IP over WDM network docx

 First fiber based optical transmission system  Mostly a single high-speed optical channel  All multiplexing done in electrical domainTDM  50Mb/s to 10Gb/s data services  WDM allow

IP over WDM network

Fang Yu

294 Class Presentation

 First fiber based optical transmission system

 Mostly a single high-speed optical channel

 All multiplexing done in electrical domain(TDM)

 50Mb/s to 10Gb/s data services

 WDM allows simultaneously transmitting multiple high-speed channels on different frequencies (Up to 160 wavelengths today)

 Total link capacity = 160 *40G =6.4 Tbps

Current Typical Protocol Stacks

IPATMSONETWDM

(20-400 Gb/s)

OTS OTS OTS OTS OTS OTS

(OTS: Optical Transport System)

Transport Layer Model

1/0 DCS

1/0 DCS

4E 4E

4E

4E

3/1 DCS 3/1 DCS

3/1 DCS 3/1 DCS

3/3 DCS Layer (DACS III)

DACS III DACS III

DACS III DACS III

ATM/IP ATM/IP

ATM/IP ATM/IP

DS1 (1.5 Mb/s) DS3

(45 Mb/s)

DS3 (45 Mb/s)

SONET ADM Layer

Core ATM/IP

Layers

Service Layers

Media Layer

CHCG

CHCG

Wavelength Path Crossconnect

Wavelength Mux Section Crossconnect

Wired

Hard-Disadvantage of Current layer Protocol Stack

Multi- Inefficient

 In IP over ATM over SONET over WDM network, 22%

bandwidth used for protocol overhead

 Layers often do not work in concert

 Every layer now runs at its own speed So, low speed

devices cannot fill the wavelength bandwidth

 When detecting of failure, different layers compete for

Disadvantage of Current layer Protocol Stack (Cont)

Multi- Functional overlap: So many layers are doing the same thing

Historical Reason for Multi-layer

Electronic Network

Simplified Protocol Stacks?

IPFrame Relay

ATMSONETWDM

IP

WDM

WDM-aware Electronic layer

Challenge for IP over WDM

network

 WDM-aware Electronic layer

 Reconfiguration and load balancing

 Protection and restoration

 Optical flow switching

1

New request 1 3

With  converters

WC

Virtual Topology Reconfiguration

 Physical topology

 Seen by optical layer

 Virtual topology: a set of nodes interconnected by light-paths (wavelength)

 Seen by electronic layer

 Reconfigure of light-paths in WDM network by

 Changing the light path connectivity between electronic switches

 Tuning of the transmitter wavelength and the switches

 Time scale of changes

 Triggered by what mechanisms

 IP routing properties (e g stability)

Reconfigurable Routing

0.05

X6

Call arrival rate

WDM ring, 20 nodes one transceiver/node call BW = 1 wavelength

Multi-layer Routing

 IP layer routing is the bottleneck of present Internet

 Solution: Routing long duration flows at lower layers

• Conventional packet routing

• Optical bypass of intermediate routers for high volume traffic

• End-to end (user-to-user) flow of entire file bypassing routers

Switching all the packets in optical layer?

 Requires intelligence in the optical layer

 Need to store packet during header

processing

 Optical buffers are extremely hard to

implement

 1 pkt = 12 kbits @ 10 Gbps requires 1.2 s of delay => 360 m of fiber)

 Optical Packet Switch still has a long way to go………

Various Optical Switching Technologies

Optical Burst Packet Switching

 Avoid electronic bottlenecks

 Decrease the cost by simplifying the

multiple layer architecture

such a network

Optical Burst Switching

 Resources are allocated using one way

reservation

 Sender sends a request

 Sender sends burst without waiting for an

acknowledgement of its reservation request

 Switch does preparation for the burst when getting the request

 Bursts can have variable lengths

 Burst switching does not necessarily require buffering

(needs to be done optically).

 Tell-and-go (TAG) – a control packet is sent out to reserve resources and then the burst is sent without waiting for acknowledgement Refresh packets are sent to keep the path alive

Main Characteristics of Optical Burst Switching

 There is a time separation(offset time) between header and data

 Header and data are usually carried on different

channels

 Header goes through sophisticated electronic processing

 Data is kept in optical domain

 Current IP over ATM over SONET over WDM network

is inefficient and redundant

 Future IP directly over WDM network

 Advantages

 Less latency

 Automatic provisioning

 Higher bandwidth utilization

 Challenge of packet directly over WDM network

 Optical buffer

 Optical burst switch is one of the proposed techniques to IP over WDM network

 John Strand, “Optical Networking and IP over Optical”, Feb 4, 2002

 Kumar N Sivarajan, “IP over Intelligent Optical Networks”, Jan 5, 2001

 Gaurav Agarwal, “A Brief Introduction to Optical Networks”, 2001

 Yang Lihong, “Optical Burst Switching”, CMU networking seminar presentation

 Vincent W S Chan, “Optical Networks: Technology and Architecture”

 Eytan Modian, “WDM-Based Packet Networks”, IEEE Communication Magazine, March 1999

 Ornan (Ori) Gerstel, Rajiv Ramaswami,, “Optical Layer Survivability—An

Implementation Perspective”, IEEE Journal on selected areas in