Office classification

Office classification
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It has been suggested that this article or section be merged into Public Switched Telephone Network. (Discuss)
AT&T PSTN Office Classification HierarchyOffice classification numbers were classifications assigned to telephone company offices before the breakup of AT&T in 1984. They were applied in the 1950s as part of organizing the system of Direct Distance Dialing (DDD). The numbers indicated an office's hierarchical function in the U.S. public switched telephone network (PSTN).

The following class numbers were used:

Class 1: Regional Center (RC) Originally to be several around the United States, then one in Missouri, but none was ever designated and the class was later used for international gateway exchanges.
Class 2: Sectional Center (SC) More than a dozen. All had plentiful trunks to all other Class 2, forming, in the main, the last possible route of a call when all more direct trunks were in use.
Class 3: Primary Center (PC) Approximately a hundred, serving local in and out traffic, and some interregional traffic. Trunk groups among Class 3 varied in size according to expected traffic; some pairs had no direct trunks between them but used an intermediate Class 3 or Class 2 office.
Class 4: Toll Center (TC) (Only if operators are present; otherwise Toll Point (TP)). These did not handle interregional traffic; only traffic in and out of their local area. Some were owned by the local telco. Late in the 20th Century this class was replaced by Access Tandems (AT) to comply with Bell System Divestiture.
Class 5: End Office (EO) (Local telephone exchange).
Any one center handles traffic from one or more centers lower in the hierarchy, especially in its region, and from higher class centers. For each call the route of first resort went by the most direct trunks to low class offices, and overflowed to higher class offices when those were occupied. Since the breakup of AT&T, these designations have become less firm.

List of device bandwidths

List of device bandwidths
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This is a list of device bandwidths: the channel capacity (or, more informally, bandwidth) of some computer devices employing methods of data transport is listed by bit/s, kilobit/s (kbit/s), megabit/s (Mbit/s), or gigabit/s (Gbit/s) as appropriate and also MB/s or megabytes per second. They are listed in order from lowest bandwidth to highest.

Whether to use bit/s or byte/s (B/s) is a matter of debate. The most commonly cited measurement is bolded. In general, parallel interfaces are quoted in byte/s (B/s), serial in bit/s.

Many of these figures are theoretical maxima, and various real-world considerations will generally keep the actual effective throughput much lower. See Measuring network throughput. The actual throughput achievable on Ethernet networks, for example (especially when heavily loaded), is a subject of hot debate.




Contents [hide]
1 TTY/Teleprinter or Telecommunications device for the deaf
2 Modems
3 ISDN
4 Computer buses
5 Computer buses (storage)
6 Computer buses (external)
7 Wireless device connection
8 Wireless networking
9 Mobile telephone interfaces
10 Wide area network
11 Local area network
12 Memory Interconnect Buses / RAM
13 Notes
14 Decimal vs. Binary Prefixes
15 See also




Note: In telecommunications, 1 kbit/s = 1 000 bit/s, NOT 1 024 bit/s. Thus, all values below use metric prefixes. 1




CONNECTION BITS BYTES
[edit] TTY/Teleprinter or Telecommunications device for the deaf
(note: TTY uses Baudot code, not ASCII. This uses 5 bits per character instead of 8, and one start and 1.5 stop bits.)

TTY (V.18) 45 bit/s 6 cps
TTY (V.18) 50 bit/s 6.71 cps
[edit] Modems
(note: serial, 1 start bit, 8 data bits, 1 stop bit: therefore 10 bits needed to transmit each byte. The exception is 110 baud which uses 2 stop bits or 11 bits per byte.)

Modem 110 baud 110 bit/s 10 B/s
Modem 300 baud (V.21) 300 bit/s 30 B/s
Modem Bell 103 (Bell 103) 300 bit/s 30 B/s
Modem 1200 (V.22) 1.2 kbit/s 120 B/s
Modem Bell 212A (Bell 212A) 1.2 kbit/s 120 B/s
Modem 2400 (V.22bis) 2.4 kbit/s 240 B/s
Modem 9600 (V.32) 9.6 kbit/s 960 B/s
Modem 14.4k (V.32bis) 14.4 kbit/s 1,440 B/s
Modem 19.2k (V.32terbo) 19.2 kbit/s 1,920 B/s
Modem 28.8k (V.34) 28.8 kbit/s 2,880 B/s
Modem 33.6k (V.34plus/V.34bis) 33.6 kbit/s 3,360 B/s
Modem 56k* (V.90) (downstream) 56.0 kbit/s 5.6 kB/s
Modem 56k* (V.90) (upstream) 33.6 kbit/s 3.36 kB/s
Modem 56k* (V.92) (downstream) 56.0 kbit/s 5.6 kB/s
Modem 56k* (V.92) (upstream) 48.0 kbit/s 4.8 kB/s
* See Notes section below for 56k caveats
[edit] ISDN
ISDN Basic rate (BRI) signalling channel (D-channel) 16.0 kbit/s 2 kB/s
Single ISDN channel (B-channel)
-(both Primary and Basic rate) 64.0 kbit/s 8 kB/s
Primary rate ISDN signalling channel (D-channel) 64.0 kbit/s 8 kB/s
[edit] Computer buses
ISA 8-Bit/4.77 MHz 38.18 Mbit/s 4.77 MB/s
ISA 16-Bit/8.33 MHz 133.33 Mbit/s 16.67 MB/s
HP-Precision Bus 23 MB/s
EISA 8-16-32bits/8.33 MHz 320 Mbit/s 32 MB/s
VME64 32-64bits 400 Mbit/s 40 MB/s
NuBus 10MHz 400 Mbit/s 40 MB/s
MCA 16-32bits/10 MHz 660 Mbit/s 66 MB/s
NuBus90 20MHz 800 Mbit/s 80 MB/s
Sbus 32-bit/25 MHz 800 Mbit/s 100 MB/s
PCI 32-bit/33 MHz 1066.66 Mbit/s 133.33 MB/s
HP GSC-1X 142 MB/s
Sbus 64-bit/25 MHz 1600 Mbit/s 200 MB/s
PCI Express (x1 link)† 2500 Mbit/s 250 MB/s
HP GSC-2X 256 MB/s
PCI 64-bit/33 MHz 2133.33 Mbit/s 266.66 MB/s
PCI 32-bit/66 MHz 2133.33 Mbit/s 266.66 MB/s
AGP 1x 2133.33 Mbit/s 266.66 MB/s
AGP 2x 4266.66 Mbit/s 533.33 MB/s
PCI 64-bit/66 MHz 4266.66 Mbit/s 533.33 MB/s
PCI-X DDR 16-bit 4266.66 Mbit/s 533.33 MB/s
PCI Express (x4 link)† 10000 Mbit/s 1000 MB/s
AGP 4x 8533.33 Mbit/s 1066.66 MB/s
PCI-X 133 8533.33 Mbit/s 1066.66 MB/s
PCI-X QDR 16-bit 8533.33 Mbit/s 1066.66 MB/s
InfiniBand single 4X 10.00 Gbit/s 1.25 GB/s
PCI Express (x8 link)† 20 Gbit/s 2 GB/s
AGP 8x 17.066 Gbit/s 2.133 GB/s
PCI-X DDR 17.066 Gbit/s 2.133 GB/s
PCI Express (x16 link)† 40 Gbit/s 4 GB/s
PCI-X QDR 34.133 Gbit/s 4.266 GB/s
HyperTransport (800 MHz, 16-pair) 51.2 Gbit/s 6.4 GB/s
HyperTransport (1 GHz, 16-pair) 64 Gbit/s 8 GB/s
PCI Express 2.0 (x32 link)† 80 Gbit/s 8 GB/s
HyperTransport (2.6 GHz, 32-pair) 166.4 Gbit/s 20.8 GB/s
† Note that PCI Express lanes use an 8B/10B encoding scheme
[edit] Computer buses (storage)
SCSI 1 12.0 Mbit/s 1.5 MB/s
PIO Mode 0 26.4 Mbit/s 3.3MB/s
PIO Mode 1 41.6 Mbit/s 5.2MB/s
PIO Mode 2 66.4 Mbit/s 8.3MB/s
Fast SCSI 2 80 Mbit/s 10 MB/s
PIO Mode 3 88.8 Mbit/s 11.1MB/s
PIO Mode 4 133.3 Mbit/s 16.7MB/s
Fast Wide SCSI 2 160 Mbit/s 20 MB/s
Ultra DMA ATA 33 264 Mbit/s 33 MB/s
Ultra Wide SCSI 40 320 Mbit/s 40 MB/s
Ultra DMA ATA 66 528 Mbit/s 66 MB/s
Ultra-2 SCSI 80 640 Mbit/s 80 MB/s
Serial Storage Architecture SSA 640 Mbit/s 80 MB/s
Ultra DMA ATA 100 800 Mbit/s 100 MB/s
Fibre Channel 1GFC (1.0625 GHz) 850 Mbit/s 106.25 MB/s
Ultra DMA ATA 133 1.064 Gbit/s 133 MB/s
Serial ATA (SATA-150) 1.2 Gbit/s 150 MB/s
Ultra-3 SCSI 160 1.28 Gbit/s 160 MB/s
Fibre Channel 2GFC (2.1250 GHz) 1.7 Gbit/s 212.50 MB/s
Serial ATA (SATA-300) 2.4 Gbit/s 300 MB/s
Serial Attached SCSI 3.0 Gbit/s 300 MB/s
Ultra-320 SCSI 2.56 Gbit/s 320 MB/s
Fibre Channel 4GFC (4.2500 GHz) 3.4 Gbit/s 425.00 MB/s
Serial Attached SCSI 2 6.0 Gbit/s 600 MB/s
Ultra-640 SCSI 5.12 Gbit/s 640 MB/s
Note that SATA and SAS use an 8B/10B encoding scheme.
Note that Fibre Channel 1GFC, 2GFC, 4GFC use an 8B/10B encoding scheme.

Note that Fibre Channel 10GFC uses a 64B/66B encoding scheme, is not compatible with 1GFC, 2GFC and 4GFC, and is used only to interconnect switches.

[edit] Computer buses (external)
Serial RS-232 commonly 9.6 kbit/s 960 B/s
Apple Desktop Bus 125 kbit/s
Serial RS-232 max 230.4 kbit/s 23.0 kB/s
USB Low Speed 1536 kbit/s 192 kB/s
Parallel (Centronics) 8.0 Mbit/s 1.0 MB/s
Serial RS-422 max 10.0 Mbit/s 1.25 MB/s
USB Full Speed 12.0 Mbit/s 1.5 MB/s
FireWire (IEEE 1394) 100 98.304 Mbit/s 12.288 MB/s
FireWire (IEEE 1394) 200 196.608 Mbit/s 24.576 MB/s
FireWire (IEEE 1394) 400 393.216 Mbit/s 49.152 MB/s
USB Hi-Speed 480 Mbit/s 60 MB/s
FireWire (IEEE 1394b) 800 786.432 Mbit/s 98.304 MB/s
FireWire (IEEE 1394b) 1600 1572.864 Mbit/s 196.608 MB/s
Cameralink base 24bit 85MHz 2.04 Gbit/s 261.12 MB/s
External SATA 2.4 Gbit/s 300 MB/s
FireWire (IEEE 1394b) 3200 3.145728 Gbit/s 393.216 MB/s
Note that FireWire (IEEE 1394b) uses an 8B/10B coding scheme.

Note that SATA uses an 8B/10B coding scheme.

[edit] Wireless device connection
IrDA-Control 72 kbit/s 9 kB/s
IrDA-SIR 115.2 kbit/s 14 kB/s
802.15.4 (2.4 GHz) 250 kbit/s 31.25 kB/s
Bluetooth 1.1 1 Mbit/s 125 kB/s
Bluetooth 2 3 Mbit/s 375 kB/s
IrDA-FIR 4 Mbit/s 500 kB/s
[edit] Wireless networking
802.11 legacy 0.125 2 Mbit/s 250 kB/s
RONJA free source optical wireless 10.00 Mbit/s 1.25 MB/s
802.11b DSSS 0.125 11 Mbit/s 1.375 MB/s
802.11b+ non-standard DSSS 0.125 44.0 Mbit/s 5.5 MB/s
802.11a 0.75 54.00 Mbit/s 6.75 MB/s
802.11g DSSS 0.125 54.00 Mbit/s 6.75 MB/s
802.11n 540 Mbit/s 67.5 MB/s
[edit] Mobile telephone interfaces
GSM CSD 2.4 to 14.4 kbit/s 300 to 1800 B/s
HSCSD upstream 14.4 kbit/s 1800 B/s
HSCSD downstream 43.2 kbit/s 5.4 kB/s
GPRS upstream 28.8 kbit/s 3.6 kB/s
GPRS downstream 57.6 kbit/s 7.2 kB/s
EDGE downstream 236.8 kbit/s 29.6 kB/s
UMTS downstream 1920 kbit/s 240 kB/s
HSDPA downstream 1.8 MBit/s to 14.4 Mbit/s 225 kB/s to 1.8 MB/s
1xEV-DO Rev. A downstream 3.1 Mbit/s 396.8 kB/s
1xEV-DO Rev. A upstream 1.8 Mbit/s 230.4 kB/s
[edit] Wide area network
DS0 64 kbit/s 8 kB/s
Satellite Internet upstream 64 kbit/s to 1 Mbit/s 8 kB/s to 128 kB/s
Satellite Internet downstream 128 kbit/s to 16 Mbit/s 16 kB/s to 2 MB/s
Frame Relay 8 kbit/s to 45 Mbit/s 1 kB/s to 5.625 MB/s
G.SHDSL 2.3040 Mbit/s 0.288 MB/s
SDSL 64 kbit/s to 4.608 Mbit/s 8 kB/s to 0.576 MB/s
G.Lite (aka ADSL Lite) upstream 512 kbit/s 64 kB/s
G.Lite (aka ADSL Lite) downstream 1.5 Mbit/s 192 kB/s
ADSL upstream 64 kbit/s to 1024 kbit/s 8 kB/s to 128 kB/s
ADSL downstream 256 kbit/s to 8 Mbit/s 32 kB/s to 1 MB/s
ADSL2 upstream 64 kbit/s to 3.5 Mbit/s 8 kB/s to 448 kB/s
ADSL2 downstream 256 kbit/s to 12 Mbit/s 32 kB/s to 1.5 MB/s
ADSL2Plus upstream 64 kbit/s to 3.5 Mbit/s 8 kB/s to 448 kB/s
ADSL2Plus downstream 256 kbit/s to 24 Mbit/s 32 kB/s to 3.0 MB/s
DOCSIS (Cable Modem) upstream 128 kbit/s to 8 Mbit/s 16 kB/s to 1 MB/s
DOCSIS (Cable Modem) downstream 384 kbit/s to 24 Mbit/s 48 kB/s to 3 MB/s
DS1/T1 1.544 Mbit/s 192.5 kB/s
E1 2.048 Mbit/s 256 kB/s
T2 6.312 Mbit/s 789 KB/s
E2 8.448 Mbit/s 1.056 MB/s
E3 34.368 Mbit/s 4.296 MB/s
DS3/T3 ('45 Meg') 44.736 Mbit/s 5.5925 MB/s
STS-1/EC-1/OC-1/STM-0 51.840 Mbit/s 6.48 MB/s
VDSL (symmetry optional) 12 Mbit/s to 100 Mbit/s 1.5 MB/s to 12.5 MB/s
VDSL2 (symmetry optional) 12 Mbit/s to 250 Mbit/s 1.5 MB/s to 31.25 MB/s
LR-VDSL2 (4 to 5 km [long-]range) (symmetry optional) 1 Mbit/s to 4 Mbit/s 128 kB/s to 512 kB/s
OC-1 51.84 Mbit/s 6.48 MB/s
OC-3/STM-1 155.52 Mbit/s 19.44 MB/s
T4 274.176 Mbit/s 34.272 MB/s
T5 400.352 Mbit/s 50.044 MB/s
OC-9 466.560 Mbit/s 58.32 MB/s
OC-12/STM-4 622.08 Mbit/s 77.76 MB/s
OC-18 933.12 Mbit/s 116.64 MB/s
OC-24 1.244 Gbit/s 155.5 MB/s
OC-36 1.9 Gbit/s 237.5 MB/s
OC-48/STM-16 2.488320 Gbit/s 311.04 MB/s
OC-96 4.976 Gbit/s 622 MB/s
OC-192/STM-64 9.953280 Gbit/s 1.24416 GB/s
10 Gigabit Ethernet WAN PHY 9.953280 Gbit/s 1.24416 GB/s
10 Gigabit Ethernet LAN PHY 10 Gbit/s 1.25 GB/s
OC-256 13.271 Gbit/s 1.65888 GB/s
OC-768/STM-256 39.813120 Gbit/s 4.97664 GB/s
OC-1536/STM-512 79.626 Gbit/s 9.95325 GB/s
OC-3072/STM-1024 159.252 Gbit/s 19.9065 GB/s
[edit] Local area network
LocalTalk 230.4 kbit/s 28.8 kB/s
ARCNET (Standard) 2.5 Mbit/s 0.3125 MB/s
Token Ring (Original) 4.16 Mbit/s 0.52 MB/s
Ethernet (10base-X) 10 Mbit/s 1.25 MB/s
Token Ring (Later) 16 Mbit/s 2.0 MB/s
Fast Ethernet (100base-X) 100 Mbit/s 12.5 MB/s
FDDI 100 Mbit/s 12.5 MB/s
Gigabit Ethernet (1000base-X) 1 Gbit/s 125 MB/s
Myrinet 2000 2 Gbit/s 250 MB/s
Infiniband 1X 2.5 Gbit/s 312 MB/s
10 gigabit Ethernet (10Gbase-X) 10 Gbit/s 1.25 GB/s
Myri 10G 10 Gbit/s 1.25 GB/s
Infiniband 4X 10 Gbit/s 1.25 GB/s
Infiniband 12X 30 Gbit/s 3.75 GB/s
[edit] Memory Interconnect Buses / RAM
SPARC MBus 2560 Mbit/s 320 MB/s
PC66 SDRAM 4264 Mbit/s 533 MB/s
PC100 SDRAM 6400 Mbit/s 800 MB/s
HP Runway bus 125MHz 64-bit 6400 Mbit/s 960 MB/s
PC133 SDRAM 8528 Mbit/s 1066 MB/s
PC1600 DDR-SDRAM (single channel) 12.8 Gbit/s 1.6 GB/s
HP Runway bus 125MHz 64-bit DDR 16 Gbit/s 2 GB/s
PC1600 DDR-SDRAM (dual channel) 25.6 Gbit/s 3.2 GB/s
PC2100 DDR-SDRAM (single channel) 16.8 Gbit/s 2.1 GB/s
PC2100 DDR-SDRAM (dual channel) 33.6 Gbit/s 4.2 GB/s
PC2700 DDR-SDRAM (single channel) 21.6 Gbit/s 2.7 GB/s
PC2700 DDR-SDRAM (dual channel) 43.2 Gbit/s 5.4 GB/s
PC3200 DDR-SDRAM (single channel) 25.6 Gbit/s 3.2 GB/s
PC3200 DDR-SDRAM (dual channel) 51.2 Gbit/s 6.4 GB/s
PC4000 DDR-SDRAM (single channel) 34.3 Gbit/s 4.0 GB/s
PC4000 DDR-SDRAM (dual channel) 68.6 Gbit/s 8.0 GB/s
PC800 RDRAM (single-channel) 12.8 Gbit/s 1.6 GB/s
PC800 RDRAM (dual-channel) 25.6 Gbit/s 3.2 GB/s
PC1066 RDRAM (single-channel) 16.8 Gbit/s 2.1 GB/s
PC1066 RDRAM (dual-channel) 33.6 Gbit/s 4.2 GB/s
PC1200 RDRAM (single-channel) 19.2 Gbit/s 2.4 GB/s
PC1200 RDRAM (dual-channel) 38.4 Gbit/s 4.8 GB/s
PC2-3200 DDR2-SDRAM (single channel) 25.6 Gbit/s 3.2 GB/s
PC2-3200 DDR2-SDRAM (dual channel) 51.2 Gbit/s 6.4 GB/s
PC2-4200 DDR2-SDRAM (single channel) 34.136 Gbit/s 4.267 GB/s
PC2-4200 DDR2-SDRAM (dual channel) 68.272 Gbit/s 8.534 GB/s
PC2-5400 DDR2-SDRAM (single channel) 42.664 Gbit/s 5.333 GB/s
PC2-5400 DDR2-SDRAM (dual channel) 85.328 Gbit/s 10.666 GB/s
PC2-6400 DDR2-SDRAM (single channel) 51.2 Gbit/s 6.4 GB/s
PC2-6400 DDR2-SDRAM (dual channel) 102.4 Gbit/s 12.8 GB/s
PC2-8500 DDR2-SDRAM† (single channel) 68.264 Gbit/s 8.533 GB/s
PC2-8500 DDR2-SDRAM† (dual channel) 164.528 Gbit/s 17.066 GB/s
2005-Feb Prototype DDR3-SDRAM ~68.224 Gbit/s ~8.528 GB/s

† Not part of official standard, modules intended for overclocking enthusiasts

[edit] Notes
56K modem V.90 and V.92 capacity can only be achieved when the upstream (service provider) end of the connection is digital. In addition, certain telecommunications administrations limit the signal strength the modem can transmit onto the telecommunications circuit, which in turn limits the actual maximum data rate to less than the theoretical maximum. In the USA, this limited the possible downstream maximum to 53.3 kbit/s
ISDN A basic rate interface (BRI) provides 2 'B' channels and one 'D' channel. Each B channel provides 64 kbit/s bandwidth and the 'D' channel carries signalling (call setup) information. Primary rate interfaces (PRI) vary depending on whether the region uses E1 or T1 bearers. In E1 regions, the PRI carries 30 B-channels and 1 D-channel; in T1 regions the PRI carries 23 B-channels and 1 D-channel. The D-channel has different bandwidth on the two interfaces.
Actual frame relay connections will vary in throughput from 8 kbit/s to 45 Mbit/s depending on configuration. Most commonly below 2 Mbit/s.
ADSL connections will vary in throughput from 64 kbit/s to several Mbit/s depending on configuration. Most commonly below 2 Mbit/s. Some ADSL & SDSL connections have a higher bandwidth than T1 but their bandwidth is not guaranteed, and will drop when the system gets overloaded where as the T1 type connections are usually guaranteed & have no contention ratios.
DOCSIS 1.0 specifications include technology that was available in the 1995–1996 timeframe, and have become very widely deployed around the world.
DOCSIS 1.1 specifications provide improved operational flexibility, security, and Quality-of-Service (QoS) features that enable real-time services.
DOCSIS 2.0 specifications provide dramatically increased upstream throughput for symmetric services.
DOCSIS 3.0 specifications are currently in development at CableLabs and will include a number of enhancements, most notably, channel bonding and support for IPv6. Channel bonding provides cable operators with a flexible way to increase upstream and downstream throughput to customers, with data rates in the hundreds of megabits and potentially gigabits per second.
Satellite internet may have a high bandwidth but also has a high latency due to the distance between the modem, satellite & hub. One-way satellite connections exist where all the downstream traffic is handled by satellite and the upstream traffic by land-based connections such as 56K modems & ISDN.




[edit] Decimal vs. Binary Prefixes
Bit rates
Decimal prefixes (SI)
Name Symbol Multiple
kilobit per second kbit/s 103
megabit per second Mbit/s 106
gigabit per second Gbit/s 109
terabit per second Tbit/s 1012
Binary prefixes
(IEC 60027-2)
kibibit per second Kibit/s 210
mebibit per second Mibit/s 220
gibibit per second Gibit/s 230
tebibit per second Tibit/s 240
“Metric” (aka decimal, SI, power of 10) prefixes are commonly misused when referring to binary quantities, i.e. computer data file sizes.

“kilo” actually means one thousand, “mega” means one million, “giga” is one billion, and so on.

However, when referring to computer data quantities, people will often say “one kilobyte” or write “1 KB”, but actually mean 1024 bytes, for example.

This misuse started decades ago, essentially due to the fact that computer data quantities are based on the power of 2, yet metric prefixes, based on the power of 10, were used for these quantities. Microsoft is probably the most noteworthy responsible party - their Windows operating systems still misuse the metric prefixes.

In 1999 the IEC introduced a formal prefix standard (IEC 60027) for binary numbers, which became an IEEE standard in 2005 (IEEE-1541), ergo:

1024 bytes is a kibibyte (KiB), 1024 KiB is a mebibyte (MiB), 1024 MiB is a gibibyte (GiB), 1024 GiB is a tebibyte (TiB), etc.

For example, Kilobyte can refer to either 1000 bytes or 1024 bytes in common speech, however the IEEE has recently defined all the kibi-, mebi-, etc. prefixes to mean 1024 and the kilo-, mega-, etc. prefixes to mean 1000, to stay in line with the rest of the metric system and end the current confusion.

Much confusion and miscommunication should end when these standardized binary number prefixes come into common use.

All of the bandwidth values listed in this article are true metric quantities, i.e. a kilobit = 1000 bits, NOT 1024 bits.


[edit] See also
Baud
Bit rate
Binary prefix
Comparison of latency and bandwidth
Measuring data throughput
Interconnection Speeds Compared

Broadband Internet access

Broadband Internet access
From Wikipedia, the free encyclopedia
(Redirected from Broadband internet)
Jump to: navigation, search

A WildBlue Satellite Internet dish.Broadband Internet access, often shortened to "broadband Internet" or just "broadband", is a high data-transmission rate internet connection. DSL and cable modem, both popular consumer broadband technologies, are typically capable of transmitting faster than dial-up modem (56 kilobits per second). The real maximum download speed of a dial-up modem is only about 48 Kilobits/second (depending on phone-line quality and distance from the phone company), and upload speed is even slower (31.2kb/sec for V.90, 44kb/sec for V.92).

It should be noted that "broadband" is a misnomer. Broadband and baseband are two different ways of sending multiple transmissions on a wire. With baseband you send a single signal over the wire, and each transmission gets a turn to go: that is, you send part of transmission A, then B, then C, then start over at A. Baseband can use either a digital or an analog line. Broadband is always analog; with broadband you can send multiple transmissions at once by sending different transmissions on different frequencies.
DSL, cable, and other high-speed Internet services are digital, not analog, and are therefore not broadband, by definition. Rather, marketing for high-speed Internet providers hijacked the term because it sounded impressive. However, for purposes of clarity, this article will continue to refer to high-speed Internet as "broadband".
"Broadband" in this context refers to the larger available bitrate, and is independent of whether the carrier is analog (broadband) or digital (baseband).

Broadband Internet access became a rapidly developing market in many areas in the early 2000s; one study found that broadband Internet usage in the United States grew from 6% in June 2000 to over 30% in 2003.[1]

Modern consumer broadband implementations, up to 30 Mbit/s, are several hundred times faster than those available at the time of the popularization of the Internet (such as ISDN and 56 kbit/s) while costing less than ISDN and sometimes no more than 56 kbit/s, though performance and costs vary widely between countries.

Contents [hide]
1 Overview
2 Technology
2.1 Multilinking Modems
2.2 Dual Analog Lines
2.3 ISDN
2.4 T-1/DS-1
2.5 Rural broadband
2.6 Satellite Internet
2.7 Stratellite
2.8 Remote DSL
2.9 DSL repeater
2.10 Power-line Internet
2.11 Wireless ISP
2.12 iBlast
2.13 WorldSpace
3 Broadband worldwide
4 See also
4.1 Broadband technologies
4.2 Broadband implementations
4.3 Broadband applications
5 External links



[edit] Overview
Broadband transmission rates Connection Transmission Speed
DS-1 (Tier 1) 1.544 Mbit/s
E-1 2.048 Mbit/s
DS-3 (Tier 3) 44.736 Mbit/s
OC-3 155.52 Mbit/s
OC-12 622.08 Mbit/s
OC-48 2.488 Gbit/s
OC-192 9.953 Gbit/s
OC-768 39.813 Gbit/s
OC-1536 79.6 Gbit/s
OC-3072 159.2 Gbit/s
Broadband is often called high-speed Internet, because it usually has a high rate of data transmission. In general, any connection to the customer of 256 kbps (0.250 Mbit/s) or more is considered broadband Internet. The International Telecommunication Union Standardization Sector (ITU-T) recommendation I.113 has defined broadband as a transmission capacity that is faster than primary rate ISDN, at 1.5 to 2 Mbit/s. The FCC definition of broadband is 200 kbit/s (0.2 Mbit/s) in one direction, and advanced broadband is at least 200 kbit/s in both directions. The Organization for Economic Co-operation and Development (OECD) has defined broadband as 256 kbit/s in at least one direction and this bit rate is the most common baseline that is marketed as "broadband" around the world. There is no specific bitrate defined by the industry, however, and "broadband" can mean lower-bitrate transmission methods. Some Internet Service Providers (ISPs) use this to their advantage in marketing lower-bitrate connections as broadband.

In practice, the advertised bandwidth is not always reliably available to the customer; ISPs often allow a greater number of subscribers than their backbone connection can handle, under the assumption that most users will not be using their full connection capacity very frequently. This aggregation strategy works more often than not, so users can typically burst to their full bandwidth most of the time; however, peer-to-peer file sharing systems, often requiring extended durations of high bandwidth, stress these assumptions, and can cause major problems for ISPs who have excessively overbooked their capacity. For more on this topic, see traffic shaping. As takeup for these introductory products increases, telcos are starting to offer higher bit rate services. For existing connections, this most of the time simply involves reconfiguring the existing equipment at each end of the connection.

As the bandwidth delivered to end users increases, the market expects that video on demand services streamed over the Internet will become more popular, though at the present time such services generally require specialized networks. The data rates on most broadband services still do not suffice to provide good quality video, as MPEG-2 video requires about 6 Mbit/s for good results. Adequate video for some purposes becomes possible at lower data rates, with rates of 768 kbit/s and 384 kbit/s used for some video conferencing applications, and rates as low as 100 kbit/s used for videophones using H.264/MPEG-4 AVC. The MPEG-4 format delivers high-quality video at 2 Mbit/s, at the high end of cable modem and ADSL performance.

Increased bandwidth has already made an impact on newsgroups: postings to groups such as alt.binaries.* have grown from JPEG files to entire CD and DVD images. According to NTL, the level of traffic on their network increased from a daily inbound news feed of 150 gigabytes of data per day and 1 terabyte of data out each day in 2001 to 500 gigabytes of data inbound and over 4 terabytes out each day in 2002.[citation needed]


[edit] Technology
The standard broadband technologies in most areas are DSL and cable modems. Newer technologies in use include VDSL and pushing optical fiber connections closer to the subscriber in both telephone and cable plants. Fiber-optic communication, while only recently being used in fiber to the premises and fiber to the curb schemes, has played a crucial role in enabling Broadband Internet access by making transmission of information over larger distances much more cost-effective than copper wire technology. In a few areas not served by cable or ADSL, community organizations have begun to install Wi-Fi networks, and in some cities and towns local governments are installing municipal Wi-Fi networks. As of 2006, high speed mobile internet access has become available at the consumer level in some countries, using the HSDPA and EV-DO technologies. The newest technology being deployed for mobile and stationary broadband access is WiMAX.


[edit] Multilinking Modems
It is possible to roughly double your dial-up capability with multilinking technology. What is required is two modems, two phone lines, two dial-up accounts, and ISP support for multilinking, or special software on your end. This option was popular with some high-end users before DSL and other technologies became available.


[edit] Dual Analog Lines
Diamond and other vendors had created dual phone line modems with bonding capability. The speed of dual line modems is faster than 90 Kilobits/second. To use this modem, the ISP should support line bonding. The Internet and phone charge will be twice the ordinary dial-up charge.


[edit] ISDN
Integrated Service Digital Network (ISDN) is an old digital telephone data service standard.

A primary ISDN line is an ISDN line with 2 data channels (DS0 - 64 Kilobits/second each). Using Internal ISDN modems, it is possible to bond together 2/more separate primary ISDN lines to reach the speed of 256 kilobit/second/ more. The ISDN channel bonding technology was used for video conference application and high-speed data transmission.

ISDN T1 (US standard) line is an ISDN lines with 24 DS0 channels and total speed of 1,544 Kilobits/second. ISDN E1 (European standard) line is an ISDN lines with 32 DS0 channels and total speed of 2,048 Kilobits/second.

Advantage:

Constant data speed at 64 Kilobits/second for each DSO channel.
Two way high speed data transmission, unlike ADSL.
One of the data channels can be used for phone conversation without disturbing the data transmission through the other data channel.
No distance limitations like ADSL.
Disadvantage:

ISDN modems and telephones are more expensive than ordinary dial up modem.
Difficulty in obtaining new ISDN lines.
When a phone call occurs, some of the bandwidth is allocated to the call, reducing the connection speed. When the call ends, the connection increases speed again. ISDN is a relatively low-cost option for rural users with otherwise terrible dial-up access speeds, but it is starting to be phased out and is no longer available in some areas.


[edit] T-1/DS-1
T-1/DS-1 is a type of service which is possible for a rural customer desiring broadband speeds, but the cost can be in the hundreds or thousands of dollars per month depending on the distance from the provider.

These are highly-regulated services traditionally intended for businesses, that are managed through Public Service Commissions (PSCs) in each state, must be fully defined in PSC tariff documents, and have management rules dating back to the early 1980s which still refer to teletypes as potential connection devices. As such, T-1 services have very strict and rigid service requirements which drive up the provider's maintenance costs and may require them to have a technician on standby 24 hours a day to repair the line if it malfunctions. (In comparison, ISDN and DSL are not regulated by the PSCs at all.)

People attempting to establish rural service via a Wireless ISP, ISDN, or T-1 will run into an additional cost issue, where the physical connection (or local loop) is considered separate from the actual Internet service provided from a Point of Presence (POP). In the US the loop alone may cost $1200 per month, and the 1.5 megabit per second business-class Internet service (with a fixed IP address and a subnet) may cost an additional $1000 per month. Attempting to reduce monthly costs by establishing your own non-profit Wi-Fi network and sharing the T-1 connection costs has an additional pitfall: your service provider may want to charge you an additional "ISP reseller's fee" of $800 per month.


[edit] Rural broadband
One of the great challenges of broadband is to provide service to potential customers in areas of low population density, such as to farmers and ranchers. In cities where the population density is high, it is easy for a service provider to recover equipment costs, but each rural customer may require thousands of dollars of equipment to get connected. A similar problem existed a century ago when electrical power was invented. Cities were the first to receive electric lighting, as early as 1880, while in the United States some remote rural areas were still not electrified until the 1940's, and even then only with the help of federally funded programs like the Tennessee Valley Authority (TVA).

Several rural broadband solutions exist, though each has its own pitfalls and limitations. Some choices are better than others, but are dependent on how proactive the local phone company is about upgrading their rural technology.


[edit] Satellite Internet
Main article: Satellite Internet
This employs a satellite in geostationary orbit to relay data from the satellite company to each customer. Satellite Internet is usually among the most expensive ways of gaining broadband Internet access, but in rural areas it is often the only viable option. However costs have been coming down in recent times to the point that it is becoming more competitive with other high-speed options.

Satellite internet also has a high latency problem caused by the signal having to travel 35,000 km (22,000 miles) out into space to the satellite and back to Earth again. The signal delay can be as much as 500 milliseconds to 900 milliseconds, which makes this service unsuitable for applications requiring real-time user input such as certain multiplayer Internet games and first-person shooters played over the connection. Despite this, it is still possible for many games to still be played, but the scope is limited to real-time strategy or turn-based games. The functionality of live interactive access to a distant computer can also be subject to the problems caused by high latency. These problems are more than tolerable for just basic email access and web browsing and in most cases are barely noticeable.

There is no simple way to get around this problem. The delay is primarily due to the speed of light being only 300,000 km/second (186,000 miles per second). Even if all other signaling delays could be eliminated it still takes the electromagnetic wave 233 milliseconds to travel from ground to the satellite and back to the ground, a total of 70,000 km (44,000 miles) to travel from you to the satellite company.

Since the satellite is being used for two-way communications, the total distance increases to 140,000 km (88,000 miles), which takes a radio wave 466 ms to travel. Factoring in normal delays from other network sources gives a typical connection latency of 500-700 ms. This is far worse latency than even most dial-up modem users experience, at typically only 150-200 ms total latency.

Most satellite Internet providers also have a FAP (Fair Access Policy). Perhaps one of the largest cons against satellite Internet, these FAPs usually throttle a user's throughput to dial-up speeds after a certain "invisible wall" is hit (usually around 200MB a day). This FAP usually lasts for 24 hours after the wall is hit, and a user's throughput is restored to whatever tier they paid for. This makes bandwidth-intensive activities nearly impossible to complete in a reasonable amount of time (examples include PtP and newsgroup binary downloading).


[edit] Stratellite
Stratosphere Satellite Stratellite is a brand name for a high-altitude stratospheric airship that would provide a stationary communications platform for various types of wireless signals currently carried by communications towers or satellites.

The advantage:

Low cost compared to transmission towers and satellite.
Easier maintenance and deployment compared to satellite.
Wide coverage area (several thousands square km).
Smaller antenna compared to Satellite.
Can be used for TV broadcasting, mobile phone/GSM, weather prediction, traffic management, emergency/security/defence applications.
Disadvantage:

Frequency allocation problem.
Possible disruption of service (clouds, heavy rain).
Collision with a meteor, high-flying jets.

[edit] Remote DSL
This allows a service provider to set up DSL hardware out in the country in a weatherproof enclosure. However, setup costs can be quite high since the service provider may need to install fiber-optic cable to the remote location. Also, the remote site has the same distance limits as the metropolitan service, and can only serve an island of customers along the trunk line within a radius of about 2 km (7000 ft).

Remote DSL access is becoming a sore point for many rural customers, as the technology has been available for some time now and phone companies keep promoting its availability, but at the same time the phone companies keep dragging their feet and are not doing anything to install the remote services. In the United States, this is particularly a problem with the very large multistate independent local exchange carriers (non-RBOCs) that serve mostly rural areas.


[edit] DSL repeater
This is a very new technology which allows DSL to travel longer distances to remote customers. One version of the repeater is installed at approximately 3 km (10,000 ft) intervals along the trunk line, and strengthens and cleans up the DSL signal so it can travel another 3 km (10,000 ft).


[edit] Power-line Internet
This is a new service still in its infancy that may eventually permit broadband Internet data to travel down standard high-voltage power lines. However, the system has a number of complex issues, the primary one being that power lines are inherently a very noisy environment. Every time a device turns on or off, it introduces a pop or click into the line. Energy-saving devices often introduce noisy harmonics into the line. The system must be designed to deal with these natural signaling disruptions and work around them.

Broadband over power lines (BPL), also known as Power line communication, has developed faster in Europe than in the US due to a historical difference in power system design philosophies. Nearly all large power grids transmit power at high voltages in order to reduce transmission losses, then near the customer use step-down transformers to reduce the voltage. Since BPL signals cannot readily pass through transformers, repeaters must be attached to the transformers. In the US, it is common for a small transformer hung from a utility pole to service a single house. In Europe, it is more common for a somewhat larger transformer to service 10 or 100 houses. For delivering power to customers, this difference in design makes little difference, but it means delivering BPL over the power grid of a typical US city will require an order of magnitude more repeaters than would be required in a comparable European city.

The second major issue is signal strength and operating frequency. The system is expected to use frequencies in the 10 to 30 MHz range, which has been used for decades by licensed amateur radio operators, as well as international shortwave broadcasters and a variety of communications systems (military, aeronautical, etc.). Power lines are unshielded and will act as transmitters for the signals they carry, and have the potential to completely wipe out the usefulness of the 10 to 30 MHz range for shortwave communications purposes.


[edit] Wireless ISP
This typically employs the current low-cost 802.11 Wi-Fi radio systems to link up remote locations over great distances, but can use other higher-power radio communications systems as well.

Traditional 802.11b was licensed for omnidirectional service spanning only 100-150 meters (300-500 ft). By focusing the signal down to a narrow beam with a Yagi antenna it can instead operate reliably over a distance of many miles.

Rural Wireless-ISP installations are typically not commercial in nature and are instead a patchwork of systems built up by hobbyists mounting antennas on radio masts and towers, agricultural storage silos, very tall trees, or whatever other tall objects are available. There are currently a number of companies that provide this service. A wireless internet access provider map for USA is publically available for WISPS.


[edit] iBlast
iBlast is a brand name for high-speed (5 Mbps), one-way digital data transmission technology from Digital TV station to users.

Advantage:

Low cost, high speed data transmission from TV station to users. This technology can be used for transmitting website / files from Internet .
Disadvantage:

One way data transmission and should be combined with other method of data transmission from users to TV station.
Privacy/security.

[edit] WorldSpace
WorldSpace is a digital satellite radio network based in Washington DC. It covers most of Asia and Europe plus all of Africa by satellite. Beside the digital audio, user can receive one way high speed digital data transmission (150 Kilobit/second) from the Satellite.

Advantage:

Low cost (US$ 100) receiver that combine digital radio receiver and data receiver. This technology can be used for transmitting website / files from Internet .
Access from remote places in Asia and Africa.
Disadvantage:

One way data transmission and should be combined with other method of data transmission from users to Worldspace HQ,
Privacy/security.

[edit] Broadband worldwide
Main article: Broadband Internet access worldwide
Broadband subscribers per 100 inhabitants, by technology, December 2005 in the OECD (source)

Rank Country DSL Cable Other Total Total Subscribers
1 Iceland 25.9% 0.1% 0.6% 26.7% 78,017
2 South Korea 13.6% 8.3% 3.4% 25.4% 12,190,711
3 Netherlands 15.7% 9.6% 0.0% 25.3% 4,113,573
4 Denmark 15.3% 7.2% 2.5% 25.0% 1,350,415
5 Switzerland 14.7% 8.0% 0.4% 23.1% 1,725,446
6 Finland 19.5% 2.8% 0.1% 22.5% 1,174,200
7 Norway 17.8% 2.9% 1.2% 21.9% 1,006,766
8 Canada 10.1% 10.8% 0.1% 21.0% 6,706,699
9 Sweden 13.3% 3.4% 3.6% 20.3% 1,830,000
10 Belgium 11.3% 7.0% 0.0% 18.3% 1,902,739
11 Japan 11.3% 2.5% 3.8% 17.6% 22,515,091
12 United States 6.5% 9.0% 1.3% 16.8% 49,391,060
13 United Kingdom 11.5% 4.4% 0.0% 15.9% 9,539,900
14 France 14.3% 0.9% 0.0% 15.2% 9,465,600
15 Luxembourg 13.3% 1.6% 0.0% 14.9% 67,357
16 Austria 8.1% 5.8% 0.2% 14.1% 1,155,000
17 Australia 10.8% 2.6% 0.4% 13.8% 2,785,000
18 Germany 12.6% 0.3% 0.1% 13.0% 10,706,600
19 Italy 11.3% 0.0% 0.6% 11.9% 6,896,696
20 Spain 9.2% 2.5% 0.1% 11.7% 4,994,274
21 Portugal 6.6% 4.9% 0.0% 11.5% 1,212,034
22 New Zealand 7.3% 0.4% 0.4% 8.1% 331,000
23 Ireland 5.0% 0.6% 1.1% 6.7% 270,700
24 Czech Republic 3.0% 1.4% 2.0% 6.4% 650,000
25 Hungary 4.1% 2.1% 0.1% 6.3% 639,505
26 Slovak Republic 2.0% 0.4% 0.2% 2.5% 133,900
27 Poland 1.6% 0.7% 0.1% 2.4% 897,659
28 Mexico 1.5% 0.6% 0.0% 2.2% 2,304,520
29 Turkey 2.1% 0.0% 0.0% 2.1% 1,530,000
30 Greece 1.4% 0.0% 0.0% 1.4% 155,418


[edit] See also

[edit] Broadband technologies
Fiber-optic communication
List of device bandwidths
Plain old telephone service (POTS)
Baseband
Narrowband
Local loop
Back-channel, a low-speed, or less-than-optimal, transmission channel in the opposite direction to the main channel

[edit] Broadband implementations
Digital Subscriber Line (DSL), digital data transmission over the wires used in the local loop of a telephone network
Local Multipoint Distribution Service, broadband wireless access technology that uses microwave signals operating between the 26GHz and 29GHz bands
WiMAX, a standards-based wireless technology that provides high-throughput broadband connections over long distances
Power line communication, wireline technology using the current electricity networks
Satellite Internet access
Cable modem, designed to modulate a data signal over cable television infrastructure
Fiber to the premises, based on fiber-optic cables and associated optical electronics
High-Speed Downlink Packet Access (HSDPA), a new mobile telephony protocol, sometimes referred to as a 3.5G (or "3½G") technology
Evolution-Data Optimized (EVDO), is a wireless radio broadband data standard adopted by many CDMA mobile phone service providers

[edit] Broadband applications
Broadband telephony
Broadband radio
Broadband receiver
Bandwidth cap

[edit] External links
Making User-Centric Broadband in Access a Reality, Alcatel, June 13, 2005, Strategy White Paper
Corporate vs. Community Internet, AlterNet, June 14, 2005, - on the clash between US cities' attempts to expand municipal broadband and corporate attempts to defend their markets
Marshall University Center for Business and Economic Research, comprehensive study of the economics of broadband internet access
Broadband Research in Canada, academic research on broadband usage, Ryerson University
UK Broadband news

CMTS

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CMTS


(Cable Modem Termination System) A computerized device that enables cable modems to send and receive packets over the Internet. It inserts IP packets from the Internet into MPEG frames and transmits them to the cable modems via an RF signal. It does the reverse process coming from the cable modems.

A DOCSIS-compliant CMTS enables customer PCs to dynamically obtain IP addresses by acting as a proxy and forwarding DHCP requests to DHCP servers. A CMTS may provide filtering to protect against theft of service and denial of service attacks or against hackers trying to break into the cable operator's system. It may provide traffic shaping in order to guarantee a specified quality of service (QoS) to selected customers. A CMTS may also provide bridging or routing capabilities.




The Cable Modem System A CMTS performs packet format conversion and DHCP addressing. It may also provide routing, bridging, filtering and traffic shaping. The combiner merges the TV programming feeds with the RF data from the CMTS.

Cable modem

Cable modem
From Wikipedia, the free encyclopedia
Jump to: navigation, search

Motorola SURFboard 5100 cable modem for broadband Internet accessA cable modem is a type of modem that provides access to a data signal sent over the cable television infrastructure. Cable modems are primarily used to deliver broadband Internet access, taking advantage of unused bandwidth on a cable television network. There were 22.5 million cable modem users in the United States during Q1 2005, up from 17.4 million in Q1 2004. They are also commonly found in Australia, Canada and Europe.

OFDM

OFDM
維基百科，自由的百科全書
跳转到： 导航, 搜尋
OFDM正在翻譯。歡迎您積極翻譯與修訂。
目前已翻譯50%，
正交分頻多工（Orthogonal frequency-division multiplexing，OFDM）有時又稱為分離複頻變調技術（discrete multitone modulation，DMT)，是一個基於分頻多工（FDM）的複雜的調變技術。OFDM主要應用在寬頻數字通信領域，常見的包括ADSL，無線區域網，數字廣播，WiMAX技術等，

Asymmetric Digital Subscriber Line

Asymmetric Digital Subscriber Line
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Please wikify (format) this article or section as suggested in the Guide to layout and the Manual of Style.

Remove this template after wikifying. This article has been tagged since October 2006.ADSL standards
ADSL
ANSI T1.413-1998 Issue 2

G.DMT
ITU G.992.1

G.Lite
ITU G.992.2

ADSL2
ITU G.992.3/4
ITU G.992.3/4 Annex J
ITU G.992.3/4 Annex L

ADSL2+
ITU G.992.5
ITU G.992.5 Annex L
ITU G.992.5 Annex M

Asymmetric Digital Subscriber Line (ADSL) is a form of DSL, a data communications technology that enables faster data transmission over copper telephone lines than a conventional modem can provide. It does this by utilizing frequencies that are normally not used by a voice telephone call, in particular, frequencies higher than normal human hearing. This signal will not travel very far over normal telephone cables, so ADSL can only be used over short distances, typically less than 5 km. Once the signal reaches the telephone company's local office, the ADSL signal is stripped off and immediately routed onto a conventional internet network, while any voice-frequency signal is switched into the conventional phone network. This allows a single telephone connection to be used for both ADSL and voice calls at the same time.

Contents [hide]
1 Explanation
2 How ADSL works
2.1 On the wire
2.2 Modulation
3 ADSL standards
4 Installation issues
4.1 Footnotes
5 See also
6 External links



[edit] Explanation
The distinguishing characteristic of ADSL over other forms of DSL is that the volume of data flow is greater in one direction than the other, i.e. it is asymmetric. Providers usually market ADSL as a service for people to connect to the Internet in a relatively passive m