10-01-K.Steenhaut & J.Tiberghien - VUB 1 Telecommunications Concepts Chapter 3.1 Packet Switched Local Area Networks

10-01-K.Steenhaut & J.Tiberghien - VUB 2 Contents Original Local Area Networks –Ethernet –Token Ring, Token bus, Cambridge ring, Liu ring, … The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Tracks –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 3 Contents Original Local Area Networks –Ethernet –Token Ring, Token bus, Cambridge ring, Liu ring, … The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Tracks –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 4 Shared Media Networks Need for Medium Access Control Protocols Commonly used in Local Area Networks The network itself has practically no storage capacity

10-01-K.Steenhaut & J.Tiberghien - VUB 5 The 7 OSI layers Applications Layer Transport Layer Networks Layer Connectivity Interoperability Internet Sublayer 1 : Physical 2 : Data Link 3 : Network 4 : Transport 5 : Session 6 : Presentation 7 : Application

10-01-K.Steenhaut & J.Tiberghien - VUB 6 The 3 lower OSI layers For Shared Medium Networks Network Internet 3 Physical Medium Access Control 2 1 Data Link Control

10-01-K.Steenhaut & J.Tiberghien - VUB 7 Contents Original Local Area Networks –Ethernet –Token Ring, Token bus, Cambridge ring, Liu ring, … The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 8 Ethernet Developed in the seventies at Xerox Parc –Invented by Lamport –Commercially supported by Digital and Intel –Still has a dominant market position Originally based on coaxial bus –Passive broadcast medium –Length limited by electrical properties of cable »Thick coaxial : 500 m »Thin coaxial : 185 m –Repeaters ( = electronic amplifiers ) allow to »extend cable length »replace coaxial bus by twisted pairs star Medium access control inspired by Aloha

10-01-K.Steenhaut & J.Tiberghien - VUB 9 Aloha (N.Abramson, F.Kuo, 1970) Communication between terminals and mainframe via geostationary satellite h = Km Propagation delay = 240 mS REPEAT Transmit data block B; Receive same block Br; ok := B = Br; IF NOT ok THEN Wait Random Delay END UNTIL ok

10-01-K.Steenhaut & J.Tiberghien - VUB 10 ALOHA Performance t : Transmission time for one data block. G :Total proposed traffic ( # of blocks in time t ) S : Throughput ( # of successful blocks in time t ) 0 <= S <= 1 p : Probability that a block will avoid collision S = G. p

10-01-K.Steenhaut & J.Tiberghien - VUB 11 ALOHA Collision Window Station A Station B 2t Blocks transmitted according to Poisson Distribution p = e - 2G S = G. e - 2G

10-01-K.Steenhaut & J.Tiberghien - VUB 12 ALOHA Throughput )S(G G

10-01-K.Steenhaut & J.Tiberghien - VUB 13 CSMA/CD operation Carrier Sense –Listen before sending Multiple Access –Everybody noticing silence can start sending Collision Detect –Stop sending when noticing that others sending –Collision fragments characterized by insufficient length and therefore discarded by MAC entity. Graceful degradation due to average repetition delay proportional to number of retransmissions

10-01-K.Steenhaut & J.Tiberghien - VUB 14 Carrier Sense A A A B B B Listen before talking (carrier sense) Send data Listen and wait No carrier sensed, transmission starts

10-01-K.Steenhaut & J.Tiberghien - VUB 15 Collision Enforcement A A B B Collision Collided signals propagate B detects collision and transmits jam AB Collided signals reach A Station A should detect the collision BEFORE it has send its last databit

10-01-K.Steenhaut & J.Tiberghien - VUB 16 Minimum packet size AB AB No carrier sensed, transmission starts Min. packet time > max. round trip delay Collided signals reach A Station A should detect the collision BEFORE it has send its last databit

10-01-K.Steenhaut & J.Tiberghien - VUB 17 Efficiency of channel

10-01-K.Steenhaut & J.Tiberghien - VUB 18 Ethernet Data Frame Preamble (7 bytes) Start Frame (1 byte) Destination Address (6 bytes) Source Address (6 bytes) Length payload (2 bytes) Payload (evt. + Padding) Frame Check Sequence (4 bytes) Min : 64 bytes Max : 1518 bytes

10-01-K.Steenhaut & J.Tiberghien - VUB 19 Thick Ethernet Thick cable Total Length <= 500 m

10-01-K.Steenhaut & J.Tiberghien - VUB 20 Ethernets with repeaters Repeaters Distance <= 3000 m Half Repeaters Optical Link

10-01-K.Steenhaut & J.Tiberghien - VUB 21 Thin Ethernets Thin cable Total Length <= 185 m

10-01-K.Steenhaut & J.Tiberghien - VUB 22 Thin Ethernets Repeaters Thin cable Distance <= 3000 m Segment Length <= 185 m

10-01-K.Steenhaut & J.Tiberghien - VUB 23 Repeaters for thin Ethernet

10-01-K.Steenhaut & J.Tiberghien - VUB 24 Ethernet over twisted pairs One or two pairs per direction

10-01-K.Steenhaut & J.Tiberghien - VUB 25 Twisted pair Ethernet (10 Mb/s) Repeaters (= hubs) Twisted pairs Distance <= 3000 m Segment Length <= 100 m Class 3 utp

10-01-K.Steenhaut & J.Tiberghien - VUB 26 Cascade of Ethernet hubs A B HUB = Set of repeaters > all frames broadcasted BBBBBBB

10-01-K.Steenhaut & J.Tiberghien - VUB 27 High-performance Ethernet (100 Mb/s) Repeaters Twisted pairs Distance <= 400m Segment Length <= 100 m 4 twisted pairs (class 3) 2 twisted pairs (class 5)

10-01-K.Steenhaut & J.Tiberghien - VUB 28 Ethernet in office buildings

10-01-K.Steenhaut & J.Tiberghien - VUB 29 Contents Original Local Area Networks –Ethernet –Token Ring, Token bus, Cambridge ring, Liu ring, … The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 30 Contents Original Local Area Networks –Ethernet –Token Ring The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 31 IEEE 802 Standards in the OSI model Broadband ~ Ethernet ~ Token Bus ~ Token Ring Metropolitan 802.? ??? IEEE Logical Link Control IEEE Management, interconnection, Upper layers interface 2 1 MAC LLC Physical 3

10-01-K.Steenhaut & J.Tiberghien - VUB 32 Contents Original Local Area Networks –Ethernet –Token Ring The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 33 Contents Original Local Area Networks –Ethernet –Token Ring The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 34 IEEE Logical Link Control Purpose : –To fit LAN’s into the general OSI framework –Correct transmission errors Services offered : –Data link multiplexing by means of LLC addresses –Data link error correction and flow control »Class 1 : Connectionless, unacknowledged service »Class 2 : Connection oriented reliable link control Sliding window protocol Window size = 128 frames. »Class 3 : Connectionless, acknowledged.

10-01-K.Steenhaut & J.Tiberghien - VUB 35 LLC Frame Format Flag : Unique bit pattern ( ) Address (2*16 bit) : allows to multiplex a single MAC address for different data links. Control (16 bit) : Controls the sliding windows Payload (variable length) : Data from layer 3 CRC (16 bit) : Redundant bits obtained by dividing the address, control and payload fields by a predefined polynomial. FlagCRCAddressControlFlag Payload

10-01-K.Steenhaut & J.Tiberghien - VUB 36 LLC bit stuffing The bit pattern should never occur in the address, control, payload and CRC fields. After 5 consecutive 1’s a 0 is inserted by the TX A 0 preceded by 5 1’s is removed by the RX Message to be transmitted : Message effectively transmitted :

10-01-K.Steenhaut & J.Tiberghien - VUB 37 LLC Frame Types Unnumbered used to set up connections used to transfer data in connectionless mode Supervisory used for managing the sliding window in connection oriented mode Information used to transfer data in connection oriented mode

10-01-K.Steenhaut & J.Tiberghien - VUB 38 Contents Original Local Area Networks –Ethernet –Token Ring The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 39 Interconnection of LAN’s Layer 7 : Application level Gateways Layer 3 : ROUTERS –Independent networks (lan or wan) interconnected by means of an internet protocol. Layer 2 : BRIDGES –Independent MAC protocols on interconnected lan’s. –Distance restrictions apply to each lan individually –Half bridges can be interconnected by any lan or wan. –Traffic between lan’s can be filtered according to MAC level addresses. Layer 1 : REPEATERS –No influence on MAC protocol –Same traffic in all interconnected lan’s

10-01-K.Steenhaut & J.Tiberghien - VUB 40 Repeaters Layer 1 Layer 2a Layer 2b Layer 3b Layer 3a Layer 1 Repeater Layer 2a Layer 2b Layer 3b Layer 3a Layer 1 Internet Data Link Medium Access Control Network

10-01-K.Steenhaut & J.Tiberghien - VUB 41 Practical Ethernets Repeaters Distance <= 3000 m Half Repeaters Optical Link

10-01-K.Steenhaut & J.Tiberghien - VUB 42 Interconnection of LAN’s Layer 7 : Application level Gateways Layer 3 : ROUTERS –Independent networks (lan or wan) interconnected by means of an internet protocol. Layer 2 : BRIDGES –Independent MAC protocols on interconnected lan’s. –Distance restrictions apply to each lan individually –Half bridges can be interconnected by any lan or wan. –Traffic between lan’s can be filtered according to MAC level addresses. Layer 1 : REPEATERS –No influence on MAC protocol –Same traffic in all interconnected lan’s

10-01-K.Steenhaut & J.Tiberghien - VUB 43 Application Level Gateways Application gateway Layer 2 Layer 3 Layer 1 Layer 5 Layer 4 Layer 7 Layer 6 Layer 2 Layer 3 Layer 1 Layer 5 Layer 4 Layer 7 Layer 6 Layer 2 Layer 3 Layer 1 Layer 5 Layer 4 Layer 7 Layer 6 Layer 2 Layer 3 Layer 1 Layer 5 Layer 4 Layer 7 Layer 6

10-01-K.Steenhaut & J.Tiberghien - VUB 44 Gateway example X400 - SMTP mail gateway X400 usersSMTP users mail gateway

10-01-K.Steenhaut & J.Tiberghien - VUB 45 Firewalls An application gateway between the Internet and an intranet is a fairly secure firewall. Intranet Internet Firewall

10-01-K.Steenhaut & J.Tiberghien - VUB 46 Interconnection of LAN’s Layer 7 : Application level Gateways Layer 3 : ROUTERS –Independent networks (lan or wan) interconnected by means of an internet protocol. Layer 2 : BRIDGES –Independent MAC protocols on interconnected lan’s. –Distance restrictions apply to each lan individually –Half bridges can be interconnected by any lan or wan. –Traffic between lan’s can be filtered according to MAC level addresses. Layer 1 : REPEATERS –No influence on MAC protocol –Same traffic in all interconnected lan’s

10-01-K.Steenhaut & J.Tiberghien - VUB 47 Routers Layer 1 Layer 2a Layer 2b Layer 3b Layer 3a Layer 1 Layer 2a Layer 2b Layer 3b Layer 3a Layer 1 Layer 2a Layer 3b Layer 2b Layer 3a Layer 3b Layer 2b Layer 3a Router

10-01-K.Steenhaut & J.Tiberghien - VUB 48 Interconnection of LAN’s Layer 7 : Application level Gateways Layer 3 : ROUTERS –Independent networks (lan or wan) interconnected by means of an internet protocol. Layer 2 : BRIDGES –Independent MAC protocols on interconnected lan’s. –Distance restrictions apply to each lan individually –Half bridges can be interconnected by any lan or wan. –Traffic between lan’s can be filtered according to MAC level addresses. Layer 1 : REPEATERS –No influence on MAC protocol –Same traffic in all interconnected lan’s

10-01-K.Steenhaut & J.Tiberghien - VUB 49 Bridges Layer 1 Layer 2a Layer 2b Layer 3b Layer 3a Layer 1 BRIDGE Layer 2a Layer 2b Layer 3b Layer 3a Layer 1 Internet Data Link Layer 2a Network

10-01-K.Steenhaut & J.Tiberghien - VUB 50 Bridges Bridge

10-01-K.Steenhaut & J.Tiberghien - VUB 51 Bridges Bridge WiFi

10-01-K.Steenhaut & J.Tiberghien - VUB 52 Bridges and multiple Network Protocols BRIDGE IP IPX

10-01-K.Steenhaut & J.Tiberghien - VUB 53 Contents Original Local Area Networks –Ethernet –Token Ring The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 54 Filtering Bridges Lan 1 Lan 2 RX Filter Buffer TX Addresses Database

10-01-K.Steenhaut & J.Tiberghien - VUB 55 Learning Bridges Frames with unknown destination are always forwarded (promiscuous mode) Source addresses of all frames are monitored and added to the database, with a time stamp. Frames with a destination address known to be on the same side as their source are not forwarded. Addresses which have not been confirmed since some time are removed from the database. The learning algorithm requires that there are no loops through the interconnected lan’s.

10-01-K.Steenhaut & J.Tiberghien - VUB 56 Spanning Tree Algorithm Root (Lowest serial Nr) Disabled

10-01-K.Steenhaut & J.Tiberghien - VUB 57 Half Bridges Any Data Link Ethernet frames are tunneled through the network interconnecting the half bridges

10-01-K.Steenhaut & J.Tiberghien - VUB 58 Backbones Half Bridges FDDI MAN ATM ISDN F.R. X25

10-01-K.Steenhaut & J.Tiberghien - VUB 59 Level 2a tunneling via level 2a intermediate network 2a 2b a 1 1 2b a 1 1 Specific labels can be added to the frames to identify data flow

10-01-K.Steenhaut & J.Tiberghien - VUB 60 Level 2a tunneling via level 2b intermediate network 2a 2b a 1 2b 1 2a 2b a 1 2b 1

10-01-K.Steenhaut & J.Tiberghien - VUB 61 Level 2a tunneling via level 3 intermediate network 2a 2b a 1 2b 3 1 2a 2b a 1 2b 3 1

10-01-K.Steenhaut & J.Tiberghien - VUB 62 Virtual LAN’s

10-01-K.Steenhaut & J.Tiberghien - VUB 63 Contents Original Local Area Networks –Ethernet –Token Ring The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 64 High performance Ethernet less collisions Data rate 10 MB/s 100 MB/s 1 GB/s Single segment (broadcast) One station per segment = no collisions (switching) Throughput

10-01-K.Steenhaut & J.Tiberghien - VUB 65 Switched LAN’s

10-01-K.Steenhaut & J.Tiberghien - VUB 66 Contents Original Local Area Networks –Ethernet –Token Ring The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 67 Cable TV Networks Head-end Trunk cables Distribution cables

10-01-K.Steenhaut & J.Tiberghien - VUB 68 Cable TV Networks frequency VTMRTBFVRTRTLTF1 7-8 MHz

10-01-K.Steenhaut & J.Tiberghien - VUB 69 Data over Cable TV frequency VTMRTBFBRTNRTLReturn 7-8 MHz Data Cable modem Cable modem

10-01-K.Steenhaut & J.Tiberghien - VUB 70 Gigabit Ethernet as MAN Head-end Distribution cables (optical fibers) Backbone (WDM optical fibers)

10-01-K.Steenhaut & J.Tiberghien - VUB 71 Contents Original Local Area Networks –Ethernet –Token Ring The IEEE 802 standards –IEEE 802.3, IEEE 802.4, IEEE 802.5,... –IEEE : Logical Link Control –IEEE : Learning bridges High Performance LAN’s and MAN's –High performance Ethernet –Metropolitan Networks –Wireless LAN's Side Track –Interconnection of data communication systems.

10-01-K.Steenhaut & J.Tiberghien - VUB 72 IEEE Management, interconnection, upper layers interface ~ Ethernet ~ Token Bus ~ Token Ring Wireless IEEE Logical Link Control 2 1 MAC LLC Physical 3 IEEE 802 Standards in the OSI model

10-01-K.Steenhaut & J.Tiberghien - VUB 73 IEEE Frequency hopping spread spectrum ??? Infrared IEEE Medium Access Control Direct Sequence spread spectrum 1 or 2 Mb/s (provisions for migration to higher speeds) One common MAC layer Provisions for a variety of physical layers

10-01-K.Steenhaut & J.Tiberghien - VUB Hidden Station A B C RTS CTS