Asynchronous Transfer Mode
ATM [Asynchronous Transfer Mode] is an asynchronous cell-switching and multiplexing bus protocol, providing scalable bandwidth to gigabits per second (Gbps). ATM resides in Layer 2 of the OSI protocol stack [Data Link Layer]. The Cell-Based physical layer specification defines the function to transport ATM cells with out using a frame structure; how ever many physical layers do require a frame.
ATM is specified to work over a number of physical layers, including:
1. Category 3 Unshieled Twisted-Pair (UTP) Wire at a data rate of
51.84Mbps [STS-1 rate] over a private UNI network.
The physical layer is defined by EIA568, using 100 ohm UTP
wire and 8-pin modular plugs [ISO 8877]
The encoding is 16-CAP with a symbol rate of 12.96MBaud.
1a. Optional sub rates of 25.92, and 12.96Mbps support longer
cable runs.
The pin out for the Media Interface Connector (MIC) at the User end
follows (the Network End is inverse Rx/Tx):
Pin 1, Transmit+, Pin 2 Transmit-, Pin 7 Receive+, Pin 8 Receive-, all
other pins are unused.
1b. Category 3 Unshieled Twisted-Pair (UTP) Wire at a data rate of
155.52Mbps [STS-3c rate] over 100-meter copper link. The
encoding is 64-CAP with a symbol rate of 25.92MBaud. Optional speeds are
listed in item 1 and 1a. The pinout remains un-changed and is listed
above.
1c. Category 3 Shielded Twisted-Pair (STP) Wire at a data rate of
155.52Mbps [STS-3c rate] over 100-meter copper link. The
encoding is 64-CAP with a symbol rate of 25.92MBaud. Optional speeds are
listed in item 1 and 1a. The pinout remains un-changed and is listed
above.
2. Physical Layer for bit rate of 25.6Mbps over a private UNI
interface. The symbol rate is 32MBaud using 4B5B encoding. Out going data is Formatted,
Scrambled, 4B/5B encoded, Serialized, and then NRZI
Encoded (the reverse occurs at the receiver). Cable impedance may be 100
ohms (UTP), 120 ohms or 150 ohms (STP), and the termination resistors
used are required to match the line impedance. The physical interface
uses the same 8-pin connector and pinout as listed above. The cable is
Category 3 [CAT-3] cable for the 100 ohm, or 150 ohm interface, and CAT-4
for the 120 ohm interface; refer to EIA568. A STP cable and STP-MIC
connector is also defined, the pin out at the user end is:
B, Transmit+, R, Receive+, G, Receive-, O, Transmit- [reverse TX/Rx at
the Network side].
3. Physical layer for a 155.52Mbps optical interface using short
wavelength multimode fiber. The coding is binary NRZ.
4. Physical layer for a 155.52Mbps optical interface over Plastic
Optical Fiber (POF), and Hard
Polymer Clad Fiber (HPCF) cabling. Designed to operate by a Transmission
Convergence (TC) sublayer, SONET/SDH based ATM TC sublayer.
5. Physical layer for a 2.4Gbps; 2488.32Mbps physical layer
specification which is based on the Synchronous Optical Network [SONET] and the Synchronous Digital
Hierarchy [SDH] standards. The fiber networks are
defined to operate between 2km and 80km (depending on the fiber). The
SONET frame is STS-48c, and the SDH frame used is VC-4-16c [both nearly
identical except for overhead bytes]. ATM is mapped into the Synchronous
Payload Envelope [SPE] by scrambling the ATM cell payload, aligning the
SPE into the frame, and then applying the SONET/SDH frame scrambler to
the frame.
5a. Physical layer for a 622.08Mbps based on the Synchronous
Optical Network [SONET] and the Synchronous Digital
Hierarchy [SDH] standards.
6. Physical layer for a 6312kbps over BNC connectors and coax
cable [ITU G.704], per MIL-C-3608. Cable impedance is 75
ohms, for an unbalanced circuit.
7. 1.544Mbps over a DS1 link, using a Bipolar Zero Substitution
[B8ZS]. This is the 24 frame multi-frame Extended Super-frame Fromat (EST)
[ANSI TI.408]
7a. 34386kbps [G.703]. The coding is High Density Bipolar, order
3; HDB3.
8. POS-PHY Level 3 [based interface] at bit rates up to 2.488Gbps
using a 8-bit [622Mbps] or 32-bit [2.4Gbps] bus running up to 104MHz
clock rate.
9. 2048kbps over an E1 physical layer interface [G.704 /
G.703].
9a. 64kbps to 1920kbps in multiples of 64kbps over a DS1 or E1
[fractional] interface.
9b. 1.544Mbps over a DS1 [full] interface. CAT-3 UTP cable,
Bipolar 8 Zero Substitution (B8ZS).
9c. 44.736Mbps over a DS3 interface.
10.: The UTOPIA bus.
Listed on its own page as a sub-topic.
ITU {International Telecommunication Union}; www.itu.int
VITA {VMEbus International Trade Association}
The ATM Forum; Approved and Draft Specs
ATM User-Network Interface Specifications (UNI):
BISDN Inter Carrier Interface (B-ICI): af-bici-0013.003
Mid-Range Physical Layer Specification for Category 3 Unshielded
Twisted-Pair: af-phy-0018.000
Physical Interface Specification for 25.6Mb/s over Twisted Pair
Cable: af-phy-0040.000
155.52Mb/s Physical Layer Specification for Category-3 Unshielded
Twisted Pair: af-phy-0047.000 [extension to af-phy-0018.000]
155.52Mb/s Physical Layer Specification for Short Wavelength
Laser: af-phy-0062.000
ATM Physical Medium Dependent Interface Specification for 155Mb/s over
Twisted Pair Cable: af-phy-0015.000
155Mb/s over Twisted Pair Cable: af-phy-0053 [Addendum to
af-phy-0015.000, added the 120 ohm interface]
155Mb/s Plastic Optical Fiber and Hard Polymer Clad Fiber PMD
Specification: af-phy-0079.001
2.4Gbps Physical Layer Specification: af-phy-0133.000
6312kbps UNI Specification: af-phy-0029.000 [Based on G.704]
622Mbps Physical Layer Specification: af-phy-0046.000
622 and 2488Mbps Cell-Bassed Physical Layer: af-phy-0128.000
E1 Physical Interface Specification: af-phy-0064.000
ATM on Fractional E1/T1: af-phy-0130.00
DS1 Physical Layer Specification: af-phy-0016.000
DS3 Physical Layer Interface Specification: af-phy-0054.000
Utopia Level 3: Multiplexed Status Mode; af-phy-0136.000,
af-phy-0142.001
Utopia Level 4: af-phy-0144.001 [Discussed on the Utopia page.
Physical Layer High Density Glass Optical Fiber Connector Annex:
af-phy-0110.000 [defines optical connectors]
DS1 Physical Layer Specification: af-phy-0016.000 [T1E1 LB93-05 ,
and ITU G.804]
Frame-Based ATM Interface (Level 3): af-phy-0143.000
E3 Public UNI: af-phy-0034.000 [34368kbps]
Wire: Workable Interface Requirements Example: af-phy-0063.000
Physical Layer Control: af-phy-0134.000
---------------
Altera Corp. {IP Cores}
Cortina Systems {ATM to Packet inter-working and ATM switching, OC3 to OC48 data rates}
Integrated Device Technology Inc. 'IDT' {T1/E1 Inverse Multiplexing for ATM}
PMC-Sierra Inc. {Many products for the ATM protocol}
TranSwitch Corp. {Cellbus interfaces}
Zarlink Semiconductor {Fractional T1/E1 DS1 Link}
IC Manufacturers {All other Chip types}
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