HIGH-SPEED PROTOCOLS IN ACTION Data networks are divided into layers, each performs a function in the transmission of data. The connectors, cables and the general electrical description of the signal (number of wires, frequency spectrum, type of modulation technique, encoding etc..) are part of the lowest layer, called the physical layer (PHY). The description of the physical layer should contain everything needed to create a link with wires and connectors. We will provide a shot description of the most commonly encountered protocols below. Ethernet The computer network standard as produced by the IEEE 802.3 working group since 1983. It has evolved from speed of a few Mb/s to 400Gb/s. The transmission medium ranges from Coax, twisted pairs to optical fiber. Readers are likely familiar with the 1000Base-T designation. The nomenclature for newer designations is shown in the table below. The encoding method scrambles the data to balance its average voltage value, X and R identify the size of
the encoding blocks. The number of lanes indicates how many data pairs (for electrical) per link. So for instance 10Base-T1 is a 10Mb/s DataStream, where the voltage is modulated directly with 1’s and 0’s over a single twisted pair (this is used in automotive and industrial applications). This nomenclature has not been implemented consistently, and short-hand descriptions are frequent. It is important to note that the physical layer will often contain a description of the connector to be used (for example, 8P8C in the table is the official name of what’s usually called an RJ45). At a minimum it will define the necessary electrical performance. A selection of popular and state-of-the-art protocol standards is provided in the table below. Ethernet cables plugged in to Ethernet switches in a server room. Photo by Jon ‘ShakataGaNai’ Davis, Wikimedia Commons
XXXXG BASE –T X 4
Ethernet Nomenclature Descriptions XXXXG : Usable speed is the amount of data per second the link can transmit BASE : Signaling spectrum refers to the frequency range used by the signaling. Baseband means there is no modulation other than the bits turning on or off. Broadband means that multiple frequency channels are individually modulated. Passband means that the signal modulation is confined to a narrow frequency band (the pass band). X , R : Encoding block size The medium designations are: T : Twisted pair wire S : Short wavelength multi-mode optical fiber (850nm) L : Long wavelength single mode optical fiber (1300nm) E (or Z): Long wavelength single mode fiber (1550nm) B : Bi-directional optical optical fiber, using different wavelengths P : Passive optical network C : Copper/Twinax K : Backplane
Ethernet Nomenclature
in Mb/s or Gb/s if followed by a G ( 10 , 100 , 1000 )
Usable Speed
Signaling Spectrum ( BASE , BROAD , PASS ) Medium Designation -T , -S , -L , -E , -Z , -B , -P , -C , -K ... Encoding Method ( X , R ) Number of Lanes ( 1 , 2 , 4 , 10 )
Popular Ethernet Protocol Standards
Name
Standard
Connector
Description
8P8C (FDDI TP-PMD standard, ANSI INCITS 263-1995)
802.3u- 1995 (24, 25)
Category 5 cable using two twisted pairs. Still very popular.
100BASE-TX
PAM-5 coded signaling, at least Category 5 cable, with
802.3ab- 1999 (40)
Category 5e copper cabling with four twisted pairs. Each pair is used in both directions simultaneously. Extremely wide adoption.
1000BASE-T
8P8C (IEC 60603-7)
802.3ap- 2007 (70) 802.3an- 2006 (55)
1000BASE‑KX
1 m over backplane
8P8C (IEC 60603-7- 4 (unscreened) or IEC 60603-7-5 (screened))
Uses Cat 6A twisted-pair wiring, four lanes at 800 MBd each, PAM-16 with "DSQ128" line code
10GBASE-T
802.3ap- 2007 (48&71) 802.3ap- 2007 (49&72)
10GBASE-KX4
1 m over 4 lanes of backplane
10GBASE-KR
1 m over a single lane of backplane
QwikConnect • July 2020
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