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Outline

Outline. A brief Historical aside Review of Transmission (Transport) Technologies, Architectures and Evolution Transporting Broadband across Transmission Networks designed for Narrowband Current Issues: Broadband IP Transport Analysis Ongoing Investigations in IP/OTN Networks.

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Outline

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  1. Outline • A brief Historical aside • Review of Transmission (Transport) Technologies, Architectures and Evolution • Transporting Broadband across Transmission Networks designed for Narrowband • Current Issues: • Broadband IP Transport Analysis • Ongoing Investigations in IP/OTN Networks

  2. A Brief Historical Aside

  3. Pre 1984 AT&T BOCs LD Bell-Labs BCS WE ME RBOCs circa 1984 US West Ameritech SouthWest Bell Bell South Nynex Bell-Atlantic Pac Bell Bellcore AT&T 1984 - 1997 LD Bell-Labs BCS WE ME AT&T circa 1997 Lucent circa 1997 LD AT&T Labs Bell-Labs BCS WE ME Qwest Telcordia Lucent AT&T Avaya Agere SBC Tellium Verizon Bell South The Bell System Legacy Today

  4. Review of Transmission(Transport) Technologies,Architectures and Evolution

  5. Opening Trivia Question • What is the difference between a DS3 (or DS1) and a T3 (or T1)?

  6. Asynchronous Data Rates • Digital Signal Level 0 DS0 64 Kb/s • internal to equipment • Digital Signal Level 1 DS1 1.544 Mb/s • intra office only (600 ft limit) • Digital Signal Level 3 DS3 45 Mb/s • intra office only (600 ft limit) • T1 Electrical (Copper) Version of DS1 1.544 Mb/s • repeatered version of DS1 sent out of Central Office • T3 Electrical (Copper) Version of DS3 45 Mb/s • repeatered version of DS3 sent out of Central Office

  7. Asynchronous Digital Hierarchy DS0 (a digitized analog POTS circuit @ 64 Kbits/s) DS3 DS1 DS0 24 DS0s = 1 DS1 28 DS1s = 1 DS3 Asynchronous Optical Line Signal N x DS3s Asynchronous Lightwave Systems typically transport traffic in multiples of DS3s i.e.... 1, 3, 12, 24, 36, 72 DS3s

  8. Asynchronous NetworkingManual DS1 Grooming/Add/Drop D S X 1 D S X 1 D S X 3 D S X 3 LW LW M13 M13 DS3 DS3 DS1 • Manually Hardwired Central Office • No Automation of Operations • Labor Intensive • High Operations Cost • Longer Time To Service

  9. Some Review Questions • What does the acronym SONET mean? • What differentiates SONET from Asynchronous technology? • What does the acronym SDH mean?

  10. The Original Goals of SONET/SDH Standardization • Vendor Independence & Interoperability • Elimination of All Manual Operations Activities • Reduction of Cost of Operations • Protection from Cable Cuts and Node Failures • Faster, More Reliable, Less Expensive Service to the Customer

  11. SONET RatesDS3s are STS-1 Mapped DS0 (a digitized analog POTS circuit @ 64 Kbits/s) STS-1 51.84 Mbits/s DS1 DS0 DS3 24 DS0s = 1 DS1 (= 1 VT1.5) 28 DS1s = 1 DS3 = 1 STS-1 SONET Optical Line Signal OC-N = N x STS-1s N is the number of STS-1s (or DS3s) transported

  12. SONET and SDH OC level STM level Line rate (MB/s) OC-1 - 51.84 OC-3 STM-1 155.52 OC-12 STM-4 622.08 OC-48 STM-16 2488.32 OC-192 STM-64 9953.28

  13. SONET Layering for Cost Effective Operations PTE PTE STE STE PTE PTE LTE LTE PTE PTE DS-3 DS-3 DS-3 DS-3 DS-3 DS-3 OC-3 TM OC-3 TM SONET Section SONET Line SONET Path PTE = Path Terminating Element LTE = Line Terminating Element STE = Section Terminating Element TM = Terminal Multiplexor DS = Digital Signal

  14. SONET Point-to-Point Network Repeater Repeater TM TM Section Line Path Section Overhead STS-1 Frame Format STS-1 Synchronous Payload Envelope STS-1 SPE Path Overhead Line Overhead

  15. SONET Ring Network Architectures

  16. Unidirectional Path Switched Ring A-B B-A Bridge Failure-free State Path Selection W B fiber 1 Bridge P A-B C A B-A Path Selection fiber 2 D

  17. Bidirectional Line Switched Ring C D Protection Working 2-Fiber BLSR B AÔC AÔC C ÔA A C ÔA

  18. Some Review Questions • Which SONET Ring Network is simpler? • Which SONET Ring Network is inefficient for distributed demand sets?

  19. Typical Deployment of UPSR and BLSR in RBOC Network Regional Ring (BLSR) BB DACs Intra-Regional Ring (BLSR) Intra-Regional Ring (BLSR) WB DACs Access Rings (UPSR) WB DACS = Wideband DACS - DS1 Grooming BB DACS = Broadband DACS - DS3/STS-1 Grooming Optical Cross Connect = OXC = STS-48 Grooming DACS=DCS=DXC

  20. Emergence of DWDM • Some Review Questions • What does the acronym DWDM mean? • What was the fundamental technology that enabled the DWDM network deployments?

  21. First Driver for DWDMLong Distance Networks WDM NE BLSR Fiber Pairs BLSR Fiber Pairs WDM NE • Limited Rights of Way • Multiple BLSR Rings Homing to a few Rights of Way • Fiber Exhaustion

  22. 40km 40km 40km 40km 40km 40km 40km 40km 40km TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM TERM 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR 1310 RPTR TERM Conventional Optical Transport - 20 Gb/s OC-48 OC-48 OC-48 OC-48 OC-48 120 km OC-48 120 km 120 km OC-48 OC-48 OLS TERM OLS RPTR OLS TERM OLS RPTR OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 Fiber Amplifier Based Optical Transport - 20 Gb/s Key Development for DWDM Optical Fiber Amplifier Increased Fiber Network Capacity

  23. Transporting Broadbandacross Transmission Networksdesigned for Narrowband

  24. Core Router Core Router RAS RAS Core Router RAS Access Router RAS RAS Access Router Core Router RAS ATM Switch ATM Switch RAS RAS RAS Core Router ATM Switch ATM Switch RAS RAS Access Router RAS Core Router RAS Access Router RAS RAS RAS Access Router ATM Access ATM Access ATM Access ATM Access Data SP Public/Private Internet Peering EtherSwitch EtherSwitch ATM Access ATM Access Backbone SONET/WDM T1/T3 IP Leased-Line Connections RAS Farms ATM Switch T1/T3 FR and ATM IP Leased-Line Connections T1/T3/OC3 FRS and CRS

  25. High Capacity Path Networking IP router • Existing SONET/SDH networks are a BOTTLENECK for Broadband Transport • Most Access Rings are OC-3 and OC-12 UPSRs while most Backbone Rings are OC-48. Transport of rates higher than OC-48 using the existing SONET/SDH network will require significant and costly changes. Clearly upgrading the SONET/SDH network everytime broadband data interfaces are upgraded based increased IP traffic is not an appropriate solution. IP router IP router STS-12c/48c/... STS-3c Existing SDH-SONET Network

  26. IP/SONET/WDM Network Architecture SONET NMS SONET XC SONET SONET ADM/LT ADM/LT WDM WDM LT LT OC-3/12 [STS-3c/12c] OC-3/12 [STS-3c/12c/48c] OC-48 EMS EMS Access OC-12/48 . . Routers/ Core IP Node . Core IP Node SONET Transport Network . Enterprise . Servers . OTN NMS OC-3/12/48 [STS-3c/12c/48c] OC-3/12/48 [STS-3c/12c/48c] l1, l2, ... Pt-to-Pt WDM Transport Network LT = Line Terminal EMS = Element Management System NMS = Network Management System IP = Internet Protocol OTN = Optical Transport Network ADM = Add Drop Multiplexor WDM = Wavelength Division Multiplexing

  27. Optical Network Evolution mirrorsSONET Network Evolution l1 l1 l2 l2 lN lN Point-to-Point WDM Line System Multipoint NetworkWDM Add/Drop WDMADM WDMADM li lk Optical Cross-ConnectWDM Networking OXC

  28. IP/OTN Architecture EMS . Core Data Node . . mc: multi-channel interface (e.g., multi-channel OC-12/OC-48) mc OTN NMS OXC EMS EMS OXC OXC mc . . Access Routers Core Data Node Core Data Node . mc Optical Transport Network . Enterprise Servers mc . . IP = Internet Protocol OTN = Optical Transport Network OXC = Optical Cross Connect WDM = Wavelength Division Multiplexing EMS = Element Management System NMS = Network Management System

  29. Broadband IP Transport AnalysisCredits to Debanjan Saha and Subir Biswas

  30. Architectural Alternatives • IP-over-DWDM: IP routers connected directly over DWDM transport systems. • IP-over-OTN: IP routers interconnected over a reconfigurable optical transport network (OTN) consisting of optical cross-connects (OXCs) connected via DWDM.

  31. Architectural Alternatives

  32. Quadruple Redundant Configuration of IP Routers at PoPs • Currently deployed by carriers to increase router reliability and perform load balancing. • Upper two routers are service routers adding/dropping traffic from the network side and passing through transit traffic. • Lower two routers are drop routers connected to client devices. • Two connections from the network port at the ingress upper (service) router to two drop ports, one in each of the lower (drop) routers. Client device sends 50% of the traffic on one of these drop interfaces and 50% on the other (it is attached to both of the drop routers). • Not required for OXCs.

  33. IP-over-DWDM: Pros and Cons Pros Cons • IP-routers with OC-48c/OC-192c interfaces and aggregate throughput reaching 100s of Gbps. • Transport functions like switching, configuration, and restoration are moved to the IP layer and accomplished by protocols like MPLS, thus providing a unifying framework. • IP routers control end-to-end path selection using traffic engineering extended routing and signaling IP protocols. • Supports the peer-to-peer model where IP routers interact as peers to exchange routing information. • Can router technology scale to port counts consistent with multi-terabit capacities without compromising performance, reliability, restoration speed, and software stability ? A big question mark.

  34. IP-over-OTN: Pros and Cons Pros Cons • Reconfigurable optical backbone provides a flexible transport infrastructure • Core OXC network can be shared with other service networks such as ATM, Frame Relay, and SONET/SDH private line services. • Allows interconnection of IP routers in an arbitrary (logical) mesh topology. • Not possible in architecture A since a typical CO/PoP has two, in some cases three, and in rare occasions four conduits connecting it to neighboring PoPs. • Adding a reconfigurable optical backbone introduces an additional layer between the IP and DWDM layers and associated overhead. • Traffic engineering occurs independently in two domains -- (i) the IP router network with its logical adjacencies spanning the OXC backbone, and (ii) the optical network which provisions physical lightpaths between edge IP routers. Could lead to inefficiency in traffic routing from a global perspective.

  35. Why Glass Through is not an Alternative? • Removes the flexibility of dynamic switching between incoming and outgoing fibers at a PoP that comes with using a router or an OXC. • Prevents organic growth of the network. Dynamic switching allows local capacity to be used to meet traffic demands between arbitrary PoPs. With glass through, bandwidth is not available at the link level but only at the segment level whose two end PoPs terminate glass through fiber paths. • Does not allow intelligent packet processing or performance monitoring of transit traffic at a PoP.

  36. Network Deployment Cost Analysis • Analysis of the two architectures from an economic standpoint. • Contrary to common wisdom, a reconfigurable optical layer can lead to substantial reduction in capital expenditure for networks of even moderate size. • Critical observation: Amount of transit traffic at a PoP is much higher than the amount of add-drop traffic. • Hence, a reconfigurable optical layer that uses OXC ports (instead of router ports) to route transit traffic will drive total network cost down so long as an OXC interface is marginally cheaper than a router interface. • Savings increases rapidly with the number of nodes in the network and traffic demand between nodes.

  37. Assumptions: Network Model • Transit traffic uses router ports in IP-over-WDM and OXC ports (only) in IP-over-OTN. • Quadruple redundant configuration of IP routers at a PoP to improve reliability and perform load-balancing. • Shortest-hop routing of lightpaths. • IP routers have upto 64 ports and OXCs have upto 512 ports (in keeping with port counts of currently shipped products). • With or without traffic restoration (diverse backup paths). • Typical CO/PoP has two, in some cases three, and in rare occasions four conduits connecting it to neighboring PoPs. Average degree = 2.5. • Routing uniform traffic (equal traffic demand between every pair of PoPs) on networks of increasing size. • Two traffic demand scenarios: uniform demand of 2.5 Gbps (OC-48) and 5 Gbps between every pair of PoPs. • Multiple routers/OXCs can be placed at each PoP to meet port requirements for routing traffic. • Core OXC network provides full grooming of OC-192 ports into OC-48 tributaries.

  38. Assumptions:Pricing • IP routers and OXCs have fixed costs and per-port costs for OC-48 and OC-192 interfaces. • Ballpark list prices for currently shipped products. • IP router: • fixed cost of $200K and • per-port cost of $100K and $250K for OC-48 and OC-192 interfaces respectively. • OXC: • fixed cost of $1M and • per-post cost of $25K and $100K for OC-48 and OC-192 interfaces respectively.

  39. 2.5 Gbps of Traffic between PoP Pairs Without Restoration Cross-over point at network size of about 18 nodes.

  40. 5 Gbps of Traffic between PoP Pairs Without Restoration Cross-over point at network size of about 15 nodes.

  41. % of Transit Traffic in the Network Without Restoration 75-85% of the total traffic is transit traffic for a network size of 50 PoPs.

  42. 2.5 Gbps of Traffic between PoP Pairs With Restoration Cross-over point at network size of less than 8 nodes.

  43. 5 Gbps of Traffic between PoP Pairs With Restoration Cross-over point at network size of less than 4 nodes.

  44. % of Transit Traffic in the Network With Restoration 80-95% of the total traffic is transit traffic for a network size of 50 PoPs.

  45. Results and Discussion • Without restoration: Network cost breakeven point occurs at network sizes of 18 and 15 nodes for 2.5 Gbps and 5 Gbps of uniform traffic respectively. • With restoration: IP-over-OTN has lower cost beyond a network size of 4-6 nodes. • IP-over-OTN becomes increasingly attractive as amount of traffic and network size grows. Savings is much more when we consider traffic restoration. • Amount of transit traffic in the network grows rapidly as network size increases. For example, without restoration, 75-85% of the total traffic is transit traffic for a network size of 50 PoPs, and with restoration, it is 80-95%. • Carrying transit traffic over OXC ports (instead of router ports) drives network cost down so long as an OXC interface is marginally cheaper than a router interface.

  46. Results and Discussion contd. ... • With traffic restoration, the economies of scale reaped from IP-over-OTN is further increased. • Each primary path in a network has a diversely routed backup path. • Transit port usage will increase substantially when we consider backup paths while the number of terminating ports remains unchanged.

  47. Case for Restoration at Optical Layer • Restoration in IP-over-WDM: Provided at the IP layer where backup paths consume router ports (like primary paths). • Restoration in IP-over-OTN: Can be provided at the optical or IP layers. In the former case, router ports are not consumed on intermediate PoPs. • Study shows substantial increase in savings for IP-over-OTN when restoration is taken into consideration. • IP-over-OTN has lower cost beyond a network size of 4-6 nodes. • As much as 80-95% of the total traffic is transit traffic for a network size of 50 PoPs.

  48. Ongoing Investigations in IP/OTN Networks • Can IP layer provide reliable service? • How much Restoration is really required for services? • Interaction of Routing Protocols with Optical Layer Restoration • Optimal Routing with Topology of IP and Optical Layers • And many more...

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