Outline A brief Historical aside Review of Transmission (Transport) Technologies, Architectures and...

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OutlineOutline

A brief Historical aside

Review of Transmission (Transport) Technologies, Architectures and Evolution

Transporting Broadband across Transmission Transporting Broadband across Transmission Networks designed for NarrowbandNetworks designed for Narrowband

Current Issues:Current Issues:Broadband IP Transport AnalysisBroadband IP Transport Analysis

Ongoing Investigations in IP/OTN NetworksOngoing Investigations in IP/OTN Networks

A Brief Historical AsideA Brief Historical Aside

LDBell-Labs WEBCS ME

AT&T 1984 - 1997

LD AT&T LabsAT&T circa 1997

Bell-Labs WEBCS MELucent circa 1997

Pre 1984 AT&T

BOCs LDBell-Labs WEBCS ME

AgereAvaya

RBOCs circa 1984US WestAmeritechSouthWest BellBell SouthNynexBell-AtlanticPac Bell

Bellcore

Telcordia

Tellium

Verizon

Bell South

AT&T Lucent

The Bell System Legacy Today

Review of Transmission(Transport) Technologies,

Architectures and Evolution

Review of Transmission(Transport) Technologies,

Architectures and Evolution

Opening Trivia QuestionOpening Trivia Question

What is the difference between a DS3 (or DS1) and a T3 (or T1)?

Asynchronous Data Rates

Digital Signal Level 0 DS0 64 Kb/sinternal to equipment

Digital Signal Level 1 DS1 1.544 Mb/sintra 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/srepeatered version of DS1 sent out of Central Office

T3 Electrical (Copper) Version of DS3 45 Mb/srepeatered version of DS3 sent out of Central Office

Asynchronous Digital Hierarchy

DS1 DS3

Asynchronous Optical Line SignalN x DS3s

28 DS1s = 1 DS324 DS0s = 1 DS1

DS0 (a digitized analog POTS circuit @ 64 Kbits/s)

Asynchronous Lightwave Systems typically transport traffic in multiples of DS3s i.e.... 1, 3, 12, 24, 36, 72 DS3s

Asynchronous NetworkingManual DS1 Grooming/Add/Drop

LW M13

• Manually Hardwired Central Office• No Automation of Operations• Labor Intensive• High Operations Cost• Longer Time To Service

DS3 DS3

Some Review QuestionsSome Review Questions

What does the acronym SONET mean?

What differentiates SONET from Asynchronous technology?

What does the acronym SDH mean?

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

SONET RatesDS3s are STS-1 Mapped

SONET Optical Line SignalOC-N = N x STS-1s

N is the number of STS-1s (or DS3s) transported

28 DS1s = 1 DS3 = 1 STS-124 DS0s = 1 DS1

(= 1 VT1.5)

DS0 (a digitized analog POTS circuit @ 64 Kbits/s)

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

SONET and SDH

STESTELTE

PTEPTE

STESTELT

PTEPTE

PTEPTEDS-3DS-3

DS-3DS-3

OC-3 TMOC-3 TMOC-3 TMOC-3 TM

SONET Line

SONET Path

SONET Section

TM = Terminal MultiplexorDS = Digital Signal

PTE = Path Terminating ElementLTE = Line Terminating ElementSTE = Section Terminating Element

SONET Layering for Cost Effective OperationsSONET Layering for Cost Effective Operations

SONET Point-to-Point Network

Repeater Repeater

Section

STS-1FrameFormat

LineOverhead

SectionOverhead Path

Overhead

STS-1 Synchronous Payload Envelope

STS-1 SPE

SONET Ring Network ArchitecturesSONET Ring Network Architectures

Unidirectional Path Switched Ring

A-BA-B

B-AB-A

Path Path SelectionSelection

Path SelectionPath Selection

fiber 1fiber 1

fiber 2fiber 2

Failure-free StateFailure-free StateBridgeBridge

BridgeBridge

Bidirectional Line Switched Ring

C C AAAACC

C C AA

WorkingWorking ProtectionProtection

2-Fiber BLSRB

Some Review QuestionsSome Review Questions

Which SONET Ring Network is simpler?

Which SONET Ring Network is inefficient for distributed demand sets?

Typical Deployment of UPSR and BLSR in RBOC Network

Regional Ring (BLSR)

Intra-Regional Ring (BLSR) Intra-Regional Ring (BLSR)

Access Rings (UPSR)

WB DACs

BB DACs

WB DACS = Wideband DACS - DS1 GroomingBB DACS = Broadband DACS - DS3/STS-1 GroomingOptical Cross Connect = OXC = STS-48 Grooming

DACS=DCS=DXC

Emergence of DWDMEmergence of DWDM

Some Review QuestionsWhat does the acronym DWDM mean?

What was the fundamental technology that enabled the DWDM network deployments?

First Driver for DWDMLong Distance Networks

• Limited Rights of Way• Multiple BLSR Rings Homing to a few Rights of Way• Fiber Exhaustion

BLSR Fiber PairsBLSR Fiber Pairs

Key Development for DWDM Optical Fiber Amplifier

120 km

OLSTERM

OLSRPTR

OLSTERM

120 km 120 km

Fiber Amplifier Based Optical Transport - 20 Gb/s

OC-48OC-48

Conventional Optical Transport - 20 Gb/s

1310RPTR

TERMTERM

40km 40km 40km 40km 40km 40km 40km 40km 40km

1310RPTR

TERMTERM1310

RPTR1310RPTR

1310RPTR

TERMTERM1310

RPTR1310RPTR

1310RPTR

TERMTERM1310

RPTR1310RPTR

1310RPTR

TERMTERM1310

RPTR1310RPTR

1310RPTR

TERMTERM1310

RPTR1310RPTR

1310RPTR

TERMTERM1310

RPTR1310RPTR

1310RPTR

TERMTERM

OC-48OC-48

Increased Fiber Network Capacity

Transporting BroadbandTransporting Broadbandacross Transmission Networksacross Transmission Networks

designed for Narrowbanddesigned for Narrowband

Transporting BroadbandTransporting Broadbandacross Transmission Networksacross Transmission Networks

designed for Narrowbanddesigned for Narrowband

T1/T3/OC3FRS and CRS

Access

Switch

Public/PrivateInternet Peering

Access

Router

T1/T3 IPLeased-LineConnections

Router

Access

Router

Access

Router

ATM Access

Access

Router

Access

Router

EtherSwitch

Router

BackboneSONET/WDM

RAS Farms

T1/T3 FRand ATM IPLeased-LineConnections

ATM Switch

ATMSwitch

Router

Data SP

High Capacity Path NetworkingHigh Capacity Path Networking

Existing SONET/SDH networks are a Existing SONET/SDH networks are a BOTTLENECKBOTTLENECK for Broadband Transport 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 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.costly changes. Clearly upgrading the SONET/SDH network everytime broadband data interfaces are upgraded based increased IP traffic is not an appropriate solution.

Existing SONET/SDH networks are a Existing SONET/SDH networks are a BOTTLENECKBOTTLENECK for Broadband Transport 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 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.costly changes. Clearly upgrading the SONET/SDH network everytime broadband data interfaces are upgraded based increased IP traffic is not an appropriate solution.

Existing SDH-SONET Network

IP router

IP router IP router

STS-3c

STS-12c/48c/...

IP/SONET/WDM Network ArchitectureIP/SONET/WDM Network Architecture

Core IPNode

SONETADM/LT

OC-3/12[STS-3c/12c]

OC-12/48

OC-3/12[STS-3c/12c/48c]

SONET Transport Network

SONETNMS

Core IPNode

Access Routers/EnterpriseServers

SONETADM/LT

SONETXC

WDMLT1, 2, ...

OC-3/12/48[STS-3c/12c/48c]

Pt-to-Pt WDM Transport Network

OC-3/12/48[STS-3c/12c/48c]

OTNNMS

IP = Internet ProtocolIP = Internet ProtocolOTN = Optical Transport NetworkOTN = Optical Transport NetworkADM = Add Drop MultiplexorADM = Add Drop MultiplexorWDM = Wavelength Division MultiplexingWDM = Wavelength Division Multiplexing

LT = Line TerminalLT = Line TerminalEMS = Element Management SystemEMS = Element Management SystemNMS = Network Management SystemNMS = Network Management System

Optical Network Evolution mirrorsSONET Network EvolutionOptical Network Evolution mirrorsSONET Network Evolution

Multipoint NetworkWDM Add/Drop

Point-to-Point WDM Line System

Optical Cross-ConnectWDM Networking

WDMADM

IP/OTN ArchitectureIP/OTN Architecture

Core DataNode

mc: multi-channel interface(e.g., multi-channel OC-12/OC-48)

mcOptical Transport Network

OTNNMS

Core Data Node

Access RoutersEnterprise Servers

Core Data Node

IP = Internet ProtocolIP = Internet ProtocolOTN = Optical Transport NetworkOTN = Optical Transport NetworkOXC = Optical Cross ConnectOXC = Optical Cross ConnectWDM = Wavelength Division MultiplexingWDM = Wavelength Division Multiplexing

EMS = Element Management SystemEMS = Element Management SystemNMS = Network Management SystemNMS = Network Management System

Broadband IP Transport Analysis

Credits to Debanjan Saha and Subir Biswas

Broadband IP Transport Analysis

Credits to Debanjan Saha and Subir Biswas

Architectural AlternativesArchitectural 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.

Architectural AlternativesArchitectural Alternatives

Quadruple Redundant Configuration of IP Routers at PoPsQuadruple 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.

IP-over-DWDM: Pros and ConsIP-over-DWDM: Pros and 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.

ConsPros

IP-over-OTN: Pros and ConsIP-over-OTN: Pros and 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.

ConsPros

Why Glass Through is not an Alternative?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.

Network Deployment Cost AnalysisNetwork 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.

Assumptions: Network ModelAssumptions: Network Model

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.

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).

Assumptions:PricingAssumptions: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.

2.5 Gbps of Traffic between PoP Pairs Without Restoration2.5 Gbps of Traffic between PoP Pairs Without Restoration

Cross-over point at network size of about 18 nodes.

2.5 Gbps uniform traffic

100015002000250030003500400045005000

0 10 20 30 40 50 60Network size (nodes)

IP-over-WDM

IP-over-OTN

Cross-over point at network size of about 15 nodes.

5 Gbps uniform traffic

IP-over-WDM

IP-over-OTN

5 Gbps of Traffic between PoP Pairs Without Restoration5 Gbps of Traffic between PoP Pairs Without Restoration

% of Transit Traffic in the Network Without Restoration% of Transit Traffic in the Network Without Restoration

% of Transit Traffic

degree = 2

degree = 3

75-85% of the total traffic is transit traffic for a network size of 50 PoPs.

Cross-over point at network size of less than 8 nodes.

2.5 Gbps uniform traffic

IP-over-WDM

IP-over-OTN

2.5 Gbps of Traffic between PoP Pairs With Restoration2.5 Gbps of Traffic between PoP Pairs With Restoration

Cross-over point at network size of less than 4 nodes.

5 Gbps uniform traffic

IP-over-WDM

IP-over-OTN

5 Gbps of Traffic between PoP Pairs With Restoration5 Gbps of Traffic between PoP Pairs With Restoration

% of Transit Traffic in the Network With Restoration% of Transit Traffic in the Network With Restoration

80-95% of the total traffic is transit traffic for a network size of 50 PoPs.

% of Transit Traffic

0102030405060708090

degree = 2

degree = 3

Results and DiscussionResults 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.

Results and Discussion contd. ...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.

Case for Restoration at Optical LayerCase 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.

Ongoing Investigations in IP/OTN NetworksOngoing 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...

Outline A brief Historical aside Review of Transmission (Transport) Technologies, Architectures and...

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