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CSCI-370/EENG-480 Computer Networks

CSCI-370/EENG-480 Computer Networks. Khurram Kazi. Examining the Optical Transport Networks Standards and Their Impact on Next Generation Networks. IP, “Next Big Thing”. ATM. PDH. SONET/SDH. Optical Transport Network (OTN). Vision Of Optical Transport Networking.

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CSCI-370/EENG-480 Computer Networks

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  1. CSCI-370/EENG-480 Computer Networks Khurram Kazi

  2. Examining the Optical Transport Networks Standards and Their Impact on Next Generation Networks

  3. IP, “Next Big Thing” ATM PDH SONET/SDH Optical Transport Network (OTN) Vision Of Optical Transport Networking GOAL: To provide a flexible, scalable, and robust Optical Transport Network, catering to an expanding variety of client signals with equally varied service requirements (flexibility, scalability, and survivability coupled with bit-rate and protocol independence). 1/10/100 Gigabit Ethernet

  4. “Idealized” Optical Network • Attributes: • Channels start anywhere, end anywhere (i.e. no per-wavelength engineering rules due to noise accumulation effects, vendor-specific wavelength plans) • Channels are format and bit-rate independent • Wavelength conversion (interchange) to minimize stranded capacity • Access to optical layer for embedded base • Support for multi-vendor environment • Easy upgrade (add bandwidth on demand) But, How to manage this network ?

  5. There are Issues with idealized vision! • Expectation for Transparency of the Optical Layer - Support for legacy and Emerging Formats in the network - PDH, SONET/SDH, ATM, GbE, IP, GFP …. • To Network Optical Channels requires an ability to Manage Optical Channels • Optical layer OAM&P (Operations, Administration, Maintenance & Provisioning) information will be needed to support Optical Networking applications • OAM is supported in form of Optical Layer “overhead”

  6. There are Issues with idealized vision! • Expectation for Transparency of the Optical Layer - Support for legacy and Emerging Formats in the network - PDH, SONET/SDH, ATM, GbE, IP, GFP …. • To Network Optical Channels requires an ability to Manage Optical Channels • Optical layer OAM&P (Operations, Administration, Maintenance & Provisioning) information will be needed to support Optical Networking applications • OAM is supported in form of Optical Layer “overhead”

  7. How Did We Get to This Point:Some SONET/SDH Basics • In SONET/SDH the networking levels are STS/HOVC and VT/LOVC path layers • The Section+Line/RS+MS levels are neither intended nor designed to support networking • Only to support monitoring of, and fault localization within, a repeatered line. • SONET/SDH signals are defined in a period in which most operators were governmental like organizations • One per country • SONET/SDH signals are defined initially under the assumption that the path endpoints are owned by the operator • Services supported by SONET/SDH networks were considered to be PDH services • DS1, E1, E3, DS3, E4

  8. Marketplace Evolved • After some years the customers wanted to own the SONET/SDH path endpoints • To benefit from the more extensive quality of service (i.e. monitoring) capabilities • As an "afterthought", one level of TCM was added to the SONET/SDH path signal specifications • Operator organizations got privatised, and many new operator organizations entered the marketplace • Bandwidth is leased from each other in an extensive way • Two levels of of overhead per path signal is now rather limited

  9. Technology Evolved • WDM technology became available, and is deployed to get around fiber shortage • The initial WDM line systems were offering essentially "virtual fibers" to the SONET/SDH network • Optical fabric technology became available recently, and will be added to the networks to provide flexible interconnect between WDM line systems, SONET/SDH terminals and Data equipment (IP Routers, Ethernet Switches, ATM Switches). • The signals routed around are SONET/SDH and GbE signals, with a strong claim of being fully transparent transported. • These SONET/SDH and GbE section level signals are not designed to support path layer characteristics, as is now required. They (unsolicited) "upgraded" to path level signals, due to the addition of optical fabric equipment to the network. • From day one, the endpoints of these signals can be owned by the customer, leaving the operator without any overhead to verify the performance of its transport.

  10. Technology Evolved • More and more customers own the endpoints of SONET/SDH signals and require transparent transport of all bits in the signal. • This makes it impossible to "steal" some bits in the frame for the operators business for OAMP.

  11. Do we have all Optical Networks? • Network is all not optical • Optical implies, analogue impairments are back in town • Every X hundred/thousand kilometers signals must be regenerated • The network looks more optical than before, while the regenerator spacing increased significantly • Since the mid-80's regenerator spacing has increased from • about 1.5 km (565 Mbit/s coax) • via 40/80/120 km (SONET/SDH) • to 500/1000/4000 km ((ultra) long haul terrestrial WDM) • Optical amplifiers are deployed at intermediate points in these spans, instead of electrical regenerators • Strong forward error correction codes are added to the original SONET/SDH signal in the regenerators to get the long regenerator spacing

  12. Do we have all Optical Networks? • Regenerators in a WDM network will also appear • At the edges of administrative domains • Providing well defined hand-off points to the next operator or customer • Around Optical Fabrics • Compensating for the incurred loss when going through the fabric (connectors, bridge & selector, MEMs) • The SONET/SDH signal is wrapped into this strong FEC signal • Bit rate of the signal is increased

  13. Alternative "OTN" • If one ignores the transparency requirement of some customers for a moment, the minimum processing in a regenerator can be defined to be: • termination of FEC frame and error correction • termination of SONET/SDH Section/RS overhead • termination of SONET/SDH Line/MS overhead • forwarding of STS/AUG bitstream • insertion of new SONET/SDH Line/MS overhead • insertion of new SONET/SDH Section/RS overhead • insertion of new FEC frame and FEC code • If needed, also STS/HOVC tandem connection overhead can be processed (either terminated, or terminated and re-inserted, or inserted). • If single instance is available and not owned by somebody else

  14. Alternative "OTN" • The regenerator circuits around optical fabric equipment may add to the above set of processes: • the TDM muxing process to create higher rate aggregate SONET/SDH signals • or, the inverse process in which a higher rate service signal is "de-aggregated" to be transported via multiple lower rate SONET/SDH signals • and vice versa in the other direction • If SONET/SDH cross connect equipment is extended with multi wavelength interfaces, it would function as electrical fabric equipment.

  15. Alternative "OTN" • The above processing would result in a SONET/SDH network extended with • Additional SONET/SDH "path level repeater" equipment (two LTEs back to back)" • Multi wavelength interfaces (OC-N, STM-N) • Providing virtual fibers • An Optical Section Connection (OS_C) function, • Management of the virtual fiber group signal transport can be implemented by means of the addition of a supervisory signal • like defined in G.709

  16. "BUT..." • But the transparent transport of SONET/SDH signals is one of the key requirements so far • We can not ignore it... • So, the SONET/SDH processing described in the above regenerator circuit is not an acceptable level of processing… • Unless the transparent transport requirement is dropped… • And thus the new applications behind it are dropped... • Wouldn't this cause a status quo then? I.e. • No enhancements in transport networking any longer, • Fiber leasing only, instead of virtual fiber leasing • to other operators and customers building their own networks • ...

  17. OTN Characteristics:" • New transport networking layer (carrier grade solution) • Next step (after SDH/SONET) to support ever growing data driven needs for bandwidth and emergence of new broadband services • Terrabit/second per fiber via DWDM lines (transport level) • Gigabit/second paths at 2.5 Gb/s, 10 Gb/s, 40 Gb/s (networking level) • Service transparency for SDH/SONET, ETHERNET, ATM, IP, MPLS • No change of SDH/SONET! • One exception; interpretation of STM-LOF alarm  + STM-AIS due to OTN fail • Enhanced OAM & networking functionality for all services • Shortest physical layer stack for data services (IP  OTN  Fiber)

  18. OTN Characteristics • Gigabit level bandwidth granularity required to scale and manage multi-Terabit networks • Wavelength level switching maximizes nodal switching capacity, the gating factor for reconfigurable network capacity • Avoids very large numbers of fine granularity pipes that stress network planning, administration, survivability, and management

  19. OTN Specifications: Where are They Being Developed? • ITU Study Groups involved: • SG13 ‘General Network Aspects’: • WP3 • WP4 • SG15 ‘Transport networks, systems and equipment’ • WP3 • WP4 • SG4 “Network Management” • Optical Inter-networking Forum; OIF • Internet Engineering Task Force; IETF • Regional standards - ANSI and ETSI

  20. OTN Architecture • Rec. G.872 “Architecture of optical transport network” (approved in Feb ‘99 and is currently being revised) • It describes the functional architecture of optical transport network using the methodology of ITU-T Rec.G.805. • It also defines : • Definition of generic requirements for management of OTN • A phased approach for interworking to ensure smooth transition

  21. Optical Channel (OCh):A network engineering and administration construct, supplying a portion of an OTN client connection. The OCh creates an “optical path” out of one or more concatenated wavelengths, with associated OAM. OCh OAM OCh OAM OCh OAM OCh OAM Optical Client Optical Client lm ln NE NE NE NE NE OTN Sub-network OTN Sub-network OTN Client Connections, Wavelengths & Optical Channels Wavelength: A particular frequency (l1..ln) within multiplexed optical signal OTN Client Connection:An “end-to-end” Optical Transport Network service between optical clients, which may cross multiple OTN sub-networks, may traverse multiple Optical Channels, and may reside within multiple successive wavelengths

  22. Building a New Transport Networking Tech • What does Optical Networking (really)? • Transport Networking at a new level of granularity: the Optical Channel (OCh) Level • Manage frequency-slots (OCh’s, single or multiple ls) instead of time-slots (e.g., VC-3/4’s) • Ability to Manage Optical Channels • Include Optical layer OAM&P (Operations, Administration, Maintenance & Provisioning) information needed to support Optical Transport Networking applications • OAM&P is supported in form of Optical Layer overheads

  23. Building OTN Tech with O/E/O Objectives • Minimise O/E/O processing in OTN • O/E/O processing at edges of administrative/vendor (sub)domains • Span engineering • O/E/O processing at edges of protected or switched domain • Span engineering (short/long route effects) • Signal Fail & Signal Degrade condition determination • If more than 1 optical transparent subnetwork is included • O/E/O processing at intermediate points • Span engineering (long line sections) • Losses in optical fabrics • O/E & E/O processing around electrical fabric

  24. G.709 - Interfaces for the OTN • G.709 specifies two sets of OTM-n interfaces: • OTM interfaces to be used when interconnecting equipment of two different operators, of an operator and a user, or of two different vendors • OTM interfaces to be used when interconnecting equipment of the same vendor • These interfaces support the: • Performance needs of future optical networks • Development of cost effective optical networks • Ability to interconnect optical network equipment of different vendors and/or operators • Ability to forward the service signal (i.e. ODUk or client) • Furthermore: • G.709 supports fault management and performance monitoring as needed in the current competitive marketplace with many operators and high quality demanding customers • G.709 is the basis of the new "managed wavelength services"

  25. In Depth Coverage of G.709

  26. Client OCh Payload Unit OH OPUk Associated overhead Wrapper OCh Data Unit OH ODUk OCh Transport Unit OH OTUk FEC OH OMSn Optical Channel OCh OPSn OTSn Optical Channel Carrier OCC OCC OCC OPS0 OH Non-associated overhead Optical Multiplex Section OH OpticalTransmission Section OTM Overhead Signal OOS OSC Optical Supervisory Channel OSC Optical Transport Module Optical Physical Section OTN Containment Relationships

  27. STM-N ODU k OCh, OTUk OCh, OTU k OCh, OTU k OMSn OMSn OMSn OPS0 OTSn OTSn OTSn OTSn OTSn OSn OTN Layer Network Trails • Example of OTSn, OMSn, OCh, OTUk, ODUk, OPS0 trails • Transport of STM-N signal via OTM-0, OTM-n and STM-N lines DXC 3R 3R LT R OCADM R LT 3R DXC 3R OTM-0 Client OTM-n STM-N Client OCXC LT Line Terminal w/ optical channel multiplexing OCADM Optical Channel Add/Drop Multiplexer OCXC Optical Channel Cross-Connect 3R O/E/O w/ Reamplification, Reshaping & Retiming and monitoring R Repeater

  28. OTN Client Connection Client Client Carrier B Carrier A Carrier C Interface Interface Interface Interface OCh-S OCh-S OCh-TC OCh-TC OCh-TC OCh-P OTN: Network Management Issues • Integrity of client signal across interfaces • Autonomous management within a domain (at all layers) • Standardized management structure across interfaces

  29. OCh Layer OMS Layer OTS Layer OCh Layer OMS Layer OTS Layer OCh OAM OCh Payload (client signal) FEC Data Client Signal and Wrapper Frame Structure Client Signal STM, ATM, IP GbE Client Signal STM, ATM, IP GbE

  30. SONET/SDH ATM PDH IP GbE GFP 1 16 17 3824 3825 4080 4 rows 4080 columns Digitally Wrapped OCh Frame Structure OCh OAM OCh Payload (client signal) FEC Data • Frame size: 4 rows (bytes) x 4080 columns (bytes) • Frame structure includes OPU, ODU, and OTU. • Frame transmission: from left to right • Overheads used for path, tandem connection (TC) and section management • FEC helps extend the reach length.

  31. Features of Digitally Encapsulated OCh Frames • Digital encapsulation of frames enable “virtual transparency” (service transparency) • Releases the Optical Network from SONET/SDH dependency • Allows for end-to-end Optical Transport Networking solutions • Forward Error Correction for increased distance • Performance Monitoring: ideal for native data services and lease of wavelengths applications • Signaling for optical channel routing and optical layer protection and restoration

  32. Building Blocks of Wrapped Frame:OPU, ODU and OTU Information Structures ADAPTER MUX Wrapper 1 OPU OTU OCh OCC Client ODU OCG-n.m + OMS OH OTS OH OTM-n.m . . . . . . . . . SONET/SDH, IPATM, GbE, . . . OMU-n.m n Client OCC ODU: OCh Data Unit OCC: Optical Channel Carrier (a tributary slot in OTM-n) OPU: Optical channel Payload Unit OMS: Optical Multiplex Section OTM: Optical Transport Module OTS: Optical Transmission OTU: OCh Transport Unit OCG: Optical Carrier Group n: represents number of wavelengths, m : represents bit rate

  33. Optical Channel Payload Unit:OPU Frame Structure Client Signal STM, IP, ATM, GbE Client SignalSTM, IP, ATM, GbE, . . . Column 1 2 3 3810 Row OCh Payload (client signal) 1 OPU OH 2 OPU Payload Area (4 x 3808 bytes) 3 4 • Client signal is mapped into OPU payload area • at fixed rate * • in floating mode (no pointer) • OPU overheads: payload and mapping specific * recommended rate: 2.48832 Gb/s (OPU1), 9.95328 Gb/s (OPU2), 39.81312 Gb/s (OPU3)

  34. Optical Channel Data Unit:ODU Frame Structure OPU (4 x 3810) Client SignalSTM, IP, ATM, GbE, . . . ….. Column 1 2 14 15 3824 Row ODU Payload 1 ODU Overhead Area 2 ODU Payload Area 3 (4 x 3824 bytes) 4 • ODU Frame size: 4 rows x 3824 columns (bytes) • ODU overhead are used for path and TC OAM&P • OPU is mapped within ODU payload in a locked mode • 1st Row of ODU overhead is for Frame alignment & OTU Overhead

  35. Optical Channel Transport Unit:OTU Frame Structure ODU (4 x 3824) Mode Locked Column 3825 4080 1 14 15 3824 Row FA OH OTUk OH OUT FEC RS(255,239) 4 x 256 bytes 1 2 Optical Transport Unit Payload ODU Payload Area 3 (4 x 3824 bytes) 4 • OTU Frame size: 4 rows x 4080 columns (bytes) • Forward Error Correction (FEC): RS(255, 239) code and • 14 bytes of overhead (bytes 1 - 7 are for frame alignment) • ODU is mapped within OTU payload in a locked mode • OTU overheads are used for OCh section management

  36. OPU/ODU/OTU Bit Rates:

  37. 15 16 3824 4080 1 OTUk OH OPUk OH Payload (client Signal) FEC FA MFAS ODUk OH 4 MFAS OH Byte 1 2 3 4 5 6 7 8 : 0000 0000 0000 0001 0000 0010 FAS OH Byte 1 FAS OH Byte 2 FAS OH Byte 3 FAS OH Byte 4 FAS OH Byte 5 FAS OH Byte 6 0000 0011 0000 0100 MFAS sequence 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 1 2 3 4 5 6 7 8 : : OA1 OA1 OA1 OA2 OA2 OA2 1111 1110 1111 1111 0000 0000 0000 0001 : ODU/OTU Frame Alignment 6 7 OA1: 11110110 OA2: 00101000 => 0xF6F6F6 282828 • MultiFrame Alignment Signal (MFAS) • may be used for 2-frame, 4-frame, …. 256-frame MultiFrame structures

  38. OTUk OH Payload (client Signal) FEC FA MFAS ODUk OH RES JC RES JC RES JC PSI NJO PJO OPUk Overheads Used for Client Mapping 15 16 3824 4080 1 4 • PSI: payload Structure Identifier • JC (bits 7 & 8): Justification Control, 2/3 majority vote in justification decision in demapping • NJO: Negative justification Opportunity • PJO: Positive Justification Opportunity Hex Code Payload Type 01 Exp. Mapping 02 Async. STM-N mapping 03 Bit Sync STM-n mapping 04 ATM mapping 05 GFP mapping 10 Bit stream with octet timing mapping 11 Bit stream w/o octet timing mapping ….. FD NULL test signal mapping FE PRBS test signal mapping

  39. PJO; Byte Stuffing OTUk OH Payload (client Signal) slightly slow! FEC FA MFAS ODUk OH JC RES OTUk OH Payload (client Signal) exact match! FEC FA MFAS JC RES Exact rate ODUk OH RES JC RES JC RES JC RES JC PSI NJO PSI NJO PJO RES OTUk OH Payload (client Signal) slightly faster! FEC FA MFAS JC ODUk OH JC RES JC RES JC PSI Once per frame, it is possible to perform +ve or -ve justification Asynchronous and Bit Synchronous Mapping Using additional byte for payload

  40. JC RES RES JC RES JC PSI NJO PJO Mapping of CBR 2.5 Gb/s Signal Into OPU1 Client Signal Client SignalSTM, IP, ATM, GbE, . . . 2.48832 Gb/s  20 ppm 15 16 17 3824 OTUk OH Payload (client Signal) FEC FA MFAS ODUk OH OPU1 • Groups of 8 successive bits (not necessarily being a byte) of CBR2G5 signal are mapped into Payload of the OPU1 • Once per OPU1 frame, it is possible to perform either a positive or a negative justification action

  41. JC RES RES JC RES JC PSI NJO PJO Mapping of CBR 10 Gb/s Signal into OPU2 Client Signal Client SignalSTM, IP, ATM, GbE, . . . 9.95328 Gb/s  20 ppm 15 16 17 3824 OTUk OH FEC FA MFAS 16FS ODUk OH Payload Payload 1905 1920 OPU2 • Groups of 8 successive bits (not necessarily being a byte) of the 10 Gb/s signal are mapped into Payload of the OPU2 • 64 Fixed Stuff (FS) bytes are added in columns 1905 to 1920 • Once per OPU2 frame, it is possible to perform either a positive or a negative justification action

  42. Mapping of CBR40 Gb/s Signal into OPU3 Client Signal Client SignalSTM, IP, ATM, GbE, . . . 39.81312 Gb/s  20 ppm 3824 15 16 17 JC RES 16FS OTUk OH FEC FA MFAS 16FS ODUk OH RES JC Payload Payload Payload RES JC PSI NJO PJO OPU3 1265 1280 2544 2560 • Groups of 8 successive bits (not necessarily being a byte) of the 40 Gb/s signal are mapped into Payload of the OPU3 • 128 Fixed Stuff (FS) bytes are added in columns 1265 to 1280 & 2545 to 2560 • Once per OPU3 frame, it is possible to perform either a positive or a negative justification action

  43. Mapping of ATM Cells into OPUk ATM Cells 15 16 17 3824 … … OTUk OH FEC FA MFAS ODUk OH …………………………... OPUk OH ….. OPUk • A constant bit rate ATM cell stream with a capacity that is identical to OPUk payload area is created by multiplexing ATM cells from a set of ATM VP signals • Rate adaptation is performed as a part of this cell stream creation process by either idle cells or by discarding cells • ATM Cell boundaries are aligned with OPUk payload byte boundaries • HEC framing is used on the recovering of the ATM cells

  44. …...……………………… … .…... Mapping of IP or Ethernet Into OPUk using GFP Variable Length GFP Frames 15 16 17 3824 OTUk OH FA MFAS FEC ODUk OH OPUk OH ….. OPUk GFP Idle • A new protocol is being defined: Generic Framing Procedure (GFP) • Encapsulation for packet based client signals (e.g, IP or Ethernet) • no need for SDH or 10 G Ethernet to encapsulate IP • Mapping of GFP frames is performed by aligning the byte structure of every GFP frame with the byte structure of the OPUk payload. • A GFP frame consists of a GFP header and a GFP payload area; frame size varies from 4 to 65535 bytes

  45. 00 PLI 00 PLI cHEC cHEC cHEC cHEC Payload Area Idle Frame Frame Multiplexing: On a frame-by-frame basis. When no frames are waiting, idle frames are inserted. Frame Delineation Algorithm: Based on detection of correct cHEC. PLI is used to find the start of the next frame Up to 65535 bytes FCS (optional) GFP Frame PLI: PDU Length Indicator cHEC: Core - Header Error Control FSC: Frame Check Sequence Generic Framing Procedure

  46. MS MS MANAGEMENT PLANE CC Connection Controller CC CC CONTROL PLANE Request Agent CC UNI CC CC RA RA CC RA E-NNI I-NNI OXC OXC OXC OXC TRANSPORT PLANE OXC OXC OXC OXC ASTN/ASON Architecture View in slide show mode Key concepts: Logical separation of transport and control, 3 types of logical interfaces

  47. Distributed Control Plane Protocols • Key Elements • MPLS-based signaling protocols for distributed connection management • RSVP-TE based for UNI, CR-LDP based for I/E-NNI • Routing protocols for topology and resource update • OSPF-TE for intra-domain, O-BGP for inter-domain • Protocol Interaction Examples • Switched Connections • Request Agent (RA) initiates connection setup via UNI (RSVP-TE based) signaling • Routing takes place via OSPF-TE and O-BGP • Connection Controllers (CC) communicate via NNI (CR-LDP based) signaling • Soft Permanent Connections • Management Plane initiates connection setup • Routing takes place via OSPF and BGP • CC communicate via NNI (CR-LDP based) signaling

  48. MS MS Management System Initiates Connection Setup Routing functions (OSPF-TE + O-BGP) find path Routing functions (OSPF-TE + O-BGP) find path OSPF-TE OSPF-TE OSPF-TE OSPF-TE O-BGP O-BGP CC CC CR-LDP CR-LDP RSVP-TE CC CC UNI CC CC RA RA CC End-user notified RA E-NNI I-NNI RSVP-TE NNI Signaling for cross-connect setup NNI Signaling for cross-connect setup Connection Controllers signal to complete cross connects Connection Controllers signal to complete cross connects User Initiates Connection Setup OXC OXC OXC OXC OXC OXC OXC OXC End-to-end Connection Established End-to-end Connection Established An Animation is worth a million words... Switched Connections Soft Permanent Connections View in slide show mode

  49. End-End Intelligent Transport Networking Solution • Multi-operator interoperability provided via open UNI and E-NNI interfaces. • Will enable the service provider to accept requests for bandwidth on demand from its customers connected to the metro access and/or metro core, connecting with transport backbone network providers to make true end-to-end bandwidth on demand a realityall the way to the access node.

  50. Local Routing Table Local Routing Table Local Routing Table Local Routing Table Local Routing Table NN Distributed Routing Control • Nodes • Keep Local Routing Tables • Exchange Routing Information Via Routing Protocols • Keep Network Capacity Inventory • Perform Topology Discovery • Perform Routing Algorithms • Restoration Schemes • Use Embedded Network Intelligence to Offer Mesh Based Restoration NN: Network Navigator

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