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IPinterconnection - 1 Copyright: si veda nota a pag. 2
IP over …… ATM … SDH … DWDM
Mario BaldiPolitecnico di Torino
(Technical University of Turin)
www.baldi.info
IPinterconnection - 2 Copyright: si veda nota a pag. 2
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IP Everywhere. Anything else?
Wide Area
?
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Which is the Best Interconnection Topology?
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Even if You Know It, You Know It only Now!
It can change on a monthly base
different customers
different customer needs
It can change on a weekly base
events
It can change on a daily base
business users during week-days, residential users during the week-end
It can change on a hourly base
business hours
evening entertainment
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IP over Photons
Routers are connected by optical fibers
The optical signal transmitted by a router is received by the other
Layer 2 framing as in any synchronous transmission
PPP
IEEE 802.3
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Pros and Cons
No overhead
Physical connections: no reconfigurability
One interface per connection
No standard management infrastructure
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IP over Dense Wavelength Division Multiplexing (DWDM)
Many transmissions with different wavelengths (colors) on the same fiber
Multiplies fiber capacity
Optical switches with wavelength routing
Layer 2 framing: PPP
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Pros and Cons
Very high capacity
Virtual connections with optical routing
No standard management infrastructure
Static multiplexing
Reconfiguration Flexibility?
One interface for many connections?
How about IP addresses?
One per physical interface?
One per wavelength?
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IP over SONET/SDH(Synchronous Optical NETworkSynchronous Digital Hierarchy)
Physical layer framing
Cross connect
Fine allocation granularity
Management framework
Layer 2 framing: PPP
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Transmission Hierarchy
PDH Hierarchy
USA
T1 - DS1
1.544 Mbps
T3 - DS3
44.736 Mbps
SDH Hierarchy
USA: SONET Europe: SDH
OC-3c / STS-3c
155.52 Mbps
STM-1
155.52 Mbps
STM-4
622.08 Mbps
OC-12c / STS-12c
622.08 Mbps
STM-12
2.4 Gbps
OC-48c / STS-48c
2.4 Gbps
OC-1c / STS-1c
51.84 Mbps
Europe
E1
2.048 Mbps
E3
34.368 Mbps
E4
139.26 Mbps
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Physical Architecture
Section: fiber optics trunk between transceivers
Line: sequence of sections between devices which operates on the frame
Path: end-to-end leased line
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Section Section Section Section
Line Line
Path
Repeater Repeater
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Protocol Architecture
Photonic Layer: fiber, laser
Section Layer: frames, OAM (Operation Administration and Management)
Line Layer: synchronization, multiplexing, switching, OAM
Path Layer: end-to-end data (bytes) transfer
Photonic Layer
Section Layer
Line Layer
Path Layer
Frame
Photonic Layer
Section Layer
Photonic Layer
Section Layer
Line Layer
Photonic Layer
Section Layer
Line Layer
Path Layer
Higher Layer Higher Layer
Light
STS-N / STM-N Block
Envelope
Terminal TerminalRepeater Multiplexer
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Frame FormatSTS-1: 810 octets every 125 s 51.84 Mbps
A1 A2 C1 J1
B1
D1
H1
B2
D4
D7
D10
Z1
D2
H2
K1
D5
D8
D11
Z2
F1
D3
H3
K2
D6
D9
D12
E2
B3
C2
G1
E1
F2
H4
Z3
Z4
Z5
Payload Payload
90 octets
9 o
cte
ts
s
sSection Overhead Line Overhead Path Overhead
Synchronous Payload Environment (SPE) 87 octets3 octets
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Pros and Cons
Standard OAM architecture
Virtual connections
One interface per connection
Static multiplexing
Limited reconfiguration flexibility
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IP over ATM(Asynchronous Transfer Mode)
Cell switching
flexible multiplexing
Semi-permanent and switched virtual connections
Layer 2 protocol
no need for layer 2 framing
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Pros and Cons
Virtual connections
Multiple connections per interface
Total reconfiguration flexibility
Support for other services (e.g., frame relay)
Flexible multiplexing
High protocol overhead (more than 10%)
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IP over FR(Frame Relay)
Frame switching
flexible multiplexing
Semi-permanent virtual connections
Layer 2 protocol
no need for layer 2 framing
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Pros and Cons
Virtual connections
Multiple connections per interface
Large installed base
No Quality of Service Guarantees
Why is another packet switching layer needed?
Because IP lacks traffic engineering capability
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MPLS(Multi-Protocol Label Switching)
Frame switching
flexible multiplexing
Dynamic virtual connections (label switched paths)
Layer 2 protocol tightly integrated with layer 3
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Pros and Cons
Virtual connections
Multiple connections per interface
One control plane: no “IP over”
No Quality of Service Guarantees