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Typical Deployment of UPSR and BLSR
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
Dense Wave Division Multiplexing (DWDM)in Long Distance Networks
WD
M N
EW
DM
NE W
DM
NE
WD
M N
E
• Limited Rights of Way• Multiple Fiber Rings Homing to a Few Rights of Way• Fiber Exhaustion
Fiber PairsFiber Pairs
DWDM versus SONET
120 km
OC-48
OLSTERM
OLSRPTR
OLSRPTR
OLSTERM
120 km 120 km
DWDM Transport - 20 Gb/s
OC-48OC-48
OC-48
OC-48OC-48
OC-48OC-48
SONET Transport - 20 Gb/s
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
TERMTERM
40km 40km 40km 40km 40km 40km 40km 40km 40km
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
TERMTERM1310
RPTR1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
TERMTERM1310
RPTR1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
TERMTERM1310
RPTR1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
TERMTERM1310
RPTR1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
TERMTERM1310
RPTR1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
TERMTERM1310
RPTR1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
1310RPTR
TERMTERM
OC-48OC-48
OC-48OC-48
OC-48OC-48
OC-48OC-48
Increased Fiber Network Capacity
T1/T3/OC3
ATM
Access
ATM
Access
ATM
Switch
Public/PrivateInternet Peering
ATM
Access
ATM
Access
Access
Router
T1/T3 IPLeased-LineConnections
Core
Router
Core
Router
Access
Router
Access
Router
ATM Access
ATM Access
RAS
RAS
RAS
RAS
RAS
RAS
RAS
RAS
Access
Router
Access
Router
EtherSwitch
EtherSwitch
RAS
RAS
RAS
RAS
RAS
RAS
RAS
RAS
Core
Router
Core
Router
BackboneSONET/WDM Remote Access Systems
T1/T3 FRand ATM IPLeased-LineConnections
ATM Switch
ATMSwitch
ATMSwitch
ATMSwitch
Core
Router
Core
Router
Example
High Capacity Path NetworkingHigh Capacity Path Networking
• 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.
• 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.
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
EMS
.
.
.
SONET ADM
OC-3/12[STS-3c/12c]
OC-12/48
OC-3/12[STS-3c/12c/48c]
SONET Transport Network
SONETNMS
Core IPNode
EMS
.
.
.
Access Routers/EnterpriseServers
OC-48
SONET ADM
SONETDCS
WDMLT
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 MultiplexADM = Add Drop Multiplex
LT = Line TerminalLT = Line TerminalEMS = Element Management SystemEMS = Element Management SystemNMS = Network Management SystemNMS = Network Management System
Evolution of Optical NetworksEvolution of Optical Networks
Multipoint NetworkWDM Add/Drop
Point-to-Point WDM Line System
Optical Cross-ConnectWDM Networking
OpticalCross
Connect
i
WDMADM
WDMADM
k
IP over OTN ArchitectureIP over OTN Architecture
Core DataNode
EMS
.
.
.
OXC
Optical Transport Network
OTNNMS
Core Data Node
EMS
.
.
.
Access RoutersEnterprise Servers
OXC
OXC
Core Data Node
EMS
.
.
.
IP = Internet ProtocolIP = Internet ProtocolOTN = Optical Transport NetworkOTN = Optical Transport NetworkOXC = Optical Cross ConnectOXC = Optical Cross Connect
EMS = Element Management SystemEMS = Element Management SystemNMS = Network Management SystemNMS = Network Management System
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
• 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.
• 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).
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
Cross-over point at network size of about 18 nodes.
2.5 Gbps uniform traffic
0500100015002000250030003500400045005000
0 10 20 30 40 50 60Network size (nodes)
To
tal
$-C
ost
(M
)
IP-over-WDM
IP-over-OTN