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In [[telecommunication]]s, '''8B/10B''' is a [[line code]] that maps [[8-bit]] symbols to [[10-bit]] symbols to achieve [[Direct current|DC]] balance and bounded disparity, and yet provide enough state changes to allow reasonable clock recovery. This means that there are just as many "1"s as "0"s in a string of two symbols, and that there are not too many "1"s or "0"s in a row. This is an important attribute in a signal that needs to be sent at high rates because it helps reduce "[[intersymbol interference]]". The code was described in 1983 by Al Widmer and Peter Franaszek in the [[IBM]] Journal of Research and Development. IBM was issued a patent for the scheme the following year.
'''Blocks''' are one of the technological means by which bans are enforced, and are also used to [[Wikipedia:dealing with vandalism|deal with vandalism]], bots, and inappropriate usernames.
As the scheme name suggests, 8 [[bit]]s of data are transmitted as a 10-bit entity called a ''Symbol'', or ''Character''. The low 5 bits of data are encoded into a 6-bit group and the top 3 bits are encoded into a 4-bit group. These code groups are concatenated together to form the 10-bit Symbol that is transmitted on the wire. The ''Data Symbols'' are often referred to as Dxx.y where xx ranges from 0-31 and y from 0-7. Standards using the 8B/10B encoding also define ''Special Symbols'' (or ''Control Characters'') that can be sent in place of a ''Data Symbol''. They are often used to indicate end-of-frame, link idle, skip and similar link-level conditions. They are referred to as Kxx.y and have different encodings from any of the Dxx.y symbols. Because 8B/10B encoding uses 10-bit symbols to encode 8-bit words, each of the 256 possible 8-bit words can be encoded in two different ways, one the bit-wise inverse of the other. Using these alternative encodings, the scheme is able to affect long-term DC-balance in the serial data stream, allowing links to be capacitively coupled.
There are three types of blocks:
* user accounts
* anonymous IPs
* IP ranges.
The encoding is normally done entirely in hardware based on lookup tables. Upper levels of the software stack should be unaware that this encoding is being used.
[[Wikipedia:Administrators|Sysops]] have the power to block any of these for any period of time, but such blocks should follow our blocking policy.
Among the areas in which 8B/10B encoding finds application are [[Fibre Channel]], [[Gigabit Ethernet]], [[InfiniBand]], [[XAUI]], and audio storage devices such as the [[Digital Audio Tape]] and [[Digital Compact Cassette]] (DCC). The related [[Eight-to-Fourteen Modulation]] is used in the [[Compact Disc]] standard. The encoding scheme used in [[10 Gigabit Ethernet]]'s 10GBASE-R [[Physical Media Dependent]] (PMD) interfaces, 64B/66B, while similarly created with consideration of DC balance, maximum run length, transition density, electromagnetic emissions, and the like, is considerably different in design.
Since September 2003 it has been possible for sysops to block usernames. This may be used to enforce bans declared by Jimbo or the arbitration committee, or to deal with cases of vandalism.
==External links==
== When blocks may be used ==
*[http://domino.research.ibm.com/tchjr/journalindex.nsf/0/b4e28be4a69a153585256bfa0067f59a?OpenDocument Original paper by Franaszek and Widmer].
*[http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&p=1&u=/netahtml/search-bool.html&r=1&f=G&l=50&co1=AND&d=ptxt&s1=4486739.WKU.&OS=PN/4486739&RS=PN/4486739 US Patent 4,486,739], the relevant document at the US Patent and Trademark Office's site.
[[Category:Computer and telecommunication standards]]
The situations when sysops are permitted to block users are given below. Blocks should not be used in other cases. In particular, blocks are not meant to be used against unpopular opinions, or one-off vandalism incidents.
[[Category:Line codes]]
[[fr:Encodage 8b/10b]]
=== Bots ===
As discussed in [[Wikipedia:bots]], bots must have prior approval on [[wikipedia talk:bots]], and must follow certain minimum standards. In any case, sysops may block any bots that appear to be "out of control" on sight.
=== Vandalism ===
:''See [[Wikipedia:Dealing with vandalism]] for detailed policy''
Sysops may, at their judgement, block IP addresses that vandalise Wikipedia. For dynamic IPs, such blocks should last 24 hours. For static IPs, such blocks should initially last 24 hours, but repeat violators may be blocked for a maximum of one month.
Sysops may also permanently block user accounts that do essentially nothing but vandalism. However, user accounts that perform a mixture of valid edits and vandalism should not be blocked in this manner. Instead, consider taking a [[wikipedia:quickpolls|quickpoll]] to decide whether accounts that go on a "vandalism spree" should be given an emergency temporary ban.
Reincarnations of blocked vandals will be reblocked if they continue vandalising, or if they edit in a way which suggests they are likely to continue vandalising - eg "YOU CAN'T BLOCK ME!!11!!", etc, etc.
Blocks should not be used against isolated incidents of vandalism.
=== Usernames ===
According to our [[Wikipedia:username|username policy]], inflammatory, deliberately confusing, and other inappropriate usernames are not allowed.
Co-operative contributors should normally just be made aware of our policy via a post on their talk page. Where a change must be forced, there are two ways this happens. If it is a mild or borderline case, or if the user is not currently editing Wikipedia, we create a sub page of [[Wikipedia:Requests for comment]] for a discussion on the user's name, to determine if there is a general consensus. Normally such discussions are left for at least a week.
In extreme cases (for instance, a username consisting of a highly offensive statement or a string of profanities), sysops make on-the-spot judgements that a username is against our username policy. They base this decision in part on discussions on the user's talk page, and the requests for comments page. They also base it on any relevant precedents. This action is controversial: see [[Wikipedia talk:Blocking policy#Usernames]].
Sysops can force a namechange by blocking the username (with an expiry time of infinite). The blocking sysop should include [[MediaWiki:UsernameBlock]] in the block message (by writing <nowiki>{{msg:UsernameBlock}}</nowiki> in the "reason" field). If a user or user talk page has already been created, the blocking sysop should add [[MediaWiki:BlockedDueToUsername]] <nowiki>{{msg:BlockedDueToUsername}}</nowiki> to it/them, but should not create a user or user talk page where one does not exist.
Care should be taken to unblock the user's IP address. To unblock the IP but not the username, wait until the user next tries to edit a page, and something like ''#1234 was blocked because they share an IP with OldUserName'' will appear at [[Special:Ipblocklist]]. Click "unblock" next to that number. Then the user can log in under their new name. This process will hopefully be improved in the future.
Note that it is entirely reasonable for an account to be blocked both for vandalism ''and'' for having an inappropriate username. In that case the IP should be left blocked, and [[MediaWiki:UsernameAndVandalismBlock]] and [[MediaWiki:BlockedDueToUsernameAndVandalism]] used instead.
=== Disruption ===
: ''This is not an actual policy. It was proposed 9th April 2004: see [[Wikipedia talk:Blocking policy#Disruptive users|talk]]''
Sysops may, at their judgement, block IP addresses that disrupt the normal functioning of Wikipedia. Such disruption is to be objectively defined by specific policies, and may include changing other user's signed comments, or making deliberately misleading edits. For dynamic IPs, such blocks should last 24 hours. For static IPs and user names, such blocks should initially last 24 hours, but repeat violators may be blocked for a maximum of one month.
Sysops may also permanently block user accounts that make lots of disruptive edits. However, blocks should not be used against isolated incidents of disruptive behaviour from otherwise productive contributors - use [[wikipedia:quickpolls|quickpolls]] instead.
This policy may be updated if some variant of the [[wikipedia:three strikes you're out policy|three strikes policy]] goes live. In that case, it would take three concurring sysops to block a disruptive user.
Reincarnations of blocked disruptive users will be reblocked if they continue being disruptive, or if they edit in a way which suggests they are likely to continue being disruptive - eg "YOU CAN'T BLOCK ME!!11!!", etc, etc.
=== Bans ===
Users that have been banned are typically blocked from editing wikipedia. Such bans may occur as the result of:
* Tempban following a [[wikipedia:quickpolls|quickpoll]]
* Ruling by [[wikipedia:Arbitration Committee|Arbitration Committee]]
* Ruling by [[user:Jimbo Wales|Jimbo Wales]]
Where it is becomes clear that a user account is a "reincarnation" of an existing banned user, the reincarnating account can likewise be blocked.
See [[wikipedia:banning policy]]
===Anonymous proxies===
Following discussion on the [http://mail.wikipedia.org/pipermail/wikien-l wikien-l mailing list], sysops are permitted and encouraged to IP-block anonymous proxies indefinitely [http://mail.wikipedia.org/pipermail/wikien-l/2004-February/010637.html]. See the entire thread for discussions about the legitimacy of using an anonymous proxy to edit Wikipedia.
===Open proxies ===
[[user:Proxy blocker]] automatically blocks open proxies.
==Effects of being blocked==
Blocked users can still see all Wikipedia pages, but the "Edit this page" link brings up a "[[MediaWiki:Blockedtext|User is blocked]]" page which explains the reason behind the block and gives information on how to request unblocking. Links and {{msg:}} includes all work as normal in the "reason" section.
The scope of the block depends on the expiry time that was entered at the time of the block, which may be "indefinite" or "infinite" (IE, until explicitly unblocked).
When an IP is blocked, or range of IPs are blocked, accounts which share that IP are automatically blocked, preventing one from simply creating a new account to avoid the block. When a logged in user is blocked, IPs of the account are also automatically blocked.
There is an internal autoblock expiry time variable, which is set to 24 hours, meaning that when a username is blocked indefinitely, their IP will be automatically unblocked 24 hours after they last accessed a page.
==Accidental blocks==
Occasionally, users with floating IPs will find that they have been blocked accidentally, due to that fact that their present IP was previously used by a vandal or hard-banned user. These blocks will disappear if IP change can be forced. If that is not possible, the block should be reported to the nearest friendly sysop via email.
Users who act so as to impersonate a previously banned user, to impersonate a known vandal, or to pretend to be engaging in vandalism, are also likely to be accidentally blocked. To avoid this problem, do not act in this way. "[http://www.jargon.net/jargonfile/d/Dontdothatthen.html Don't do that then]".
== How to block ==
Sysops may go to [[Special:Specialpages|Special pages]] and select the "Block a user/IP address" link. This takes them to [[Special:Blockip]], which has further instructions. [[Special:Blockip]] is also accessible via the [block] link that appears next to each non-logged in user on [[Special:Recentchanges|recent changes]].
Expiry times are entered in the GNU standard format, which is described in the [http://www.gnu.org/software/tar/manual/html_chapter/tar_7.html tar manual]. Alternatively, a block may be "indefinite" or "infinite", meaning the block is permanent, until a sysop explicitly unblocks the account.
If you don't enter an expiry time, you will see an error message.
For information about blocking ranges of addresses, see [[m:Range blocks|Range blocks]].
== Unblocking ==
[[Special:Ipblocklist]] contains a list of all currently blocked users and IPs. Sysops will see a link to [unblock] next to each user. After clicking this, you should type in the reason that you are unblocking the user and then click the ''Unblock this address'' button. Sysops are able to unblock themselves by following this procedure.
Sysops may unblock users if:
* They were blocked in violation of this policy.
* The reason for blocking no longer applies.
* The block has lasted too long.
* In other appropriate cases
The last is a bit woolly! The point is that there are no hard and fast guidelines on unblocking. Sysops must use their common sense and good judgement. In controversial cases, it's probably better to discuss things first.
== See also ==
[[Special:Ipblocklist]], [[Wikipedia:Block log]], [[Wikipedia talk:Block log|Block log archives]]
[[ja:Wikipedia:投稿ブロックの方針]]
[[simple:Wikipedia:Bans and blocks]]
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