to avoid latency Considerably higher forwarding rates at DLL and NL

15 Åbo Akademi Network, 2009

16 Åbo Akademi Network: Core

17 Some issues with Åbo Akademi s network Naming Convention Extended hierarchy Uplink bottlenecks Fault tolerance Firewall bottleneck Old network Core

18 Naming Conventions Person dependency User friendly names Structured names Encoded information <type><building><wiring closet><device number>- <aggregation tree>-<core tree>.<domain> eswty bct-ct.abo.fi

19 Aggregation and core level trees

20 Extended hierarchy

21 Extended hierarchy: model

22 Extended hierarchy: Ethernet delay

23 Extended hierarchy: ping response

24 Extended hierarchy: database entry

25 Uplink bottlenecks

26 Uplink bottlenecks: model

27 Uplink bottlenecks: queuing delay

28 Fault Tolerance: model

29 Fault Tolerance: effect of failure on devices

30 Proposed 10GbE network core

31 Proposed redundant architecture at aggregation and edge layers

32 Conclusions Network has accumulated some complexity Reasons Arbitrary growth Limited resorces Lack of stringent security needs Main skeleton old

33 Problems Problems => obstacles to efficiency Switched network architecture Aggregation of bandwidth Extension of hierarchy Bottlenecks Lack of FT Naming convention Old technology backbone

34 Solutions Solutions Upgrade backbone Delete further depths Partial mesh topology with device addition Structured naming convention

35 Bluetooth

36 Bluetooth 1994: Ericsson s interest in connecting phones to laptops 1998: Special Interest Group (SIG) Ericsson, IBM, Intel, Nokia, Toshiba Goal: wireless standard for interconnectin computing and communication devices using short-range, low-power, inexpensive wireless radios 1999: Bluetooth 1.0 Mobile phones, laptops, headsets, printers, keyboards, mice, gameboxes, watches, music players, navigation units Devices find and connect to each other: pairing Securely transfer data 2004: Bluetooth 2.0, higher data rates 2009: Bluetooth 3.0, interoperability with for high throughput transfer 2010: Bluetooth 4.0, low-power operation

37 Bluetooth Architecture Piconet master is connected to slave wireless devices Slaves may be asleep (parked) to save power Two piconets can be bridged into a scatternet

38 Bluetooth Applications / Protocol Stack Profiles give the set of protocols for a given application 25 profiles, including headset, intercom, streaming audio, remote control, personal area network,

39 Bluetooth profiles Audio and video usage: 6 profiles Intercom profile: two phones as walkie-talkies Headset and hands-free profiles: voice communication between headset and base station Streaming stereo-quality audio and video: portable music player to headphones, from digital camra to TV, etc Human interface device profile: connecting keyboards and mice to computers Other: Mobile phone or computer receive images from a camera, send images to printer Other: mobile phone as remote for (bluetooth enabled) TV Other: enable networking, eg PAN profile lets devices form an ad-hoc network, or remotely access other network (802.11) Higher-layer information exchange: synchronization profile lets mobile phone get data from computer when leaving and collecting data from it when it returns Some profiles serve as building blocks for other profiles Generic acces profile: all of the other profiles built on it: establish and maintain secure links between master and slaves Other generic profiles: basics of object exchange, audio and video transport Would have been possible to only have 2 profiles? One for file transfer and one for streaming real-time communication

40 Bluetooth protocol stack Physical radio layer -> OSI and 802 physical layer Radio transmission and modulation Inexpensive system Link control (baseband) -> bit analogous to MAC sublayer + physical layer elements How the master controls time slots, how slots grouped into frames Link manager Establishment of logical channels between devices: power management, pairing and encryption, QoS Lies below host controller interface line Protocols below the line: implemented on Bluetooth chip Protocols above the line: implemented on the Bluetooth device that hosts the chip L2CAP (logical link control adaption protocol) Frames variable-length messages + reliability Profiles each defines a slice of the protocol stack for a particular purpose

41 Bluetooth Radio / Link Layers Radio layer FHSS, 2.4GHz band> all nodes in piconet hop simultaneously: slot timing and pseudorandom hop sequence dictated by master Adaptive frequency hopping, excludes channels where there are other RF signals Modulation> FSK and PSK, 1-3 Mbps Link layer TDM with timeslots of 625 microsecs for master and slaves Master sends in even slots, (all) slaves share the odd slots Links undergo pairing (user confirms passkey/pin) to authorize them before use Synchronous Connection Oriented for periodic slots in each direction Real-time data, eg phone conversations Frames never retransmitted, instead, forward error correction used Asynchronous CL for packet-switched data available at irregular intervals Best effort basis

42 Bluetooth Frames Time is slotted; enhanced data rates send faster but for the same time; addresses are only 3 bits for 8 devices (a) (b) (a) (b)

43 Personal Area Network Connect devices over the range of a person Example of a Bluetooth (wireless) PAN:

44 Some practicalities Are you registered (MinPlan)? Exams: 25.5 and 8.6 Registration to exams via MinPlan, ONE WEEK before (respectively 18.5 and 1.6) Third exam: 15.6 Registration via ing Christel Engblom at TWO WEEKS before, meaning 1.6

45 Some exercises with difficulties Sliding window Problems 13-16, Chapter 12 Problem 28, Chapter 13

46 Exam Lectures Exercise Sessions 2-5 Pay attention to Topologies Flow and Error Control Ethernet, WLAN, Token Bus, Token Ring, ATM LAN Efficiency (estimate efficiency of..) Connecting LANs SNMP Compare topologies, access methods, frame structures