Additional Materials for

1 TOC

 Frames  Error Control, Correction & Detection Schemes  Flow Control  Sublayers of the Data Link  HDLC & PPP  Media Access Control (MAC)  IEEE802.3 families (Ethernet)  Requirements for the Data Link, and Bridges

Information Network 1 / 20132012 2 Frames

Information Network 1 / 20132012 3 Frame

 Data link layer Protocol Data Unit (PDU) – Defining the frame borders (delimiters)  Can determine if any failures (bit errors) was made – Adding error-detecting / error-correcting code to bit sequences in order to delimit the appropriate frame length  Frame header – error detection and flow control – control information

01111110 address control data checksum 01111110

header payload

Information Network 1 / 20132012 4

Frame Synchronization (1)

 Character-based frame synchronization – transmits data based on character unit. • CCITT X.21 – physical layer frame is 8bit – coding format ASCII(IA5) – Insertion of a special character at the header and footer of the data transmission. • STX, ETX – Data identification by DLE (Data Link Escape) • Possibility to “escape” special character sequences during transmission of binary data • character stuffing

Information Network 1 / 20132012 5 Frame Synchronization (2)

Original Data

“B” DLE “A”

Transmission Sequence

ETX DLE “B” DLE DLE “A” STX DLE

transmission

data frame

character stuffing

Information Network 1 / 20132012 6 Frame Synchronization (3)

 Bit-sequence-based frame synchronization – A special bit sequence is inserted to the data header and footer. • synchronization – Insertion of a bit sequence composed of the “same” bit • bit stuffing – special bit sequence only appears at the frame header and footer – e.g. • special bit sequence： 01111110 • if sender detects “11111” in data, it “stuffs” a “0” right after. • if receiver detects “11111” in data, it deletes the following stuffed “0”.

01111110 address control data checksum 01111110

Information Network 1 / 20132012 7 Frame Synchronization (4)

Original Data

０１０１１１１１１１１１１００１１

Transmission Sequence

end bit pattern start bit pattern ０１１１１１１０ ０１００１１１１１０１１１１１００１１ ０１１１１１１０

transmission

bit stuffing

Information Network 1 / 20132012 8 Error Control, Correction & Detection Schemes

Information Network 1 / 20132012 9 Error Detection with Parity Bit

 A parity bit is a bit (0 or 1) that is added to a block of data – ensure that data is not corrupted during the transfer process – detect single bit error • if 2 bits are flipped instead of one, the parity check will pass and an error will be missed  Every 7 bits of data may include a parity bit – If the data transmission protocol is set to an odd parity, each packet must have an odd parity – If it is set to even, each packet must have an even parity

Odd parity Even parity • Initial value: 1010101 (four 1s) • Initial value: 1010101 (four 1s) • Parity bit added: 1 • Parity bit added: 0 • Transmitted value: 10101011 • Transmitted value: 10101010 • Result: odd parity (five 1s) • Result: even parity (four 1s)

Information Network 1 / 20132012 10 Cyclic Redundancy Check (1)

 It can detect consecutive bits error (burst error)  Adds a failure detection CRC check bit after the frame.  Polynomial representation of the bit sequence. – n-bit sequence

• (an-1, ….., a1, a0) ※ ai : 0 or 1 – polynomial expression n-1 2 • F(x)=an-1x +…+a2x +a1x+a0  Calculates polynomial expression. – modulo 2 – equivalent to an eXclusive OR

Information Network 1 / 20132012 11 Cyclic Redundancy Check (2)

 Calculation procedure – Generate the generator polynomial G(x) of order r (r < m) – In the case a node sends an m-bit frame, the polynomial expression is M(x) (order m-1)

– Generate xrM(x) by adding r bits “0” to the frame tail. – Calculate a remainder R(x) by dividing the polynomial expression xrM(x) by G(x).

– Generate F(x), the code to be sent • F(x) = xrM(x) + R(x)

Information Network 1 / 20132012 12 Cyclic Redundancy Check (3)

 Error detection – F(x) is always divisible by G(x) – If F(x) is not divisible by G(x), there is a remainder – Burst error less than r-bit long is detectable – Other remainders depend on G(x)

Information Network 1 / 20132012 13 Standardized CRC (1)

 Typical standards – CRC-12 • x12+x11+x3+x2+x+1 – CRC-16 • x16+x15+x2+1 – CRC-32 • x32+x26+x23+x22+x16+x12+ x11+x10+x8+x7+ x5+x4+x2+x+1 – CRC-CCITT • x16+x12+x5+1

 There exist many other CRC standards.

Information Network 1 / 20132012 14 Standardized CRC (2)

 Application – CRC-12 for 6-bit character expression – CRC-16 and CRC-CCITT for 8-bit character expression  Detection Characteristics (CRC-16 and CRC-CCITT) – all single- and two-consecutive-bit errors – all odd-bit number errors – burst errors less than 16-bit long – 99.997% of burst errors less than 17-bit – 99.998% of burst errors more than 18-bit

Information Network 1 / 20132012 15 Error Correction Code

 Error Correction Code – Hamming code – Distance between codes • “a”-bit error detection ： >a+1 • “b”-bit error correction ： >2b+1

a

1 1 b

Information Network 1 / 20132012 16 Flow Control

Information Network 1 / 20132012 17 Flow Control

 Flow Control Protocols deal with how to send sequences of DLL frames  They have two jobs: – Recover from lost frames – Prevent buffer overflows  must receive same set of frames in the same order they were sent  Automatic Repeat Request (ARQ) – Stop-and-wait – Go-back-N – Selective-repeat

Information Network 1 / 20132012 18 Unrestricted

 Sender send  Problem: receiver’s buffers  Receiver waits to receive may fill up

Information Network 1 / 20132012 19 Stop-and-wait ARQ (1)

Sender t1 t5

t4

t1 t2 t3 Receiver

t1: Round Trip Time t2: Frame Transmission Time t3: Frame Processing Time t4: ACK Transmission Time t5: ACK Processing Time

Information Network 1 / 20132012 20 Stop-and-wait ARQ (2)

 Procedure – Waiting to receive ACK on each frame transmission – Setting a sender timer greater than

2t1+t2+t3+t4 – Retransmission when sender timer times out.  Characteristics – Simple – The buffer never contains more than one frame for the receiver and the sender – Line usage rate is extremely bad

Information Network 1 / 20132012 21 Go-back-N ARQ (1)

 Procedure – Improving Stop-and-Wait Protocol. – Transmitting a frame in series. – Error detection • A frame in which an error has been detected is dropped until the frame is correctly received.

• No ACK is returned until the frame is correctly received.

Information Network 1 / 20132012 22 Go-back-N ARQ (2)

Time out for Frame3

!! 1 2 3 4 5 3 4 5 6

1 2 4 5 3 4 5 6

Information Network 1 / 20132012 23 Go-back-N ARQ (3)

 Characteristics – Wastefulness : upon error detection, correct frames received after the error are also dropped. • Especially, setting a bigger value to the retransmission timer is a disadvantage. – On the sender side, a buffer is necessary for retransmission. • For frames that did not receive an ACK, buffering is necessary to enforce retransmission. • The “N” in Go-back-N corresponds to the number of frames sent without receiving an ACK (on-the-fly frames) • Buffer depends on the retransmission timer value.

Information Network 1 / 20132012 24 Selective-Repeat ARQ (1)

 Methods – Improving Go-back-N protocol. – Only retransmitting necessary frames (erroneous frames).  Characteristics – Transmission efficiency is better than Go-back-N. • Not dropping correct frames uselessly. – Processing is complex. • Needs a buffer on the receiver side. • Frame sequence control is necessary.

Information Network 1 / 20132012 25 Selective-Repeat ARQ (2)

Time out for Frame3

!! 1 2 3 4 5 3 6 7 8

1 2 4 5 3 6 7 8

Information Network 1 / 20132012 26 Flow control

 Stop-and-Wait and Go-back-N don’t have a complex processing on the receiver side.  In Selective-Repeat, sequence control is enforced on the receiver side. – Buffer on the receiver side – When sender-side processing does not perform well, there is a possibility that an overflow occurs on the receiver side.  Flow control – Overflow control between the receiver and sender using some methods.

Information Network 1 / 20132012 27 Window Flow Control

 Window flow control – W : window size • Considering a same buffer size for the receiver. – On sender side, let Nr be in (1) the number of already sent frames, (2) those that did not receive an ACK. – Transmitting until Nr < W – Sliding window flow control

Information Network 1 / 20132012 28 Windows Flow Control

Sender keep frame until ACK is received sent frame sendable frame（maximum size W)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 …

already received ACK last sent frame if sent If ACK is received move to right move to right Receiver received frame receivable frame（maximum size W)

0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 …

already transmitted ACK if received if ACK is sent last received frame Informationmove to rightNetwork 1 / 2012move to right 29

Summarize – Role Allocation

 Role allocation depends on a system design  Various solutions exist

Transport sequence assurance flow control Network retransmission surveillance of network error detection and correction Data Link frame range

Information Network 1 / 20132012 30 Sublayers of the Data Link

Information Network 1 / 20132012 31 From monolithic structure to sub-layered structure

 Data link basic concepts were formed from the technologies using point-to-point connection type data link back in the 1960s.  LAN standardization from the late 1970s moved to sub-layered structure. – Architecture of ISO/OSI 8802 and IEEE802 groups. – Constructing a common IEEE802.2 (ISO8802/2) (LLC) – IEEE802.x specialized for each medium

Information Network 1 / 20132012 32 Sublayers of the Data Link Layer

ISO/OSI Local Area CCITT Data link Network Layer Network Definitions (8802) Layer Definition

Logical Link 8802/2 LLC Control Sublayer CCITT X.25 Data link Layer (HDLC/LAPB) Media Access 8802/3 8802/4 8802/5 Control Sublayer CSMA/CD Token Bus Token Ring

Physical Layer

Information Network 1 / 20132012 33 Logical Link Control (LLC) (1)

 Unacknowledged Connectionless Service (LLC type1) – Transmitting frame without synchronization between sender and receiver. – No special processing, upon error detection. • Enforcing error control in upper layers. – Control method for high speed and errorless links. – LAN, real-time traffic (voice/speech)

 Acknowledged Connection-oriented Service (LLC type2) – Setting up a connection, before data transmission • Enabling synchronized processing between sender and receiver – Ensuring reliability (error and sequence) – Processing is usually complex – For low speed and error-prone links

Information Network 1 / 20132012 34 Logical Link Control (LLC) (2)

 Acknowledged connectionless Service (LLC type3) – Receiver sends ACK for each frame. – Enforcing error control at data link layer level – Improving reliability  Unacknowledged Connection-oriented Service – Not ensuring reliability (error and sequence) – Control method for high speed and errorless links.

Information Network 1 / 20132012 35 Media Access Control (MAC) (1)

Data link layer provides packet send/ receive service to network layer

Physical Layer provides binary send/receive to data link layer

Different media have different constraints about multiple nodes accessing the medium

We want to reserve the medium for a longer space of time!

Information Network 1 / 20132012 36 Media Access Control (MAC) (2)

MAC layer provides medium access service to the data link layer

A separate protocol is needed to implement the service for each different transmission medium

Next class: learn about channel allocation (multiplexing)

Information Network 1 / 20132012 37 HDLC & PPP

Information Network 1 / 20132012 38 High-Level Data Link Control (HDLC)

 A bit-oriented synchronous data link layer protocol developed by the ISO  It provides both connection-oriented and connectionless service  It is still widely used nowadays even if it is an old protocol – Employed in public networks such as ISDN – Existing online network, e.g., online banking system

Information Network 1 / 20132012 39 HDLC Frame (1)

 Address: identifies a communication station (terminal)  Control: information for communication control  Data: information to be transmitted  Checksum: CRC-CCITT

Information Network 1 / 20132012 40 HDLC Frame (2) – Control Field

Control field of: (a) an information frame (b) a supervisory frame (c) an unnumbered frame

Information Network 1 / 20132012 41 HDLC Frame (3) – Control Field

 Definition of three main types of frames: – Information frame (I-frame) • carry the data to be transmitted for the user • flow- and error-control data are piggybacked on an information frame – Supervisory frame (S-frame) • provide the ARQ mechanism when piggybacking is not used – Unnumbered frame (U-frame) • provide supplemental link control functions, e.g., link termination

Information Network 1 / 20132012 42 X.25

 WAN: Wide Area Network – This technology was built at a time when LAN (Local Area Network) and WAN were connected through different technologies – A communication network used by telephone engineers • Nowadays, almost extinct • e.g., ISDN  Approved as an international standard – CCITT standard → ITU-T standard  Layer 1 – Layer 3 of the OSI reference model – Network layer： PLP – Data link layer： HDLC (ITU-T), LAPB (CCITT) – Physical layer： X.21 bis

Information Network 1 / 20132012 43 X.25 Network Model

DTE DTE DCE PSN

PSE DCE

DTE: Data Terminal Equipment DCE: Data Circuit terminating Equipment DTE PSE: Packet Switch Exchange DCE PSN: Packet Switch Network

Information Network 1 / 20132012 44 Point-to-Point Protocol (PPP)

 PPP design requirement (RFC 1557) – Packet framing: encapsulation of network-layer datagram in data link frame • Carry network layer data of any network layer protocol (not just IP) at the same time • Ability to demultiplex upwards – Bit transparency: must carry any bit pattern in the data field – Error detection: (no correction) – Connection liveness: detect signal link failure to network layer – Network layer address negotiation: endpoint can learn/configure each other’s network address  Error recovery, flow control, data re-ordering are all relegated to higher layers  PPP over SONET/SDH – 2-point connection in large-scale or long-distance

Information Network 1 / 20132012 45 PPP Data Control Protocol

 Before exchanging data in the network layer, data link peers must do the following: – configure PPP link (max frame length, authentication) – learn/configure network layer information – For IP: carry IP Control Protocol (IPCP) messages to configure/ learn IP address

Information Network 1 / 20132012 46 PPP Phase Diagram

 A simplified phase diagram for bringing a line up and down.

Information Network 1 / 20132012 47 Media Access Control (MAC)

Information Network 1 / 20132012 48 Access Channel

 Two types of “links”: – Point-to-point • PPP for dial-up access • Point-to-point link between Ethernet switch and host – Broadcast (shared wire or medium) • Traditional Ethernet • 802.11 wireless LAN

Information Network 1 / 20132012 49 MAC Protocols (1)

 Single shared broadcast channel – Two or more simultaneous transmissions by nodes: interference – Collision if node receives two or more signals at the same time  Ideal Media Access Protocol – When one node wants to transmit, it can send at rate R – When M nodes want to transmit, each can send at average rate R/ M – Fully decentralized: • No special node to coordinate transmissions • No synchronization of clocks, slots – Simple

Information Network 1 / 20132012 50 MAC Protocols (2)

Three techniques:  Channel Partitioning – Divide channel into smaller “pieces” (time slots, frequency, code) – Allocate piece to node for exclusive use  Random Access – Channel not divided, allow collisions – “Recover” from collisions  Taking turns – Nodes take turns – Nodes with more to send can take longer turns

Information Network 1 / 20132012 51 TDMA (1)

 Time Division Multiple Access – Access to channel in "rounds" – Divide the medium into different time slots – Each station gets fixed length slot • Length = packet transmission time in each round – A single frame is composed of N slots – Terminal uses a specific slot – Unused slots go idle frame (N=8)

terminal B terminal A

Information Network 1 / 20132012 52 TDMA (2)

 Slot reservation and release – Easy: Statistically multiplexing • Assigned by administrator beforehand – Dynamic assignment is complex • Special function is necessary in terminals  Time synchronization – Slot is determined on a time basis – Time synchronization between terminals and switching nodes is necessary

Information Network 1 / 20132012 53 TDMA (3)

Time-Division fails with heterogeneous traffic

Information Network 1 / 20132012 54 From TDMA to ATM (digression)

 TDMA is a widely used medium access technology – It is simple as it is multiplexing technology – Can guarantee its performance – TDMA is still used in many products • Based on STM (Synchronous transfer mode) • Synchronous networks were widely used until now  TDMA has hardships to accommodate LAN traffic – No guarantee for terminal’s time synchronization – Unable to estimate bandwidth used by terminal beforehand  Arrival of ATM – Accepts LAN traffic – Aims at performance using multiplexing like TDMA – Asynchronous Transfer Mode

Information Network 1 / 20132012 55 FDMA

 Frequency Division Multiple Access – Channel spectrum divided into frequency bands – Each station assigned fixed frequency band – Unused transmission time in frequency bands go idle

1

2

Frequency 3

Time

Information Network 1 / 20132012 56 FDMA (2)

Frequency-Division fails with bursty traffic

Information Network 1 / 20132012 57 OFDM

 Orthogonal Frequency Division Multiplexing  State-of-the-art high bandwidth digital communication use OFDM – Terrestrial Video Broadcasting in Japan and Europe – ADSL High Speed Modem – WLAN such as IEEE 802.11a/g/n – WiMAX as IEEE 802.16d/e – 4G

Information Network 1 / 20132012 58 Digital Modulation Basics

 Digital modulation modulates three parameters of sinusoidal signal.

– A, θk, fc,

s(t) = A⋅cos(2π ⋅ fc ⋅t +θk )  Three type digital modulation: – ASK : Amplitude Shift Keying – PSK : Phase Shift Keying – FSK : Frequency Shift Keying

 OFDM uses combination of ASK and PSK such as – Quadrature Amplitude Modulation (QAM)

Information Network 1 / 20132012 59 Symbol Waveform

Digital Information 1 0 1 0 0 carrier

ASK

PSK

FSK

Symbol length

Information Network 1 / 20132012 60 Japan Terrestrial Television Broadcasting (1)

 Integrated Services Digital Broadcasting for Terrestrial Television Broadcasting (ISDB-T)  Full service area coverage on 2006 – Analog Service ended in 2011  5.6MHz BW is divided into 13 OFDM segments (~430 kHz BW) – HDTV or SDTV: 12 segments – Mobile TV : 1 segment

Information Network 1 / 20132012 61 Japan Terrestrial Television Broadcasting (2)

NHK public paper: http://www.nhk.or.jp/strl/publica/bt/en/le0020.pdf

Information Network 1 / 20132012 62 Random Access Protocols

 When node has packet to send – Transmit at full channel data rate R – No a priori coordination among nodes – Classical shared-medium problem: radio antenna  Two or more transmitting nodes ➜ “collision”  Random access MAC protocol specifies: – How to detect collisions – How to recover from collisions  Example of protocols: – ALOHA – Slotted ALOHA – CSMA • CSMA/CD • CSMA/CA

Information Network 1 / 20132012 63 Pure ALOHA (1)

 History – Developed in the ALOHA system at the University of Hawaii – Two wireless lines • Terminal -> host (uplink) • Host -> terminal (downlink) – Develop shared medium access for two wireless lines  Basic idea: – Each terminal runs independently – Transmission as soon as a terminal has data to send – Receiver sends ACK for data • ACKs sent on separate frequency, so never collide • If ACK is not returned within the RTT (Round Trip Time), it is treated as a packet collision – Back off process • Generation of a random number in [0,K] : r • Retransmission after r seconds

Information Network 1 / 20132012 64 Pure ALOHA (2)

 Collision – Wait random amount of time and resend – Randomization is essential

Information Network 1 / 20132012 65 Pure ALOHA (3) – weakness

 Each terminal autonomously accesses the medium – Performance is naturally bad due to the chaotic access – Systematic order leads to a complexity of the system  Frequent collisions cause performance degradation – Increase of the number of access terminals – Increase of the traffic load  Back-off time – K – Affects communication performance

Information Network 1 / 20132012 66 Slotted ALOHA (1)

 Slotted ALOHA – Enhanced version of pure ALOHA – Transmission time is divided into time slots – Transmission from terminals is made to follow time slots – Employing “systematic order” – Chaotic line access collision becomes slot contention – Reduces occurrence of contention – Improves performance (throughput 18.4%→36.8%)

Information Network 1 / 20132012 67 Slotted ALOHA (2)

 Basic idea: – All frames same size – Time is divided into equal size slots, time to transmit 1 frame – Nodes start to transmit frames only at beginning of slots – Nodes are synchronized – If 2 or more nodes transmit in slot, all nodes detect collision – Frames delayed until beginning of the next slot

Information Network 1 / 20132012 68 Pure ALOHA vs Slotted ALOHA

 Both use randomization after collision  Slotted reduces probability of collision – If frame is ready in middle of period: • In Pure ALOHA, I will begin sending and destroy any currently sending frames • In Slotted ALOHA, I will wait and only destroy other waiting frames

Information Network 1 / 20132012 69 CSMA (1)

 Carrier Sense Multiple Access  Senses the medium to confirm whether it is used before transmission – If the medium is not being used, data is transmitted ASAP – Collision unfortunately occurs due to transmission delay – If another terminal transmits a packet within RTT/2, collision occurs • Time for the transmission spreads along the medium

Information Network 1 / 20132012 70 CSMA (2)

 In case a carrier is detected – 1-persistent • channel free: send immediately • channel busy: send once it is free – non-persistent • channel free: send immediately • channel busy: send after random amount of time – (slotted) p-persistent CSMA • channel free: transmit with prob p • channel busy: repeat algorithm next slot  In case a collision occurs – Wait some time (randomly determined), sense the medium again

Information Network 1 / 20132012 71 CSMA (3)

 CSMA also comes in two flavours – Collision Detection (/CD) • Can ascertain if two data frames have collided • Used in Ethernet 802.3 protocol family – Collision Avoidance (/CA) • Channel is reserved using special frames • Data frames will never collide • Used in Wireless LAN 802.11 protocol family

Information Network 1 / 20132012 72 MAC Throughput Performance

Information Network 1 / 20132012 73 Taking Turn MAC Protocols

 Channel partitioning MAC protocols: – Share channel efficiently and fairly at high load – Inefficient at low load: • Delay in channel access • 1/N bandwidth allocated even if only 1 active node  Random access MAC protocols – Efficient at low load: • Single node can fully utilize channel – high load: • Collision overhead  Taking turns protocols – Two implementations: Polling & Token

Information Network 1 / 20132012 74 Token Passing

 Employed in 802.4 (Token Bus), 802.5 (Token Ring)  FDDI is also a type of Token Passing (more complex)  Method – a token is passed around between nodes in a certain order – a node with the token can communicate – token holding timer  Characteristics – unlike contention type data link, degradation is not enforced during high load periods – for this reason, token bus and token ring are preferred

Information Network 1 / 20132012 75 Historical Transition

Slotted ALOHA Pure ALOHA

CSMA/CD CSMA (Ethernet)

Token Ring FDDI (gone)

TDMA ATM (gone)

Information Network 1 / 20132012 76 Ethernet (IEEE 802.3 Family)

Information Network 1 / 20132012 77 Ethernet

 LAN technology based on CSMA/CD  Standardized as IEEE802.3 – 10Mbps, base-band transmission – 1500octet MTU – Designed and developed as bus type LAN • Coaxial cable and Transceiver • 10Base5, 10Base2  Emergence of 10BaseT technology using UTP cables – Cabling in star topology – Emerging hub and switch

Information Network 1 / 20132012 78 Fast Ethernet

 100Mbps Ethernet – Medium is UTP/CAT5 as well as optical fiber – Direct switchover from 10 Mbps Ethernet environment – Bidirectional 100BaseT • Wider bandwith due to bidirectional data transmission – Auto-sense / Auto-negotiation • Connection type is automatically determined – 10BaseT/100BaseT, Unidirectional / Bidirectional • Interoperability

Information Network 1 / 20132012 79 Gigabit Ethernet (IEEE802.3z)

 1Gbps  Bidirectional data channel technology – Half-channel is 1Gbps – Full duplex  Transmission medium is optical fiber – 1000Base-SX (Short-wavelength), 1000Base-LX (Long- wavelength)  Most of the current products today obey IEEE802.3z standard – Interoperability deployment is progressing steadily – NICs altogether with switches are widespread

Information Network 1 / 20132012 80 Gigabit Ethernet (IEEE802.3ab)

 New Gigabit Ethernet standard – 1000Base-T – UTP – 1Gbps Ethernet – Maximum 100m

Information Network 1 / 20132012 81 Ethernet Family Strengths

 Rapid spread of Fast Ethernet – Simple switchover from 10BaseT – Many cheap products – Substitute 10BaseT networks for Fast Ethernet

 Does not require special network management – Plug-and-play – Significant difference with ATM

Information Network 1 / 20132012 82 Comparison of Ethernet Technology

Ethernet Fast Ethernet Gigabit Ethernet

Data Rate 10Mbps 100Mbps 1Gbps

CAT 5 UTP 100m 100m 100m (CAT5+/6) STP/Coax 500m 100m N/A

Multi-mode Fiber 2Km 412m (hd*) 550m 2Km (fd*) Single-mode Fiber 25Km 20Km > 5Km

*IEEE half duplex/full duplex note: IEEE 802.3z

Information Network 1 / 20132012 83 Ethernet’s address

 6 octet (48 bit)  First three octets defined by IEEE, identify the vendor  The following three octets are assigned by the vendor  IEEE MAC address  “00:a0:cc:7c:47:16”

Assigned by IEEE Assigned by vendor

00 a0 cc 7c 47 16

Information Network 1 / 20132012 84 10Gbps Ethernet

 IEEE802.3ae – Standardized by IEEE on June 2002  Divided into WAN use and LAN use – WAN PHY • Using SONET frame – Considering interoperability with SONET/SDH • ～300m, wavelength: 850nm • 10km, wavelength: 1310nm • 40km, wavelength: 1550nm – LAN PHY • Using Ethernet Frame • ～300m, wavelength: 850nm • 10km, wavelength: 1310nm • 40km, wavelength: 1550nm • 10km, wavelength: 1310nm – Introduced in the market in 2002 • 10GBASE-LR serial (1310nm) • 10GBASE-EX4(1550nm WWDM） • Transmission distance: 10Km – 50Km

Information Network 1 / 20132012 85 40Gbps/100Gbps Ethernet

 IEEE802.3ba – Standardized by IEEE on June 2010

 Goal: To support fast networks over 10Gbps – Only supports full-duplex communication – Preserves the current standard framesize – Supports a transmission quality characterized by a BER (Bit Error Rate) better or equal to 10-12 at the interface with upper layers – Supports OTN（Optical Transport Network)

– Provides physical layer specifications which support 40Gbps operation over: • SMF >10km • OM3 MMF >100m • Copper cable assembly >7m • Backplane >1m

– Provides physical layer specifications which support 100Gbps operation over: • SMF >40km or >10km • OM3 MMF >100m • Copper cable assembly >7m

Information Network 1 / 20132012 86 40Gb/s Ethernet Single-mode Fibre PMD

 IEEE802.3bg – Standardized by IEEE on March 2011 – PMD: Physical Medium Dependent  Improvements: – Support a BER better than or equal to 10-12 at the MAC/PLS service interface – Support a MAC data rate of 40 Gb/s – Use the 40GBASE-R PCS and PMA – Use only existing electrical and logical interfaces from IEEE Std 802.3 as modified by IEEE P802.3ba – Provide Physical Layer specification which support 40 Gb/s operation over at least 2 km on SMF. – Provide optical compatibility with existing carrier 40Gb/s client interfaces (OTU3/STM-256/OC-768/40G POS).

Information Network 1 / 20132012 87 Future of Ethernet

 Terabit Ethernet – P802.3bj under discussion – 4x25G Multi-mode fiber links for up to 100m – Single-mode fiber link is under consideration to increase distance of 2km  Network Partitioning – “Switch agnostic” NIC Partitioning (NPAR) – Up to four virtual ports per physical port • Virtual ports: NIC, FCoE, or iSCI  OpenFlow – Create research control plane – Fast provisioning of virtual networks – Speed up innovation in networking

Information Network 1 / 2013 Requirements for the Data Link, and Bridges

Information Network 1 / 20132012 89 Today’s data link requirements

 Wide bandwidth

 Large scale

 Virtualization

 Coverage expansion

Information Network 1 / 20132012 90 Development of data link technologies

 Wide bandwidth  Switched media

 Large scale  Bridges

 Virtualization  VLAN

 Coverage expansion  Broadband wireless, residential access, etc.

Information Network 1 / 20132012 91 Wide bandwidth：shared media → switched media

 High-bandwidth and commodity LAN  Spread of Processor Interconnect Technology

medium access Non-blocking crossbar switch

Information Network 1 / 20132012 92 Shifting to switched media

 Confusing switched media and shared media carries out significant problems  Failure of demonstration is caused by this

Shared media Voice Video Video Wireless LAN (MPEG2) (MotionJPEG)

Voice Video Video Video Video Switched media (MPEG2) (MotionJPEG) (D1) (HD D1) Ethernet

1996 1998 2000 2002 2004 2006

Information Network 1 / 20132012 93 Large scale： Bridges

 Compatibility between physical limitations and LAN convenience – Coverage, capacity

Wiring in floor：coax （~100m）

Wiring between buildings：optical fiber （~5km）

Information Network 1 / 20132012 94 Bridge basics: Transparent bridge

 Host is not aware of the bridge  Transparent bridge – No modification of MAC frame – Promiscuous: capture all flowing packets – Administrator builds the bridge forwarding table

Transparent A C bridge E G

1 2 B D F H

Fwd to 1 A, B, C, D Fwd to 2 E, F, G, H

Information Network 1 / 20132012 95 Learning bridge

 When a frame destined to an unknown MAC is received – Forward to other ports (flooding) – Record source host → register to the forwarding table  When a frame destined to a known MAC is received – Forward to appropriate port  Broadcast transmission – Received by all active hosts in a same medium

A C E G

1 2 B D F H

Construct a table with learning

Information Network 1 / 20132012 96 Loops in learning bridges

 Based on the previous algorithm, what would happen if A sends a frame to G?

A G

1 2 4 5 3 B 6

C F D 7 9

8 10 E

Information Network 1 / 20132012 97 Spanning tree bridges

 Spanning tree

A G

1D 2D 4R 5D 3D B 6A C F R: root port D D: designated port 7D 9D A: alternative port

8D 10R E

Information Network 1 / 20132012 98 More various technologies

 VLAN – Network virtualization – Nowadays, VLAN is frequently used – Single medium, multiple-network installation  WDM  MPLS  Broadband wireless, residential access, WiMAX, …

 Keep on studying more and if you are interested…

Information Network 1 / 20132012 99