Internet DRAFT - draft-matavka-gopher-ii
draft-matavka-gopher-ii
Network Working Group T. Matavka
Internet-Draft
Updates: 1436, 4266 (if approved) W. Faust
Intended status: Informational August 6, 2015
Expires: February 7, 2016
Gopher-II: The Next Generation Gopher WWIS
draft-matavka-gopher-ii-03
Abstract
The Gopher protocol is over twenty years old. Changing practices and
unofficial extensions have caused Gopher as currently used to differ,
but remain largely compatible with, the technical specifications
first established in its first informational document, *The Internet
Gopher Protocol (a distributed document search and retrieval
protocol)*, known as *RFC 1436*. Therefore, this document attempts
to establish a contemporary specification of the Gopher
communications protocol, departing as little as possible from current
practice.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on February 7, 2016.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
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carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Changes from RFC 1436 and 4266 . . . . . . . . . . . . . 3
2. Basic Gopher Transactions . . . . . . . . . . . . . . . . . . 4
2.1. Menu Transaction . . . . . . . . . . . . . . . . . . . . 4
2.2. Index Transaction . . . . . . . . . . . . . . . . . . . . 5
2.3. Simple Text Transaction . . . . . . . . . . . . . . . . . 5
2.4. Binary Transaction . . . . . . . . . . . . . . . . . . . 5
2.5. Details . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. Line Terminators . . . . . . . . . . . . . . . . . . . . . . 6
4. Selector Formats . . . . . . . . . . . . . . . . . . . . . . 7
4.1. Type Codes . . . . . . . . . . . . . . . . . . . . . . . 7
4.2. GopherIIbis: Metadata in Gopherspace . . . . . . . . . . 8
5. Gopher Menus . . . . . . . . . . . . . . . . . . . . . . . . 9
5.1. Note on the terminating full stop . . . . . . . . . . . . 10
6. Requesting Data . . . . . . . . . . . . . . . . . . . . . . . 10
7. Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . 11
8. Requesting and Receiving Metadata . . . . . . . . . . . . . . 12
8.1. The `INFO` Record . . . . . . . . . . . . . . . . . . . . 13
8.2. The `ADMIN` Record . . . . . . . . . . . . . . . . . . . 13
8.3. The `VIEWS` Record . . . . . . . . . . . . . . . . . . . 14
8.4. The `ABSTRACT` Record . . . . . . . . . . . . . . . . . . 15
9. Errors . . . . . . . . . . . . . . . . . . . . . . . . . . . 15
9.1. Error Codes . . . . . . . . . . . . . . . . . . . . . . . 16
10. Titles in Gopher . . . . . . . . . . . . . . . . . . . . . . 17
11. Linking to Web Addresses . . . . . . . . . . . . . . . . . . 18
12. Algorithm to use with selectors . . . . . . . . . . . . . . . 20
13. Representation of Gopher Addresses . . . . . . . . . . . . . 21
14. Gopher Policy Files . . . . . . . . . . . . . . . . . . . . . 22
14.1. Capability Policy . . . . . . . . . . . . . . . . . . . 22
14.2. Robot Access Restrictions Policy . . . . . . . . . . . . 25
14.3. Administrator Contact File . . . . . . . . . . . . . . . 28
15. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 29
16. Security Considerations . . . . . . . . . . . . . . . . . . . 29
17. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 30
18. References . . . . . . . . . . . . . . . . . . . . . . . . . 30
18.1. Normative References . . . . . . . . . . . . . . . . . . 30
18.2. Informative References . . . . . . . . . . . . . . . . . 31
Appendix A. Summary of Changes from RFC 1436 . . . . . . . . . . 32
Appendix B. Change Log . . . . . . . . . . . . . . . . . . . . . 32
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B.1. Changes from -00 to -01 of this specification . . . . . . 32
B.2. Changes from -01 to -02 of this specification . . . . . . 32
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 32
1. Introduction
The over-riding aim of this document is to author a contemporary
specification of the Gopher world-wide information system, without
falling short of reflecting actual practice and without breaking
compliance with RFC 1436 [RFC1436]. This document shall attempt to
describe, and, where necessary, update current practice as regards
the means of handling errors, line and file terminators, policy
files, TITLE selectors, the URL: re-direction scheme, and new
selector types not compliant with RFC 1436. This document is not to
be construed as a replacement for RFC 1436; it merely complements it.
Gopher is a lightweight, client/server-oriented query/answer
protocol, functioning as a world-wide information system (WWIS) and
facilitating access to remote servers of any description. The
protocol and software permit users of a wide variety of desktop
systems to browse, search, and retrieve documents residing on
multiple distributed server machines. Gopher is unique among world-
wide information systems in that it encourages data to be sent in
textual form and that it imposes a strict hierarchy on content,
making it a protocol that is fast to transmit, receive, and search.
This, in turn, makes it useful in high-latency, low-bandwidth
communications, such as mobile links. In fact, Gopher provides the
ideal method for transmitting information from and to mobile devices.
1.1. Terminology
NOTE: The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL
NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in
this document are to be interpreted as described in RFC 2119
[RFC2119]. Furthermore, backticks (`) around a string mean that it
is to be interpreted literally.
1.2. Changes from RFC 1436 and 4266
GopherII remains broadly compatible with the original Gopher; a
client compatible with the original implementation of Gopher will be
able to browse GopherII servers with a minimum of problems. The only
difference in strict-compatibility terms arises in the new selector
types (including, but not limited to, one distinguishing "plain text"
from "ASCII markup document"). That said, although these new
selectors are not described in RFC 1436, most existing Gopher clients
will ask for user input when attempting to process an unfamiliar
selector, and these selectors have been in de facto use for some
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time, such that current Gopher clients will be compatible with them
already.
GopherII modifies the original specification in eight ways. Aside
from the aforementioned new selector types, GopherII introduces the
concept of the so-called policy file. Policy files are configuration
files sent from the server to the client in ASCII form with a defined
syntax. Three policy files are defined in this document: the
capability policy, which defines architectural details of the server
(including information about the file system); the administrator
contact file, which defines the geographical location of the server
as well as the entity responsible for its maintenance, and the robot
access restrictions policy, which defines etiquette to be followed by
Gopher search engines. The word 'etiquette' is here used because,
like human codes of behaviour at mealtime, it is non-binding.
Policy files account for three of the substantive changes from
original Gopher. GopherII also adds HTTP-style error codes, a
mechanism for titling the Gopher client window or tab, and
establishes a backward-compatible method for linking to HTTP
addresses. The final change is that GopherII adds support for the
metadata system known as Gopher+ (GopherIIbis in this document),
although this part of the GopherII specification is entirely
optional.
2. Basic Gopher Transactions
There are four broad forms of basic transactions in Gopher:
o Menu Transaction;
o Index Transaction;
o Simple Text Transaction; and
o Binary Transaction.
The precise composition of these transactions is elucidated below.
2.1. Menu Transaction
o Client : [Open Connexion]
o Client : Send [selector<CR><LF>]
o Server : Send <Menu>
o Server : Send .
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o Server : [Close Connexion]
2.2. Index Transaction
o Client : [Open Connexion]
o Client : Send [selector<TAB>query parameters<CR><LF>]
o Server : Send [<Menu>]
o Server : Send .
o Server : [Close Connexion]
2.3. Simple Text Transaction
o Client : [Open Connexion]
o Client : Send [selector<CR><LF>]
o Server : Send [<Simple Text>]
o Server : Send .
o Server : [Close Connexion]
2.4. Binary Transaction
o Client : [Open Connexion]
o Client : Send [selector<CR><LF>]
o Server : Send [<Raw Binary Data>]
o Server : DO NOT send .
o Server : [Close Connexion]
2.5. Details
The fourth step of each transaction, with the exception of the binary
type, is OPTIONAL. Servers MAY send a full-stop character after
sending a menu, index, or text; if they do, clients MUST accept it.
Further information may be found in the appropriate sub-section.
Gopher servers are normally found on TCP port 70. Clients MUST
assume this port if no other port is specified. When a client opens
a connection to a server, the server MUST accept the connection but
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say nothing, waiting for a CR/LF-terminated selector string from the
client. The client MAY then send the selector string followed by CR/
LF (or nothing to retrieve the root menu from the server, which MUST
always be type 1). The server MUST then send the requested content
and close the connection.
3. Line Terminators
ASCII, the international standard that governs the interchange of
plain-text information between computer systems, is nothing more or
less than a table mapping each character (letter, number, space, or
symbol) to a numerical code, which is then converted to binary and
written to disc. Its necessity was seen long before the advent of
the electronic monitor, so some of its more unique quirks must be
understood in view of the time period of which it was a product.
Historically, input and output was through a specially-adapted
typewriter, and the ASCII convention reflects this in the codes it
uses to terminate lines of text.
In ASCII, there are two codes, both having physical equivalents in
the real world, that signal the end of the line: the Carriage Return
(abbreviated C/R, CR, or c/r) and the Line Feed (abbreviated L/F, LF,
or l/f). Originally, the term *carriage return* was used for a
command that caused the assembly holding the paper (the carriage) to
return to the right so the machine was ready to type again on the
left side of the paper (assuming a left-to-right language). On the
other hand, the *line feed* moved the paper upwards, allowing the
carriage to type on the following line.
Different operating systems traditionally signal the end of a line in
different ways. UNIX and its descendants (including Mac OS X), the
operating systems most likely to run on a server, use the line feed
alone. CP/M, DOS, and Microsoft Windows use the sequence of carriage
return and line feed (CR/LF). Obsolete versions of Mac OS (up to,
and including, System 9) use the carriage return alone.
All programmes using Gopher MUST always use the Microsoft standard of
CR/LF, irrespective of the operating system they run on. Both
internal Gopher commands and policy files MUST comply with this
standard. Other text files SHOULD use standard Gopher format, but
this is not strictly required as a matter of technical form; the
client MUST be capable of converting to and from all variants of line
terminators. The recommendation stands for the benefit of non-
compliant clients only.
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4. Selector Formats
4.1. Type Codes
The following selectors are defined by RFC 1436:
Type Treat As Meaning
0 TEXT Plain text file
1 MENU Menu
2 EXTERNAL CCSO flat database (formerly used as telephone
directories); other databases
3 ERROR Error message
4 TEXT Macintosh BinHex file
5 BINARY Binary archive (zip; rar; 7-Zip; gzip; tar)
6 TEXT UUEncoded archive
7 INDEX Query a search engine or CGI script
8 EXTERNAL Telnet to: VT100 series server
9 BINARY Binary file (see also 5)
+ - Redundant server
T EXTERNAL Telnet to: tn3270 series server
g BINARY GIF format graphics file (TODO: Why not use I?)
I BINARY Any image file.
The `+` selector indicates a mirror of the previous item in the menu,
and MUST behave as though it had the same type as that entry. For
example:
5Download software /software.zip gopher.example.com 70
+example.net mirror mirror.example.net /example.com/software.zip 70
+Another mirror mirror2.example.com /software.zip 70
Additionally, the following selectors have been in common use and are
made official here. If a client does not have the capability to
display a particular item type, it SHOULD treat it as a more generic
item type, passing it off to the operating system (itemtype p
"implies" itemtype 0, etc.).
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Type Treat As Meaning
c BINARY Calendar file (Kim Holviala)
d BINARY Word-processing document (MS
Word; OpenOffice.org;
WordPerfect); PDF document
h TEXT HTML document
i - Informational text (not
selectable)
p TEXT Page layout or markup document
(TeX; LaTeX; PostScript; Rich
Text Format)---these documents are
all plain text, but contain ASCII
tags" that make the document
prettier when sent through a
special program.
m BINARY Electronic mail repository (also
known as MBOX) (Kim Holviala)
s BINARY Audio recordings (files that
consist of audible, but no
visible, data) (Wesley Teal)
x TEXT eXtensible Markup Language
document (Wesley Teal)
; BINARY Video files (files that consist
of both audible and visible
data) (Wesley Teal)
Filetypes `4`, `6`, `h`, `p`, and `x` SHOULD send as text (itemtype
0). This way, the text appears directly on the user's terminal
without being downloaded (unless the appropriate command is given to
the client, i.e. `CTRL/S`). It is vital to note that text
information can be sent via binary (with the minor inconvenience
noted above), as binary files contain a greater range of information
than ASCII. However, binary files, if sent via text, will be
irreparably ruined, as this effectively passes raw eight-bit data
through an ASCII filter. In the case of confusion, the owner/
operator of the server should simply mark the file as binary to
ensure that it transfers safely.
4.2. GopherIIbis: Metadata in Gopherspace
It is sometimes useful to transmit data about GopherII selectors.
This is known as "metadata": the *meta* construction is derived from
the Greek for "beyond", and refers to concepts which are abstractions
from other concepts intended to complete or add to the latter. For
instance, in psychology, metamemory refers to an individual's ability
to remember that he has remembered something. In plain English,
metadata refers to data about data.
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GopherIIbis is an OPTIONAL, but recommended, addition to the basic
GopherII specification. That said, it is optional only in the sense
that a GopherII client MAY EITHER display the relevant information in
accordance with the specification, or ELSE ignore it entirely. To be
conformant with GopherII, Gopher clients MUST be capable of handling
GopherIIbis metadata. A GopherII client that displays GopherIIbis
metadata may be referred to as being compliant with GopherIIbis.
The name of the GopherIIbis extension is pronounced "gopher-two-biss"
or "gopher-two-beess". In typeset text, the French word "bis" should
be *italicised* so as to set it off visually. The name of the
GopherIIbis extension reflects that it is merely an addition, or an
iteration, of the GopherII protocol.
5. Gopher Menus
Menu (type 1) content has the following format:
T<itemtext>^I<selector>^I<host>^I<port>
Where:
o `^I` is the ASCII character corresponding to the `Tab` key
o `T` is the type code, which MUST be run together with the item
text
o <selector> is the selector string to send to the specified server
o <host> is the server to send the selector to
o <port> is the port on the server to connect to
If the server understands how to send and receive GopherIIbis
metadata, it MUST indicate this fact by adding a fourth tab character
(^I) and a plus sign after the port number. For example:
T<itemtext>^I<selector>^I<host>^I<port>^I+
If the client does not understand GopherIIbis metadata, it MUST
ignore the trailing ^I+.
Note on `i` item type: For the `i` item type, Selector, Server, and
Port are mostly ignored, but MUST be there anyway. In that case, the
host SHOULD be set to placeholder value `example.com`, and the port
SHOULD be set to placeholder value `0` (zero). One exception to
their being ignored is TITLE entries. These have TITLE as the
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selector value; host and port SHOULD again be set to aforementioned
placeholder values.
5.1. Note on the terminating full stop
Per RFC 1436, a terminating full stop (.) character followed by CR/LF
should be sent on a line by itself after the end of the content, with
exceptions for binary data. This terminating full stop has caused no
end of trouble ever since. Many, if not most, modern Gopher servers
omit this terminating full stop. Therefore, the practice suggested
in RFC 1436 is DEPRECATED and the following practice is RECOMMENDED.
o Servers MAY send the full stop; clients MUST accept it
o Servers SHOULD send the full stop after menus and may OPTIONALLY
send it after other files
o Clients SHOULD display the full stop at the end of menus, if sent,
to notify the user that this is the end of the menu
o Clients SHOULD NOT include the full stop in other output, in case
that output has some significance which the full stop may disrupt.
o Clients SHOULD NOT consider a full stop significant, unless it
occurs immediately before the connection is terminated.
6. Requesting Data
A conformant GopherII client requests data from the server by
transmitting the selector string, a carriage return, and a line feed.
For instance, to retrieve the file `services.txt`, the client sends
services.txt[CR][LF]
GopherIIbis handles things in a slightly more complicated way. In
addition to a selector string, a GopherIIbis-compliant request
contains a *format* string, a data flag indicating the presence or
absence of a data block, and an OPTIONAL data block.
The reason for the inclusion of the format string is because
GopherIIbis allows one selector to point to multiple versions of the
same file, in multiple languages. For instance, the same file in
Portable Document Format, PostScript format, Rich Text Format, and
plain text may be available, and each of these may be available in
British English, American English, Canadian French, and Continental
French. The format string, therefore, is the desired MIME type of
whichever format is being requested, followed by the ISO country and
language codes in the following format:
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selector^Imime/type la_CO^I1[CR][LF]datadatadatadata
The number 1 above is the file flag. It can be either 1 or 0. If it
is 1, it means that the client is not only requesting data, but also
*sending* it. This is useful for example when querying a relational
database on a Gopher server (this usage is now rare). An example
would be:
services.txt^Itext/plain fr_CA^I0[CR][LF]
7. Data Transfer
When a file is requested by a Gopher client, a Gopher server
incompatible with GopherIIbis simply sends the requested data as soon
as it gets the request from the client. GopherIIbis servers, on the
other hand, have three options when given a GopherIIbis-compliant
request (i.e. one that ends in ^I+).
If the size of the file in bytes is known, the server SHOULD transmit
a plus sign, the size, and the combination of carriage return and
line feed, then the file. For example, if the size of file
`report.tex` is known to be 64096 bytes, the server SHOULD transmit:
+64096[CR][LF]\documentclass{article}[CR][LF]\begin{document}...
If the size of the file is not known, there are two ways to proceed.
One of them is to send the character string `+-1` prior to beginning
transmission of the data proper, and end the transmission with a full
stop (.) on a line by itself, followed by carriage return and line
feed. For example:
+-1[CR][LF]data data[CR][LF]data data data data[CR][LF].[CR][LF]
It is RECOMMENDED that most textual data of unknown length be
transmitted this way. The exception is when there is a possibility
of the full stop appearing on a line by itself; this, of course,
would terminate the connexion. There is no choice when sending non-
textual (binary) data: it MUST NOT be terminated with a full stop.
In either of the two cases above, the string to send is `+-2`. This
instructs the client that the data will be terminated when the
connexion is closed, and furthermore, that the length of the data is
unknown. For example:
+-2[CR][LF]binarydata <connexion severed by host>
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8. Requesting and Receiving Metadata
A GopherIIbis client may request the metadata for a specific selector
by sending a string in the following form:
<selector>^I![CR][LF]
The trailing tab and exclamation mark is what distinguishes a request
for data from a request for metadata. The metadata returned is of
the following form:
+INFO: 0lpryce.txt^IRest in peace, Lane Pryce^Igopher.scdp.com^I70+
+ADMIN:
Admin: Roger Sterling <roger@scdp.com>
Mod-Date: Fri Feb 13 08:22:11 2015 <20130213082211>
+VIEWS:
text/plain: <10k>
application/postscript: <100k>
application/latex: <50k>
application/pdf: <120k>
+ABSTRACT:
Yesterday, our beloved partner Lane Gordon Pryce died of suicide in
his Manhattan home. He was 55.
In general, data intended to be read by the computer will be enclosed
in angle brackets (`<` and `>`). A graphical client may, for
example, provide a GUI menu of all possible document views with
graphical icons of the file type and tool-tips of the file size.
These are far from the only available metadata records; only the
`INFO` record is mandatory, and it MUST be transmitted first of all.
The `ADMIN` record is RECOMMENDED, and if it is included, it must be
transmitted *directly* after the `INFO` record.
It is also possible to retrieve only a *specific* record or range of
records. For example, to retrieve only the views and the abstract, a
client may send:
<selector>^I!+INFO+ADMIN[CR][LF]
Finally, it is possible to retrieve metadata for an *entire
directory*. Of course, this is relatively bandwidth-intensive (for a
56k link) but a modern Ethernet connexion should have no problem with
it. The reason for the requirement of an `INFO` record for every
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selector should now be abundantly clear: the `INFO` record serves to
separate metadata for one file from metadata for another. For
example:
<selector>^I&[CR][LF]
The only difference between a request for a *single* file's metadata
and a request for that of a whole directory is that a single-file
request uses an exclamation mark, whereas a whole-directory request
uses an ampersand ("and sign", &).
It is even possible to request a specific record from every selector
in the directory, by appending the requested fields to the command
string as above.
8.1. The `INFO` Record
The `INFO` record is MANDATORY in every metadata listing. It
contains the same data as the Gopher selector, with a plus sign at
the end, per GopherIIbis style. It MUST always be present, and it
MUST always be the first metadata record present. The `INFO` record
serves to separate metadata listings when more are sent at the same
time.
8.2. The `ADMIN` Record
To promote accountability, the `ADMIN` record is also MANDATORY in
every metadata listing. It MUST contain fields for `Admin` (the name
and contact information for the administrator of the file) and `Mod-
Date` (the date of last modification) as seen in the example below:
+ADMIN:
Admin: Roger Sterling <roger@scdp.com>
Mod-Date: 01 January 2015 <YYYYMMDDhhmmss>
The time of last modification MUST be in 24-hour format.
If the metadata listing is for the results of a database search, such
as Veronica, it SHOULD also include fields for `Score` (a whole-
number ranking of the relevance of the result to the search query)
and for `Score-Range` (the lowest and highest possible relevance
scores), as per the following example:
+ADMIN:
Admin: Margaret Olson <m.olson@scdp.com>
Mod-Date: 13 February 2015 <YYYYMMDDhhmmss>
Score: 100
Score-Range: 0 150
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The first number in the `Score-Range` field is the *lower bound*, and
the second number is the *upper bound*.
Several other fields are optional. `Site` is the name of the
Gopherhole, `Org` is the name of the business or individual who owns
the Gopherhole, `Loc` is the owner's location (city, district, and
country), `Geog` is the owner's geographic co-ordinates, and `TZ` is
the time zone in the format GMT+[01..11]. For example:
+ADMIN:
...
Site: S|C|D|P Main Site
Org: Sterling|Cooper|Draper|Pryce Inc.
Loc: New York, NY, USA
Geog: 40N 173W
TZ: GMT-05
The `Author` may also be given, as may be the `Creation-Date` and
`Expiration-Date`, in the same format as the `Mod-Date`.
8.3. The `VIEWS` Record
Although the main selector might be for only one format of a file
(such as Rich Text Format), the same file may be available in many
other formats, such as Plain Text for older systems, LaTeX for
typesetters, PDF for displaying on screen, PostScript for printing on
a graphical printer, and many more.
The `VIEWS` record in GopherIIbis allows for serving multiple
variants of the same file, using what are known as MIME file
descriptors, Content-Types, or Internet media types. The `VIEWS`
field also allows for viewing the same file in multiple languages and
even in multiple dialects of the same language---in this case, the
relevant abbreviations are known as ISO-639 language codes and
ISO-3166 country codes. These are generally at least somewhat
intuitive (`CA` for Canada, `GB` for Great Britain, `en` for
English), but a full list may be found on the ISO Web site.
This is an example of a `VIEWS` record allowing for the selection of
a plain text, Rich Text, and PDF of the same file in American
English, Peninsular Portuguese, and Brazilian Portuguese:
+VIEWS
text/plain en_US: <32K>
text/plain pt_PT: <34K>
text/plain pt_BR: <34K>
text/rtf en_US: <55K>
text/rtf pt_PT: <60K>
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text/rtf pt_BR: <66K>
application/pdf en_US: <120K>
application/pdf pt_PT: <132K>
application/pdf pt_BR: <133K>
The `VIEWS` record SHOULD be ranked according to the administrator's
idea of which view is preferred. On an American site catering to
English speakers, the `en_US` files should be listed first of all.
Likewise, on a site of any language catering to scientists, LaTeX
source should always come first of all.
8.4. The `ABSTRACT` Record
It is RECOMMENDED that every selector on a GopherIIbis-compliant
server have an `ABSTRACT` record. The `ABSTRACT` record contains a
*brief* description of the item (no more than a paragraph long) to
assist the reader in determining its purpose. Similarly, it is also
RECOMMENDED that the root directory of every Gopher server (that is,
what one gets when one requests metadata for the server itself with
no selector) contain an `ABSTRACT` record with the name, postal
address, eMail address, and telephone number of the person
responsible for the site. For example:
+ABSTRACT
The life and times of Professor Albert Einstein, Swiss patents clerk
and discoverer of four great scientific theories in one miraculous
year.
9. Errors
Although undesirable in communication, errors do occur in Gopher, and
their handling is crucial for a user-friendly Gopher experience, and
one which conforms to this document.
When an error is encountered, the server MUST return a menu whose
first item bears itemtype `3`. All other ways of signalling an
error, such as redirecting to a Gopher error menu, an image, or
(worst of all) an HTML page, are PROHIBITED.
The selector string for itemtype `3` is the text of the error. It is
the responsibility of the server application to have understandable
and accurate strings for error handling. As they are well-understood
and common, HTTP-style error codes are acceptable and RECOMMENDED;
however, they SHOULD also be followed by a clear, legible description
of the error in both English and the local language.
Errors are handled in GopherIIbis in a slightly different fashion.
When an error occurs in response to a GopherIIbis-compliant query,
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the server sends two minus signs, followed by an error code, a
description of the error, and a full stop. The error code SHOULD be
in the three-digit style elucidated in the next sub-subsection, but
the numbers 1, 2, and 3 MUST also be understood and handled
correctly, also as defined in "Error Codes". An example of a
GopherIIbis error follows:
--404[CR][LF]The file requested could not be found.[CR][LF].[CR][LF]
The decision of whether to send a GopherII error string or a
GopherIIbis error string is governed by the type of query received.
If the query was compliant with GopherIIbis, a GopherIIbis error MUST
be sent. In all other cases, a GopherII error MUST be sent.
9.1. Error Codes
This is a listing of numeric error codes used in Gopher; due to
Gopher's simplicity, it lacks most of the errors possible in HTTP.
Codes beginning with 4 can generally be traced to the client; codes
beginning with 5 are usually due to the server.
400 Bad Request The request could not be understood by the server
due to malformed syntax.
401 Unauthorised The request requires authentication. For example,
the received query value (as password) does not match the expected
value.
403 Forbidden The request was received, but not filled.
404 Not Found The server could not find anything matching the
requested URL. If the condition is known to be permanent, use
error code 410 (Gone).
408 Request Time-out The client did not produce a request within the
time that the server was prepared to wait.
410 Gone The requested resource is no longer available at the server
and no forwarding address is known. This condition is expected to
be considered permanent. If this is unknown, use error code 404
(Not Found).
500 Internal Server Error The server encountered an unexpected
condition which prevented it from fulfilling the request.
501 Not Implemented The server does not support the functionality
required to fulfil the request.
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503 Service Unavailable The server is currently unable to handle the
request due to temporary overload/maintenance.
An earlier version of the GopherIIbis extension, known as Gopher+,
used error codes `1`, `2`, and `3`. Error code `1` signifies an
unavailable item (similar to the 400-series errors), error code `2`
signifies an unavailable server (similar to the 500-series errors),
and error code `3` signifies an item that has moved. Provision was
made to create new error codes. This is now DEPRECATED; the *ad hoc*
creation of new errors does not accord with the ethos of a formalised
Internet protocol.
10. Titles in Gopher
No mention of menus with titles exists per RFC 1436. When one simply
browses about Gopherspace, this does not matter; for bookmarking and
Gopher crawlers, such as Veronica-2, however, this presents a large
problem.
A Gopher TITLE resource has the following format:
i<titletext>^ITITLE^Iexample.com^I0
It is identical to a normal informational resource (itemtype `i`);
the selector string, however, is set to the specific value, `TITLE`.
The composition of the above format is as follows:
o `^I` is the ASCII character corresponding to a press of the `Tab`
key
o The type code MUST be `i` (information)
o The selector string MUST be `TITLE`
o There is no server to connect to; the dummy text used in place of
the server SHOULD be `example.com`
o There is no port to connect to; the placeholder number SHOULD
therefore be `0` (zero).
A Gopher client that conforms to the above `TITLE` specification
SHALL render it in one of two ways, depending on the placement of the
resource. If the `TITLE` is the *first* resource in the document, it
SHALL be considered its principal `TITLE` and used *wherever a
principal title is needed* (window headings, bookmarks, etc.);
furthermore, it SHOULD be rendered in a different size, font, and/or
colour to the remainder of the document. In *all other* cases, it
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SHALL be considered a subordinate `TITLE` and SHOULD be rendered in a
different size, font, and/or colour to the remainder of the document,
but smaller and/or with less emphasis than the main title.
If a non-compliant Gopher client receives a `TITLE` resource as per
above, it will render it as plain informational text. As the main
`TITLE` must be on the first line of a menu, it will appear visually
similar to a title in any case, although not rendered as such.
11. Linking to Web Addresses
It is now possible, and common, to link to documents, preferably in
HTML, on the World Wide Web, Gopher's younger, more widespread
cousin, from Gopher itself, using a two-part system: a `URL:`
selector on the Gopher (local) end, and a *redirect page* (following
rules as set out below) on the HTTP (remote) end. There are no
compliance requirements for Gopher servers, with one exception:
servers MUST follow the bulleted list located immediately after the
example redirect page.
A Gopher client SHALL, when it sees a selector with a path starting
with `URL:`, interpret the path as a URL. It SHALL ignore the host
and port components of the Gopher selector, using those components
from the URL instead, if applicable.
`URL:` selectors SHOULD NOT be used if it is possible to link to the
required content and protocol by any other means. In particular, the
following protocols SHALL NOT be used with the URL: selector.
o gopher
o telnet (VT100-compatible)
o tn3270
Authors SHOULD NOT link to any document not of HTML type unless
absolutely necessary; linking to non-HTML documents will break
compatibility with non-compliant Gopher browsers.
A Gopher `URL:` selector MUST take the following format:
h<itemtext>^IURL:<address>^I<localhost>^I<localport>
URL:` selectors are, for the most part, identical to standard HTML
selectors, but composed of particular data:
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o The item type corresponds to the type of document on the remote
end. Most typically, this is a Web page authored in HTML;
therefore, the item type is most commonly `h`.
o <itemtext> is the text of the link; this can be almost anything.
o <address> is the full URL, preceded by the string `URL:`. For
example, this could be `URL:http://www.example.com`
o <localhost> is the server that the link *originated* from; this
MUST be ignored by a compliant client, but MUST also be sent by a
compliant server
o <localport> is the port that the link *originated* from; this MUST
be ignored by a compliant client, but MUST also be sent by a
compliant server
It is possible for a non-compliant Gopher client to follow a link to
an HTML page, as long as the server is compliant, by the following
means: when the client receives a command to follow a `URL:`
selector, it will contact the server that provided the menu, as the
originating host and port are *mandatory* per this specification.
When a Gopher server receives a request from a client beginning with
the string `URL:`, it SHALL write out an HTML document that redirects
the browser to the appropriate place. A conforming example of such a
document is as follows:
<HTML>
<HEAD>
<META HTTP-EQUIV="refresh" content="2;URL=http://www.example.com/">
</HEAD>
<BODY>
You are following an external link to a Web site. You will be
automatically taken to the site shortly. If you do not get sent
there, please click <A HREF="http://www.example.com/">here</A> to go
to the web site.
<P>
The URL linked is:http://www.example.com/">
<P>
<A HREF="http://www.example.com/">http://www.example.com/</A>
<P>
Thanks for using Gopher!
</BODY>
</HTML>
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This document may be any desired by the server authors, but MUST
adhere to the following requirements.
o It SHALL provide a refresh of a duration of 10 seconds or less
o It SHALL NOT use `IMG` tags, frames, or have any reference
whatsoever to content outside that particular file, with the sole
exception of the link to the real destination.
o It SHALL NOT use JavaScript.
o It SHALL adhere to the W3C HTML 4.0 standard.
When a non-compliant Gopher client finds a reference to a HTML file
(type `h`), it will open up the file via Gopher, receiving the
redirect document using a Web browser. The Web browser will then be
redirected to the actual link destination.
Compliant Gopher clients will simply render the target directly.
12. Algorithm to use with selectors
Here is a description for a hypothetical algorithm for parsing item
types, splitting them into levels of interaction.
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PROTOCOL
--------
Type Description What to do
0 Brief text Render directly line by line.
1 Menu Request and analyse menu. If it
contains '3' error node, print
error.
Else, render menu in new window.
7 Index/Search
Server
DATA NODES
----------
Type Description What to do
4, 9, g, I, c, Binary file Request and analyse file. If it
d, m, s, ; contains '3' error node, print
error. Else, does plug-in exist?
If yes, display. If no, save to
disc.
6, p, x Text file Request and analyse file. If it
contains '3' error node, print
error. Else, print on screen.
h, 2, 8, T Link Treat as URL.
5 Archive File Request and analyse file. If it
contains '3' error node, print
error. Else, does plug-in exist?
If yes, display. If no, save to
disc.
For instance, if the client is incapable of handling images as it is
text-only, the algorithm above would have it save to disc.
13. Representation of Gopher Addresses
This section is greatly indebted to RFC 4266 [RFC4266].
A Gopher address, or uniform resource locator, takes the form:
gopher://<host>:<port>/<gopher-path>
where <gopher-path> is one of:
o <gophertype><selector>
o <gophertype><selector>%09<search>
o <gophertype><selector>%09<search>%09<gopher+_string>
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If :<port> is omitted, the port defaults to 70. <gophertype> is a
single-character field to denote the Gopher type of the resource to
which the URL refers. The entire <gopher-path> may also be empty, in
which case the delimiting `/` is also optional and the <gophertype>
defaults to `1`.
<selector> is the Gopher selector string. Selector strings are
arbitrary sequences of characters; they MUST NOT, however, contain
the characters corresponding to horizontal tab, line feed, or
carriage return. Gopher clients specify which item to retrieve by
sending the Gopher selector string to a Gopher server. It is
important to know that within the <gopher-path> itself, there are no
reserved characters, so one may be arbitrarily creative when creating
selector names.
Note that some Gopher <selector> strings begin with a copy of the
<gophertype> character, in which case that character will occur twice
consecutively. The Gopher selector string may be an empty string;
this is how Gopher clients refer to the top-level directory on a
Gopher server.
If the URL refers to a search to be submitted to a Gopher search
engine, the selector is followed by an encoded tab `%09` and the
search string. To submit a search to a Gopher search engine, the
Gopher client sends the <selector> string (after decoding), a tab,
and the search string to the Gopher server.
14. Gopher Policy Files
It is often useful to provide information to Gopher clients that MAY,
but need not, be read by a human being. It is for this reason that
policy files exist. This document enumerates two types of policy
files, formally known as the Capability Policy and the Robot Access
Restriction Policy, but also informally known under their filenames:
`caps.txt` and `robots.txt`, respectively.
14.1. Capability Policy
It is RECOMMENDED, when hosting a public-access Gopher server, to
include a capability policy. Although it is, ultimately, the choice
of the owner or operator of the server, a capability policy (or caps
file) can be useful for clients querying the server for certain
information without using extensions such as Gopher+.
The purpose of a capability policy is so that a server can instruct a
client on how properly to parse selectors in its filesystem; it
ensures that the client can understand how files on the server are
organised. The scheme used in the current implementation of caps can
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handle POSIX (UNIX and related operating systems), FAT/NTFS (used by
Microsoft Windows), and HFS (used by all versions of Apple Mac OS,
including OS X, which is otherwise POSIX-compatible). For technical
reasons, capability policies cannot handle VMS or Files-11 paths;
however, owing to their open interface, the specification can be
arbitrarily extended.
A capability policy is quite simple in its composition: it is a plain
text file with no more than seventy characters per line in the root
directory of a Gopher server with the name
caps.txt
and beginning with the six characters
CAPS[CR][LF]
caps.txt
Because of the constrained name and location of the policy, it is a
trivial matter to verify if one exists or not; the address is always
of the form <gopher://gopher.example.com/1/caps.txt>, with the real
name of the server substituting for `example`. The server should
accept both `caps.txt` and `/caps.txt` as selectors, and return the
same content for both.
A caps file contains *keys*, *values*, and *comments*.
Keys can be compared to labelled containers for data; for instance,
the key `ServerSoftware` is a container for the name of the Gopher
software running on the server. Keys in capability policies are
always alphanumeric (i.e., composed of letters and numbers only) and
generally are in CamelCase (each individual word within the key
capitalised). The data in these containers is called a value; values
can use letters, numbers, and symbols. Keys and values are connected
by the equals (=) sign. Any amount of whitespace (spaces and tabs)
around the equals sign is acceptable.
Anything not conforming to the syntax
SomeKey = Value
is ignored (treated as a comment). To be compliant with GopherII,
comments must begin with a hash (#) sign. More importantly, they
must be on a line to their own.
Below is an example caps file.
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CAPS
CapsVersion=1
ExpireCapsAfter=3600
PathDelimeter=/
PathIdentity=.
PathParent=..
PathParentDouble=FALSE
PathEscapeCharacter=\\
PathKeepPreDelimeter=FALSE
ServerSoftware=Bucktooth
ServerSoftwareVersion=0.2.9
ServerArchitecture=AIX
ServerDescription=IBM Power 520 Express, 2x4.2GHz POWER6 CPU, 8G RAM
ServerGeolocationString=Southern California, USA
ServerSupportsStdinScripts=TRUE
ServerAdmin=gopher@floodgap.com
DefaultEncoding=utf-8
The `CapsVersion` field is self-explanatory, with one note: it should
always be the *first* field in the file, so that an incompatible
later format might be detected by the client. The `ExpireCapsAfter`
field tells the client the recommended cache expiry time (that is,
the time between fetching and re-fetching the caps file) in
*seconds*. `3600` as above means one hour, and so on.
The `Path` variables `PathDelimeter` [sic!], `PathIdentity`,
`PathParent`, `PathParentDouble`, `PathEscapeCharacter`, and
`PathKeepPreDelimeter` [sic!] refer to attributes of the file system.
The above example is correct for a UNIX system, including Mac OS X.
`PathDelimeter` refers to how the server separates folders from each
other; Unix machines use `/`, Microsoft machines use `\`, and
obsolete Macs use `:`. `PathIdentity` refers to the shorthand used
by an operating system to mean "this directory"; UNIX machines use
`.`. `PathParent` refers to the shorthand for "the directory
immediately above", and is `..` on UNIX and Microsoft systems.
`PathParentDouble` refers to an oddball feature of obsolete Macs: two
consecutive path delimiters are used to refer to the parent
directory. For all systems other than pre-OS X Macintoshes,
`PathParentDouble` should be FALSE. `PathEscapeCharacter` tells the
client the escape character for quoting delimiters when they appear
in selectors; most of the time, this is `\\`. `PathKeepPreDelimiter`
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tells the client not to cut everything up to the first path
delimiter; most of the time, this should be `FALSE`.
The `Server` variables `ServerSoftware`, `ServerSoftwareVersion`,
`ServerArchitecture`, `ServerDescription`, and
`ServerGeolocationString` are freetext descriptions of the server
software and version, operating system ("architecture"), server
hardware (`Server Description`), and location on the Earth.
Finally, `ServerAdmin` is an eMail contact address for the server
administrator, and `DefaultEncoding` is the default text encoding for
content types 0 and 1.
14.2. Robot Access Restrictions Policy
WWIS robots, also known as spiders, crawlers, or wanderers, are
computer programmes that, without human intervention, recursively
travel throughout linked pages or directories on an information
system (that is, by repeatedly travelling up and down a tree) and
store the copies of these files at an independent location. The
process of programmatically gathering information in this manner is
called crawling or spidering.
Many sites, in particular search engines (such as Google on the World
Wide Web, or Veronica on Gopher), use spidering as a means of
providing up-to-date data. Robots are mainly used to create a copy
of all the visited pages for later processing by a search engine that
will index the downloaded pages to provide fast searches. Robots can
also be used for redundancy; data can be preserved by a third party
in case the original server becomes inaccessible.
In 1993 and 1994, however, there were occasions where robots had
visited locations on the Web at which they were not welcome.
Inexperienced or heavy-handed use of robots caused situations where
servers were swamped with requests at a high rate of speed; or, the
same files were retrieved repeatedly. Both could cause denial of
service. In other situations, robots traversed parts of servers that
were unsuitable, such as temporary information or server-side
scripts, especially those with side-effects (such as polls). Abuse
of robots was also an issue, and continues to be one now; for
instance, electronic mail addresses have been harvested with knowing
intent to distribute unsolicited mail ('spam').
These incidents indicated the need for established mechanisms for
Gopher servers to indicate to robots which parts of their server
should not be accessed. This specification addresses this
requirement with an operational solution, adapted from the identical
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method used on sites using the Hypertext Transfer and File Transfer
Protocols.
The method used to exclude robots from a Gopher server is formally
known as the Robot Access Restrictions Policy (RARP) and consists of
placing a plain-text file specifying, in simple and user-friendly
syntax, which robots may access which directory. The policy file, if
it exists, MUST be accessible via Gopher on the local address
/robots.txt
A possible drawback of this single-file approach is that only a
server administrator can maintain such a list, not the individual
document maintainers on the server. This can be resolved by a local
process to construct the single file from a number of others, but if,
or how, this is done is outside of the scope of this document.
Furthermore, Gopher administrators should bear in mind that the Robot
Access Restrictions Policy works largely on the honour system. Many
crawlers can be set to ignore the policy, and it is trivial to write
this capability into a new crawler.
The policy file consists of one or more records, separated by one or
more blank lines, terminated by the CR/LF string as usual in Gopher.
Each record contains two or more lines of the form
<field>:<value>
The field name is not case-sensitive. Comments (lines to be ignored
by robots themselves, but useful to robot operators and others) start
with the hash (#) character and end with the line terminator (CR/LF).
A value can share a line with a comment. A record starts with at
least one `User-agent` field, followed by at least one `Disallow`
field. There are two further, optional fields: `Crawl-delay`, as
well as `Allow`.
The value of the `User-agent` field is the name of the robot whose
access policy is being described. If more than one `User-agent`
field is present, the record is describing an identical access policy
for each robot. This field is to be interpreted broadly. The
recommended implementation of access policies in the robot's code is
for a case-insensitive sub-string match, without version information.
Since one is describing an access policy for at least one robot, at
least one `User-agent` field is required. The value `*` (quotes
excluded) describes access policy for any robot not matching any
previous records; therefore, if listed, it SHOULD be listed last of
all. If it is not listed last of all, anything below it will be
ignored.
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The value of the `Disallow` field specifies a partial URL that is not
to be visited. This can be a full path, or a partial path. Any
address that begins with this value will not be retrieved; for
instance, the line Disallow: /help would disallow `/help/index.html`;
`/help/faq.html`; as well as `/help.html`. Conversely, the line
Disallow: /help/ would allow `/help.html`, but nothing in the
directory `/help/`. An empty `Disallow` field indicates that all
addresses can be retrieved. As one is defining policy and not simply
listing the names of robots, at least one `Disallow` field is
required per record.
One can also add specific exceptions to the locations disallowed by
using the `Allow` field.
The `Crawl-delay` field is also supported; this field indicates the
number of seconds to wait between successive requests to the same
server; the value must be an integer with no units.
The following is an example of a well-built policy file: # Robot
Exclusion File for gopher://gopher.scdp.com # If you wish to crawl
gopher.scdp.com, please contact # lane.pryce@scdp.com to apply for an
exemption. Our terms of # service are available at
gopher://gopher.scdp.com/0/tos.txt. User-agent: baiduspider User-
agent: googlebot User-agent: msnbot User-agent: bingbot User-agent:
naverbot User-agent: seznambot User-agent: slurp User-agent: teoma
User-agent: yandex Disallow: /cgi-bin/ # Dynamically generated
scripts Disallow: /images/ # This consumes bandwidth! Disallow:
/tmp/ # Temporary files---blink, gone! Disallow: /private/ # No
peeking! Allow: /images/logo.jpg # Main logo. Mirror this if
possible. Crawl-delay: 10 User-agent: * Disallow: / # If you have
received authorisation to crawl this site, and are # getting denied,
please contact support@scdp.com, or dial # (212) 555 0169. This site
is copyright Sterling, Cooper, Draper, # and Pryce, 2012.
In plain terms, this server allows major search engines Baidu,
Google, Bing, Naver, Seznam, Teoma, Yahoo, and Yandex to mirror the
site freely, with the exception of everything in the directories
/cgi-bin/, /tmp/, and /private/, as well as everything with the
exception of the single file logo.jpg in the directory /images/. So
as to not unduly slow the server down, the policy file requests that
search engines wait ten seconds between requests. All other robots
are prohibited from accessing the site.
Examples such as the following SHOULD NOT be used except in very rare
situations. Robots generally cause more good than harm, and
excluding them entirely, as this anti-social user would, does not
make Gopher a healthy place.
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# Piss off!
User-agent: *
Disallow: /
14.3. Administrator Contact File
It is worth remembering that computers, like anything else, are
fallible and prone to error. When failure occurs in Gopherspace, the
person in the best position to rectify it is the system
administrator. Furthermore, users may have questions or comments,
also best directed to the system administrator. For this reason,
each Gopher server MUST have a file in its top-level directory with
the name *about.txt* and a RECOMMENDED selector string of *About* or
*About this server* (equivalents in the local language are
permissible, but an English translation is similarly RECOMMENDED).
It is the Gopher equivalent of a Unix user's finger output.
Since this file is intended to be readable by humans and not
computers, it does not have a defined file format. However, it
should have a short description of the server's contents, as well as
the contact details of the server administrator and any other key
employees, such as the legal department. A well-structured contact
file looks as follows:
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Sterling|Cooper|Draper|Pryce
============================
Welcome to SCDP! We are a full-service advertising and marketing
agency staffed by a team of diverse, senior professionals with a
flair for solid strategy and compelling creative output. Our team
produces unique television, radio, print, and Web advertisements
for a range of industries.
Our ability to identify and communicate your greatest benefit to
your customers is our greatest benefit to you. We find out what
makes you truly unique. We have built an excellent team: each
member is an advertising specialist in their own right.
Photography, programming, writing, design, strategy---you name it,
we have a creative for that.
System Administrator: Margaret Olson
Telephone: (212) 555 0169 x808
Address: 13, Madison Avenue,
New York, N.Y.,
U.S.A.
eMail: peggy.olson@scdp.com
Skype: peggyXolson
All prospective clients:
Please contact Creative Director Donald Draper at extension 069.
Legal issues:
For all legal and financial issues, please contact Lane Pryce
at extension 777.
15. IANA Considerations
Nothing within this document should be taken to imply that any
actions are to be undertaken by the Internet Assigned Numbers
Authority.
16. Security Considerations
Security in GopherII is dependent on the connexion on which it runs.
Normal GopherII (that is, running on "straight" TCP) is insecure
simply by virtue of the protocol. Sensitive information, such as
credit card numbers, must not be sent over a standard Gopher link.
It is permissible to run GopherII over SSL, in which case all
security considerations that apply for working HTTPS apply also for
GopherIIs.
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17. Acknowledgements
Thanks go to John Klensin for his invaluable assistance in regards to
the IETF process, his constructive criticism, and his calm demeanour
even when others just could not keep their tempers in check.
Thanks also go to the members of the Gopher mailing list for keeping
the Gopher protocol alive. Thanks go specifically to the Gopher
developers: to Matjaz Mesnjak for his Windows-compatible, graphical
Gopher client and his simple Motsognir Gopher server; to Dr Cameron
Kaiser for Veronica-II, the next generation of Gopher search engine,
for the Bucktooth Gopher server, for the Overbite extension for
Mozilla Firefox, and for his tireless work on GopherVR, the only full
virtual-reality Gopher client; to Kevin Veroneau for his Gopher
Application Framework; and to Kim Holviala for the Gophernicus Gopher
server.
Finally, my thanks go to Thomas E. Dickey and the others who have
put in valuable work on the Lynx browser. I thank them because,
rather than remove Gopher support in a misguided attempt to plug
security holes, they have in fact continued to improve this side of
their software, and they have succeeded in making the finest text-
mode Gopher client bar none.
18. References
18.1. Normative References
[Anklesaria1993]
Anklesaria, F., "Gopher+: upward compatible enhancements
to the Internet Gopher protocol", 1993.
Anklesaria, Farhad; Lindner, Paul; McCahill, Mark P.;
Torrey, Daniel; Johnson, David; Alberti, Bob (1993). **
Retrieved 23 May, 2012, from
<gopher://gophernicus.org/0/doc/gopher/gopher+.txt>
[RFC1436] Anklesaria, F., McCahill, M., Lindner, P., Johnson, D.,
Torrey, D., and B. Albert, "The Internet Gopher Protocol
(a distributed document search and retrieval protocol)",
RFC 1436, DOI 10.17487/RFC1436, March 1993,
<http://www.rfc-editor.org/info/rfc1436>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
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18.2. Informative References
[CapsRef] Kaiser, C., "Welcome to caps!", 2010.
Kaiser, Cameron (2010). *Welcome to caps!* Retrieved 23
May, 2012, from <gopher://gophernicus.org/0/doc/gopher/
gopher-caps.txt>
[Floodgap]
Floodgap, "Floodgap's caps file".
<gopher://gopher.floodgap.com/0/caps.txt> - Floodgap's
caps file
[Goerzen2012]
Goerzen, J., "Links to URL", 2002.
Goerzen, John (2002). *Links to URL.* Retriever 23 May,
2012, from <gopher://gophernicus.org/0/doc/gopher/
hURL.txt>
[GopherHistory]
??, ?., "A paper on the history of Gopher".
<gopher://jgw.mdns.org/9/REFS/56817068-PIL3254-Internet-
Gopher-PPL- Alberti.pdf> -- A paper on the history of
Gopher
[RelatedDocs]
??, ?., "gophernicus.org".
<gopher://gophernicus.org/1/doc/gopher/> - A number of
documents relating to gopher, including the RFCs
[RFC4266] Hoffman, P., "The gopher URI Scheme", RFC 4266, DOI
10.17487/RFC4266, November 2005,
<http://www.rfc-editor.org/info/rfc4266>.
[UpdatedGopher]
??, ?., "The "Updated Gopher RFC" thread", 2012.
The "Updated Gopher RFC" thread (started May 8 2012) on
the gopher-project mailing list
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Appendix A. Summary of Changes from RFC 1436
In broad strokes, RFC 1436 is compatible with this document; an "old"
Gopher client should be fully capable of browsing a GopherII server.
GopherII can be considered simply a refinement of the RFC 1436
concept; while RFC 1436 lays out a viable protocol, it leaves a lot
of small-scale implementation detail up to the makers of client
software. While a sort of gentleman's agreement did manifest itself,
and while this gentleman's agreement was in some places almost
universal (the `i` itemtype, for example, with only Microsoft
Internet Explorer as the nonconforming Gopher client) it did lack
standardisation, which is what this document remedies. More
specifically:
o c, d, h, i, p, m, s, x, ; itemtypes.
o extension formerly known as Gopher+
o terminating full-stop behaviour
o what to put in the title bar (`TITLE` resource)
o links to HTTP urls
o policy files
Appendix B. Change Log
B.1. Changes from -00 to -01 of this specification
Converted to RFC standard format for legibility; added security
considerations section.
B.2. Changes from -01 to -02 of this specification
Added acknowledgements and changes from original Gopher RFC's.
Removed placeholder text.
Authors' Addresses
Ted Matavka
Email: n.theodore.matavka.files@gmail.com
Wolfgang Faust
Email: wolfgangmcq@gmail.com
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