Transcript Kurs HLN

Part IV: Carriers, Traffic Mgt, and Trends
•
•
•
Carrier Technologies
– SDH/SONET
– WDM
– xDSL
Traffic Management
– Definitions and Traffic Models
– ATM Services
Trends
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 1
ETH Zürich
Synchronous Digital Hierarchy – SDH
SONET: Synchronous Optical Network.
 ANSI-SONET (U.S.A.) and ETSI-SONET (Europe).
 SDH: Synchronous Digital Hierarchy (international):

•
•
•
•
Synchronous
frames: 125 s
Integration of ATMand STM-based
data.
Compatibility with
existing equipment
and signaling.
Support of various
transmission rates.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
Transmission User Data
Rate in Mbit/s Rate in Mbit/s
STS-1
51,84
50,12
STS-3 STM-1
155,52
150,336
STS-9 STM-3
466,56
451,008
STS-12 STM-4
622,08
601,344
STS-24 STM-8
1244,16
1202,688
STS-36 STM12
1866,24
1804,032
STS-48 STM-16
2488,32
2405,376
STS-192 STM-64
9953.28
9621.504
STS-x: Synchronous Transfer Signal level x
STM-y: Synchronous Transport Modul level y
SONET
CM IV – 2
SDH
ETH Zürich
SONET – Architecture
Section: Fiber-optical cable between sender/receiver.
 Line: Sequence of sections.

•

Unchanged internal signal and channel structure.
Path: Interconnection of two devices.
Path
Terminals
Line
Section
Terminals
Line
Section
SONET
Repeater
Multiplexer
(STE)
(PTE + LTE)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
Section
Add-Drop
Multiplexer
(LTE)
CM IV – 3
Section
Repeater
(STE)
SONET
Multiplexer
(PTE + LTE)
ETH Zürich
SONET – Frame (STS-1)
The frame length is 125 s.
 Rows and columns are used.
 Transmission from left to right by rows.
 Frames contain user data and additional control
data as well as timing information.

0 s
Transport
overhead
(3 columns)
STS - Frame:
(3+6) * (3+87) Octett
 810 Octett
Synchronous Payload
Environment
(87-1 columns)
Section
overhead
(3 rows)
Line
overhead
(6 rows)
Path overhead (1 column)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 4
125 s
Brutto data:
810 Octett / 125 s
 51,84 Mbit/s
User data:
810 - [3*(3+6) + 1*(3+6)] Octett
 49,536 Mbit/s
ETH Zürich
SONET – Frame (STS-N)
Basic frame: STS-1 with 810 octets.
 Higher rate SONET channels formed by
octet-interleaving of multiple STS-1 inputs:

•
•
•
•
STS-N rate is formed from N STS-1 inputs.
Advantage: STS-1 line cards remain operable in an
Synchronous Payload
STS-1-to-STS-N multiplexor. Transport
overhead
Environment
STS-N frame:
0 s (3*3 columns)
((87-1) * 3 columns)
90 * N columns per
Section
overhead
row, including
(3 rows)
Overhead
Payload
4 * N columns of
Line
5.184 Mbit/s
150.336 Mbit/s
interface overhead. overhead
(6 rows)
Example:
Path overhead (1*3 columns) 125 s
STS-3 = STM-1 (155.52 Mbit/s)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 5
ETH Zürich
SONET – Localization of Payload
Pointer H1 and H2 contain values for number of
payload bytes inbetween H3 and J1.
 Direct access to single channels.
 No (de-)multiplexing necessary.
 Payload may be located in two STS-1 frames.

Frame
N
(9 rows)
H1 H2
(9 rows)
Frame
N+1
(9
rows)
H1 H2
Path overhead
(1 column)
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
H3 is used as padding byte.
CM IV – 6
ETH Zürich
SDH Network Topologies
Point-to-Point
Terminal
Point-to-Point
Terminal
Point-to-point configuration
with 1:4 protection channel sharing
Point-to-Point
Terminal
Add/Drop
Multiplexer
Point-to-Point
Terminal
Linear Add/Drop Route
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 7
ETH Zürich
Fiber Optic Networks Revisited
Traditional use of fibers:
Optical Fiber
Laser

Receiver
Current transmission capacities:
• 2.5 Gbit/s (OC-48)
• 10 Gbit/s (OC-192)

Lasers available for 850 nm, 1310 nm and 1550 nm
wavelength.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 8
ETH Zürich
Wavelength-Division Multiplexing
Dense* Wavelength-Division Multiplexing (DWDM):
Optical Fiber
Array of
Photodetectors
Array of Lasers l1 l2 l3 l4

Current available transmission capacities:
• 96 lasers at 2.5 Gbit/s = 240 Gbit/s (OC-4608)
• 32 lasers at 10 Gbit/s = 320 Gbit/s (OC-6144)
• Soon 128 lasers at 10 Gbit/s > 1 Tbit/s
(=1.000.000.000.000 bits/s)
* „Dense“ WDM: More than 10 lasers used simultaneously. Today: WDM usually means dense WDM.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 9
ETH Zürich
Breaking the Internet Gridlock

Utilizing publically available infrastructure:
• How to serve private users with sufficient bandwidth?
• How to interconnect two enterprise sites with an at least
medium bandwidth solution?

Solution possibilities:
• Hybrid fiber/coax (HFC) technology: any configuration of
fiber-optic and coaxial cable that is used to distribute local
broadband communications:
– Shared downstream bandwidth, up to 30 Mbit/s.
• Wireless cable.
• xDSL (Digital Subscriber Lines).

Deployment: 650 M customers on twisted pair.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 10
ETH Zürich
ADSL Technology – Overview (1)

Twisted pair access to the information highway:
• Delivering video und multimedia data.
• Avoids the replacement of existing cabling.
• Transformation of existing telephone network into
a multi-service network by applying modulation.
• Use of full copper frequency spectrum (app. 1.1 MHz).
144 kbit/s (POTS)
16 … 640 kbit/s
Server
Core Network
Internet
*)
ADSL Existing ADSL
Modem Copper Modem
1.5 … 9 Mbit/s *) depending on
the implementation
architecture
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 11
ETH Zürich
ADSL Technology – Overview (2)

ADSL Forum Reference Model:
Vc
Va
UC-2
U-C U-R
U-R2
T-SM
T-P
T
Digital
Broadcast
T.E.
Broadband
Network
ATU-C
Narrowband
Network
ATU-C
Network
Management
ATU-C
Access
Node
Splitter
Splitter
POTS-C
PSTN
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
POTS-R
Phonesets
CM IV – 12
ATU-R
ATM-SM
Premises
Distribution Network
ETH Zürich
DSL Comparison
DSL
Scheme
Downstream
[kbit/s]
Upstream
[kbit/s]
Voice
Support
IDSL
UDSL
SDSL
HDSL
ADSL
VDSL
144
1,000
160 – 1,168
2,048
1,500 – 8,000
1,500 – 25,000
144
300
160 – 1,168
2,048
64 – 800
1,600
Active
Splitterless
No
No
Passive
Passive
ADSL:
HDSL:
IDSL:
SDSL:
UDSL:
VDSL:
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
Asymmetric DSl
High bit-rate DSL
ISDN DSL
Symmetric DSL
Universal DSL
Very high bit-rate DSL
CM IV – 13
ETH Zürich
ADSL Technology – Capabilities

Data rates depend on:
•
•
•
•
Length of copper line,
Wire gauge,
Presence of bridged taps, and
Cross-coupled interference.
95% of todays loop plants
meet these measures.
 Requires advanced digital
signal processing and
advanced coding schemes
to deal with varying noise
figures.

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 14
Data Rate
[Mbit/s]
1.5 or 2
1.5 or 2
6.1
6.1
Wire Gauge Distance
[mm]
[km]
0.5 (26 AWG)
0.4 (24 AWG)
0.5 (26 AWG)
0.4 (24 AWG)
5.5
4.6
3.7
2.7
Duplex
Downstream
Bearer Channels Bearer Channels
[kbit/s]
[Mbit/s]
n*1.536 1.536
3.072
4.608
6.144
n*2.048 2.048
4.096
C Channels 16
64
Optional
160
Channels 384
544
576
ETH Zürich
ADSL Technology – DMT Modulation

To work simultaneously with
POTS on copper line.
Discrete Multitone (DMT) Modulation
• Lower 4 kHz are used
by POTS.
POTS each 4 kHz (32 QAM) 1.4 MHz
• Discrete Multi Tone (DMT):
256 separate
Data rate = No of channels * no of bits/channel * modulation rate
Theoretical max upstream: 25*25*4k = 1.5 Mbit/s
sub-frequencies
Theoretical max downstream: 249*15*4k = 14.9 Mbit/s
from 64 kHz.

Amplification varies
dependent
on frequency.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 15
ETH Zürich
ADSL Network Architectures (1)

ADSL-ATM network architecture, point-to-point:
DSLAM: Digital Subscriber Line Access Multiplexor
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 16
ETH Zürich
ADSL Network Architectures (2)

ADSL-ATM including L2TP:
LAC:
LAC:Local
LocalAccess
AccessCarrier
Carrier
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 17
ETH Zürich
Part IV: Carriers, Traffic Mgt, and Trends
•
•
•
Carrier Technologies
– SDH/SONET
– WDM
– xDSL
Traffic Management
– Definitions and Traffic Models
– ATM Services
Trends
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 18
ETH Zürich
Traffic Engineering Definition

Traffic Engineering is the task of mapping traffic
flows onto an existing physical topology.

The goals of traffic engineering are:
• Minimization of packet loss and packet delay.
• Optimization of network resources (avoiding overload
situations through load balancing).

Traffic engineering “applications” allow for a precise
control of how traffic flows are placed within a
routing domain.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 19
ETH Zürich
Policies and Mechanisms

Traffic engineering consists of:
• Traffic management (short-term) and
• Network planning (long-term).

Traffic management:
• Set of policies and mechanisms for satisfying a range of
diverse application service requests.
• Acting across: diversity and efficiency.
• Subsumes traditional ideas of congestion control:
– An overloaded resource suffers from service
degradation.
– Policies scale back demand or restrict access.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 20
ETH Zürich
Traffic Models

Goal of effectively managing traffic requires:
• Requirements of individual applications and organizations.
• Their typical „behavior“.

Traffic Models:
• Summarize „expected behavior“.
• Obtained by detailed traffic measurements or amenable to
mathematical analysis.
• State of the art in traffic modelling:
– Telephone traffic model and
– Internet traffic model.
• Change of applications make these models to change!
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 21
ETH Zürich
Telephone Traffic Model

Call arrival model:
• How are calls placed?
• Interarrival times drawn from an exponential distribution
(poisson process models all arrivals).
• Memoryless (certain time elapse does not tell the future).

Call holding-time model:
• Call holding-times drawn from an exponential distribution:
– Call longer than x decreases exponentially with x.
• Heavy-tailed distribution in recent studies:
10
0.01
0.0001
P(T>t) 0.000001
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
20
30
t
Heavy-tailed
Exponential
CM IV – 22
ETH Zürich
Internet Traffic Model

Parameters to characterize applications:
•
•
•
•

Distributions of interarrival times between app. invocations.
Duration of a connection.
Number of bytes transferred during a connection.
Interarrival times of packets within a connection.
Note: There is little consensus on models!
• E.g., interarrival times: Exponential or Weibull.
• Effective means: Measurements to fit to statistical model.
• LAN traffic differs heavily from WAN traffic.
– More local bandwidth, tendency for longer holding times,
higher peak data rates.
– Expensive wide area bandwidth, less volume.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 23
ETH Zürich
Time Scales of Traffic Management
Time Scale
Less than one
RTT
(Cell level)
One or more
RTTs
(Burst level)
Session
(Call level)
Day
Weeks and more
Mechanism
Scheduling, buffer management
Regulation, policing
Routing (connection less)
Error detection and correction
Feedback flow-control
Retransmission
Renegotiation
Signalling
Admission-control
Service pricing
Routing (connection-oriented)
Peak-load pricing
Capacity Planning
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 24
Net Endsystem




















ETH Zürich
Service Categories

ATM offers six service categories:
•
•
•
Real-time services using resource reservation.
Non-real-time services without resource reservation.
Non-real-time services with partial resource reservation.

Sources have to comply to a previously negotiated
traffic characteristic (traffic contract).

Conforming traffic is transported with the negotiated
quality of service guarantees.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 25
ETH Zürich
Real-Time Services (1)

CBR (Constant Bit Rate):
•
•
•
Traffic: constant, Peak Cell Rate (PCR).
QoS parameter: max. Cell Transfer Delay (maxCTD),
Cell Delay Variation (CDV), Cell Loss Ratio (CLR).
Example: uncompressed video/audio data.
Peak Cell Rate defines a temporal distance: T = 1/PCR.
Cells have to be evenly spaced in time.
marked or dropped
T
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
T
CM IV – 26
T
T
ETH Zürich
Real-Time Services (2)

rt-VBR (Real-Time Variable Bit Rate):
•
•
•
Traffic: Peak Cell Rate (PCR), Sustainable Cell Rate
(SCR), Maximum Burst Size (MBS).
QoS parameter: maxCTD, CDV, CLR.
Example: compressed video / audio data
T = 1/PCR
TS = 1/SCR
t  T with mean value  TS
marked or dropped
t
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
t
CM IV – 27
t
t
ETH Zürich
Non-Real-Time Services (2)

ABR (Available Bit Rate):
•
•
•
Traffic: Peak Cell Rate (PCR) and Minimum Cell Rate
(MCR), flow control mechanism mandatory.
"QoS parameter": minimum cell loss.
Flow control mechanism determines the
Allowed Cell Rate (ACR).
Link Rate
PCR (Peak Cell Rate)
ACR
(Allowed Cell Rate)
Dynamically changed
by the flow control.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
dynamic
reserved
CM IV – 28
MCR (Minimum Cell Rate),
may be 0.
ETH Zürich
Usage Parameter Control


Test, whether a cell stream conforms to a given
traffic characteristics.
Generic Cell Rate Algorithm: GCRA(T, ).
•
•

Virtual Scheduling Algorithm or
Continuous-State Leaky Bucket.
Input parameters: T = 1/PCR,  = CDVT.

T
OK


T
T
OK
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
OK
CM IV – 29
Not OK
OK
ETH Zürich
Peak Cell Rate Conformance
For CBR traffic, it is sufficient to test peak cell rate.
 Usage Parameter Control takes places at the
network interfaces.

GCRA(T,0)
Shaping
GCRA(T, *)
UPC
Physical
Private
UNI
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
Private
ATM
CM IV – 30
GCRA(T, )
Shaping
UPC
Public
ATM
Public
UNI
ETH Zürich
Part IV: Carriers, Traffic Mgt, and Trends
•
•
•
Carrier Technologies
– SDH/SONET
– WDM
– xDSL
Traffic Management
– Definitions and Traffic Models
– ATM Services
– IP Services
Trends
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 31
ETH Zürich
Use of Network Protocols
80
70
60
IP
SNA
IPX
RFC 1490
Others
50
40
30
20
10
0
1994
1996
1998
2000
2002
IP is the only protocol that matters anymore!
Source: Gartner Group
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 32
ETH Zürich
Data Traffic is Overtaking Voice
Data
Volume
Voice
Source: CIENA Corp.
Today
Data
Time
POTS
Voice-Centric
Data-Centric
POTS
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
DATA
CM IV – 33
ETH Zürich
Effect on (Carrier) Networks

Everything will be data, soon.

The only protocol that matters is IP.

Networks have to accomodate for the exponential
traffic growth.
It makes sense to design networks for IP only!
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 34
ETH Zürich
Technology Trends

Chip performance doubles every 18 months
(Moore‘s Law).

Modern chips can switch packets as fast as ATM
cells.

New router architectures have appeared:
• Routing at Gigabit/s speed
• Routers support traffic management with thousands of
queues per interface
• Routers interface directly to DWDM
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 35
ETH Zürich
Layer upon Layer...
IP
ATM
IP
IP
Sonet
ATM
Sonet
IP
DWDM
DWDM
DWDM
DWDM
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 36
ETH Zürich
Traffic Multiplexing in the Backbone
DWDM
ADM
Sonet
ADM
OC-48
OC-48
Nx
OC-48
OC-48
DWDM Ring

Multiplexing of IP traffic over ATM or Sonet no
longer required.

Segmentation of IP packets into ATM cells not
possible at OC-48.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 37
IP
ATM
Sonet
DWDM
ETH Zürich
Optical Internet Backbones (1)
Nx
OC-48
DWDM
ADM
IP
DWDM
OC-48
DWDM Ring

Most important objective: high bandwidth.

No „Quality of Service“, but „Classes of Service“

IP-centric Control (no SONET, no ATM).

Traffic engineering using MPLS.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 38
ETH Zürich
Optical Internet Backbones (2)
Optical Crossconnects
IP routers
Router network
Optical network

Optical network: Provides point-to-point connectivity
between routers („lightpaths“).

„Lightpaths“ have fixed bandwidth (e.g. OC-48).

„Lightpaths“ define virtual topology, which may be
static by design.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 39
ETH Zürich
Conclusions

Transporting data using IP will be the key task of the
„New Public Network“.
IP over ATM can not keep up with the very highspeed backbones (SAR!).
 IP over DWDM or IP over Sonet needs to solve the
traffic engineering problem.
 IP over ATM will remain for small ISPs or large
enterprise networks due to its proven reliability and
traffic management capabilities.

© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 40
ETH Zürich
References (1)
•
•
•
M.-C. Chow: Understanding SONET/SDH;
1995, Andan Publisher, Holmdel, New Jersey, U.S.A.,
ISBN 0–9650448–2–3.
The Sonet Home Page; URL: http://www.sonet.com, 1999.
CIENA Inc.: Fundamentals of DWDM; URL:
http://www.ciena.com, 1999.
•
D. Ginsburg: Implementing ADSL; Addison-Wesley,
Reading, Massachusetts, U.S.A., July, 1999,
ISBN 0-201-65760-0.
•
M. de Prycker: “Asynchronous Transfer Mode – Solution for
Broadband ISDN”, 3rd Edition, 1995, Prentice Hall,
Englewood Cliffs, New Jersey, U.S.A., ISBN 0–13–
342171–6.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 41
ETH Zürich
References (2)
• X. Xiao, L. M. Ni: Internet QoS: A Big Picture; IEEE Network
Magazine, Vol. 13, March/April 1999, pp 8 – 18.
• C. Schmidt, M. Zitterbart: Reservierung von Netzwerkressourcen – Ein Überblick über Protokolle und Mechanismen;
Praxis der Informationsverarbeitung und Kommunikation,
Vol. 18, No. 3, 1995, pp 140 – 147.
• L. Zhang, S. Deering, D. Estrin, S. Shenker, D. Zappala:
RSVP: A New Resource ReSerVation Protocol; IEEE
Network, Vol. 7, No. 5, September 1993, pp 8 – 18.
• The SWITCHlan backbone network; available at the URL:
http://www.switch.ch/lan, 1999.
• C. Metz: IP Routers: New Tool for Gigabit Networking; IEEE
Internet Computing; November/December 1998, pp. 14-18.
© 2000 B. Stiller, B. Plattner ETHZ-TIK, D. Bauer IBM Research
CM IV – 42
ETH Zürich