Download IP: Addresses and Forwarding - ECSE

IP over SONET and Optical
Networks
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
[email protected]
http://www.ecse.rpi.edu/Homepages/shivkuma
Based in part on slides of Nick McKeown (Stanford)
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
1
Overview
Internet Core Transport Evolution & Trends
 SONET
 Optical Networking: Components
 Control plane:
 Overlay model, peer model
 Issues: provisioning, restoration, routing, traffic
engineering

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
2
Telephony: Multiplexing




Telephone Trunks between central offices carry
hundreds of conversations: Can’t run thick bundles!
Send many calls on the same wire: multiplexing
Analog multiplexing
 bandlimit call to 3.4 KHz and frequency shift onto
higher bandwidth trunk
Digital multiplexing: convert voice to samples
 8000 samples/sec => call = 64 Kbps
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
3
Telephony: Multiplexing Hierarchy



Pre-SONET:
 Telephone call: 64 kbps
 T1 line: 1.544 Mbps = 24 calls (aka DS1)
 T3 line: 45 Mbps = 28 T1 lines (aka DS3)
Multiplexing and de-multiplexing based upon strict
timing (synchronous)
 At higher rates, jitter is a problem
 Have to resort to bit-stuffing and complex
extraction => costly “plesiochronous” hierarchy
SONET developed for higher multiplexing aggregates
 Use of “pointers” like C to avoid bit-stuffing
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
4
Digital Telephony in 1984
DS1
M13
• Switches
• Leased Line
DS3
Fiber Optic
Transmission
Systems
M13
DS1
DS1 Cross
Connect
Fiber
M13
Central
Office
Central
Office
No Guaranteed
Timing
Synchronization
Key System Aspects:
• M13 Building Blocks
• Asynchronous Operation
• Electrical DS3 Signals
• Proprietary Fiber Systems
• Brute Force Cross Connect
• AT&T Network/Western
Electric Equipment
DS3
DS1
Central
Office
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
5
Post-AT&T Divestiture Dilemmas
• Switches
• Leased Line
• LAN Services
• Data Services
Different
Carriers,
Vendors
M13
DS1
Internal
DS3 Cross
Connect
Needs:
• Support Faster Fiber
• Support New Services
• Allow Other Topologies
• Standardize Redundancy
• Common OAM&P
• Scalable Cross Connect
Support
Other
Topologies,
Protect Fibers
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
6
SONET
Synchronous Optical Network
 Layer 1 Standards For Communication over
Fiber Optic (and Electrical) Links
 Facilitates:
 Fiber Optic Link Speed Increases
 Variety Of Topologies and Grooming Functions
 Operations, Administration, Maintenance, and
Provisioning (OAM&P)
 Used As Telephony Carrier Equipment And CPE
Interconnect

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
7
Equipment Types
Path
Sections
PTE
Repeaters
• Section Termination (STE)
Line
SONET End
Device - I.e.
Telephony
Switch, Router
• Line Termination (LTE)
• Path Termination (PTE)
PTE
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
8
STS-1 Frame Format
90 Bytes
Or “Columns”
9
Rows
Small Rectangle =1 Byte
Frame Transmission
• Top Row First, Sent Left To Right
• 125 ms/Frame
• 810 Bytes/Frame
• 51.84 Mbps Rate
• Frame Contains One Payload
STS = Synchronous Transport Signal
Rensselaer Polytechnic Institute
9
Shivkumar Kalyanaraman
STS-1 Headers
Section Overhead (SOH)
90 Bytes
Or “Columns”
9
Rows
Line Overhead (LOH)
Path Overhead (POH)
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
10
Headers: Section Overhead (SOH)
Rcv
SOH
A1
=0xF6
B1
BIP-8
Xmt
SOH
A2
=0x28
J0/Z0
STS-ID
E1
Orderwire
F1
User
D1
D2
D3
Data Com Data Com Data Com
Section Overhead
• 9 Bytes Total
• Originated And Terminated By All
Section Devices (Regenerators,
Multiplexers, CPE)
• Other Fields Pass Unaffected
Selected Fields:
•A1,A2 - Framing Bytes
•BIP-8 - Bit Interleaved
Parity
• F1 User - Proprietary
Management
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
11
Headers: Line Overhead (LOH)
H1
Pointer
Xmt
LOH
Xmt
SOH
Rcv
LOH
Rcv
SOH
Xmt
SOH
Rcv
SOH
B2
BIP-8
H2
H3
Pointer Pointer Act
K1
K2
APS
APS
D4
D5
D6
Data Com Data Com Data Com
D7
D8
D9
Data Com Data Com Data Com
D10
D11
D12
Data Com Data Com Data Com
S1
Sync
Line Overhead
• 18 Bytes Total
• Originated And Terminated By All
Line Devices (Multiplexers, CPE)
• LOH+SOH=TOH (Transport OH)
M0
REI
E1
Orderwire
Selected Fields:
•H1-3 - Payload Pointers
•K1, K2 - Automatic
Protection Switching
• D4-D12 - 576 kbps
OSI/CMIP
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
12
Headers: Path Overhead (POH)
PTE
PTE
STE
Frame N
Frame N+1
J1
Trace
B3
BIP-8
Frame N
Frame N+1
C2
Sig Label
Path Overhead
• H1,H2 fields of LOH points to
Beginning of POH
•POH Beginning Floats Within Frame
• 9 Bytes (1 Column) Spans Frames
• Originated And Terminated By All
Path Devices (I.e. CPE, Switches)
• STE Can Relocate Payload
G1
Path Stat
F2
User
H4
Indicator
Selected
fields:
•BIP-8 - Parity
• C2 - Payload
Type Indicator
• G1 - End End
Path Status
Z3
Growth
Z4
Growth
Z5
Tandem
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
13
SPE
Synchronous Payload Envelope
• Contains POH + Data
• First Byte Follows First Byte Of POH
• Wraps In Subsequent Columns
• May Span Frames
• Up To 49.536 Mbps for Data:
•Enough for DS3
Defined Payloads
• Virtual Tributaries
(For DS1, DS2)
• DS3
• SMDS
• ATM
• PPP …
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
14
Accommodating Jitter
Positive Stuff
Negative Stuff
• To Shorten/Lengthen Frame:
• Byte After H3 Ignored; Or H3 Holds Extra Byte
• H1, H2 Values Indicate Changes - Maximum Every 4 Frames
• Requires Close (Not Exact) Clock Synch Among Elements
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
15
STS-N Frame Format
90xN Bytes
Or “Columns”
N Individual STS-1 Frames
Composite Frames:
• Byte Interleaved STS-1’s
• Clock Rate = Nx51.84 Mbps
Examples
STS-1
51.84 Mbps
STS-3
155.520 Mbps
STS-12 622.080 Mbps
STS-48 2.48832 Gbps
STS-192 9.95323 Gbps
Complex demultiplexing !!
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
16
STS-Nc Frame Format
90xN Bytes
Or “Columns”
Transport Overhead: SOH+LOH
Concatenated mode:
• Same TOH Structure And Data Rates As STS-N
• Not All TOH Bytes Used
• First H1, H2 Point To POH
• Single Payload In Rest Of SPE
• Accommodates FDDI, E4, data
Current IP over SONET technologies use concatenated
mode: OC-3c (155 Mbps) to OC-192c (10 Gbps) rates
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
17
SONET Network Elements
D+R
DS1s
TM
ADM
MN
MN
MN
MN
DCC
D+R
D+R
DS1s
Nonstandard, Functional Names
TM: Terminal Mux
ADM: Add-Drop Mux
DCC: Digital Cross Connect
(Wideband and Broadband)
MN: Matched Node
D+R: Drop and Repeat
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
18
Topologies
ADM
DCC
ADM
ADM
ADM
2 Fiber Ring
DCC
Each Line Is
Full Duplex
ADM
ADM
ADM
DCC
Each Line Is
Full Duplex
ADM
ADM
ADM
4 Fiber Ring
DCC
Uni- vs. BiDirectional
ADM
ADM
All Traffic Runs Clockwise,
vs Either Way
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
19
Automatic Protection Switching (APS)
ADM
ADM
ADM
ADM
ADM
ADM
Line Protection Switching
Path Protection Switching
Uses TOH
Trunk Application
Backup Capacity Is Idle
Supports 1:n, where n=1-14
Uses POH
Access Line Applications
Duplicate Traffic Sent On Protect
1+1
Automatic Protection Switching
• Line Or Path Based
• Revertive vs. Non-Revertive
• Restoration Times ~ 50 ms
• K1, K2 Bytes Signal Change
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
20
Protection Topologies - Linear

Two nodes connected to each other with two or
more sets of links
Working
Protect
Working
(1+1)
Protect
(1:n)
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
21
Protection Topologies - Ring

Two or more nodes connected to each other with
a ring of links
 Line vs. Drop interfaces
 East vs. West interfaces
W
D
E
L
E
L
W
Working
Protect
W
E
E
W
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
22
Protection Topologies - Mesh

Three or more nodes connected to each other
 Can be sparse or complete meshes
 Spans may be individually protected with
linear protection
 Overall edge-to-edge connectivity is protected
through multiple paths
Working
Protect
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
23
Packet Over SONET (POS)
Special Data Scrambler
• 1+ x43 Polynomial
Standard PPP Encapsulation
• Protects Against Transmitted
• Magic Number Recommended
• No Address and Control Compression Frames Containing Synch Bytes
Or Insufficient Ones Density
• No Protocol Field Compression
PPP
FCS
Byte
Stuff
Scrambling
Standard CRC Computation
• OC3 May Use CRC-16
• Other Speeds Use CRC-32
SONET
Framing
SONET Framing
• OC3, OC12, OC48, OC192 Defined
• C2 Byte = 0x16 With Scrambling
• C2 Byte = oxCF Without (OC-3)
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
24
Quick History of Optical Networking
1958: Laser discovered
 Mid-60s: Guided wave optics demonstrated
 1970: Production of low-loss fibers
 Made long-distance optical transmission possible!
 1970: invention of semiconductor laser diode
 Made optical transceivers highly refined!
 70s-80s: Use of fiber in telephony: SONET
 Mid-80s: LANs/MANs: broadcast-and-select
architectures
 1988: First trans-atlantic optical fiber laid
 Late-80s: EDFA (optical amplifier) developed
 Greatly alleviated distance limitations!
 Mid/late-90s: DWDM systems explode
 Late-90s:
Intelligent Optical networks Shivkumar Kalyanaraman
Rensselaer
Polytechnic Institute

25
Geometrical Optics
Fiber Made of Silica: SiO2 (primarily)
 Refractive Index, n = cvacuum/cmaterial
 ncore > ncladding

n~1.43
n~1.45
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
26
Geometrical Optics (cont.)

Basics “Laws”: Refraction and Reflection
Reflection:
1r = 1
 Refraction:
n1sin 1 = n2sin 2 (Snell’s Law)
 If 2 = /2: Total Internal Reflection
 then 1 =sin-1 (n2/n1), “Critical Angle”

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
27
Geometrical Optics (cont.)
Light propagates by total internal reflection
 Modal Dispersion: Different path lengths cause
energy in narrow pulse to spread out
 T = time difference between fastest and
slowest ray

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
28
Optical Transmission
Attenuation
Dispersion
Nonlinearity
Reflectance
Transmitted data waveform
Waveform after 1000 km
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
29
Fiber Attenuation
Two windows:
 1310 & 1550 nm
 1550 window is
preferred for longhaul applications
 Less attenuation
 Wider window
 Optical amplifiers

1550
window
1310
window
l
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
30
Fiber Dispersion
Dispersion ps/nm-km
Normal fiber
Non-dispersion shifted fiber (NDSF)
>95% of deployed plant
18
Wavelength
0
l
1310 nm
1550nm
Reduced dispersion fibers
Dispersion shifted fiber (DSF)
Non-zero dispersion shifted fibers (NZDSF)
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
31
Dispersion
Interference



Dispersion causes the pulse to spread as it travels
along the fiber
Chromatic dispersion is important for singlemode
fiber
 Depends on fiber type and laser used
 Degradation scales as (data-rate)2
Modal dispersion limits use of multimode fiber to
short distances
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
32
Single vs. Multimode Fiber
Silica-Based Fiber Supports 3 Low-Loss
“Windows”: 0.8, 1.3 , 1.55 m m wavelength
 Multimode Fibers Propagate Multiple Modes of
Light
 core diameters from 50 to 85 m m
 modal dispersion limitations
 Single-mode Fibers Propagate One Mode Only
 core diameters from 50 to 85 m m
 chromatic dispersion limitations (pulse
spreading)

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
33
Polarization Mode Dispersion (PMD)
 Most
severe in older
fiber
 Caused by several
sources
 Core shape
 External stress
 Material
properties
 Becomes an issue at
OC-192
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
34
Four-Wave Mixing (FWM)



Creates in-band
crosstalk that can not be
filtered
Problem increases
geometrically with
 Number of ls
 Spacing between ls
 Optical power level
Chromatic dispersion
minimizes FWM
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
35
Multiplexing: WDM
TDM: Time Division
Multiplexing
 10Gb/s upper limit
 WDM: Wavelength
Division Multiplexing
 Use multiple
carrier frequencies
to transmit data
simultaneously

B b/s
1
NB b/s
2
N
1
2
N
l1
l2
lN
B b/s
l1l2... lN
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
36
Erbium-Doped Fiber Amplifier (EDFA)
40-80 km
Terminal
Terminal
Regenerator - 3R (Reamplify, Reshape and Retime)
120 km
Terminal
Terminal
EDFA - 1R (Reamplify)
Terminal
Terminal
Terminal
Terminal
Terminal
EDFA amplifies all ls
Terminal
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
37
EDFA Enables DWDM!
EDF
EDF
...
Optical
Isolator
WDM
Coupler
...
WDM
Coupler Optical
Filter
Optical
Isolator
DCF
1480
Pump
Laser
980
Pump
Laser


EDFAs amplify all ls in 1550 window simultaneously
Key performance parameters include
 Saturation output power, noise figure, gain
flatness/passband
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
38
Optical Couplers
Combines & splits signals
 Wavelength independent or dependent

Power(Output1) =  Power(Input1)
 Power(Output2) = (1- ) Power(Input1)
 Power splitter if =1/2: 3-dB coupler
 Used to construct simple optical switches

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
39
Multiplexers, Filters, Routers

Filter selects one
wavelength and
rejects all others

Multiplexor combines
different wavelengths
Router exchanges
wavelengths from one
input to a different
output

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
40
Characteristics of Filters
Low insertion loss
 Loss independent of
SOP
 Filter passband
independent of
temperature
 Flat passbands
 Sharp “skirts” on the
passband

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
41
Gratings
Constructive interference
at wavelength l and
grating pitch, a, if
a[sin(i) - sin(d)] = m l
 m = order of the grating

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
42
Bragg Gratings
Bragg wavelength is
l0 = 2 neff
where  is period of
grating
 If incident wave has
wavelength l0, it is
reflected by Bragg
grating

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
43
Fabry-Perot Filters
Fabry-Perot filter also called F-P interferometer
or etalon
 Cavity formed by parallel highly reflective mirrors
 Tunable filter

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
44
Pre-DWDM: Second Gen. Optical Nets
Broadcast and Select
 Passive broadcast to all receivers
 Number of nodes limited by finite number of
wavelengths and power splitting
 Wavelength Routing
 Allows simultaneous lightpaths using same
wavelengths
 Power not broadcast to unwanted receivers

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
45
Second Generation Optical Nets
Node
C
c
l1 l2 l3
B
l3
Star
l1
Node
A
E
Coupler
l1
l2
l1 l2 l3 Node
l1 l2 l3
A
B
l1
l2
D
Wavelength Conversion
at Node D
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
46
1552
1553
1554
1555
1556
0
1
2
3
4
5
6
7
Amplify
1557
Rx
Laser
External
Modulator
1310 nm
1551
DWDM Filter
1550
0
1
2
3
4
5
6
7
Optical Combiner
DWDM System Design
15xx nm
15xx nm
Rx
Reamplify
Reshape
Retime
1310 nm
Tx
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
47
Protection for IP over DWDM
Optical Cloud


Optical protection is not sufficient
 Only protects transmission infrastructure
Layer 3 must provide path restoration
 Opportunity for differentiation at the service level
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
48
Eg: 40l DWDM
GSR 12000
SR OC-48 PoS
TX
TX
TX
l1
l2
l3
RC
100 km
25 dB
RC
RC
500 km
RC
TX
GSR 12000
SR OC-48 PoS
TX
RC
Error-free transmission over 20,000
kms without SONET regeneration
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
49
Eg: 16l DWDM and OC-192 Ring
Working
Protect
PRS
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
50
IP over Optical Networks (IPO)
Removing the transport layers
Today
Traditional
Tomorrow
IP
IP Over ATM
POS
ATM
IP
IP
IP-OG
SONET
ATM
SONET
IP
Optical
Optical
Optical
Optical
Lower Cost, Complexity, & Overhead
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
51
IPO: Control Planes
Traditional SONETbased approaches
Layering (overlay)
approaches
Direct MPlSbased approach
IP
IP
ATM
ATM
IP
SONET
IP
SONET
WDM Layer
IP
IP
Physical Optics Layer
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
52
Multi-Protocol Lambda Switching
Packet Label Switch Router (LSR)
Link 1: label 3 
Link 6: label 9
Control information
physically coupled
with data
3
Switching fabricOutput buffers
Link 1
Link 4
Link 2
Link 5
9
Link 3
Link 6
Lambda Switch Router (lSR)
Ethernet (e.g.,
outband control
channel/network)
Fiber 2: lambda blue
 Fiber 4: lambda red
Fiber 1
Control information
physically decoupled
from data
Control
Demu
x
Optical switching
fabric
Converters
(optional)
OSC
Mux
Fiber 4
Fiber 2
Fiber 5
Fiber 3
Fiber 6
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
53
Multi-Protocol Lambda Switching
Key Elements Overview
Coordinate jointly with LSP control.
Wavelength channel
signaling: setup/teardown,
protection/ restoration
Neighbor
discovery,
monitoring
Link
Management
Protocol
ConstraintBased Routing
Signaling
protocols
w. extensions
Topology/resource
distribution
Extended IGP
protocols
(OSPF, IS-IS)
Added optical
metrics
Link-state
database w.
extensions
Rensselaer Polytechnic Institute
54
Shivkumar Kalyanaraman
Link-Level Restoration Overview
Original Channel Pair
C
D
B
7
A
5
4
7
3
1
10
7
12
14
5
7
4
E
9
New Channel Pair
Drop port


Drop port
A lightpaths is locally restored by selecting an
available pair of channels within the same link
If no channel is available then the end-to-end
restoration is invoked
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
55
End-to-End Restoration Overview
F
G
8
7
H
9
5
7
A
5
4
7
8
Shared
Backup
Path
Primary
Path
B
4
C
3
1
D
10
7
12
14
Local
Restoration
Failure
Drop port
5
7
4
E
9
Drop port
A shared backup path is “soft-setup” for each
restorable primary path
 When local restoration fails, triggers are sent to
the end-nodes via signaling
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute

56
IP-SONET-WDM using POS
IP/PPP/HDLC packet
mappings to SONET
frames (OC-48, OC-192)
IP routing
protocols (OSPF,
BGP)
Gigabit IP Router
Gigabit IP Router
Mux
Demux
SONET
SONET
Point-to-point
DWDM links
(linear or ring
SONET
topologies)
Wavelength
laser
transponders
Wideband
receivers
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
57
IP-Optical using Signaled Overlay
Optical network
IP
border
router
SONET DCS
Core
OXC
IP address
registration Border
OXC
NMS control
IP
border
router
Border
OXC
UNI
UN
I
SONET DCS
Endpoint
reachability,
service discovery
Modified IP-MPLS
protocols or proprietary
signaling/routing
Software signaling
interface
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
58
IP-Optical using Peer Model
Lambda switch routers
(lSR), switch purely on
wavelengths
Label edge router
(LER)
IP and optical
domains
“optical LSP”
IP/MPLS
client router
OXC
(lSR)
OXC IP addresses
IP/MPLS
client router
Modified IGP and signaling
protocols
OXC
(lSR)
Router IP
addresses
Full peering
Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
59
Summary
Internet Core Transport Evolution & Trends
 SONET
 Optical Networking: Components
 Control plane:
 Overlay model, peer model
 Issues: restoration, routing, traffic engineering

Shivkumar Kalyanaraman
Rensselaer Polytechnic Institute
60