Copyright © Philip M. Parker, INSEAD. Terms of Use.
Definition: Jitter |
JitterNoun1. Small rapid variations in a waveform resulting from fluctuations in the voltage supply or mechanical vibrations or other sources. Source: WordNet 1.7.1 Copyright © 2001 by Princeton University. All rights reserved. |
| Domain | Definition |
Computing | Jitter Random variation in the timing of a signal, especially a clock. (1995-01-16). Source: The Free On-line Dictionary of Computing. |
Aerospace | 1. Instability of the signal or trace of a cathode-ray tube.2. Small rapid variations in a waveform due to deliberate or accidental electrical or mechanical disturbances or to changes in the supply voltages, in the characteristic of components, etc. (references) |
Electrical Engineering | Unwanted fluctuations in the shape or timing of pulses in a sequence of pulses. Source: European Union. (references) |
Post & Telecom | In television, a synchronisation fault in a receiver leading to jerky and irregular displacement of the picture. Source: European Union. (references) |
| A perceptible instability of the time base of a reproduced video signal. Source: European Union. (references) | |
Public Administration | A short-term variation of the pulse spacing of an otherwise regular pulse train. (Gloss. of Comm. , EM. Smith); In telephony, the measurement, in degrees out of phase that an analog signal deviates from the referenced phase of the main data-carrying signal; often caused by alternating-current components in a telecommunications network(1). Source: European Union. (references) |
Source: compiled by the editor from various references; see credits. | |
(From Wikipedia, the free Encyclopedia)
In telecommunication, jitter is an abrupt and unwanted variation of one or more signal characteristics, such as the interval between successive pulses, the amplitude of successive cycles, or the frequency or phase of successive cycles.
Jitter may be specified in qualitative terms (e.g. amplitude, phase, pulse width or pulse position), or quantitative terms (e.g. mean, RMS, or peak-to-peak displacement).
The low-frequency cutoff for jitter is usually specified at 1 Hz.
For clock jitter, there are two main parameters: period jitter and cycle to cycle jitter
Period jitter consists of peak to peak period jitter and RMS period jitter. The peak to peak period jitter is the difference between the maximum and minimum period of the clock signal. The RMS period jitter is the standard deviation of the peak to peak period jitter.
Cycle to cycle jitter is the variation from one period to the next adjacent period of the signal. In order to determine the variation between adjacent periods, all consecutive periods need to be measured. The peak to peak period jitter is the worst case of cycle to cycle jitter.
See also:
Source: Federal Standard 1037C and MIL-STD-188
- drift
- wander
- runt pulse
- glitch
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Jitter."
(From Wikipedia, the free Encyclopedia)
In the fields of telecommunications and computer networking, the traffic engineering term Quality of Service (QoS) can mean two related but distinct things.In circuit-switched networks it refers to the probability of being able to initiate a call to another party. In packet-switched networks it refers to the probability of the network meeting a given traffic contract, or in many cases is used informally to refer the probability of a packet passing between two points in the network.
Problems
Back when the Internet was created, nobody saw the need or the feasability of QoS applications, so the whole thing runs on a "best effort" system. There were 4 "type of service" bits and three "precedence" bits provided in each message, but they were largely unused. There are many nasty things that can happen to packets as they wing their way from place to place, and they result in the following problems, as seen from the point of view of the sender and receiver:
- dropped packets - the routers might fail to deliver (drop) some packets if they arrive when their buffers are already full. All of the packets might be dropped, or none of them, depending on the state of the network, and there's no way to tell which in advance. The receiving application must ask for this information to be retransmitted, and this will often cause a severe hiccup in transmission.
- delay - it might take a long time for your packet to reach it's destination, because it gets held up in long queues, or takes a more indirect route to avoid congestion. Alternatively, it might be very fast, there is no way to predict which in advance.
- out-of-order delivery - the Internet often delivers packets in a different order to the order that they were sent, because they get sent on different routes, which requires special protocols to avoid having your website displayed upside down, or with the introduction right at the bottom, or similar errors.
- error - sometimes packets are misdirected, or mixed up together, or corrupted, while en route. The receiver has to detect this and, just as if the packet was dropped, ask the sender to repeat itself.
Applications requiring QoS
A traffic contract (SLA, Service Level Agreement) specifies guarantees for the ability of a network/protocol to give guaranteed performance/throughput/latency bounds based on mutually agreed measures, usually by prioritising traffic. A defined Quality of Service may be required for certain types of network traffic, for example:
These types of service are called inelastic, meaning that they require a certain level of bandwidth to function - if they get more than that they can't use it, and if they get less, then they can't function at all. By contrast, elastic applications can take advantage of however much or little bandwidth is available.
- streaming multimedia may require guaranteed throughput
- IP telephony may require strict limits on jitter and delay
- a safety-critical application, such as remote surgery may require a guaranteed level of availability (this is also called hard QoS.
Obtaining QoS
There are essentially two ways to provide QoS garantees. The first is simply to provide lots of resources, enough to meet the expected peak demand with a substantial safety margin. This is nice and simple, but some people believe it to be expensive in practice, and can't cope if the peak demand increases faster than predicted: deploying the extra resources takes time.
The second one is to require people to make reservations, and only accept the reservations if the routers are able to serve them reliably. Naturally, you can then charge people money for making reservations! There are two popular variations on this:
DiffServ are typically used with:
- IntServ
- DiffServ
Network equipment, that supports DiffServ and perhaps IntServ, are called multilayer network equipment. A switch that supports DiffServ and perhaps IntServ is called a multilayer switch.
- weighted round robin, WRR.
- RED, WRED - Lessens the possibility of port queue buffer tail-dropss and this lowers the likelihood of TCP global synchronization.
- Traffic shaping
- A number of port queue bufferss.
- VLAN IEEE 802.1p and IEEE 802.1D.
However, the market has not yet favoured QoS services. Some people believe that this is because a "dumb" network that offers sufficient bandwidth for most applications, most of the time, is already economically stable, with little incentive to deploy non-standard stateful QoS-based applications.
Internet peering arrangements are already complex, and there appears to be no enthusiasm among providers for supporting QoS across peering connections, or agreement about what policies should be supported in order to do so.
QoS skeptics further point out that if you are dropping many packets on elastic low-QoS connections, you are already dangerously close to the point of congestion collapse on your inelastic high-QoS applications, without any way of further dropping traffic without violating traffic contracts.
to do: mention Paris Metro pricing as a minimal QoS policy
QoS problems with some technologies
The following proporties may only be used on end ports, but not on server, backbone or other ports, that mediates many concurrent flows.
IEEE 802.3x "flow"-control are not a real flow control, but instead a queue-control. An example of a IEEE 802.3x problem are "head of Line"-blocking. Many of todays switches have IEEE 802.3x on as default - even on uplink/backbone ports.
- half duplex - link collisions make delay variations (jitter), because the packets are delayed with each collision by the backoff-time.
- Port queue buffer IEEE 802.3x "flow"-control.
Quote from: Network World, 09/13/99, 'Flow control feedback': "...Hewlett-Packard points out that quality of service is a better way to handle potential congestion, and Cabletron and Nortel note that QoS features can't operate properly if a switch sends [IEEE 802.3x] pause frames...."
This quote suggests that QoS and IEEE 802.3x are incompatible.
An ethernet connection with 100 Mbit/s full duplex instead of 100 Mbit/s half duplex increases the effective speed from ca. 60-100 Mbit/s half duplex to 200 Mbit/s (100 Mbit/s transmit + 100 Mbit/s receive).
See also:
- ATM
- Internet
- Network congestion avoidance
- PSTN
- Traffic Shaping
- 802.11e: Quality of Service enhancements for WiFi standard 802.11b
External addresses
- IEEE 802.1 P,Q - QoS on the MAC level, 24.4.1999, Niclas Ek
- IEEE 802.1 LAN/MAN Bridging & Management
- "Good old days" IP QoS: Type of Service in the Internet Protocol Suite
- On the Effects of the IEEE 802.3x Flow Control in Full-Duplex Ethernet LANs, Oliver Feuser, Andre Wenzel, University of Bonn
- sslug.dk: Hyggemøde tirsdag den 11. juni 2002: Båndbreddebegrænsning
- sslug.dk: Hyggemøde tirsdag den 11. juni 2002: Båndbreddebegrænsning. Eksempler
- Linux Advanced Routing & Traffic Control
- Linux Advanced Routing & Traffic Control, HowTo
- lartc.org: The Wonder Shaper
- WRR and WIPL
- Packeteer PacketShaper 2500: Traffic Control on Autopilot, September 4, 2000, By David Newman
- Packeteer PacketShaper
Source: adapted by the editor from Wikipedia, the free encyclopedia under a copyleft GNU Free Documentation License (GFDL) from the article "Quality of Service."
Crosswords: Jitter |
| Specialty definitions using "jitter": all-frequency jitter ♦ maximum tolerable input jitter ♦ phase hit, phase jump ♦ systematic jitter. (references) |
| Domain | Usage | |
Movie/TV Titles | Jitter Bughouse (1948) | |
Source: compiled by the editor from various references; see credits. | ||
| Domain | Title |
Books | |
Theater & Movies |
|
Source: compiled by the editor from various references; see credits. | |
| "Jitter" is generally used as a noun (singular) -- approximately 90.00% of the time. "Jitter" is used about 10 times out of a sample of 100 million words spoken or written in English. Its rank is based on over 700,000 words used in the English language. Some parts-of-speech are not covered due to the samples used by the British National Corpus. (note: percents less than one-hundredth of one percent have been omitted) |
| Parts of Speech | Percent | Usage per 100 Million Words | Rank in English |
| Noun (singular) | 90% | 9 | 117,287 |
| Lexical Verb (infinitive) | 10% | 1 | 339,140 |
| Total | 100.00% | 10 | N/A |
Source: compiled by the editor from several corpora; see credits.
Expressions using "jitter": fortuitous distortion jitter ♦ fortuitous jitter ♦ maximum tolerable input jitter ♦ phase jitter ♦ pulse jitter ♦ systematic jitter. Additional references. | |
| Hyphenated Usage | |
Beginning with "jitter": jitter-bug. | |
| Source: compiled by the editor from various references; see credits. | |
| The following statistics estimate the number of searches per day across the major English-language search engines as identified by various trade publications. Hyperlinks lead to commercial use of the expression at Amazon.com. |
| Expression | Frequency per Day |
jitter | 56 |
jitter bug | 9 |
jitter measurement | 6 |
anti jitter | 4 |
bug jitter june | 4 |
monitor jitter | 4 |
jitter pcr | 4 |
bug dance jitter | 3 |
clock diy jitter low | 3 |
definition jitter | 3 |
clock edd jitter virtual wfq | 2 |
timing jitter | 2 |
adaptive buffer jitter | 2 |
audio cd cd drive hawk jitter low player | 2 |
clock jitter low | 2 |
clock jitter | 2 |
jitter noise phase | 2 |
| Source: compiled by the editor from various references; see credits. | |
| Language | Translations for "jitter"; alternative meanings/domain in parentheses. | |
Albanian | jam nervoz, jam i shqetësuar. (various references) | |
Arabic | غضب (aggravate, anger, annoy, be angry, be irritated, chafe, crab, dander, displease, embitter, enrage, exasperate, exasperation, fire, flounce, fret, fume, gall, get on his nerves, get smb.'s goat, go mad, grumpiness, harrow, heat, incense, indignation, inflame, infuriate, irascibility, ire, irritate, irritation, itch, lose one's shirt, mad, madden, miff, nettle, offend, outcry, outrage, peeve, pet, pique, pout, provoke, rage, resentment, rile, rough, ruffle, seethe, soreness, sour, spite, spleen, twit, vex), إنرفز (be irritated, get on his nerves, get the needle, irritate). (various references) | |
Bulgarian | треперя (cower, dither, judder, niddle-noddle, palpitate, pulsate, quake, quaver, quiver, shake, shiver, thrill, tremble, tremor, vibrate, waver), нервнича. (various references) | |
Chinese | 发抖 (jitters, Shivered, shivering, shudder, Shuddered, shuddering). (various references) | |
Czech | nervóznì pobíhat. (various references) | |
Danish | jitter (pulse jitter), vibreren (bouncing, jumping, pulse jitter), impulsinstabilitet (pulse jitter), dirren (bouncing, jumping, pulse jitter). (various references) | |
Dutch | synchronisatiestoring (bouncing, jumping), springen v.h.beeld (bouncing, jumping), pulsdribbel (pulse jitter), onregelmatige vervorming (fortuitous distortion, fortuitous distortion jitter, fortuitous jitter, pulse jitter), instabiliteit (instability), impulspositieruis (phase jitter, phase wander), impulsonstabiliteit (pulse jitter), dribbel (pulse jitter), danseffekt (bouncing, jumping), bibber-effekt (phase jitter, phase wander), beeldsprong (bouncing, jumping), beeldbibber (bouncing, jumping). (various references) | |
Farsi | عصبانی شدن(ز.ع.-امر.), عصبانی بودن , بی ثباتی (Inconsistency, Instability, Variation), باعصبانیت سخن گفتن , باعصبانیت رفتارکردن . (various references) | |
Finnish | vapina (pulse jitter, unsteadiness), värinä (fibrillation, flicker, quiver, shiver, trembling, tremor, vibration). (various references) | |
French | vacillement d'une impulsion (pulse jitter), scintillement, sautillement, instabilité d'image, instabilité de phase, gigue (jig), ficher, être nerveux. (various references) | |
German | Jitter (pulse jitter), zittern (dodder, flicker, oscillate, oscillation, palpitate, palpitation, quail, quake, quaking, quaver, quavering, quiver, quivering, shake, shakiness, shaking, shiver, shivering, shudder, sweat, throb, to jitter, to shake (shook, tremble, trembling, tremor, trepidation, vibrate, waver, wobble), Schwankung (fluctuation, oscillation, rocking, shaking, swaying, vacillation, variability, variation), Fluktuieren (fluctuate), flattern (be chucked, be flung, be in a flap, dance, flacker, flap, flat its wings, flicker, flutter, fly, quiver, shimmy, stream, thrashing, to flacker, to flutter, to jitter, to shimmy, to stream, toss, wave, waver, wobble), Bildsprung (bouncing, jumping), Bildinstabilität (bouncing, jumping). (various references) | |
Greek | μαρμαρυγή (gleam, shimmer), αυξομείωση (fading, fading of signals, fluctuation, pulse jitter), τρέμουλο (quaver), τρεμούλιασμα (quaver, shivering, trembling, tremor, tremulousness, trill), τρομώδης μεταβολή (pulse jitter), διακύμανση (fluctuation, pulsation, range, variance). (various references) | |
Hebrew | ל"תעצבן (be irritated, get irritated, get the needle). (various references) | |
Hungarian | vizsgaláz, szurkolás, citerázás. (various references) | |
Italian | tremolio d'immagine (bouncing, jumping), scintillamento (sparking), instabilit di fase, fluttuazione degli impulsi (pulse jitter). (various references) | |
Japanese Kanji | ジカルボン酸 (dicarboxylic acid, dicyanogen, diphenyl, diphtheria, distemper, distoma, dysprosium, dystrophy, feminine form of gigolo, gigolette, gigolo, gigue, Givenchy, Gypsy, gypsy look, Holy War, Japanese Industrial Standard, Jekyll and Hyde, jib, jig, jigsaw puzzle, JIS, JIS mark, jitterbug, syphilis, zig-zag, zigzag demonstration, ZIP code, Zipangu, Zipper, Zippo). (various references) | |
Japanese Katakana | ジッター . (various references) | |
Korean | 불안감 (jitters). (various references) | |
Pig Latin | itterjay.(various references) | |
Portuguese | instabilidade de um impulso (pulse jitter), instabilidade de imagem (bouncing, jumping), instabilidade de fase, flutuação (float, floatage, floatation, flotation, waft, wavering). (various references) | |
Russian | нервничать (feel nervous, get the needle, have the needle), дрожать (chatter, dither, dodder, flutter, jar, palpitate, quake, shake, shiver, shivered, thrill, tingle, tremble). (various references) | |
Serbo-Croatian | nervozno govoriti, biti nervozan. (various references) | |
Spanish | jitter (bouncing, jumping), vacilación de un impulso (pulse jitter), temblor (dither, quake, quaver, quiver, quivering, shake, shakiness, shiver, temblor, tremble, trembling, tremor), inestabilidad de la imagen (bouncing, jumping), inestabilidad de fase, inestabilidad (fluidity, instability, shakiness, unsteadiness), fluctuación (fluctuation, oscillation), estar nervioso (twitter). (various references) | |
Swedish | vara nervös. (various references) | |
Thai | กระวนกระวาย (fidget, gnaw, nervous), ความกระวนกระวายใจ. (various references) | |
Turkish | sinirlenmek (be riled at, be steamed up, become angry, blow one's stack, bridle up, bristle up, cut up rough, flame up, flap, flare, flare out, get angry, get hot, get the willies, go off at half-cock, grow hot, lose one's temper, worry), sinirden titremek. (various references) | |
Ukrainian | нервувати (chafe, raise a dust, unnerve). (various references) | |
| Source: compiled by the editor from various translation references. | ||
Derivations | |
Words beginning with "jitter": jitterbug, jitterbugged, jitterbugging, jitterbugs, jittered, jitterier, jitteriest, jitteriness, jitterinesses, jittering, jitters, jittery. (additional references) | |
| |
"Jitter" is suggested in spellcheckers for the following: gitter, Gittler, jeeter, jeter, jetta, jetter, Jictar, jitar, jite, jitt, jittar, jitti, joiter, juter, jutter. (additional references) | |
| Source: compiled by the editor, based on several corpora (additional references). | |
Scrabble® Enable2K-Verified Anagrams | |
Direct Anagrams: trijet. | |
| Words within the letters "e-i-j-r-t-t" | |
-1 letter: titer, titre, trite. | |
-2 letters: rite, tier, tire, tret. | |
-3 letters: ire, jet, rei, ret, tet, tie. | |
-4 letters: er, et, it, re, ti. | |
| Words containing the letters "e-i-j-r-t-t" | |
+1 letter: jettier, jitters, jittery, trijets. | |
+2 letters: jittered. | |
+3 letters: interject, introject, jitterbug, jitterier, jittering. | |
+4 letters: interjects, introjects, jitterbugs, jitteriest, rijsttafel, trajecting, trajection. | |
+5 letters: interjected, interjector, introjected, jitteriness, rijsttafels, trajections. | |
| Source: compiled by the editor from various references; see credits. SCRABBLE® is a registered trademark. All intellectual property rights in and to the game are owned in the U.S.A and Canada by Hasbro Inc., and throughout the rest of the world by J.W. Spear & Sons Limited of Maidenhead, Berkshire, England, a subsidiary of Mattel Inc. Mattel and Spear are not affiliated with Hasbro. | |
| 1. Definition 2. Crosswords 3. Usage: Modern 4. Usage: Commercial | 5. Usage Frequency 6. Expressions 7. Expressions: Internet 8. Translations: Modern | 9. Derivations 10. Anagrams 11. Bibliography |
Copyright © Philip M. Parker, INSEAD. Terms of Use.
