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Jaringan Telekomunikasi

Institut Teknologi Telkom

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Classifications of Computer Networks: LAN, MAN, WAN

Point-To-Point Connection and Shared Medium LAN Topology: Star, Ring, Bus

Typical LANs

- Ethernet (CSMA/CD)

- LocalTalk (CSMA/CA)

- Wireless LAN- Token Ring

- FDDI

Unicast, Broadcast, Multicast

Lecture 4

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IEEE mendefinisikan jaringan wilayah lokal (LAN)sebagai sebuah jaringan komunikasi untukmenghubungkan berbagai perangkat (contohnyapersonal computer, workstation, printer, perangkatpenyimpanan file) yang dapat mengirimkan data padadaerah terbatas, biasanya dalam suatu fasilitasperkantoran/organisasi

Laju data LAN, jumlah divais maksimum yangterhubung ke LAN, jarak antar divais, danpengembangan jaringan bergantung pada:

Media transmisi yang digunakan

Teknik transmisi (baseband atau broadband)

Protokol pengaksesan jaringan

Konfigurasi perangkat seperti repeater, bridge, router,hub, switch

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Lecture 4

Classifications of Computer Networks

LANLocal Area Network: A network that spans a small geographic area, suchas a single building or buildings close to each other.

Examples: Ethernet, LocalTalk, Token Ring, FDDI, ATM

PANPersonal Area Network

MANMetropolitan Area Network: A network that can span a geographic areathe size of a city.Example: DQDB

WANWide Area Network: A network that can span a large geographic area,e.g., multiple cities, countries or continents.Examples: ARPANET, X.25, Frame Relay, SMDS, ATM

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Lecture 4

Point To Point Connection Network

point-to-point networkprovides a dedicated link between any twocomputers/devices

- dedicated link: used by only two computers and not shared with others- high security and privacy- (N2-N)/2 links are needed for N computers/devices

45 links (N=10), 4950 links (N=100), 499500 links (N=1000)- Such network is not used in practical because of its cost and inflexibility

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Lecture 4

Shared Communication Channel/Medium in LAN

Shared Medium

- wire, cable, fiber- radio, infrared,

Key natures of LAN:- Media type: wired/wireless, twisted pair/cable/fiber, radio/infrared- Topology: network shape/connection method- Protocol: how to use shared medium, media access control technique

a) TDM: only one computer can send data in a timeb) Frame: transfer element, each LAN has its own frame format

- Bit rate: usually from 1Mbps~1Gbps

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Bus

Ring

Star

Extended Star

Hirarki

Mesh

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Lecture 4

LAN Topologies

Star Topology

Ring Topology

Bus Topology

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Topologi yang menggunakan single backbone segment yang terhubungsecara langsung ke semua host.

Setiap komputer disambung dengan T Bus (Bus berbentuk T) dan keduaujung sambungan diberi resistor 50 ohm.

Semua perangkat jaringan yang terhubung dalam topology bus dapatmelihat semua sinyal yang melintas dalam single backbone tersebut.

Keuntungan: Murah, karena tidak memakai banyak media dan media yang dipakai

sudah umum (banyak dalam pasaran)

Setiap komputer dapat saling berhubungan langsung.

Kerugian:

Sering terjadi hang / crash, yaitu bila lebih dari satu pasang memakaibus yang sama.

Tidak dapat dipakai secara bersamaan dalam satu waktu, harusbergantian atau ditambah relay.

Jika single backbone terputus maka jaringan rusak. Trafik yang padatdan sering terjadinya collision paket data.

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Lecture 4

Ethernet Bus Topology

Media: Coax cable, twisted pair, fiberTopology: Logic bus (physically may be bus or star)Transmit: Only one can transmit at any time, all others receive transmissionSpeed: 10Mbps, 100Mbps (fast Ethernet) and 1000Mbps (gigabit Ethernet)Status: Most popular LAN and widely usedHistory: Invented at Xerox (Palo Alto Research Center) in 1970s

Defined a DIX standard by Digital Equipment, Intel and XeroxIEEE currently controls Ethernet standards

Project 802.3Ethernet

Define media, voltages, encoding, data rates, frames, wiring,

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Lecture 4

When to start transmit CSMA

All computers connect a bus and only one can transmit at a time Who can?No central control when computers transmit on the bus.Ethernet employs CSMA to coordinate transmission among multiple computers

CSMA (Carrier Sense with Multiple Access)- MA (Multiple Access): multiple computers are attached, any can access bus- CS (Carrier Sense): computer wanting to transmit listen carrier before send

wait if medium is busy (another computer is transmitting)transmit if medium is idle (no one transmits)

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Lecture 4

When to start transmit CSMA/CD

Collision

Even with CSMA, two computers may transmit simultaneously- Both find it idle and begin transmitting in almost a same time- Two signals exist in medium, interfere each other, call collision

CD (Carrier Detection)- Monitor outgoing signal

- Stop transmissions after collision is detected- Each waits random time in [0, S]- listen the bus and transmit again if it is idle- Wait random time in [0, 2S] if collisions is detected again- Double waiting time range [0, 2kS] when k+1 collisions detected

called exponential backoff, very effective in practical

Animation

Animation

http://cis.k.hosei.ac.jp/~jianhua/course/com/animation/Ethernet2.htmlhttp://wwwcis.k.hosei.ac.jp/~jianhua/course/com/animation/Ethernet2.htmlhttp://cis.k.hosei.ac.jp/~jianhua/course/com/animation/Ethernet3.htmlhttp://wwwcis.k.hosei.ac.jp/~jianhua/course/com/animation/Ethernet3.htmlhttp://cis.k.hosei.ac.jp/~jianhua/course/com/animation/Ethernet3.htmlhttp://wwwcis.k.hosei.ac.jp/~jianhua/course/com/animation/Ethernet3.htmlhttp://cis.k.hosei.ac.jp/~jianhua/course/com/animation/Ethernet2.htmlhttp://wwwcis.k.hosei.ac.jp/~jianhua/course/com/animation/Ethernet2.html

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Lecture 4

LocalTalk Bus Topology

reserve

transmit

Media: Coax cable, twisted pairTopology: Logic bus (physically may be bus or star)Transmit: Only one can transmit at any time, all others receive transmissionSpeed: 230Kbps ~

Status: IEEE Project 802.4, Apples Macintosh computers, low cost & easyinstallCSMA/CA: Using CSMA to listen and transmit

Using CA (collision avoidance)rather than CD (collision detection)- send a short message to reserve the bus if it is idle- transmit a frame if reservation is successful (no collision)

- listen and reserve again

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Menghubungakan suatu host dengan host berikutnya dan antar hostyang terakhir dengan host yang awal sehingga terbentuk seperticincin dari kabel.

Tiap node hanya terkoneksi secara fisik dengan node yangada di sebelahnya (kanan dan kirinya).

Media transmisi yang dipakai dapat berupa twisted pair,kabel coaxial dan serat optik .

Keuntungan:

Seperti Topologi Bus

Penggunaan sambungan point to point membuat

transmission error dapat diperkecilKerugian:

Data yang dikirim bila melalui banyak komputer, transferdata menjadi lambat.

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Lecture 4

Token Ring Ring Topology

Media: Twisted pair (TW), fiberTopology: Logic ring (physically may be ring or star)Transmit: Bits flow in single direction from sender, next, destination to send

Speed: 4, 16 or 100MbpsStatus: IEEE Project 802.5, first developed by IBMToken: A permission to send data across the ring

Only one token in a ring and the token rotates one by oneIf no data to be sent, computer passes received token to the nextWhen a computer obtains the token, it can send a single packet

A packet travels around entire ring and finally arrives source

tokenPayloadSD AC FC DAdd SAdd CRC ED FS

SD AC ED

Token frame (3 bytes)

Data frame

Up to 4550 bytes

Animation Animation

SD: Start DelimiterAC: Access Control

ED: End DelimiterFC: Frame ControlFS: Frame Status

http://cis.k.hosei.ac.jp/~jianhua/course/com/animation/TokenRing1.htmlhttp://wwwcis.k.hosei.ac.jp/~jianhua/course/com/animation/TokenRing1.htmlhttp://cis.k.hosei.ac.jp/~jianhua/course/com/animation/TokenRing2.htmlhttp://wwwcis.k.hosei.ac.jp/~jianhua/course/com/animation/TokenRing2.htmlhttp://cis.k.hosei.ac.jp/~jianhua/course/com/animation/TokenRing2.htmlhttp://wwwcis.k.hosei.ac.jp/~jianhua/course/com/animation/TokenRing2.htmlhttp://cis.k.hosei.ac.jp/~jianhua/course/com/animation/TokenRing1.htmlhttp://wwwcis.k.hosei.ac.jp/~jianhua/course/com/animation/TokenRing1.html

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Mengkoneksikan semua kabel dari tiap host ke centralpoint sebagai konsentrator.

Konsentrator ini biasanya berupa hub atau switch.Keuntungan:

Akses ke server cepat Dapat menampung banyak user yang melakukan banyak

proses ke server User dapat lebih banyak dibanding BusKerugian:

Bila ada dua user yang ingin berhubungan (berkomunikasi)

harus melalui server dulu sehingga ada kemungkinanterdapat error bila sambungan masing-masing user keserver kurang baik.

Apabila konsentrator rusak maka jaringan rusak.

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Mirip dengan extended star tetapi ia tidak punyakonsentrator.

Sistemnya terhubung ke komputer yang mengontroltraffic dalam topology.

Tiap host punya koneksi sendiri ke semua host yangada dalam jaringan.

Karena tiap node terkoneksi ke semua node, makadata dapat dikirimkan melalui beberapa jalur yangada.

Mesh

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Jaringan komputer umumnya menggunakan tipe jaringanethernet, di mana topologi bisa berupa bus, dan star.

Mode pengiriman digunakan CSMA merupakan salah satu skemadalam proses pengiriman paket, di mana pemakainyamendeteksi kanal lebih dahulu apakah kanal sibuk atukahsedang bebas, sebelum proses pengiriman paket.

Bila pemakai mendeteksi kanal dalam keadaan bebas (idle),maka paket akan dikirimkan.

Sedangkan bila kanal terdeteksi dalam keadaan sibuk (busy),maka pengiriman paket ditunda untuk beberapa saat. Collisionantar paket masih mungkin terjadi.

Untuk itu dibuat suatu perbaikan metode CSMA dengan namaCSMA/CD (Carrier Sense Multiple Access with CollisionDetection), yang sering disebut juga dengan metode ListenWhile Talk (LWT).

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Token Ring merupakan salah satu protokol untuk LAN yang menggunakankendali transmisi terdistribusi dan telah distandarisasi oleh IEEEnomor 802.5.

Kendali transmisi pada Token Ring dilakukan oleh bit-bit token yang

beredar sekeliling jaringan ring dari stasiun ke stasiun berikutnya.Bit-bit tersebut ditransmisikan secara serial melalui media transmisifisik dan akan mengalami delay tiap melalui stasiun di dalamjaringan ring.

Setiap stasiun akan membangkitkan kembali dan akan meneruskansetiap bit ke stasiun berikutnya. Jadi stasiun-stasiun dalam Ringjuga berfungsi sebagai regenerator dan repeater.

Suatu stasiun tujuan yang telah diberi alamat akan menyalin informasiyang dikirim stasiun awal bila informasi tersebut lewat, dan stasiunawal akan menghapusnya bila informasi tersebut telah membentuksatu loop penuh mengelilingi ring.

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FDDI (Fiber Distributed Data Intrface) digunakan dengan kabel fiber

opticFDDI menggunakan arsitektur dual-ring dengan arah penjalaran data

yang saling berlawanan, yaitu primary dan secondary ring

Selama keadaan jaringan yang normal, maka ring primer yang

digunakan untuk pentransmisian data, dan ring sekunder dalam

posisi idle.

FDDI biasanya digunakan sebagai backbone berkecepatan tinggi sebab

mendukung bandwidth yang besar dan lebih jauh jangkauannya

dibandingkan kabel tembaga.

Lect e 4

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Lecture 4

FDDI Ring Topology

Media: Fiber (Fiber Distributed Data Interconnect) or cable (CDDI)Topology: Two ringsTransmit: Bits can flow in 2 directions for improving reliabilitySpeed: 100 MbpsStatus: ANSI standard, expensive than Ethernet and Token RingToken: A permission to send data across the ring

Only one token in a ring and the token rotates one by oneIf no data to be sent, computer passes received token to the nextWhen a computer obtains the token, it can send a single packet

A packet travels around entire ring and finally arrives source

PayloadSD FC DAdd SAdd CRC ED FS

SD FC ED

Data frame

Up to 4550 bytes

Token frame (3 bytes)

Features: multiple frames for MM data or RT trans.

Lecture 4

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Lecture 4

Wireless LAN Bus Topology

Media: Air (infrared, spread spectrum, narrowband microwave)Topology: Logic busTransmit: Only one can transmit, not all others can receive transmission

depended upon transmitting energy and distanceSpeed: 1~10Mbps (infrared), 1~20Mbps (spread), 10~100Mbps (MW)

Status: IEEE Project 802.11, many products from different companiesCSMA/CA: Using CSMA to listen and transmit

Using CA (collision avoidance)rather than CD (collision detection)- send a short message to reserve the medium if it is idle- transmit a frame if reservation is successful (no collision)- listen and reserve again

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Wireless LAN: small range (< 100m)

IEEE 802.11 (similar to Ethernet)

- Defined by IEEE (Institute for Electrical and Electronic Engineers)

- Access control: CSMA/CD (only one can send each time similar to TDMA,listen and transmit if no other transmission, otherwise wait)

- Speed: 2Mbps (infrared), >10Mbps (Microwave, 2.4/5.2GHz)

HIPERLAN- Defined by ETSI (European Telecommunication Standard Institute)

- Access control: dynamic TDMA

- Speed: 25Mbps (5GHz) and 155Mbps (17GHz)

HomeRF

- Defined by Home Radio Frequency Working Group (Industry, 1998)

- Access control: similar IEEE 802.11 with priority and reservation control

- Speed: 10Mbps (2.4GHz), support both data, voice and streaming

Bluetooth

- Defined by Bluetooth Special Interest Group (SIG, industry)

- Access control: TDD (Time Division Duplex) with circuit and packet switch

- Speed:1M~10bps

Lecture 4

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Lecture 4

Lecture 4

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Lecture 4

Address and Frame

All stations (computers/devices) on shared-media LAN receive all transmissionsEach station assigned unique number, called station address or

hardware address fixed by manufacturer,configured manually or electronicallyprovided dynamically by software

A sender specifies destination address and source address in its frame header

Source stationSource address

Destination stationDestination address

Frame data or PayloadHeader Trailer

Dest Addr Sour Addr

Packet

Lecture 4

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Lecture 4

Destination Address and Transmission Mode

Packet can be sent to:- Single destination (station address) called unicast (1-to-1)

- All stations (a special address), called broadcast (1-to-all)- Subset of stations (special addresses), called multicast (1-to-m)

Ethernet- Each station has 48bits (6 bytes) unique address assigned by manufacturer- Broadcast address: all 1s address (111111)

- Multicast address: [1xxx], half of addresses reserved for multicast

unicast broadcast multicast

Lecture 4

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Lecture 4

Ethernet Frame Format

Preamble: 64bits (8 bytes) for receiver synchronization with incoming signalDestination address and source addressFrame type (2 bytes):

- 0000~05DC Reserved for use with IEEE LLC/SNAP- 0800 Internet IP Version 4

- 8008 AT&T Corporation- 8014 Silicon Graphics Corporation network games- 8137-8138 Novell Corporation IPX-

Data or Payload: Minimum 46 bytes and maximum 1500 bytes

CRC (4 bytes): Cyclic redundancy check

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Exercise

1. Prove that the total number of links in a point-to-point networkwith N computers is (N2-N)/2

2. For each of bus, star and ring topologies, discuss theconsequences if a station has broken.

3. In most technologies, a sending station can choose the amount of

data in a frame, but the frame header is a fixed size. Calculatethe percentage of bits in a frame devoted to the header, trailerand preamble for the largest and smallest Ethernet frame.

4. Assume a one megabyte file must be send from one computer toanother (both are connected to a same 10BaseT Ethernet).

What is the minimum time to send the file across the network?What is the minimum time across a Fast Ethernet? Across agigabit Ethernet?

5. Give the definitions and examples of unicast, broadcast andmulticast, respectively.