Post on 26-Mar-2015
1
Andreas IßleiberAndreas Ißleiberaisslei@gwdg.deaisslei@gwdg.de
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
2
Results and facts from the ADSL field test in Göttingen Results and facts from the ADSL field test in Göttingen
Characteristics of the xDSL Technologies Overview of the different xDSL Technologies Criteria for suitable ADSL-Devices Measurements of bandwidth, measuring methods Modulation methods DMT vs. CAP Structure of the Ericsson ADSL-System Integration in our existing Network, called GöNET (University Network) Connection of Institutes and Students´ hostel (dormitory) to ADSL Perspectives, Results, Interoperabiliy, future plans
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen, eMail: aislei@gwdg.de
Index:
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
3
Fast data-communication on old copper wiresFast data-communication on old copper wires
The DSL-Technologie was introduced for the first time at the end of the 80's by Bell core in the USA
So far only the frequency range between 3-4Khz in the telephone network was used for data transmission
Because of signal-to-noise ratio (S/N) in the telephone network, usable bandwidth confined to approx. 30-35 Kbit/s, (see V.34 Modems)
By reduction the (S/N-ratio), the bandwidth in one direction can be improved (see 56 Kbit/s modem technology, downstream).
The idea at that time was to use the higher frequency range for the digital data communication
Copper line, usually installed nowadays in telecommunication networks, can deliver higher bandwidths than 30-35 kbps
Telephone-switching-centers reduce substantially the bandwidth a direct connection between both ends is necessary for an ADSL operation (leased
lines, no bandwidth-limiting switching centers) Better modulation techniques combined with higher frequency range can clearly
improve the data rates
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen, eMail: aislei@gwdg.de
xDSL-Technologies:
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
4
Fast data-communication on old copper wiresFast data-communication on old copper wires
xDSL is a general term for the different DSL techniques
The xDSL technologies differ in...
Transfer frequency System impedances Signal levels Modulation methodsAttainable data rate reachable distance
xDSL-Devices are called simply „modem“
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen, eMail: aislei@gwdg.de
xDSL Technologies:
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
5
Fast data-communication on old copper wiresFast data-communication on old copper wires
HDSL...
first generation of xDSL technology Needs 2 or 3 copper pairs, ADSL needs only one! pairUsed symmetrical transferrates in send- and receive-directionData rate: 1,544 Mbit/s or 2,048 Mbit/s
SDSL
the modulation procedure is the same as HDSLuses only one copper-pairsmaller reachable distance compared with HDSL (distance between user and provider)
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen, eMail: aislei@gwdg.de
HDSL and SDSL:
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
6
Fast data-communication on old copper wiresFast data-communication on old copper wires
(A)synchronus (D)igital (S)ubscriber (L)ineADSL, is an improvement of the HDSL technique Very promising technique, good relationship between bandwidth and reachable distance Defined in ANSI Standard (ANSI: T1.413)Uses only one copper-pairCharacterized by the typical asynchronous data transmission rates matches to the typical internet-user behavior, because..
high datarate from provider to user up to 8 Mbit/s (Downstream) a lower datarate of 0,8Mbit/s from user to the provider (Upstream)
Adaptive modulation procedure, which automatically (dynamically) adapts to different line qualities
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen, eMail: aislei@gwdg.de
ADSL-Technique:
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
7
Fast data-communication on old copper wiresFast data-communication on old copper wires
(V)ery-High-Data-Rate (D)igital (S)ubscriber (L)ineAn ADSL-similar TechnologieUses the asynchronous transfer mode (see ADSL)Uses only one copper-pairdepends on the line length, VDSL allows data rates up to 52MBit/sin downstream direction (low distance: up to a few hundret meters)VDSL devices are not available todayVDSL uses frequency ranges up to 30MHz, but possible distance is shorter, compared with ADSL line qualities and patches extremely limit available bandwidthUsable for high-speed inhouse connections
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen, eMail: aislei@gwdg.de
VDSL-Technique:
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
8
xDSL-Data at a glance:xDSL-Data at a glance:
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
xDSL-Type HDSL SDSL ADSL VDSL Bitrate (Upstream) 1,544 Mbit/s
2,048 Mbit/s 1,544 Mbit/s 2,048 Mbit/s
16-768 Kbit/s 1,5-2,3 Mbit/s
Bitrate (Downstream)
1,544 Mbit/s 2,048 Mbit/s
1,544 Mbit/s 2,048 Mbit/s
1,5-8 Mbit/s 13-52 Bit/s
No of pairs 1 (1,544 Mbit/s) 2 (2,048 Mbit/s)
1 1 1
Max. distance 3-5 km 2-3 km 2-5,5 km 0,3-1,5 km Usable bandwidth 240kHz 240kHz bis 1,1 MHz bis 30MHz
9
Criteria for the selection of suitable ADSL devices Criteria for the selection of suitable ADSL devices
High attainable bandwidth Stable ADSL-Modulationmethods
DMT, Discrete MultiToneCAP, Carrierless Amplitude/Phase Modulation
Large bridgeable distance High availability compared with analog modem connections High stability Ability to connect entire networks over ADSL to the university backbone Simple integration into our existing network infrastructure A central ADSL-Management (SNMP) Costs
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
10
Testing the transferrates, measurement methodsTesting the transferrates, measurement methods
ADSL ADSL
SnifferEthernet-
packet generator
DA-30Receiver/packet counter
100 m pair
0,6mm²
isolated Ethernet
Ethernetpacketsfrom 151 ...1514Byte
Ethernet packets with different packet length were transmitted over the ADSL-Line. Thus collisions (CSMA/CD) can be avoided (isolated Ethernet)
The recipient (DA30) counted the incomming ethernet packets per second The measurement was made in UP- and DOWN-Streamdirection The result shows the max. transfer rate in [bits/s]
The ethernet packet size was changed in an range from 64 to 1514 Byte The Interframe gap is set to 20µs (constant)
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
11
DMT is much more stable compared to CAP, because it better adjusts to the transfer characteristic of the copper wireswires. For this reason DMT improves the bandwidths.
DMT and CAP works with „Rate Adaption“ , which can automatically adapts to the different line qualities
DMT uses smaller gradations than CAP (32 KBit/s by DMT) (300 KBit/s by CAP) and can better react to changing line qualities
Modulations Methods DMT and CAPModulations Methods DMT and CAP
Depend on the line-quality (noise) and frequency range; number of bits, which are transmitted by using DMT with one channel, may vary
– POTS-Splitter (analog telephone)– Upstreamband– Downstreamband
DMT partitions the frequency ranges in 4 KHz-steps 32 x 4 khz (for upstream) and 256 x 4 khz (for downstream)
20Khz
PO TS UP-Stre am DOWN-Stre am
40Khz 100Khz 1100khz
20Khz
PO TS
40Khz 100Khz 1100khz
CAPCAP
DMTDMT
f
f
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
The ADSL frequency band of approx. 30... 1100 kHz is separated into three different areas :
12
Bandbreite[Paketgröße]
309730973083307330503030
2670
2157
1547
920
9671021 1042 1051 1057 1063 1061 1067 1069 1069
0
500
1000
1500
2000
2500
3000
3500
0 200 400 600 800 1000 1200 1400 1600
Framesize [byte]
Ban
dw
idth
[kb
ps]
Bandwidth Up kbit/s
Bandwidth Down kbit/s
Transferrates of the 3COM TCH (Total Control Hub)Transferrates of the 3COM TCH (Total Control Hub)Because of the used
modulation method (CAP) , the TCH in our test lab environment has a max. data rate of only 3 MBit/s (downstream).
The ethernet packet size has an influence on the max. data rate (low processor performance)
The relation between Ethernet-overhead and transfered data is worse with smaller packages, however it has no substantial influence on the attainable bandwidth
With small package size, the ADSL-System sends/receives more packages/s, which „stresses“ clearly the processor of the ADSL system
3COM TCH und Viper DSL
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
13
Transferrates of the Ericsson ANxDSLTransferrates of the Ericsson ANxDSL
Bandbreite[Paketgröße]
8214
761
74447109
78598207
8720
666868427209
4354
2633
764764 764 766 767 816 766 770 767 766
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
0 200 400 600 800 1000 1200 1400 1600
Framesize [byte]
Ban
dw
idth
[kb
ps]
The relation between UP/DOWN-Stream is adjusted automatically
The Upstream rate can be increased by manual adjustment of the UP/DOWN relation. In this case, downstream rate will be reduced
Already with small ethernet packets, transfer rates of 7MBit/s are achieved
The upstream rate is constant and independent of the ethernet-packet-size
With DMT as modulation method, a higher data transmission rate is attainable
as experience proves
downstream
upstream
ANxDSL
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
In some cases, the bandwidth can be improved by tuning the UP/Downstreamvalue manually. If it runs stable, we can fix this values afterwards
14
Structure and implementation of Structure and implementation of the Ericsson-ADSL-Systemsthe Ericsson-ADSL-Systems
ANxMS HPOV
ADSL-NT
Ethernet/Fastethernet
ATM-Switch
ANxDSL, 30 Kanäle
CP
Ethernet
Ethernet
Telefon (analog)
Zweidraht Telefonleitung
Management
STM1 / 155MBit
Internet
ATM
SUN Sparc 5
über POTS-Splitter
Ethernet
Behind the ADSL-NT (Network Terminal), an entire network ! (not only one PC) can be connected
A SUN Sparcstation acts as Control Processor (CP) and manages the ADSL-connections
Another SUN Sparcstation contains the management system, operates under HP-Openview
The connection to the backbone network is made by the ANxDSL system via STM1 over an ATM-SWITCH (which can make RFC1483 conforming connections) to the Ethernet
The NT operates as bridge, protocolls other than TCP/IP will be transfered (e.g. IPX/SPX)
For each ADSL connection, a " PVC „-call must be created
In this case, the use of an ethernet switch ist necessary to separate the local ethernet traffic from the adsl network
1. RFC 1483: Multiprotocol Encapsulation over ATM Adaption Layer 5
On the user side an ADSL-NT (called Network Terminal) will be used. The NT has one ATM-Port, one Ethernet port (RJ45), as well as a simple telephone port, separated by a POTS-Splitter
NT
8 Mbit/s 0,8 Mbit/s
A central Rack (ANxDSL) contains up to 30 ADSL-Lines (two lines per slot-card)
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
15
Inplementation in the University-Network GöNETInplementation in the University-Network GöNET
So far 33 buildings were successfully connected to the GöNET over ADSL. Most of it had no link before, or only insufficient connections with dial modems.
The max. bandwidth is good enough for an Internet access today
The institutes feel the Internet access over ADSL-lines as stable and very fast compared with older connection technologies like modems
Each ADSL connection can be done within 10 minutes (..10 Minuten to make the ATM cross-connection in the management system)
The University of Goettingen has its own extended telephone network, which is an ideal prerequisite for the use of a central ADSL system like Ericsson´s ANxDSL
For a connection over ADSL, a leased line without any „switches station“ is necessary
Some institutes were could not connect (for financial reasons), with other media (e.g. LWL, radio lan, laser)
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
Some institutes/student´s hostels are connected over Telekom lines
The data rates with Telekom lines are, because of different line lengths, smaller compared with the GÖNET internal lines, but good enough for basic internet access
16
Connection of Institutes and Students´ hostel (dormitory) to ADSL
Bandwidth reducing factors: Bandbreite [Leitungslänge]
7840
4352
7968
7968
7968
7456
7264
6720
7968
7712
6688
5824
6560 65
92
4736
4320
5536
3872
2304
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
500
800
1700
1900
2000
2000
2000
2600
2700
2750
2900
2900
3200
3500
3500
3600
3650
5100
6200
Leitungslänge [m]
Ba
nd
bre
ite
[kb
it/s
]
DownUp
– diameter– Tapering – Use of line with different
square– Patches– Isolation defects
A linear dependency between line length and bandwidth is not given, because the line qualities are very different
In Göttingen, lines with cross sections of 0.4 and 0.6 mm² are used
Wire, with more than one patches and different diameters
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
In two cases, we had connection problems, because both lines were bundled in one large cable. The reason for this instable connection was crosstalk between both lines.
17
- Interoperability : ADSL-Devices from different manufacturers are not compatible. ADSL from 3COM and Ericsson or Ascend normally don´t work together, 3COM offers a compatible NT unit.
+/- ADSL cannot replace a high(est) speed connection (like ATM, Fastethernet, Gigabit), but ADSL can be an intermediate solution, until faster connections are available
Further extension, Results, PerspectivesFurther extension, Results, Perspectives
+ ADSL is cheaper than other connections like radio lan, laser bridges and mostly sufficient in such environments
+ Because of the positive experiences and the demand of the institutes, the ADSL system in Goettingen was extended in 1999 by further 30 (if necessary 60) channels. If necessary, we will get the next ADSL-rack containing further 30 channels.
+ Today, we have 58 channels, 33 of it are in use. The last 25 channels will be connected in the next few weeks.
+ The bit rates, which the ADSL management displays, can be achieved in normal use. With FTP, the transfer rates over ADSL are usually 5%..10% below the values given by the management (gross values)
- ADSL is not the best solution for institutes, which need very fast connections to the Universitynetwork, because of the different up/downstremrates. Some customers (e.g. in Göttingen -> Geophysics) need to transfer large data to the GWDG-parallel computer IBM SP2.
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen
- Because of crosstalk(NEXT) and other disturbances, ADSL cannot connect a greater number of institutes simultaneous on the same cable bundle
18
More information ...More information ...
http://www.gwdg.de/adsl/vortraege
This and other lectures about ADSL...
For further information...
http://www.gwdg.de/adsl
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen, eMail: aisslei@gwdgde
eMail: aisslei@gwdg.de
Andreas Ißleiber, Gesellschaft für wissenschaftliche Datenverarbeitung Göttingen