Data Rates - or Speeds

Just show me the Tables !!!

(the tables are listed here also - but with descriptions included)

*** also see http://www.zytrax.com/tech/data_rates.htm 

*** this page explains the speeds - for detailed descriptions of the complex T-carrier system - see the T1 and T3 pages

Here the DSx or T-Carrier Table and the STS-STM-OC Table describe the families of data rates, or speeds.  In addition, we list most of the common data rates in a separate table.

There are two main, standardized Telecom families of data rates - and a number of other data rates (for example, Ethernet/Fast-Ethernet/ Giga-Ethernet, etc.).

DSx vs Tx - yes, there is a slight difference between, for example, a DS1 and a T1.  They describe identical data rates - but DSx is at the equipment, and Tx is on the cable.  

The Tx Acronym - no one ever states what the "T" stands for (you can search the web, fruitlessly), but it sometimes is said to mean Terrestrial, and other times is said to mean Transmission.

Plesiochronous Systems (DSx/Tx/Ex) vs Synchronous Systems (STS/STM/OC)

SDH (Synchronous Digital Hierarchy) is a standard technology for synchronous data transmission on optical media. It is the international equivalent of Synchronous Optical Network. Both technologies provide faster and less expensive network interconnection than the traditional PDH (Plesiochronous Digital Hierarchy) systems, such as the T-carrier.

Synchronous means the systems that connect to each other are running on a master clock (Stratum-1 clock, which is nuclear and therefore virtually exactly timed), and the data is timed perfectly.  

Plesiochronous means "almost (but not) synchronous," - this means the systems that connect to each other are running at the same data rate but are on separate clocks.  The clocks, of course, can be off slightly, which means the data is not timed perfectly.  To get around this, "stuff bits" are inserted by the faster of the two systems - the stuff bits are meaningless bits, inserted only for timing correction, and they must be marked as stuff bits so that the receiving end can remove them..

The following tables list the standard data rates for DSx/Tx/Ex systems, and the Synchronous Transport or Optical Carrier systems.  SONET bases it's data rates on the STS/STM/OC system.  

Speed & Data Rate  vs  Bandwidth & Capacity

Data can be any type of information.  But with computers and networks, the fundamental block of Data is the Bit (1 or 0) and the Byte (a group of eight bits).  Bits and Bytes are numeric information.  This numeric info can be encoded at the sending end and decoded (interpreted) at the receiving end to represent any type of info.  For example, alphabetic characters can be encoded/decoded into numbers using ASCII code.  

Speed, or Data Rate, is simply the speed that the data is flowing from one point to another, through some type of physical medium, or pipe.

The pipe or circuit, may be one channel or multiple channels.  For example, a DS0 is one channel at 64 Kbps - whereas a DS1 is 1.544 Mbps, but consists of 24 channels at 64 Kbps.

IMPORTANT - data is bidirectional (flows in both directions) .  The data rate or speed is the value of how fast data flows in one direction.  The aggregate data rate is 2 times that !!  For example, a T1 has data flowing at 1.544 Mbps, in one direction, and it has 1.544 Mbps flowing in the other direction as well.  This is a symmetric circuit since the speeds are the same.  Most circuits are symmetric.  However, there are examples of assymetric, such as ADSL (Asymmetric DSL).

Bandwidth or "capacity," describes how wide the pipe is - which corresponds to the maximum rate that the bits can be sent through pipe or the channels in the pipe. 

How Channels in a Pipe are Separated (TDM) - in telecom, channels are separated by TDM (Time Division Multiplexing).  This is where groups of bits (frames) take turns in entering the pipe for transmission.  Then at the receiving end these groups of bits are separated again.  For example, a DS1 is actually 24 DS0's being sent in alternating groups of bits, using TDM (see the T1 page).

The T-Carrier Standards

If you EVER find the official original T1 standards paper, that defines the basics - please email me.  Originally, ANSI came up with the first T1 standard document. But now there are tons of T-carrier standards documents !!!  A few common ones I have seen mentioned are ANSI T1.403-1998, T1.-107-1995, T1.107a-1990, etc

 If you are wealthy, all the ANSI and T1 Committee standards can be found and bought from https://www.atis.org/atis/docstore/searchform.asp (about $250 each).  Actually, the T1 Committee has been split up into several new groups.  The one that deals with T-carrier stuff the most is the T1X1 group (see http://www.t1.org/t1x1/_x1-prj.htm for a listing of all their documents).

DSx/Tx/Ex/Jx Data Rates

The following speeds include several DS levels (such as DS1C, DS2, and DS4) that you will rarely, if ever encounter.  The DS2 is a building block of the DS3 (7 DS2's = 1 DS3) - you won't see it as an available access speed for a circuit, but it's there.  

DSx/Tx/Ex  -  North America, Europe & ROW, and Japan
Digital Signal  DS 
Level
Data Rate DS0 Multiple U.S. T-carrier Europe & ROW E-carrier Japan J-carrier
DS0 0 64 Kbps 1 - -  
DS1 1 1.544 Mbps 24 T-1 - J-1
-   2.048 Mbps 32 - E-1  
DS1c   3.152 Mbps 48 - -  
DS2 2 6.312 Mbps 96 T-2 - J-2
    7.786 Mbps 120     J-2 (alt)
-   8.448 Mbps 128 - E-2  
    32.064 Mbps 480     J-3
-   34.368 Mbps 512 - E-3  
DS3 3 44.736 Mbps 672 T-3 -  
    97.728 Mbps 1440     J-4
-   139.264 Mbps 2048 - E-4  
DS4/NA   139.264 Mbps 2176 - -  
DS4 4 274.176 Mbps 4032 - -  
DS5 5 400.352 Mbps 5760      
-   565.148 Mbps 4 E4 channels - E-5 J-5

For a T1 if you multiply 24 x DS0 (64,000) you do NOT get 1.544 Mbps (that would be 24 * 64,000 = 1.536 Mbps). The extra bits are lost between 'frames' where a frame consists of one 8 bit sample for each of the 24 channels (remember the DS0 basics). So every 192 bits (24 x 8 = 192) we add a 'frame separator' bit to give 193 bits per frame. The final arithmetic is 193 bits x 8K samples = 1.544 Mbps. Easy really.

If you do the same arithmetic for DS1C, T2 etc. the above will not give the right answer. In short above T1 things get even messier with M-Frames and M-subframes. Its mind numbing stuff and if you really want to know you need ANSI T1.107-1995 and lots of coffee.

The T-carrier system, introduced by the Bell System in the U.S. in the 1960s, was the first successful system that supported digitized voice transmission. The original transmission rate (1.544 Mbps) in the T-1 line is in common use today in Internet service provider (ISP) connections to the Internet. Another level, the T-3 line, providing 44.736 Mbps, is also commonly used by Internet service providers. Another commonly installed service is a fractional T-1, which is the rental of some portion of the 24 channels in a T-1 line, with the other channels going unused.

Digital signal X is based on the ANSI T1.107 guidelines. The ITU-TS guidelines differ somewhat.  The T-carrier system is entirely digital, using pulse code modulation and time-division multiplexing. The system uses four wires and provides duplex capability (two wires for receiving and two for sending at the same time). The T-1 digital stream consists of 24 64-Kbps channels that are multiplexed. (The standardized 64 Kbps channel is based on the bandwidth required for a voice conversation.) The four wires were originally a pair of twisted pair copper wires, but can now also include coaxial cable, optical fiber, digital microwave, and other media. A number of variations on the number and use of channels are possible.

In the T-1 system, voice signals are sampled 8,000 times a second and each sample is digitized into an 8-bit word. With 24 channels being digitized at the same time, a 192-bit frame (24 channels each with an 8-bit word) is thus being transmitted 8,000 times a second. Each frame is separated from the next by a single bit, making a 193-bit block. The 192 bit frame multiplied by 8,000 and the additional 8,000 framing bits make up the T-1's 1.544 Mbps data rate. The signaling bits are the least significant bits in each frame.

 

OC/STS/STM Data Rates

These are standards that describe data rates.  Unfortunately the world did not agree on one standard, so we have two systems in place:   SONET (Synchronous Optical Network) for North America and SDH (Synchronous Digital Hierarchy) for the rest of the world.

North America Terms

Europe and ROW Terms

OC and STS speeds are part of the SONET (Synchronous Optical Network) United States system. Optical Carriers are typically known by their OC-xn number where n is a multiple of the OC-1 rate of 51.84 Mpbs

STM speeds are part of the SDH (Synchronous Digital Hierarchy) European and ROW (Rest Of World) system. 

Conversion 
STM-n = STS-3n = OC-3n

For example:
  STM-1 =  STS-3 = OC-3 = 155.52 Mbps

SDH vs SONET  -  Both systems are standards for synchronous data transmission on an optical media (fiber) - and their speeds are identical.  However, SDH is an international standard, while SONET is a North American standard.  Therefore, in the United States you will rarely hear speeds stated in STS-x or STM-x terms - instead they will be stated in OC-x terms.

North America uses an STS-x format for frames (packets) and Europe an STM-x (Synchronous Transport Module) format. 

*** four OC-3 or STM-1 circuits can be aggregated to form a 622.08 Mbps circuit designated as OC-12 or STM-4.

*** the current state of the art maximum data rate is the OC-192 or STM-64 circuit, which operates at rate of just under 10 Gbit/s.

 

Optical Signal Hierarchy

Hierarchy Data Rate SONET SDH OCx
Level Zero 155.52 STS-3 STM-1 OC-3
Level One 622.08 STS-12 STM-4 OC-12
Level Two 2488.32 Mbps STS-48 STM-16 OC-48
Level Three 9953.28 Mbps STS-192 STM-64 OC-192

 

OC  vs  STS  vs  STM  Data Rates
Optical Carrier Data Rate
(Line Rate)
Overhead Rate Payload-SONET (SPE)
(Data Rate - Overhead)
User Data Rate (Mbps) SONET
STS
(ANSI)
SDH
STM
(CCITT)
OC-1 51.84 Mbps 1.728 Mbps 50.112 Mbps 49.536 STS-1 --
OC-3 155.52 Mbps 5.184 Mbps 150.336 Mbps 148.608 STS-3 STM-1
OC-9 466.56 Mbps   451.044 Mbps 445.824 STS-9 STM-3
OC-12 622.08 Mbps 20.736 Mbps 601.344 Mbps 594.824 STS-12 STM-4
OC-18 933.12 Mbps   902.088 Mbps 891.648 STS-18 STM-6
OC-24 1244.16 Mbps   1202.784 Mbps 1188.864 STS-24 STM-8
OC-36 1866.24 Mbps   1804.176 Mbps 1783.296 STS-36 STM-12
OC-48 2488.32 Mbps 82.944 Mbps 2.4 Gbps 2377.728 STS-48 STM-16
OC-192 9953.28 Mbps 331.776 9.6 Gbps 9510.912 STS-192 STM-64
OC-768 40Gbit/s 1327.104 38.5 Gbps - STS-768 STM-256
OC-3072 160Gbit/s   - - STS-3072 STM-1024

 

SDH uses the following Synchronous Transport Modules (STM) and rates: STM-1 (155 megabits per second), STM-4 (622 Mbps), STM-16 (2.5 gigabits per second), and STM-64 (10 Gbps).

Definitions

STS-1  Synchronous Transport Signal 1: SONET standard for transmission over OC-1 optical fiber at 51.84 Mbps.

STS-n  Synchronous Transport Signal "n" : (where n is an integer) SONET standards for transmission over OC-n optical fiber by multiplexing "n" STS-1 frames, (e.g., STS-3 at 155.52 Mbps STS-12 at 622.08 Mbps and STS-48 at 2.488 Gbps).

STS-nc  Synchronous Transport Signal "n" concatenated: (where n is an integer) SONET standards for transmission over OC-n optical fiber by multiplexing "n" STS-1 frames, (e.g., STS-3 at 155.52 Mbps STS-12 at 622.08 Mbps and STS-48 at 2.488 Gbps but treating the information fields as a single concatenated payload).

STM  Synchronous Transfer Module: STM is a basic building block used for a synchronous multiplexing hierarchy defined by the CCITT/ITU-T. STM-1 operates at a rate of 155.52 Mbps (same as STS-3).

STM-1  Synchronous Transport Module 1: SDH standard for transmission over OC-3 optical fiber at 155.52 Mbps.

STM-n  Synchronous Transport Module "n" : (where n is an integer) SDH standards for transmission over optical fiber (OC-'n x 3) by multiplexing "n" STM-1 frames, (e.g., STM-4 at 622.08 Mbps and STM-16 at 2.488 Gbps).

STM-nc  Synchronous Transport Module "n" concatenated: (where n is an integer) SDH standards for transmission over optical fiber (OC-'n x 3) by multiplexing "n" STM-1 frames, (e.g., STM-4 at 622.08 Mbps and STM-16 at 2.488 Gbps, but treating the information fields as a single concatenated payload).

 

SONET

 SDH

SPE

VC

STS-SPE

Higher Order VC (VC-3/4/4-Nc)

STS-1 frame

STM-0 frame (rarely used)

STS-1-SPE

VC-3

STS-1 payload

C-3

STS-3c frame

STM-1 frame  AU-4

STS-3c-SPE

VC-4

STS-3c payload

C-4

STS-12c/48c/192c frame

STM-4/16/64 frame   AU-4-4c/16c/64c

STS-12c/48c/192c-SPE

VC-4-4c/16c/64c

STS-12c/48c/192c payload

C-4-4c/16c/64c

RFC2615 - Table Comparing SONET and SDH entities

 

SONET SPE's

SDH VC's

STS-3c-SPE

VC-4

STS-12c-SPE

VC-4-4c

STS-48c-SPE

VC-4-16c

STS-192c-SPE

VC-4-64c

RFC2615 - the only currently supported SONET/SDH SPE/VCs 
(SONET SPE's = Synchronous Payload Envelopes, are basically the same thing as SDH VC's = Virtual Containers):

Virtual Tributaries and Virtual Containers

** SONET and SDH Payloads and Envelopes

SONET:   SPE (Synchronous Payload Envelope)      VT (Virtual Tributary) 

SDH:    VC (Virtual Container - ROW)   AU (Administrative Unit)   TU = Tributary Unit (used in RoW)

SONET is designed to support a wide variety of payloads. The SONET node accepts these payloads and multiplexes them into a SONET envelope called an SPE (Synchronous Payload Envelope). These payloads are called virtual tributaries (VTs) in North America and virtual containers (VCs) in SDH. 

SDH/SONET defines a way or packaging capacity into Virtual Containers (VCs) which may be Higher Order Virtual Container (HVC) or Lower Order Virtual Containers (LVC). The term Tributary Unit (TU - used in RoW) or Virtual Tributary (VT - North America) describes a method of mapping PDH (e.g. T1) carriers onto SDH/SONET.

SONET SDH
Name Speed
(Mbps)
Name Speed
(Mbps)
VT-1.5 1.728 VC-11 1.728
VT-2 2.304 VC-12 2.304
VT-3 3.456 - -
VT-6 6.912 VC-2 6.912
STS-1 50.112 VC-3 48.960
STS-3c 150.336 VC-4 150.336

GigE Speeds

The standards for high-speed Ethernet are GbE, or GigE (Gigabit Ethernet at 1 Gbps which equals 1000 Mbps), and 10 GbE (10 Gbps).  GbE can use Cat6 copper cable but preferably fiber, while the 10 Gbps speed requires fiber.  As far as the circuit speed required, GbE (1 Gbps) requires an OC-24, and 10 GbE (10 Gbps) requires an OC-192.  Virtually no SONET network providers offer OC-24 circuits, so to transmit GbE across a fiber link, you would need to purchase either an OC-12 and just accept that you will only get 622 Mbps, or get an OC-48 and accept a huge amount of wasted bandwidth.  Or you could buy non-SONET dark fiber and run your GbE across it (although DF is expensive !!).

Common Data Rates

This table shows the stated data rates for the most important end-user and backbone transmission technologies.

 
Technology Speed Physical Medium Application
GSM mobile telephone service 9.6 to 14.4 Kbps RF in space (wireless) Mobile telephone for business and personal use
High-Speed Circuit-Switched Data service (HSCSD) Up to 56 Kbps RF in space (wireless) Mobile telephone for business and personal use
Regular telephone service (POTS) Up to 56 Kbps twisted pair Home and small business access
Dedicated 56Kbps on frame relay 56 Kbps Various Business e-mail with fairly large file attachments
DS0 64 Kbps All The base signal on a channel in the set of Digital Signal levels
General Packet Radio System (GPRS) 56 to 114 Kbps RF in space (wireless) Mobile telephone for business and personal use
ISDN BRI: 64 Kbps to 128 Kbps
PRI: 23 (T-1) or 30 (E1) assignable 64-Kbps channels plus control channel; up to 1.544 Mbps (T-1) or 2.048 (E1)
BRI: Twisted-pair
PRI: T-1 or E1 line
BRI: Faster home and small business access
PRI: Medium and large enterprise access
IDSL 128 Kbps Twisted-pair Faster home and small business access
AppleTalk 230.4 Kbps Twisted pair Local area network for Apple devices; several networks can be bridged; non-Apple devices can also be connected
Enhanced Data GSM Environment (EDGE) 384 Kbps RF in space (wireless) Mobile telephone for business and personal use
satellite 400 Kbps (DirecPC and others) RF in space (wireless) Faster home and small enterprise access
frame relay 56 Kbps to 1.544 Mbps Twisted-pair or coaxial cable Large company backbone for LANs to ISP
ISP to Internet infrastructure
DS1/T-1 1.544 Mbps Twisted-pair, coaxial cable, or optical fiber Large company to ISP
ISP to Internet infrastructure
Universal Mobile Telecommunications Service (UMTS) Up to 2 Mbps RF in space (wireless) Mobile telephone for business and personal use (available in 2002 or later)
E-carrier 2.048 Mbps Twisted-pair, coaxial cable, or optical fiber 32-channel European equivalent of T-1
T-1C (DS1C) 3.152 Mbps Twisted-pair, coaxial cable, or optical fiber Large company to ISP
ISP to Internet infrastructure
IBM Token Ring/802.5 4 Mbps (also 16 Mbps) Twisted-pair, coaxial cable, or optical fiber Second most commonly-used local area network after Ethernet
DS2/T-2 6.312 Mbps Twisted-pair, coaxial cable, or optical fiber Large company to ISP
ISP to Internet infrastructure
Digital Subscriber Line (DSL) 512 Kbps to 8 Mbps Twisted-pair (used as a digital, broadband medium) Home, small business, and enterprise access using existing copper lines
E-2 8.448 Mbps Twisted-pair, coaxial cable, or optical fiber Carries four multiplexed E-1 signals
cable modem ** 512 Kbps to 52 Mbps
(see "explanation" below)
Coaxial cable (usually uses Ethernet); in some systems, telephone used for upstream requests Home, business, school access
Ethernet 10 Mbps 10BASE-T (twisted-pair); 10BASE-2 or -5 (coaxial cable); 10BASE-F (optical fiber) Most popular business local area network (LAN)
IBM Token Ring/802.5 16 Mbps (also 4 Mbps) Twisted-pair, coaxial cable, or optical fiber Second most commonly-used local area network after Ethernet
E-3 34.368 Mbps Twisted-pair or optical fiber Carries 16 E-l signals
DS3/ T-3 44.736 Mbps Coaxial cable ISP to Internet infrastructure
Smaller links within Internet infrastructure
OC-1 51.84 Mbps Optical fiber ISP to Internet infrastructure
Smaller links within Internet infrastructure
High-Speed Serial Interface (HSSI) Up to 53 Mbps HSSI cable Between router hardware and WAN lines
Short-range (50 feet) interconnection between slower LAN devices and faster WAN lines
Fast Ethernet 100 Mbps 100BASE-T (twisted pair); 100BASE-T (twisted pair); 100BASE-T (optical fiber) Workstations with 10 Mbps Ethernet cards can plug into a Fast Ethernet LAN
Fiber Distributed-Data Interface (FDDI) 100 Mbps Optical fiber Large, wide-range LAN usually in a large company or a larger ISP
T-3D (DS3D) 135 Mbps Optical fiber ISP to Internet infrastructure
Smaller links within Internet infrastructure
E-4 139.264 Mbps Optical fiber Carries 4 E3 channels
Up to 1,920 simultaneous voice conversations
OC-3/SDH 155.52 Mbps Optical fiber Large company backbone
Internet backbone
E-5 565.148 Mbps Optical fiber Carries 4 E4 channels
Up to 7,680 simultaneous voice conversations
OC-12/STM-4 622.08 Mbps Optical fiber Internet backbone
Gigabit Ethernet 1 Gbps Optical fiber (and "copper" up to 100 meters) Workstations/networks with 10/100 Mbps Ethernet plug into Gigabit Ethernet switches
OC-24 1.244 Gbps Optical fiber Internet backbone
SciNet 2.325 Gbps (15 OC-3 lines) Optical fiber Part of the vBNS backbone
OC-48/STM-16 2.488 Gbps Optical fiber Internet backbone
OC-192/STM-64 10 Gbps Optical fiber Backbone
OC-256 13.271 Gbps Optical fiber Backbone

** Cable modem note:  rhe upper limit of 52 Mbps on a cable is to an ISP, not currently to an individual PC. Most of today's PCs are limited to an internal design that can accomodate no more than 10 Mbps (although the PCI bus itself carries data at a faster speed). The 52 Mbps cable channel is subdivided among individual users. Obviously, the faster the channel, the fewer channels an ISP will require and the lower the cost to support an individual user.