https://www.ics.uci.edu/~rohit/IEEE-L7-http-gopher.html
Who Killed Gopher?
An Extensible Murder Mystery
By Rohit Khare // December 23, 1998
As best our forensics team can reconstruct, a serial killer
first surfaced in the beginning of 1991, born of an
academic's midnight hack gone awry. NeXTstep users, you see
-- precisely the kind of object-oriented revolutionaries
that would think they could get away with inventing a brand
new protocol for a mature Internet.
The first victim was the campus phonebook: it dismembered
the whole corpus into tiny bits of `hypertext', left
hanging together by search strings alone. Here we see its
modus operandi: not content to slice information into neat
lists or trees, it left behind completely unstructured
graphs littered with redirects hither and yon across the
Internet to co-conspirators' servers.
Hegemonic fantasies drove it to assimilate more and more
multimedia formats at each node. Crude at first, shoveling
any old file through an 8-bit clean channel, it grew more
explicit until it could label text, images, audio, even
compound documents. By now, it can even masquerade behind
several renderings, negotiating whatever face -- or
language! -- pleases the victim.
As a protocol, it was a blunt weapon: aim a socket at the
target, send a one-line demand, and slurp down the response
until the connection died. The crazy way it grew from there
is proof itself that the killer dropped out of Application
Layer Protocol design school at an early age it shows no
understanding of the basics of TCP, botching handshakes,
slow-start, server-sends-first-byte, even tripping over the
Nagle timer. Instead, in a stroke of streetwise punk
genius, it stayed 'simple' enough that any two-bit Telnet
client could take a hit.
And what an addictive product it was! Workgroupies were
seduced by the ease of installing new servers and authoring
new content -- and pushing free software helped the lock-in
cycle along. The killer preyed on individual users'
self-esteem by promising instant fame^*, in the form of a
backlink from the master list of servers.
^*Anyone have firm attribution for the famous quote, "On
the Internet, everyone will be famous for 15 people"?
Soon, it was assimilating more than bags of bits: it was a
gateway drug to harder services. Scripts, database lookups,
even long-established news, file, and email access
transactions were reduced to mere documents in a menu. The
address sent in the 'demand' grew into a miniature RPC.
All the while, with every new user, every new server, every
nugget of information it wrested from 'legacy' protocols,
the killer bled off a little more of the Internet's
bandwidth -- getting away with murder with every handshake!
Such profligacy is no idle threat: for a while, the killer
was the largest share of application packet traffic on the
national NSFNET backbone.
Or was that the victim?
Did the killer come knocking on port 70 or port 80? From
boombox.micro.umn.edu or info.cern.ch? Bearing the
imprimatur of campus administrators or physicists? Are we
hunting gophers or spiders?
Dial 'H' For Murder
In fact, the profile in Table 1 fits both suspects to a
'T'. In the early '90s, an interesting drama played out
between two contenders for the first integrated,
interactive internet information retrieval protocols --
neither of which, arguably, had any technical reason to
exist.
That's not to say the systems weren't inevitable: everyone
suspected there'd have to be an easier way to use the
Internet in the '90s than UNIX shell experience. That
encompasses innovations in user interface, authoring
formats, and above all, resource identification. It does
not, however, motivate the original editions of the Gopher
and HyperText Transfer Protocols. They were painfully
trivial hacks that did nothing FTP didn't already handle.
So here begins our mysterious tale: why either protocol
ever rose to prominence in the first place; and how the
fratricidial drama eventually played out. Understanding how
HTTP killed gopher may lead us to the forces which may, in
turn, topple HTTP.
Science proves a blind alley, though. Their fates were
decided not on technical merits, but on economic and
psychological advantages. The 'Postellian' school of
protocol design focused on engineering 'right' solutions
for core applications (batch file transfer, interactive
terminals, mail and news relays) anchored in unique
transport layer adaptations (slow-start, Nagle timers, and
routing as respective examples). Our two specimens are
'post-Postel', in their details and in their adoption
dynamics. They are stateless; they don't have (Gopher) or
dilute (HTTP) the theory of reply codes; they scale poorly,
imperiling the health of the Internet; and they are
'luxuries' for publishing discretionary information, not
Host Requirements which must be compiled into every node.
Burrowing into Gopher
While the Web was arguably invented a few months before
Gopher, the latter was the first to garner public notice.
By the fall of 1994, RFC 1689's census of information
retrieval tools estimated there were 4,800 Gophers, and
1,200 anonymous FTP archives, but only 600 Webs. Early and
"explosive" adoption had a lot to do with Gopher's
"fiercely simple" design, and hence its wide availabilty on
a number of students' (DOS, Windows, Mac, NeXT) and campus
IS departments' (UNIXes, VMS, VM/CMS, MVS) platforms.
It was designed by the microcomputer support folks at the
University of Minnesota for a teletext-like Campus-Wide
Information System (CWIS). The original prototype was a
multicolumn tree-browser pioneered for the NeXTstep file
browser. Each scrolling column had a list of titles;
clicking on an entry would either display that file in the
pane below, or load the child directory listing in the
column to the right.
Naturally, the messages on the wire follow directly: open a
connection to the target server on port 70; send a one-line
'selector' string; get back either the file itself, or a
list of further selector lines, each prefixed by a
character indicating the type of file it points to. Table 2
lists the rudimentary type system Gopher shipped with,
illustrating on one hand its ambitions to assimilate new
media types and on the other what a thin skein it was
around protocol- and platform-specific data formats.
The flip side of 'thin skein' is 'ease of implementation',
though. In effect, Gopher was a (very!) poor man's version
of FTP, sans authentication, navigation, authoring, or
bulk/restartable transfers. It only used TCP as a
half-duplex fopen() call. It just happened that some of the
"files" it transferred were menus, in a Gopher-specific,
tab-delimited, US-ASCII format. So a Gopher server did
little more than read files out of a specified directory
tree; and clients could be hacked out of spare Telnet
client code.
A little further up the evolutionary tree, servers allowed
scripts and other programs to be served as well. Rather
than copying a file back across the socket, it connected it
to some process's output. Similarly, multiprotocol clients
could recognize a non-Gopher selector and switch to another
language (as for phonebook queries). "Gateways exist to
seamlessly access a variety of non-Gopher services such as
ftp, WAIS, USENET news, Archie, Z39.50 (1992 rev), X.500
directories, Sybase and Oracle SQL servers, etc."
The base protocol didn't leverage TCP well, though. For
example, TCP's three-way handshake ends with a packet from
the server to the client -- so even when the client opens
the connection, the server can send data first for free.
Gopher did not have a server-hello message, and thus no
version number to key upgrades off of. To signal the end of
a particular transmission, Gopher borrowed the SMTP/NNTP
convention of <CR><LF>.<CR><LF>. This only worked for its
own menu format, though -- as soon as an actual file was
transferred, TCP FIN had to be used as the EOF.
This left lots of socket buffers in the FIN_WAIT state at
the server side, just like the Web. At the same time, the
Gopher Team was planning to scale to Internet-wide use.
They did plan for redundant backup servers: a '+' line was
an alternate for the selector on the previous line. They
maintained a master list of publically-accessible servers,
which was in turn indexed regularly by Veronica (Very Easy
Rodent-Oriented Net-wide Index to Computerized Archives, by
analogy to the Archie FTP server index).
In the long-run, though, no one ever plastered Gopher
selectors on shirts and lunch trucks and golf tees...
Spinning the Web
"The key insight I credit Tim Berners-Lee with, is the
URL: the idea that there's a Uniform Resource Locator
that says I can point at any bit of information on the
Internet." -- some obscure Web scholar in Stephen
Segaller's new book Nerds 2.01: A Brief History of the
Internet
If anything, Tim's original Web manifesto was even more
ambitious than Gopher's. Its hook for assimilating "the
entire universe of network-accessible information" was the
URI, which is able to subsume entire namespaces as merely
one more scheme (telnet:, mail:, and so on). URIs reduced
operational instructions on how to access a resource to a
declarative address. For example, contrast the one-line
ftp: URL with the MIME message/external-body part for FTP
access -- logins, passwords, alternate sites, alternate
directories, alternate formats. As RFC 1630 intended "URIs
may, if necessary, be passed using pen and ink."
But while URIs were the innovative essence of the Web, the
other two legs of the triad were less steady. HTML is
merely a markup language which makes it natural to embed
URIs as hyperlinks. URIs could just as well have been
popularized as a pointer format within Rich Text Format,
PostScript, LaTeX, or any other language. HTTP is merely a
lookup protocol which makes it natural to resolve http:
URLs or gateway to other schemes. URIs could just as well
have been popularized as a naming interface to existing
clients for FTP, Gopher, News, etc.
Somehow, though, HTTP/0.9 took root. It is a famously
'simple' protocol, arguably even less useful than Gopher.
Here is its entire grammar:
Simple-Request = "GET" SP Request-URI CRLF
Simple-Response = [ Entity-Body ]
That's right: it only supported one method, GET, and
required a new TCP connection for every transaction. Even
the 1.0 edition, which eventually added authentication and
navigation and simultaneous transfers of several files for
a single "page", had no excuse to be born when FTP was on
the shelf. Except that HTTP had broken authentication,
nonstandard conventions for navigating directories and
welcome/index/home pages, and ran spectacularly afoul of
slow-start for each of its typically-small file transfers.
If HTTP/0.9 was really shipped for no better reason than
that programming separate FTP-Control and FTP-Data channels
seemed too hard, why did it survive? Many of the earliest
"web" sites were, in fact, just ftp: URLs. The saving grace
was 1.0's new metadata headers. It augmented the one-line
request with additional fields for authentication,
arguments modifying the method, and information about the
user-agent's preferred languages and formats. The entity
bodies it returned were prefixed by MIME Content-Types,
last-modified dates, base-URI, and more. This information,
finally, was what took HTTP beyond the realm of file
transfer to hypertext transfer.
The headers are how HTTP's adoption cycle diverged from
Gopher's. Both servers were simple to install and author
content for -- there was even a hybrid gn server which
could vend files over both port 70 and 80. There were kudos
for new sites, in the form of the Web Virtual Library
project at CERN, and later W3C, and early search engines
like Brian Pinkerton's NeXTstep DigitalLibrarian-derived
WebCrawler. The client was the defining wedge. Graphical
web browsers leveraged rich HTML text with MIME media type
headers to display graphical images, to launch helper
applications, and present multilingual content.
Extensibility: the fingerprint of a killer
The straw that broke the Gopher's back wasn't even a
feature of HTTP per se. The synergy of HTML and HTTP in the
graphical browser began with FORMs, through refresh META
tags, up through scripting and applet OBJECTs. While one
protocol stayed lean, the other opened up so much headroom
that it grew into a beast so complex even today's base 1.1
specification takes 160+ pages.
An avalanche of new headers modified GET to only retrieve
the full entity if-modified-since an existing copy, or only
a specified byte-range; enhanced security with keyed-digest
passwords; even reverse-engineered state back into HTTP
using 'cookies.' HTTP reply codes were added for payments,
for cache validation, for upgrading to new protocols.
Entirely new functionality could be grafted on HTTP using
new methods. WebDAV added LOCK and PUT; collections which
allowed MOVE and COPY on entire swaths of URLspace; and
even went beyond new headers to encoded additional
parameters in XML. Conversely, HTTP was borrowed wholesale
for new protocols for printing (IPP), multiparty call setup
(SIP), and event notification (RVP).
Politically, any server or client could inaugurate a new
method; third-parties could even thread themselves into the
proxy chain and filter messages in transit. Proxies exist
to add public annotations (Crit-Link Mediator), anonymize
access (Lucent Personal Web Assistant), convert file
formats (ProxiNet for PalmIIIs), language translation
(AltaVista's BabelFish can be so hacked), and content
filtering (PICS). Decentralized extensiblity was key to
HTTP's adoption. Rather than waiting for the IETF standards
process to revise a canonical table of one-letter content
codes, for example, MIME headers could deploy new
content-types on the spot.
At the same time, uncontrolled divergence reduces the value
of the Web platform as the probability of compatible
extensions matching up declines. New versions of HTTP would
appear to be one solution, but there is little political
will to empanel a standing working group to review a
grab-bag of extensions for 1.2, 1.3, ... 39.7 and so on.
What is neccessary? Some hook for identifying extensions,
the level of support required, and which parts of URLspace
are so extended.
W3C has been promoting such mechanisms for years -- three
calendar years! -- to better "Lead the [Controlled]
Evolution of the World Wide Web." At first, the motivating
scenarios were complex economic and social negotiations
(payments, content selection, privacy, cryptographic
algorithms, &c). Early revisions of PEP advertised
preference lists of alternative extensions, applied in
pipelined sequence. PEP could also transport metadata about
which extensions applied to other resources and required
orders.
Though PEP remained a W3C experiment, the basic ideas of 1)
packaging an entire extension -- methods, headers,
encodings and all -- behind a single name and 2) indicating
clearly if an extensions was required or optional for 3)
the next hop or end-to-end were reincarnated as the
Mandatory proposal. The current draft defines four header
fields enumerating the URIs of the extensions which apply
(Man: and Opt: for client and server; C-Man: and C-Opt: for
the next hop). To interoperate with the installed base, any
request with mandatory extensions prefixes the method name
with 'M-', which forces 1.0 and 1.1 servers to fail with
"501 Not Implemented."
Transport: the Achilles' heel
By April 1995, Web usage passed Gopher's share as well as
every other Internet application protocol as a fraction of
NSFnet backbone usage. Even patching its bandwidth leaks
with 1.1's persistent connections can't mask HTTP's
inefficient waste of Internet resources. Its content base
has grown so immense that caching alone can't reduce
bandwidth demand by a significant margin for the average
user or ISP. Former strengths have now become liabilities:
full 'English' headers, stateless transactions, full
enumeration of client capabilities once critical for
debugging now inflate request packets while progressive
rendering of composite web pages places a premium on
simultaneous downloads (aggravating the share of packets
wasted on handshakes and delayed by slow-start).
Individually, these phenomena have appeared in application
protocols before -- and were nipped in the bud by active
involvement by transport protocol folks, or coevolved with
TCP. When Telnet generated a packet per keystroke, even on
links where you could type faster than the ACKs returned,
the Nagle timer throttled TCP down to batching keystrokes
into a single packet per round-trip. When file transfers
immediately swamped LANs, slow-start eased up to limit
congestion.
So when HTTP presents its demand for many small transfers
in parallel immediately, there are solutions on the shelf.
Some vendors are already marketing "accelerators" which
rely on matched encoders at server and client, like
Sitara's SpeedServer. Unfortunately, these approaches
aren't backward compatible with HTTP as-is -- nor as simple
to code.
W3C's HTTP-NG (Next Generation) project sees it as a
three-layer problem: message transport, remote invocation,
and "The Classic Web Application" (TCWA). At the bottom,
they propose a multiplexing protocol which combines all the
traffic destined for a single web server into a single TCP
connection. This allows the conversations regarding
individual transfers to be diced up independently: an
intelligent server might respond with the first few
critical bytes of all the images in the first packet. A
fully specified W3Mux layer still needs to address flow
control (gating the relative priority of the subchannels
without starving them), simultaneous open (which TCP does
allow), and lots of interoperability testing.
The middle layer 'compresses' the data to be transferred by
marshalling arguments in native data types rather than
English. So numbers would be sent as integers; dates as
binary fields; and strings as reusable tokens. The tip of
their proposal (reaching into the cloudy heights of
improbability, some critics might say) is reengineering the
Web as a distributed object system, modeled as operations
on data structures rather than documents.
Building the Perfect Beast
Having slain Gopher (and a host of other competitors), the
Web appears to be expanding in all directions today. Just
as the SMTP state machine defined a style or protocol
design for a generation, every new application these days
seems to ape HTTP's state-less style -- if only to
piggyback a free ride through firewalls at port 80. The
Internet Architecture Board is on the verge of issuing
guidelines to rein in this tendency. First, the HTTP port
should be reserved for protocols which manipulate the kind
of information already in web servers. WebDAV is OK, since
it extends documents; IPP would not, since it uses POST as
a barn door for its printing procedure calls. Second, HTTP
should not be referenced by-copy. Lots of other efforts
want to 'borrow' a few headers for authentication or
navigation and end up copying text into other specs,
raising the scepter of divergent versions. Third, HTTP is
not a valid precedent for MIME users -- it plays fast and
loose with certain rules which enable absolute
interoperablity through mail gateways. HTTP allows bare
<CR> and <LF> as well as inventing a new Content-Encoding:
process.
The IAB guidelines are a reminder that HTTP still occupies
a limited niche in the space of possible Transfer
Protocols. True, its message format can encode any MIME
entity, even live data streams -- but only from the server
to the client. True, its address format can point at
anything -- but even then it can't encode whether the
resource is expected to be secured, paid for, or otherwise
reprocessed. And it is most certainly restricted to
one-to-one, synchronous, request-response (client-pull)
interaction. All the various hacks to 'push' data to groups
of subscribers are, well, hacks: automatic polling, shared
caches, and "we will mail your response within two working
days".
The moral, then, for would-be sucessors to HTTP is to pick
another niche and follow the network effects.
Internet-scale event notification, for example, requires
true push and subscriber management. Current efforts to
shove presence information through HTTP may succeed, but
any larger shift to event-based integration could catalyze
a new, symmetric protocol which allows servers to initiate
connections back to clients. Simply compressing existing
HTTP traffic without adding new functionality faces a
powerful entrenched competitor. Adding programmability,
whether betting on HTTP-NG or the Mandatory scheme, is an
attempt to harness network effects between all the
communities that have been angling to extend HTTP to their
application. Yet, the rewards for cooperation are spread
thin: only the server which simultaneously supports HTTP,
WebDAV, and Internet Printing Protocol would gain from a
common syntax for those extensions.
And now we are left back where we started: the mystery of
protocol adoption. Reuse, extensiblity, simplicity are all
tricks to reduce the cost of implementing a new protocol --
but that doesn't mean the market as a whole will make the
most efficient decision. If you're a Gopher, it may just
bury you :-)
The morbid conceit of this article was inspired by the
first-rate book Aramis by French historian of technology
Bruno Latour. It told the tale of two decades of R&D on a
Parisian peoplemover system in the first person -- the
train itself speaking of its struggle to become, and its
death.
______________________________________________________
Table 1. Fingerprints of a murderer -- Spider or Gopher?
Vitals
Academic NeXTstep hack, about 8 years old; birthmark at
port 70 or 80
First Victim
Notorious primary use was for mere phonebooks; gatewayed
queries to existing campus database and represented results
as hypertext nodes
Disguise
Began without any meaningful type system at all, but soon
grew past file extensions to vend multimedia information,
even negotiating formats
Modus Operandi
Open a new connection, send a one-line demand for the
information at a given address, then receive the response
until connection dies
Come-on
Infiltrate small workgroups with small, easy, and free
tools, promising acceptance with a simple `backlink' from a
master list of servers
Serial Victims
Reaching beyond the degenerate case of static information,
its addresses became entry points to scripts, databases,
and other `stateless' servers
Motive
Even its first manifesto laid out hegemonic plans: to
incorporate, by reference or by proxy, every other Internet
information service.
______________________________________________________
Table 2. Gopher's rudimentary type system used character codes to
prefix selector lines. Gopher+ later added content negotiation.
0
File
1
Directory
2
CSO phone-book server
3
Error
4
BinHexed Mac file
5
DOS binary file
6
Uuencoded Unix file
7
Index-Search server
8
Text-based telnet session
9
Binary file
+
Redundant server
T
Text-based tn3270 session
g
GIF image file
I
Any image file
______________________________________________________
Table 3. RFCs and Internet-Drafts discussed in this issue.
RFC
Date
Title and Comments
1436
Mar 1993
The Internet Gopher Protocol
Described a `fiercely simple' request-response protocol and
menu format
1630
June 1994
Universal Resource Identifiers
Raised the stakes from Gopher's own selectors to any
namespace
1689
Aug 1994
Status Report on Networked Information Retrieval: Tools and
Groups
A wonderful archaeological census of competing protocols,
many now extinct
1945
May 1996
HyperText Transfer Protocol 1.0
Also defined the more primitive 0.9 GET. Even 1.0 only
added HEAD and POST
2068
Jan 1997
HyperText Transfer Protocol 1.1
A vastly expanded contender with better caching, security,
and extensibility
2227
P. Std.
Oct 1997
Simple Hit-Metering and Usage-Limiting for HTTP
Entire RFC defined a single Meter:
2396
D. Std.
Aug 1998
Uniform Resource Identifiers: Generic Syntax
The deceptively small definitive grammar took years to
hammer out
TBA
P. Std
Dec 1998
Extensions to HTTP for Distributed Authoring
Adding locks, collection-resources, and namespace
operations took major reengineering
I-Draft
Nov 1997
PEP -- an Extension Mechanism for HTTP
`Protocol Extension Protocol' had negotiation policies for
pipelining message processors
I-Draft
July 1998
HTTP State Management Mechanism
Cookies took three years from a quick, risky hack to a
reasonably secure mechanism
I-Draft
Aug 1998
On the use of HTTP as a Substrate for Other Protocols
Official -- conservative -- IESG and IAB guidance on port
assignment, URI schemes, and HTTP security
I-Draft
Sep 1998
HTTP Authentication: Basic and Digest
A companion specification for nonexistent (UUencoded
passwords!) and new security.
I-Draft
Nov 1998
HTTP Extension Framework
Pared down to headers which label `Mandatory' and optional
extensions of each message
I-Draft
Nov 1998
Upgrading to TLS Within HTTP/1.1
Using the Upgrade: for Transport Layer Security, in lieu of
a dedicated port like https: at 443
