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The Medium Access Control Sublayer

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cally-carlson
113 diapositives · 1.4K Views · Nov 20, 2014

The Medium Access Control Sublayer. Chapter 4. Data Link Layer – Accessing the Media. Menyatakan bahwa DDL berkaitan dengan NL dan PL serta menjalankan baik software and hardware. Data Link Sub layers. LLC MAC. Media Access Control Techniques.

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  1. The Medium Access ControlSublayer Chapter 4

  2. Data Link Layer – Accessing the Media • Menyatakanbahwa DDL berkaitandengan NL dan PL sertamenjalankanbaik software and hardware.

  3. Data Link Sub layers LLC MAC

  4. Media Access Control Techniques • Menjelaskanpentingnya controlling access ke media Tanpapengontrolan • Bergantian • Semakintinggitingkatpengontrolan-nyasemakinbesar overhead nya.

  5. Teknik Media Access Control • Media access control : • Mengatur peletakkan frame data ke media. • Ada beberapa metode untuk mengendalikan akses ke media. • Teknik pengendalian akses media didefinisikan bila dan bagaimana nodes men-share media.

  6. Teknik Media Access Control • Metodadari media access control dilakukantergantungpada: • Berbagi Media – biladanbagaimana node berbagike media. • Topologi - Bagaimanahubunganantar node yang nampakpada data link layer

  7. Teknik Media Access Control - berbagi media • Menyatakanduametode media access control untukberbagi media dandasarkarakteristikdari masing2.

  8. Teknik Access Control – berbagi media • Duametoda yang seringdipakaiadalah : • CSMA/Collision Detection • Pada CSMA/Collision Detection (CSMA/CD), node akanmemonitor media apakahadasinyal data, • Bilatidakada, berarti media free (kosong) sehingga node akanmengirim data .

  9. Teknik Access Control – berbagi media • Bilasuatusinyalterdeteksidanmenandakanbahwaada node lain yang sedangmengirim data padasaat yang bersamaan, semuaperangkatakanberhentimengirimdanakanmengulangbeberapasaatkemudian. Metodeini yang akhirnyadipakaioleh Ethernet.

  10. Teknik Access Control – berbagi media • CSMA/Collision Avoidance • Pada CSMA/Collision Avoidance (CSMA/CA), node akanmemeriksaapakah media kosongatautidak. • Bila media kosong (free) maka node akanmengirimnotifikasipada media untukkeperluanakanmenggunakannya. • Kemudian node akanmengirimkandatanya. Metodeinidipakaioleh 802.11 wireless networking technologies

  11. Teknik Media Access Control – tidakberbagi media • Media access control protocols untuk non-shared media • Membutuhkansedikitatautanpakontrolsebelummenempatkan frame pada media.. • Protocol inimempunyaiaturandanprosedur yang sederhanauntuk media access control. • Topologi point-to-point .

  12. Teknik Media Access Control • Menggambarkantujuandaritopologi logical danidentifikasibeberapatopologi logical yang umum.

  13. Teknik Media Access Control • Indetifikasikarakteristikdaritopologi multi-access danmendiskripsikanimplikasi media aksesbilamenggunakantopologiini.

  14. Teknik Media Access Control • Identifikasikarakteristikdaritopologi ring danmendiskripsikanimplikasi media aksesbilamenggunakantopologiini.

  15. PermasalahanAlokasiKanal. • Static Channel Allocation in LANs and MANs • Dynamic Channel Allocation in LANs and MANs

  16. Dynamic Channel Allocation in LANs and MANs • Station Model. • Single Channel Assumption. • Collision Assumption. • (a) Continuous Time.(b) Slotted Time. • (a) Carrier Sense.(b) No Carrier Sense.

  17. Diasumsikandandisepakatibersamabahwa : Slotted time • Time divided as interval-interval discretetime (slot) • transmision frame always start at the beginning of the slot. Carrier Sense • Station always sense the line before use it.

  18. No Carrier Sense • station not always sense the line before use it. • After a few of time, the station know the transmission fail or not.

  19. Multiple Access Protocols • ALOHA • Carrier Sense Multiple Access Protocols • Collision-Free Protocols • Limited-Contention Protocols • Wavelength Division Multiple Access Protocols • Wireless LAN Protocols

  20. The first Protocol : ALOHAProtocol • Pure Aloha • Slotted) Aloha • Univesity of Hawaii year : 1970 • Norman Abramson • Radio Packet Network

  21. Pure ALOHA Basic Idea : • User possible to transmit anytime if they have the data • Sender will knows the frame was send damage or not after 270 ms • No Sense system • Using contention system

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

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

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

  25. Persistent and Nonpersistent CSMA Presistent CSMA : • If station has data  sense the line • The line busy  station wait for a several time • The line empty  send the frame • If Collision occurred station wait for a few time then try to re-send • Call1 presistentbecause the probability of transmit = 1, if the line is empty. Presistent : ALWAYS detect the line until really empty

  26. Persistent and Nonpersistent CSMA Comparison of the channel utilization versus load for various random access protocols.

  27. The possibility collision occure: • Station detect the line ‘ empty ‘ but maybe the packet just sent from another station not yet arrive. This because of the delay propagation. • 2 stations at the same time wait the line which has been used by the another station. If the transmission just finish then the both stations together send the packet and access the line. COLLISION!!

  28. Packet Time delay : The Duration time between packet sent by the sender until ALL packets receive by the receiver. very important

  29. CSMA/CD • CD : Collision Detection • After know there was a collision  cancel the transmission, without waiting the sending frame finish • Reduce the time and bandwidth • MODUL used in CSMA / CD has 3 periods : • transmit • contention • idle

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

  31. Collision-Free Protocols • At CSMA/CD probably will collide in the interval “ Contention” • If ( length of line) large and frame is short – the critical time (contention) more longer  handle by Bit map Protocol

  32. At the Collision Free Protocol : • Access to the channel by the Station, same as a sequence of the bit map • Every stasion has the unique allocation time for access the line and cannot use by another stasion. • If the stasion not ready when their turn comes up, they must wait their turn in the next period.

  33. Collision-Free Protocols The basic bit-map protocol. Example :There are, 8 stations, 8 contention slot Interval divided into 2 : contention danframe

  34. Binary Count Down The overhead of the protocol = 1 bit per station. That will develop by using the same length of address and broadcasting to the network. Every position of bit from the different station must OR and called Binary Count Down. How to Compare is as: Example : 0010,0100,1001,1010

  35. Collision-Free Protocols (2) The binary countdown protocol. A dash indicates silence.

  36. Wireless LAN Protocols A wireless LAN. (a) A transmitting. (b) B transmitting.

  37. Wireless LAN Protocols (2) The MACA protocol. (a) A sending an RTS to B. (b) B responding with a CTS to A.

  38. Ethernet • Ethernet Cabling • Manchester Encoding • The Ethernet MAC Sublayer Protocol • The Binary Exponential Backoff Algorithm • Ethernet Performance • Switched Ethernet • Fast Ethernet • Gigabit Ethernet • IEEE 802.2: Logical Link Control • Retrospective on Ethernet

  39. Ethernet Cabling The most common kinds of Ethernet cabling.

  40. 10Base5  disebut juga Thick Ethernet, dihubungkan dengan Vampire tap. • Pd 10Base5 dihubungkan ke transceiver yang mempunyai el-circuit sbg pendeteksi collision • Controller bertanggung jawab thd essembling data kedalam format yang sesuai. • 10Base2  disebut juga Thin Ethernet dihubungkan dengan BNC yang mem- bentuk T junction  BNC T junction connector.

  41. 10BaseT menggunakan Twist pair cable dilengkapi dengan HUB • Pd 10BaseT – tidak ada share cable, masing2 stasiun dihubungkan ke HUB dengan dedicated cable. • 10BaseF  menggunakan Fiber Optik - mahal, - mempunyai security/ noise imunnity yang bagus - lebih susah pemasangannya dp yang lainnya - digunakan terutama untuk antar bangunan

  42. Ethernet Cabling (2) Three kinds of Ethernet cabling. (a) 10Base5, (b) 10Base2, (c) 10Base-T.

  43. Untuk mendeteksi kabel putus, bad-tap dll digunakan teknik dengan menggunakan echo  disebut time domain reflectometry.

  44. Ethernet Cabling (3) – Cable Topologies a) Linear (Room-room) b) Spine (basement-roof) c) Tree (general topology) d) Segmented (per segment)

  45. Ethernet Cabling (4) (a) Binary encoding, (b) Manchester encoding, (c) Differential Manchester encoding. Ethernet tidak menggunakan Diff M.E

  46. Ethernet MAC Sublayer Protocol Frame formats. (a) DIX Ethernet, (b) IEEE 802.3. DIX = DEC, Intel, Xerox

  47. Coax Cable segment ( 500 m max ) Coax cable Transceiver cable 50 m max Transceiver and connection to coax cable - 100 m max per segment stasiun Batasan-batasan single Ethernet cable segment

  48. Konfigurasi Ethernet - Yang “besar” stasiun Seg 2 Seg 1 repeater Seg 3 Kabel koox Remote repeater Seg 4 Seg 5 Point to point link

  49. Collision Window - minimum packet size Periode waktu dari mulainya transmisi, selama stasiun pada“vulnareble to collision”. Contoh dalam kondisi terjelek sebagai berikut : Bila waktu propagasi sinyal dari ujung ke ujung jaringan adalah : 22,5 sec yaitu = 225 bit times pada 10 Mbps

  50. A t + st • Sesaat sebelum paket A sampai, B mengirim paket  tabrakan • A mendengar ada tabrakan setelah : (t+22,5)+22,5 sec atau : 45 sec = 450 bit time sesudah A mulai mengirim Collision Window : 450 bit time B Pada saat ‘ t’ mulai transmisi t + 22.5 paket dari A hampir sampai di B