Communication In Smart Grid Part1 (Basics of Networking)

Transcription

1 Communication In Smart Grid Part1 (Basics of Networking) Informatik 7 Rechnernetze und Kommunikationssysteme

2 Distinguishing characteristics of Smart Grid Increase use of digital information and control technology Dynamic Optimization of grid operations and resources with full cyber security Deployment and integration of distributed resources and generation Deployment of smart technologies for metering, and smart distribution control Integration of smart appliances and consumer devices 1

3 Smart Grid: The Energy Internet 2-way flow of electricity and information Enabled by ICT Infrastructure 2

4 What Will the Smart Grid Look Like? Dynamic pricing High use of variable renewables Energy management systems Distributed storage Distributed generation and microgrids Bidirectional metering Electric vehicles Ubiquitous networked sensors Smart meters and real time usage data Smart appliances 3

5 Possible Communication Infrastructure for Smart Grid 4

6 Basics of Networking (take the internet as example) 1 what is the Internet? 2 network edge end systems, access networks, links 3 network core packet switching, circuit switching, network structure 4 delay, loss, throughput in networks 5 protocol layers, service models 6 networks under attack: security 5

7 What s the Internet: nuts and bolts view Internet: network of networks Interconnected ISPs protocols control sending, receiving of msgs e.g., TCP, IP, HTTP, Skype, Internet standards RFC: Request for comments IETF: Internet Engineering Task Force mobile network home network institutional network global ISP regional ISP 6

8 What s the Internet: a service view Infrastructure that provides services to applications: Web, VoIP, , games, e- commerce, social nets, provides programming interface to apps hooks that allow sending and receiving app programs to connect to Internet provides service options, analogous to postal service mobile network home network global ISP regional ISP institutional network 7

9 What s a protocol? human protocols: what s the time? I have a question introductions specific msgs sent specific actions taken when msgs received, or other events network protocols: machines rather than humans all communication activity in Internet governed by protocols protocols define format, order of msgs sent and received among network entities, and actions taken on msg transmission, receipt 8

10 What s a protocol? Ex. Transmission Control Protocol(TCP)? a human protocol and a computer network protocol: Hi Hi What is the time? 2:00 Thanks time Connection Establishment TCP connection request TCP connection response Get <file> TCP connection close TCP is Connection Oriented Protocol Connection Termination 9

11 What s a protocol? Ex. User Datagram Protocol (UDP) a human protocol and a computer network protocol: What is the time?? UDP Packet (speech) 2:00 UDP Packet (speech) time UDP is Connectionless Protocol 10

12 TCP or UDP? Depends on Applications What is more important? to hear the whole call (100%) with delay(few seconds) OR 90% with low delay (few ms) Some Smart Grid application will use TCP and other will use UDP TCP is suitable for price signal UDP is suitable for PMU reading (30 reading /second ) 11

13 A closer look at network structure: network edge: hosts: clients and servers servers often in data centers mobile network global ISP access networks, physical media: wired, wireless communication links network core: interconnected routers network of networks home network institutional network regional ISP 12

14 Access networks and physical media Q: How to connect end systems to edge router? residential access nets institutional access networks (school, company) mobile access networks keep in mind: bandwidth (bits per second) of access network? shared or dedicated? 13

15 Access net: digital subscriber line (DSL) central office telephone network DSL modem splitter voice, data transmitted at different frequencies over dedicated line to central office DSLAM DSL access multiplexer ISP use existing telephone line to central office DSLAM data over DSL phone line goes to Internet voice over DSL phone line goes to telephone net < 2.5 Mbps upstream transmission rate (typically < 1 Mbps) < 24 Mbps downstream transmission rate (typically < 10 Mbps) 14

16 Maximum Data Rate of a Channel Nyquist s theorem relates the data rate to the bandwidth (B) and number of signal levels (V): Max. data rate = 2B log 2 V bits/sec Shannon's theorem relates the data rate to the bandwidth (B) and signal strength (S) relative to the noise (N): Max. data rate = B log 2 (1 + S/N) bits/sec How fast signal can change How many levels can be seen 15

17 Decibels (db) Engineers like to express signal-to-noise ratio in decibels (db) using the following quantity: 10log 10 (S/N) Example: a signal-to-noise ratio of 100 is expressed as 20dB Example: a signal-to-noise ratio of 30dB is the same as 10^(30/10) or

18 Example : Telephone System 3 khz, V = 256, Max. data rate = 2* 3000 (log2(256) = 48kbps 17

19 Example Conventional telephone system Engineered for voice Bandwidth is 3000Hz SNR ~= 30dB Effective capacity is: 3000log 2 (1+1000) ~= 30kbps Conclusion: dial-up modems have little hope of exceeding 28.8Kbps 18

20 Operation of ADSL using discrete multitone modulation. 19

21 Bandwidth versus distance over Category 3 UTP for DSL. 20

22 Power Line Communication PLC = No new wires: Emerging Technology Use of Power grid for communication Extensive infrastructure "Every" building DATA PV/T Controller Smart meter Electricity demand Battery µchp Boiler Heat storage 21 Heat demand

23 Access net: cable network cable modem splitter cable headend Channels V I D E O V I D E O V I D E O V I D E O V I D E O V I D E O D A T A D A T A C O N T R O L frequency division multiplexing: different channels transmitted in different frequency bands 22

24 Access net: cable network cable headend cable modem splitter data, TV transmitted at different frequencies over shared cable distribution network CMTS cable modem termination system ISP HFC: hybrid fiber coax asymmetric: up to 30Mbps downstream transmission rate, 2 Mbps upstream transmission rate network of cable, fiber attaches homes to ISP router homes share access network to cable headend unlike DSL, which has dedicated access to central 23 office

25 Access net: home network wireless devices often combined in single box to/from headend or central office cable or DSL modem wireless access point (54 Mbps) router, firewall, NAT wired Ethernet (100 Mbps) 24

26 Enterprise access networks (Ethernet) institutional link to ISP (Internet) institutional router Ethernet switch institutional mail, web servers typically used in companies, universities, etc 10 Mbps, 100Mbps, 1Gbps, 10Gbps transmission rates today, end systems typically connect into Ethernet switch 25

27 Wireless access networks shared wireless access network connects end system to router via base station aka access point wireless LANs: within building (100 ft) b/g (WiFi): 11, 54 Mbps transmission rate wide-area wireless access provided by telco (cellular) operator, 10 s km between 1 and 10 Mbps 3G, 4G: LTE to Internet to Internet 26

28 Host: sends packets of data host sending function: takes application message breaks into smaller chunks, known as packets, of length L bits transmits packet into access network at transmission rate R link transmission rate, aka link capacity, aka link bandwidth packet transmission delay 2 host time needed to transmit L-bit packet into link = = 1 two packets, L bits each R: link transmission rate L (bits) R (bits/sec) 27

29 Physical media bit: propagates between transmitter/receiver pairs physical link: what lies between transmitter & receiver guided media: signals propagate in solid media: copper, fiber, coax, power line unguided media: signals propagate freely, e.g., radio twisted pair (TP) two insulated copper wires Category 5: 100 Mbps, 1 Gpbs Ethernet Category 6: 10Gbps 28

30 Physical media: coax, fiber coaxial cable: two concentric copper conductors bidirectional broadband: multiple channels on cable HFC fiber optic cable: glass fiber carrying light pulses, each pulse a bit high-speed operation: high-speed point-to-point transmission (e.g., 10 s- 100 s Gpbs transmission rate) low error rate: repeaters spaced far apart immune to electromagnetic noise 29

31 Power Line Communication (PLC) Narrow-band PLC Typical data rate is 100s of kbps Broadband PCL Typical data rate is Several Mbps 30

32 Physical media: radio signal carried in electromagnetic spectrum no physical wire bidirectional propagation environment effects: reflection obstruction by objects interference radio link types: terrestrial microwave e.g. up to 45 Mbps channels LAN (e.g., WiFi) 11Mbps, 54 Mbps wide-area (e.g., cellular) 3G cellular: ~ few Mbps satellite Kbps to 45Mbps channel (or multiple smaller channels) 270 msec end-end delay geosynchronous versus low altitude 31

33 The network core mesh of interconnected routers packet-switching: hosts break application-layer messages into packets forward packets from one router to the next, across links on path from source to destination each packet transmitted at full link capacity 32

34 Packet-switching: store-and-forward L bits per packet end-end delay = 2L/R (assuming zero propagation delay) source R bps R bps destination takes L/R seconds to transmit (push out) L-bit packet into link at R bps store and forward: entire packet must arrive at router before it can be transmitted on next link one-hop numerical example: L = 7.5 Mbits R = 1.5 Mbps one-hop transmission delay = 5 sec more on delay shortly 33

35 Packet Switching: queuing delay, loss A R = 100 Mb/s C B queue of packets waiting for output link R = 1.5 Mb/s D E queuing and loss: If arrival rate (in bits) to link exceeds transmission rate of link for a period of time: packets will queue, wait to be transmitted on link packets can be dropped (lost) if memory (buffer) fills up 34

36 Two key network-core functions routing: determines sourcedestination route taken by packets routing algorithms forwarding: move packets from router s input to appropriate router output routing algorithm local forwarding table header value output link dest address in arriving packet s header 35

37 Alternative core: circuit switching end-end resources allocated to, reserved for call between source & dest: In diagram, each link has four circuits. call gets 2 nd circuit in top link and 1 st circuit in right link. dedicated resources: no sharing circuit-like (guaranteed) performance circuit segment idle if not used by call (no sharing) Commonly used in traditional telephone networks 36

38 Circuit switching: FDM versus TDM FDM Example: 4 users frequency TDM time frequency time 37

39 Packet switching versus circuit switching packet switching allows more users to use network! example: 1 Mb/s link each user: 100 kb/s when active active 10% of time N users 1 Mbps link circuit-switching: 10 users packet switching: with 35 users, probability > 10 active at same time is less than.0004 * Q: how did we get value ? Q: what happens if > 35 users? 38

40 Packet switching versus circuit switching is packet switching a slam dunk winner? great for bursty data resource sharing simpler, no call setup excessive congestion possible: packet delay and loss protocols needed for reliable data transfer, congestion control Q: How to provide circuit-like behavior? bandwidth guarantees needed for audio/video apps still an unsolved problem 39

41 How do loss and delay occur? packets queue in router buffers packet arrival rate to link (temporarily) exceeds output link capacity packets queue, wait for turn packet being transmitted (delay) A B packets queueing (delay) free (available) buffers: arriving packets dropped (loss) if no free buffers 40

42 Four sources of packet delay A transmission propagation B nodal processing queueing d nodal = d proc + d queue + d trans + d prop d proc : nodal processing check bit errors determine output link typically < msec d queue : queueing delay time waiting at output link for transmission depends on congestion level of router 41

43 Four sources of packet delay A transmission propagation B nodal processing queueing d nodal = d proc + d queue + d trans + d prop d trans : transmission delay: L: packet length (bits) R: link bandwidth (bps) d trans = L/R d trans and d prop very different d prop : propagation delay: d: length of physical link s: propagation speed in medium (~2x10 8 m/sec) d prop = d/s * Check out the Java applet for an interactive Dr.-Ing. Abdalkarim animation Awad on trans vs. prop delay 42

44 Caravan analogy ten-car caravan toll booth 100 km 100 km toll booth cars propagate at 100 km/hr toll booth takes 12 sec to service car (bit transmission time) car~bit; caravan ~ packet Q: How long until caravan is lined up before 2nd toll booth? time to push entire caravan through toll booth onto highway = 12*10 = 120 sec time for last car to propagate from 1st to 2nd toll both: 100km/(100km/hr)= 1 hr A: 62 minutes 43

45 Caravan analogy (more) ten-car caravan toll booth 100 km 100 km toll booth suppose cars now propagate at 1000 km/hr and suppose toll booth now takes one min to service a car Q: Will cars arrive to 2nd booth before all cars serviced at first booth? A: Yes! after 7 min, 1st car arrives at second booth; three cars still at 1st booth. 44

46 Example Find the time required to send a packet of size 100 bytes using a narrow band PLC with data rate 100kbps. The cable length is 1km and the propagation speed is 1.5*10 8 Delay prop =1000m/1.5*108=6.7 us Delay tran =100byte/100kbps=100*8bit/100000bit/s= =8 ms Delay total =8ms ms= ms 45

47 average queueing delay Queuing delay R: link bandwidth (bps) L: packet length (bits) a: average packet arrival rate traffic intensity = La/R La/R ~ 0: avg. queueing delay small La/R -> 1: avg. queueing delay large La/R > 1: more work arriving than can be serviced, average delay infinite! La/R ~ 0 La/R -> 1 46

48 Some Smart Grid Applications Requirements 47

49 Some Smart Grid Applications Requirements 48

50 Real Internet delays and routes what do real Internet delay & loss look like? traceroute program: provides delay measurement from source to router along end-end Internet path towards destination. For all i: sends three packets that will reach router i on path towards destination router i will return packets to sender sender times interval between transmission and reply. 3 probes 3 probes 3 probes 49

51 Real Internet delays, routes traceroute: gaia.cs.umass.edu to 3 delay measurements from gaia.cs.umass.edu to cs-gw.cs.umass.edu 1 cs-gw ( ) 1 ms 1 ms 2 ms 2 border1-rt-fa5-1-0.gw.umass.edu ( ) 1 ms 1 ms 2 ms 3 cht-vbns.gw.umass.edu ( ) 6 ms 5 ms 5 ms 4 jn1-at wor.vbns.net ( ) 16 ms 11 ms 13 ms 5 jn1-so wae.vbns.net ( ) 21 ms 18 ms 18 ms 6 abilene-vbns.abilene.ucaid.edu ( ) 22 ms 18 ms 22 ms 7 nycm-wash.abilene.ucaid.edu ( ) 22 ms 22 ms 22 ms ( ) 104 ms 109 ms 106 ms 9 de2-1.de1.de.geant.net ( ) 109 ms 102 ms 104 ms 10 de.fr1.fr.geant.net ( ) 113 ms 121 ms 114 ms 11 renater-gw.fr1.fr.geant.net ( ) 112 ms 114 ms 112 ms 12 nio-n2.cssi.renater.fr ( ) 111 ms 114 ms 116 ms 13 nice.cssi.renater.fr ( ) 123 ms 125 ms 124 ms 14 r3t2-nice.cssi.renater.fr ( ) 126 ms 126 ms 124 ms 15 eurecom-valbonne.r3t2.ft.net ( ) 135 ms 128 ms 133 ms ( ) 126 ms 128 ms 126 ms 17 * * * 18 * * * 19 fantasia.eurecom.fr ( ) 132 ms 128 ms 136 ms trans-oceanic link * means no response (probe lost, router not replying) 50

52 Packet loss queue (aka buffer) preceding link in buffer has finite capacity packet arriving to full queue dropped (aka lost) lost packet may be retransmitted by previous node, by source end system, or not at all A buffer (waiting area) packet being transmitted B packet arriving to full buffer is lost 51

53 Why layering? dealing with complex systems: explicit structure allows identification, relationship of complex system s pieces layered reference model for discussion modularization eases maintenance, updating of system change of implementation of layer s service transparent to rest of system e.g., change in gate procedure doesn t affect rest of system 52

54 ISO/OSI reference model presentation: allow applications to interpret meaning of data, e.g., encryption, compression, machine-specific conventions session: synchronization, checkpointing, recovery of data exchange Internet stack missing these layers! these services, if needed, must be implemented in application needed? application presentation session transport network link physical 53

55 Internet protocol stack application: supporting network applications FTP, SMTP, HTTP transport: process-process data transfer TCP, UDP network: routing of datagrams from source to destination IP, routing protocols link: data transfer between neighboring network elements Ethernet, (WiFi), PPP physical: bits on the wire application transport network link physical 54

56 Internet protocol stack application: supporting network applications FTP, SMTP, HTTP application transport network link HTTP request GET /index.html HTTP/1.1 physical 55

57 Internet protocol stack transport: process-process data transfer TCP, UDP Sender SYN Receiver application transport SYN+ACK ACK+Request Data ACK For example (TCP) network link physical Sender SYN ACK+Req ACK Receiver SYN+ACK Data 56

58 Internet protocol stack network: routing of datagrams from source to destination IP, routing protocols Distination interface cost Receiver (IP= ) Routing Table Where should I send the Packet? to interface 1 or 2 or 3? application transport network link physical Sender 1 Receiver

59 Internet protocol stack link: data transfer between neighboring network elements Ethernet, (WiFi), PPP Example: 1. Wait for data 2. Data received 3. Is the medium free? 4. Yes: send and wait for ACK 5. No :wait a random time 6. Go to step 3 7. ACK received? Go to step 1 application transport network link physical Data Sender ACK 1 Receiver

60 Internet protocol stack physical: bits on the wire Example: application transport network link physical Sender 1 Receiver

61 segment datagram frame message H l H t H n H t H n H t M M M M source application transport network link physical Encapsulation link physical switch H l H n H n H t H t H t M M M M destination application transport network link physical H l H n H n H t H t M M network link physical H n H t M router 60

62 Network security field of network security: how bad guys can attack computer networks how we can defend networks against attacks how to design architectures that are immune to attacks Internet not originally designed with (much) security in mind original vision: a group of mutually trusting users attached to a transparent network Internet protocol designers playing catch-up security considerations in all layers! 61

63 Bad guys: put malware into hosts via Internet malware can get in host from: virus: self-replicating infection by receiving/executing object (e.g., attachment) worm: self-replicating infection by passively receiving object that gets itself executed spyware malware can record keystrokes, web sites visited, upload info to collection site infected host can be enrolled in botnet, used for spam. DDoS attacks 62

64 Bad guys: attack server, network infrastructure Denial of Service (DoS): attackers make resources (server, bandwidth) unavailable to legitimate traffic by overwhelming resource with bogus traffic 1. select target 2. break into hosts around the network 3. send packets to target from compromised hosts target 63

65 Bad guys can sniff packets packet sniffing : broadcast media (shared Ethernet, wireless) promiscuous network interface reads/records all packets (e.g., including passwords!) passing by A C src:b dest:a payload B 64

66 Spoofing Example: Spoofing Sending s with a fake sender address Simple Mail Transport Protocol (SMTP), do not do authentication Generally, it is a simple process which used often in spam s 65

67 Privacy Fridge AC EV Abtastrate 1/Minute 66

68 Load Dis-aggregation Dryer Load AC EV Dishwasher Washing Machine Fridge 67

69 Load Dis-aggregation Dryer AC Fridge EV Dishwasher washing machine Fridge 68

70 What is the problem of smart meter reading? Number of persons in the home Times when home empty Devices and appliances used Patterns of sleep Measures of wealth 69

71 Security in Smart Grid Injecting false data to cause a damage Manipulating smart meter data to gain financial benefits. 70

72 Bibliography Smart Grid: Technology and Applications, 2012, ISBN , Wiley, by Janaka Ekanayake, Kithsiri Liyanage, Jianzhong Wu, Akihiko Yokoyama, Nick Jenkins Smart Grid : Applications, Communications, and Security by Lars T. Berger and Krzysztof Iniewski Computer Networks A Top-Down Approach, James F. Kurose and Keith W. Ross Computer Networks A Top-Down Approach (Slides) 71