Optical Networks Jean-Michel Dricot BEST Course

Transcription

1 Optical Networks Jean-Michel Dricot BEST Course

2 Introduction 2/50

3 Tier-1 Core Network: the Internet Overall Internet traffic 500 TBytes/second. Capacity doubles every two years One second of Internet in 2008 = 1 year usage in /50

4 Tier-1 Core Network: the Internet Internet routes largely matches that of pre-existing trade and communicating networks. 4/50

5 Tier-2 Core Network: Europe The pan-european data network 5/50

6 Tier-2 Core Network: Level3 6/50

7 Tier-3 Core Network: Belgacom Core Network 7/50

8 Tier-3 Core Network: Deutsche Telekom 8/50

9 Private Network: BELNET 9/50

10 Data Tsunami 10/50

11 SONET / SDH 11/50

12 SONET / SDH Networks Synchronous digital hierarchy (SDH Europe) and Synchronous Optical NETwork (SONET US) introduced in the 1980s, paving the way for a worldwide, unified network structure. ideal for network providers: efficient, economical network management system flexible: can accommodate to Ethernet, IP, voice, data etc. Carrier grade network high availability : five nines : % of the time fault recovery through redundancy in less than 50 ms Based on a Time Division Multiplex (TDM) 12/50

13 Network Core: Circuit Switching End-end resources reservation link bandwidth, switch capacity dedicated resources: no sharing guaranteed performance Implementations real circuits leased line, optical fiber at the sending side of the transmission link and suffer a delay. The Internet best effort to deliver packets in a timely manner, but it does not make any gua Multiplexing in Circuit-Switched Networks Acircuit in a link is implemented with either frequency-division mul (FDM) or time-division multiplexing (TDM). With FDM, the freque trum of a link is divided up among the connections established across virtual circuits setup and teardown on demand Figure 1.13 A simple circuit-switched network consisting of four switches and four links 13/50

14 of bandwidth 4 khz. For TDM, the time domain is segmented into frames, with four time slots in each frame; each circuit is assigned the same dedicated slot in the revolving TDM frames. For TDM, the transmission rate of a circuit is equal to the frame rate multiplied by the number of bits in a slot. For example, if the link transmits 8,000 frames per second and each slot consists of 8 bits, then the transmission rate of a circuit is 64 kbps. NetworkProponents resources of packet (e.g., switching bandwidth) have always divided argued into that circuit temporal switching timeslots is wasteful because the dedicated circuits are idle during silent periods. For example, timeslots allocated to source-destination pair Network Core: TDMA resource timeslots FDM idle if not used by owning call (no sharing) 4KHz Ressources reservation Link managed by the network, dynamically or not Frequency 4KHz depends on the expected QoS (quality of service) TDM Key: Slot Frame Time 2 All slots labeled 2 are dedicated to a specific sender-receiver pair. Figure 1.14 With FDM, each circuit continuously gets a fraction of the bandwidth. With TDM, each circuit gets all of the bandwidth 14/50

15 The components of a SDH network 15/50

16 The components of a SDH network The mixture of different applications is typical of data transported by SDH Topology: ring or mesh structure Current SDH networks consist of four NE types. Regenerators regenerate the clock and amplitude of distorted signals Terminal multiplexers combine multiple streams Add/drop multiplexers insertion and extraction of high speed streams Digital cross-connects rearrangement and interconnection of STMs 16/50

17 The components of a SDH network 17/50

18 Layer model Subdivided into various layers directly related to the SONET topology. The lowest layer is the very physical layer transmission medium: glass fiber The regenerator section is the path between regenerators. used for signalling, link failure detection, congestion, etc. The line represents a connection point in the network PoP Point of Presence The path section is the end-to-end route between the circuit source and the circuit destination 18/50

19 Layer model 19/50

20 The STM-1 frame format Data container defined by TU-T recommendation G Mbps frame first level of the synchronous digital hierarchy It comprises a byte matrix of 9 rows and 270 columns Transmission is row by row (upper-left corner to lower-right corner) frame repetition rate is 125 µs Each byte in the payload represents a 64 kbps channel (telephony legacy) 20/50

21 The STM-1 frame format 21/50

22 The STM-1 frame format : SOH First nine bytes in each of the nine rows ITU-G.707 makes a distinction between the regenerator section overhead (RSOH) and the multiplexer section overhead (MSOH) bytes have a different purposes for regenerator / section management Used for congestion avoidance, clock drifting compensation, line loss detection, etc. Active network Interleaving of signalling and data 22/50

23 The STM-1 frame format : SOH 23/50

24 The STM-1 frame format : AU Pointers Used to localize individual virtual containers in the payload of the synchronous transport module. Each container represents fixed source-destination path aggregation of sub-containers Figure 11. Schematic diagram of C-3 mapping MSOH AU pointer RSOH J1 B3 C2 G1 F2 H4 F3 K3 N1 H1 H1 H1 H2 H2 H2 H3 H3 H3 Fixed justification J1 B3 J1 C2 B3 J1 G1 C2 B3 F2 G1 C2 H4 F2 G1 F3 H4 F2 K3 F3 H4 N1 K3 F3 N1 K3 N1 C-3 34 Mbps 84 24/50

25 Add / Drop Operations Allows extraction from and insertion into the high-speed bit streams in SDH. Enables ring structure setup, which is crucial for high reliability. 25/50

26 Digital Cross-Connect Switching procedures DXC m/n: m hierachical order of the input port n hierarchical order of the traffic component handled by the DXC Examples DXC 4/4: Switch VC4 payload, traffic routing in core network, restoration DXC4/1: routing of customer traffic, consolidation, local service restoration Versatile manipulation of the STM 26/50

27 Transmission at higher hierarchy levels The STM-N frame structures are basically N times the STM-1 structure. The following hierarchy levels are defined in SDH H signal and ate hierarchy SONET Signal Bit Rates (Mbps) Equivalent SDH Signal STS-1 OC STM-0 STS-3 OC STM-1 STS-12 OC STM-4 STS-48* OC STM-16 STS-192* OC STM-64 STS-768 OC STM-256 The hierarchy levels shown in Table 2 closely match the plesiosynchronous bit rates commonly used in these countries. Of all the levels listed, only STS-1, OC-3, OC-12, 27/50

28 Transmission at higher hierarchy levels STM-256 STM-64 STM-16 STM-4 STM-1 x1 x1 x1 x1 x1 AUG256 x4 AUG64 x4 AUG16 x4 AUG16 x4 AUG16 x1 x1 x1 x1 x1 AU-4-256c AU-4-64c AU-4-16c AU-4-4c AU-4 VC-4-256c VC-4-64c VC-4-16c VC-4-4c VC-4 x3 TUG-3 x1 TUG-3 VC-3 C-4-256c C-4-64c C-4-16c C-4-4-c C-4 ATM/IP: 38,338,560 kbps ATM/IP: 9,584,640 kbps ATM/IP: 2,396,160 kbps ATM/IP: 599,040 kbps ATM: 149,760 kbps E4: 139,264 kbps STM-0 x3 x1 Pointer processing AU-3 VC-3 x1 x7 x7 TUG-2 x1 x3 TU-2 TU-12 VC-2 VC-12 C-3 C-2 C-12 ATM: 48,384 kbps DS3: 44,736 kbps E3: 34,368 kbps ATM: 6,874 kbps DS2: 6,312 kbps ATM: 2,144 kbps E1: 2,048 kbps Figure 9. Mapping in SDH x4 TU-11 VC-11 C-11 ATM: 1,600 kbps DS1: 1,544 kbps 28/50

29 and Japan, which use a 1544 kbps primary rate (formed by combining 24 channels), Transmission see Figure at1. higher hierarchy levels mmary of plesiochronous transmission rates 5. Japanese standard kbps North American standard European standard kbps x 4 x kbps x kbps x 6 x kbps x kbps kbps kbps 2. order x kbps x kbps x 4 1. primary rate x kbps x kbps x 4 x 24 x kbps 29/50

30 Error and Alarm Monitoring Several alarm and error messages are integral to SDH detect defects and anomalies. coupled with network sections and the corresponding overhead information. 30/50

31 Error and Alarm Monitoring 31/50

32 Automatic protection switching (APS) Two types of protection architecture in Automatic protection switching (APS) linear protection mechanism for point-to-point connections ring protection mechanism can take on many different forms Both mechanisms use spare circuits to provide the back-up path. Switching is controlled by the overhead bytes. The switchover is triggered by a defect such as LOS. An acknowledgment in the backward channel initiates switching at the far end. Objectives protection very short term: ms. Switching to spare elements restoration in seconds of minutes by rerouting the data paths 32/50

33 APS Linear protection A 1:1 architecture includes 100 % redundancy spare line for each working line Economic considerations have led to the use of 1:N architecture, particularly for long-distance paths. The 1+1 and 1:N protection mechanisms are standardized in ITU-T recommendation G /50

34 APS Ring protection Cost-effective method for linking several network elements by ITU-T recommendation G.841 Unidirectional rings 34/50

35 APS Ring protection Bidirectional line-switched ring Bidirectional rings with four fibers provide even greater protection because each fiber pair transports both working and protection channels or 1:1 protection, which is 100 percent redundant. 35/50

36 Telecommunications management network Operation, administration, maintenance, and provisioning (OAM&P), monitoring network performance and checking for error messages Performed using the simple network management protocol (SNMP). 36/50

37 WDM / Ethernet GEPON 37/50

38 WDM Multiple wavelengths inside the same optical fiber each colored clients gets a specific λ one λ per source-destination pair entirely in the optical domain (faster, no optical-electrical-optical conversion) Capacity ranging from 10 Gbps to 100 Gbps (DWDM 192λ) Spectral dispersion implies regular regeneration 10 GE 1 GE STM-16 PoP a Multiplexeur Multiplexer Injection de plusieurs Injection longueurs of d onde multiple dans wavelengths une même fibre in one fiber Amplificateurs Line de ligne Amplifiers shelter DCM Demultiplexer Démultiplexeur PoP b 10 GE 1 GE STM-16 Transpondeur Adapter Booster (transceiver): sends and receives at Émetteur a single wavelength et récepteur laser Fixé à une longueur d onde précise, ou réglable Compensation Module de of Préamplificateur spectral Compensation dispertion Pre-amp Transpondeur Adapter de Dispersion 38/50

39 WDM Flavors DWDM longer distances (e.g., 100km, Gbps), very expensive applications: Tier-1 Internet backbone, λ, 40 Gbps CWDM short distances (e.g., 60 km for 2.5 Gbps), easier to implement, inexpensive applications: fiber to the home (FTTH), Ethernet 1-10 Gbit/s limitation: 18λ maximum 39/50

40 WDM Regeneration WDM signals are sensitive to attenuation (photons are absorbed) in the finer: 0.20 db/km chromatic dispersion Every km these issues must be compensated re-amplify amplification of the signal strength re-shape compensation of the chromatic dispersion re-time conversion photonic-electrical-photonic domains complete regeneration re-amplify amplification of the signal strength In some (expensive) cases, DWDM can reach 100km without regen. 40/50

41 s retenues 1/4 WDM Regeneration 13 41/50

42 Optical Add and Drop Multiplexer OADM Used for the routing of different channels of light (lightpaths) into or out of a single mode fiber (SMF). Works entirely in the photonic domain. modifications WDM Signals Signaux WDM Multiple dans wavelengths FON WDM Signaux Signals WDM Multiple dans FON wavelengths c WDM Transpondeur Transponder WDM Extracts a given λ Monomode / Interface B&W Multimode Fiber 42/50

43 GEPON Carrier Ethernet Architectures 43/50

44 GEPON Gigabit Passive Optical Network Facilitates another (higher bandwidth) broadband access technology Complementary with VDSL deployment: DSL limits to 100m, FO to 10km Capacity: downstream Gbps, upstream Gbps Passive because network only consists of passive light transmission components (fiber links, splitters and couplers) great cost savings for the provider (more reliable and less costly to operate/troubleshoot) PONs use a Point-to-Multi-Point (P2MP) topology 44/50

45 GEPON Disadvantages of other technologies given the example of ATM Waste of bandwidth: corrupted cell invalidates entire datagram Huge overhead Ethernet frame: 1500 bytes payload + 18 bytes header/checksum ATM cells: 48 bytes payload + 5 bytes header Large datastreams have much more overhead when using ATM cells Costs: ATM is about 8 times more expensive than Ethernet. Advantages of Ethernet in PONs PON downstream traffic is broadcasted (IPTV) Ethernet already uses CSMA/CD to operate in shared media Full optical-domain 45/50

46 GEPON Architecture 46/50

47 GEPON Terminology ODN Optical Distribution Network transmission from the OLT towards the users and vice versa. It utilizes passive optical components OLT Optical Line Termination service provider endpoint of a PON ONT Optical Network Termination device that terminates the PON and presents native service interfaces to the user. Located on the customer s premises. ONU Optical Network Unit is the PON-side half of the ONT, terminating the PON, and may present one or more converged interfaces, such as xdsl or Ethernet, toward the user. 47/50

48 Convergence 48/50

49 Conclusion 49/50

50 Conclusion Convergence towards all-ip and all-ethernet networks with carrier-grade capabilities. Optical networking becomes less complex, more transparent and relies on upper layers. SDH, WDM, Ethernet : principales alternatives mises en œuvre pour le transport dans les réseaux publics "Clients" du transport PSTN/ISDN/Mobile (CS) (voix, data, circuits) +LL Data(VPN), Internet(,WEB, ), VoIP,, TV IP E1 CSEoE Content servers FC, ESCON, FICON TDM ( n x E1 s) PPP Ethernet ATM PoS GbE EoS EoW xdsl PDH GFP SDH WDM OTH GFP Support : Cu Supports : Coax,Hz Supports : F.O., Hz Public networks (H-504) Support : F.O. Bases Transmission ("version" light") Ed /09 Page 49/50 50/50