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Lecture Note on Dense Wave Division Multiplexing (DWDM) Typical Deployment of UPSR and BLSR 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 WDM NE Fiber Pairs WDM NE Dense Wave Division Multiplexing (DWDM) in Long Distance Networks • Limited Rights of Way • Multiple Fiber Rings Homing to a Few Rights of Way • Fiber Exhaustion Fiber Pairs DWDM versus SONET 40km 40km 40km 40km 40km 40km 40km 40km 40km 1310 1310 1310 1310 1310 1310 1310 1310 TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR TERM 1310 1310 1310 1310 1310 1310 1310 1310 TERM TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR 1310 1310 1310 1310 1310 1310 1310 1310 TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR TERM 1310 1310 1310 1310 1310 1310 1310 1310 TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR TERM 1310 1310 1310 1310 1310 1310 1310 1310 TERM TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR 1310 1310 1310 1310 1310 1310 1310 1310 TERM TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR 1310 1310 1310 1310 1310 1310 1310 1310 TERM TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR 1310 1310 1310 1310 1310 1310 1310 1310 TERM RPTR RPTR RPTR RPTR RPTR RPTR RPTR RPTR TERM SONET Transport - 20 Gb/s OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 120 km 120 km OLS TERM OLS RPTR 120 km OLS RPTR OLS TERM DWDM Transport - 20 Gb/s Increased Fiber Network Capacity OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 OC-48 Public/Private Internet Peering Example Core Core Router Router RAS RAS EtherSwitch Core Access Router Router RAS RAS RAS Access ATM Switch Core ATM Switch RAS Router EtherSwitch Router RAS RAS RAS ATM Switch Core ATM Switch Router RAS ATM Access Access Router RAS RAS Core RAS Router Access RAS Router ATM Access RAS RAS Backbone SONET/WDM T1/T3/OC3 ATM Access Switch Router T1/T3 IP Leased-Line Connections ATM ATM ATM ATM Access Access Access Access T1/T3 FR and ATM IP Leased-Line Connections Remote Access Systems High Capacity Path Networking IP router IP router STS-12c/48c/... IP router STS-3c Existing SDH-SONET Network • 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 everywhere is not an appropriate solution. IP/SONET/WDM Network Architecture OC-3/12 [STS-3c/12c] OC-48 EMS Access Routers/ Enterprise Servers . . . SONET DCS SONET NMS SONET ADM OC-3/12 [STS-3c/12c/48c] SONET ADM EMS OC-12/48 SONET Transport Network Core IP Node Core IP Node . . . OTN NMS OC-3/12/48 [STS-3c/12c/48c] WDM LT l1, l2, ... WDM LT Pt-to-Pt WDM Transport Network IP = Internet Protocol OTN = Optical Transport Network ADM = Add Drop Multiplex OC-3/12/48 [STS-3c/12c/48c] LT = Line Terminal EMS = Element Management System NMS = Network Management System Evolution of Optical Networks Point-to-Point WDM Line System Multipoint Network WDM Add/Drop Optical Cross-Connect WDM Networking l1 l2 lN l1 l2 lN WDM ADM WDM ADM li lk Optical Cross Connect IP over OTN Architecture EMS Core Data Node . . . OTN NMS OXC EMS OXC OXC Access Routers Enterprise Servers . . . Core Data Node IP = Internet Protocol OTN = Optical Transport Network OXC = Optical Cross Connect Optical Transport Network EMS Core Data Node . . . EMS = Element Management System NMS = Network Management System Architectural Alternatives Quadruple Redundant Configuration of IP Routers at PoPs • Currently deployed by carriers to increase router reliability and perform load balancing. • Two routers are service routers adding/dropping traffic from the network side and passing through transit traffic. • Other two routers are drop routers connected to client devices. • Two connections from the network port at the ingress service router to two drop ports, one in each of the 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). 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. • 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. Assumptions: Network Model • Transit traffic uses router ports in IP-overWDM and OXC ports (only) in IP-overOTN. • Quadruple redundant configuration of IP routers at a PoP to improve reliability and perform load-balancing. • Typical 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 or 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. • 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). Pricing Assumptions • IP routers and OXCs have fixed costs and per-port costs for OC-48 and OC-192 interfaces. • 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. 2.5 Gbps of Traffic between PoP Pairs Total $-Cost (M) 2.5 Gbps uniform traffic 5000 4500 4000 3500 3000 2500 2000 1500 1000 500 0 IP-over-WDM IP-over-OTN 0 10 20 30 40 Network size (nodes) Cross-over point at network size of about 18 nodes. 50 60 5 Gbps of Traffic between PoP Pairs 5 Gbps uniform traffic Total $-Cost (M) 8000 7000 IP-over-WDM IP-over-OTN 6000 5000 4000 3000 2000 1000 0 0 10 20 30 40 Network size (nodes) Cross-over point at network size of about 15 nodes. 50 60