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

T

SO

NE

T/S

DH

MU

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Ad

d/D

rop

MU

X

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T/S

DH

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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