Detailed historical online network services and Internet delivery dates and
5th day of October 2009,
Don E. Sprague
The history of computer networking has 4 basic parts. They are:
1 Base building evolution - 1949 to 1984,
2 Structured rapid expansion - 1984 to 1995,
- (Government Internet contract 1988 to 1995),
3 Protocol consolidation and conversion 1995 to1996, and
4 Natural growth 1996 to today.
Before computers, in 1809, there was telegraph being used for electronic mail and electronic business. People and business order
products electronically using telegraph and then teletype. The first national defense computer work began in 1949 and it eventually
included online services. In 1953, work began on the first commercial online ordering system which was an airlines reservation
system. In 1962, work began on a US military network that was a forerunner of the work that led to the development of the Internet
Protocol. In the mid 1970's, IBM computer repairmen uses a hand held online computer to record service reports, order parts and do
other online activity using the telephone company text networks. In 1980, the Electronic Customer Support Architecture and Strategy was
written. It was the first business model for interconnection of all users on all networks to enable any to any for business and private
electronic communication. In 1982, Videotext in France allowed people to dial in and place online orders. In 1983, The IBM
Information Network was the first network to formally adopt the architecture and business model to interconnect all users on all
network. In 1988, The government team working on Internet Protocols recognized that Internet Protocols could not compete with the
1980 commercial business model unless they adopted the open commercial any to any business model. They enlisted the help of Al
Gore to get funding to hire companies to develop a new Internet protocol and to get the law changed to allow business to be conducted
by networks using the Internet Protocol. Due to the Internet Fair Use Rules, business could not legally be conducted on the
government funded Internet until the mid 1990's. By definition, the name "Internet" is not tied to the Internet Protocol. Therefore, the
name Internet is a generic name that applies to any to any interconnected networks and designs including the commercial path which
began with the introduction of the 1980 Electronic Customer Support architecture and first implementation by the IBM Information
Network in 1983. All Internet business models are based on the original 1980 business model.
Base building evolution 1949 to 1984
SAGE: The First National Air Defense Network
August 29, 1949, was the beginning of SAGE (Semi-Automatic Ground Environment). It eventually become an online national air
defense system. In 1952, MIT selected IBM to build the computer to be the heart of SAGE. In 1956, IBM delivered the prototype of the
computer to be used in SAGE. When fully deployed in 1963, SAGE included 23 centers. Ultimately, 54 systems were installed, all
collaborating with each other. The SAGE system remained in service until January 1984, when it was replaced with a next-generation air
AT&T’s Dataphone became the first commercial modem. It converted digital computer data to analog signals for transmission across
phone lines. Prior to this product, computers could only be linked or “interconnected” within the same facility. Both before this product
and after this product, computers were “interconnected” and exchanging data. This product allowed connections outside the building.
Without the AT&T accomplishment, or a comparable accomplishment, we wouldn’t have the Internet by any name.
Technical plan - preceded military, Arpanet, Internet and IP
Business plan - Yes but does not directly apply to building toward eventual Internet
IBM Virtual Network (VNET) anecdotally informally began. VNET was an internal use only network. It supposedly began when 2 people
at different IBM facilities informally established a connection. Gradually more people in more locations established informal connection.
Eventually in about 1970, it became a formal managed network. The VNET grew to be much larger than the Arpanet ever accomplished.
The VNET did have a government use spinoff called BITNET that was modeled after VNET.
Technical plan - Initially no, Eventually yes but didn’t directly continued to eventual Internet
Business plan - Initially no, Eventually yes but didn’t build toward Internet. It was specific as closed to IBM Internal.
US Air Force initiates work on what became the Arpanet. It was a defense and military project that provided the technical requirements
for a military network.
Technical plan - became base for military Arpanet and eventual term “Internet” and IP.
Business plan - Military oriented and doesn’t apply to build toward what we know of as the commercial Internet. It was specific as a
closed military network.
Sabre: The First Online Reservation System
The First Online Reservation System got its start in 1953 as a result of a discussion between an IBM Salesman and the president of
American Air lines. The Sabre reservation system was built in 1960, with lessons learned from IBM’s project to build the SAGE (Semi-
Automatic Ground Environment) air defense computer system. By the end of 1964, the two interconnected computes and thousands of
terminals were handling 7500 reservations per hour.
The American Standard Code for Information Interchange was made available,. This standard permitted machines from different
manufacturers to “interconnect” into a “network” and exchange data.
This accomplishment contributed to growth of commercial services that were in place before the mid 1990s when they changed to use
Technical plan - defined cross computer communication or “interconnections” of computers and ”networks” which preceded military IP
cross computer technical plan.
Business plan - NONE or does not apply.
IBM announced the IBM 360. After that computer hit the market, computer based electronic communication became viable on a much
larger scale. Various parties engaged in developing computer to terminal and computer to computer communication.
Technical plan - existed but only indirectly applies to military, Arpanet, Internet and IP. The IBM 360 was used by all levels of business
and government. It was one of the early computers used for electronic delivery of services.
Business plan - existed but only indirectly builds toward eventual Internet. See technical plan.
Over the next few years, thousands of business and government networks were developed. They were separate independent networks
that had no external interconnections. IBM had developed SNA (System Network Architecture) which was a language for orderly
“interconnections” between “networks” and computers as well as terminal to computers. Thousands of companies and various levels
of government were using IBM’s SNA or other providers communication protocols as well as standards developed languages. IBM’s
SNA was the defacto standard because of it’s dominate wide scale level of acceptance and use with millions of users.
Technical plan - existed but doesn’t apply to government military Arpanet and Internet. Does apply to commercial “interconnections” of
business networks and delivery Internet type online network services.
Business plan - existed but doesn’t build toward eventual Internet. Does apply to commercial “interconnections” of business networks
and delivery of Internet type online network services.
ARPA awarded contract to BBN to build the ARPANET.
Technical plan - continued to build toward military Arpanet and eventual Internet name and IP.
Business plan - didn’t build toward eventual Internet. It was specific as a closed military network.
ARPANET physical network linking four nodes. This setup came years after the Sabre online reservation system was operating.
Arpanet also came years after the standards were defined to allow “interconnections” of different computers. I listed just a few of the
examples of prior work with interconnecting computers. There are only two significant aspects of the first bit transmission on that day in
1969 that was one year after the contract to build and 7 years after the initial requirement. It was just the first day for another network and
it was the first connection failure for that additional network. It was a LOGON attempt that failed after L O was sent. It took additional
work to catch up with other existing networks that had been sending LOGON and performing work for years. However; Arpanet is
affiliated with the NSF which ultimately awarded a contract to IBM, MCI and Merrit system in 1988 to develop and build another network
and they called the Internet.
Here is an analogy for the military requirement resulting in the Internet. A few years after airplanes were first made, the military bought
some of the airplanes. Then the military asked for some special features like gun mounts. Many years later, the military hired some
companies to build an aircraft carrier. Then the military hired some companies to build a soft land airplane that it used on aircraft
carriers. Then airplane companies were allowed to use some of the new soft land stuff the military uses on it’s airplanes. Therefore,
since the military has a soft land airplane that land on aircraft carriers, and business used some of the soft land technology the
government requested for their airplanes, then the military gave us airplanes. But we all know that airplanes came first and military
aircraft came second and soft land stuff came third. The same applies to the Internet. Now we all can understand that electronic
services delivery came first, then IP came second, the Internet name came third, with the conversion of older larger networks services to
the use of IP and the Internet name for the prior existing services came fourth.
It seems that the NSF had something old and bought something new. The semblance of an architecture for Arpanet specified that it
was to be used for government, academic, and research only. It was for military advanced research projects. It specifically excluded any
form of business use. Other existing networks were already being used by and for business. The same fair use rules also still applied
to the 1988 NSF Internet to specifically prohibit any communication other than government, academic, and research without any
If the Arpanet and the NSF never existed, the ISP Internet provided services did and would have continued to exist almost as they are
today and would have arrived at the same time they arrived. The name “Internet” probably wouldn't be used. Instead, it might have
continued to be called online or network services or e business or global network. It might have simply become known as the “ENet”.
Technical plan - continued to build toward military, Arpanet and eventual Internet Protocol. Didn’t build to Internet we know of today.
Business plan - didn’t build toward eventual Internet. It was specific as a closed military network or government internal networks.
IBM computer repairmen used a small hand held computer about the size of a brick It had a keyboard and display and communicated
through the telephone company text services. The repairmen received dispatch information, entered and uploaded service repair
records, and ordered parts among other things. That hand held device is a forerunner of the smart phone.
CompuServe became the first major commercial online service provider in the USA. It was a dominate service provider through the
1980s and was ultimately purchased by AOL. This is one example of a predecessor of the ISP Internet that we know of today. Although
it didn’t evolve to become “the ISP Internet”, it did become “one of the ISPs” that make up the Internet.
This is a perfect example of one of the service providers that evolved to become part of the Internet. It existed years before the IP and the
Internet name became available for commercial business use. It simply changed protocols.
Technical plan - existed but doesn’t apply to military Arpanet and Internet. Does apply to commercial delivery Internet type online network
Business plan - existed but doesn’t build toward eventual Internet. Does apply to commercial delivery Internet type online network
The Electronic Customer Support Architecture and strategy was first written. An IBM Washington System Center representative coined
the phrase; “anything that can be recorded electronically can be delivered electronically”. From that beginning, he wrote a paper that
contained the initial e business or Electronic Customer Support Architecture and Strategy.
Technical plan - NONE
Business plan - This requirement was specifically created with the intent of defining an architecture and strategy that provides a path for
what to do and how to get to the generic Internet environment we know of today.
BITNET Bitnet which stands for Because It is Time was established. It was modeled after IBM’s VNET. While BITNET had fair use
rules like Arpanet, it wasn’t military based. It was for widespread education and research communication with a wider audience than
Arpanet so it had more connections than Arpanet. In a very short time it had all state governments and most if not all higher education
facilities connected at several locations. It had thousand of connections when it converted to the Internet Protocol.
Technical plan - existed but doesn’t apply to military Arpanet and Internet
Business plan - existed but doesn’t build toward eventual Internet. It was closed to business just as the military Arpanet and Internet
were closed to business.
IBM Information Network, later named the IBM Global Network was made available. The Global Network began as another Value Added
Network (VAN). The Global Network became the fastest growing of all network service providers. It is one of the most successful pre-
ISP Internet type service providers of all the various VANs and online service providers. It continued its growth through the 1980s and
1990s. It eventually changed it’s protocol emphasis from IBM’s SNA to IP. During it’s rapid growth pre-Internet phase it acquired a
competing Value Added Network that was delivered by Seras. The combined larger VAN became known as Advantis. Before it made the
switch to becoming another ISP in the 1990s, it was the biggest customer of the three largest telephone companies in the USA. In
addition to using more transmission facilities of the three phone companies than any of their other customers, it had significant in
house owned transmission facilities. When it became an ISP, the Internet growth monitors were able to add huge numbers of Internet
hosts and links and users. These existing users and networks were counted as new Internet growth numbers instead of existing
connections that simply converted to IP and the Internet. After the conversion to the Internet Protocol, the global network was purchased
by AT&T. As a part of AT&T it is still a major provider of service in the ISP Internet
This is a perfect example the Internet numbers showing rapid growth when actually, the business already existed using a different
protocol or language. The Internet growth numbers don’t have a field for conversion to IP and another field for new networking business.
The NSF people had to be aware of this business in 1988 and it must have influenced their thought process when they unofficially
ignored the fair use rules allowing their new network to compete instead of languish. The employees of all three companies hired to
build the NSFs new network in 1988 also had to be aware of the IBM Global Networks existing rapid growth and it’s electronic customer
support architecture and strategy.
Technical plan - existed and apples to eventual Internet. It’s plan was specific to be open to all technology and have cross technology
communication to allow and encourage complete “interconnections” of all users on all “networks”. .
Business plan - It specifically included the philosophy that any user on any network using any technology should and would be able to
communicate with any user on any network using any technology. It’s business plan was inline with it’s Architecture and Strategy that
was based on the IBM Electronic Customer Support Architecture and Strategy. The same person authored both the initial IBM ECS
paper and the IBM GN architecture and strategy. This activity was visible in the networking world. Eventually; all other public and private
use networks had to adjust their business plans to coincide with the Global Network architecture and strategy. The eventual ISP
Internet exactly matches the results specified in the Global Network Architecture and Strategy.
Minitel Videotex online service was announced in France. Users could make online purchases and perform various online activities
including chat similar ISP Internet chat capability. It converted to the Internet Protocol and became an ISP. It is still a large successful
ISP that predated the US government’s NSF Internet contract by 3 years. It predates the ISP Internet by 13 years.
This service would have continued to be a success without the US government’s NSF entry into the Internet contract.
This is another perfect example the Internet numbers showing rapid growth when actually, the business already existed using a
The NSF people had to be aware of this business and it must have influenced their thought process.
This is one example of international network services and online services. Both commercial and governments worldwide were
deploying networks and online services years before the NSFs contracts and it’s IP and Internet merger with older larger existing
Technical plan - existed and apples to the ISP Internet
Business plan - When Minitel began, it had a business plan that was and still is consistent with the ISP Internet we know today.
2 Structured rapid expansion - 1983 to 1995,
Until 1983 all the Value Added Networks and Online service providers were focused on their niche. Most were also country specific. The
military Arpanet had spun off other government networks and they were focused with fair use rules that prohibited any business.
The IBM Information Network adopted the Business Model that became the Internet Business Model. It’s Electronic Customer Support
activity kicked off it’s rapid growth. The IBM ECS paper written in 1980 became the basis for the Business Model and the Information
Network Architecture and Strategy. It conducted a series of activities to exploit the Business Model and architecture and strategy
resulting in a rapid expansion of it’s customer base between 1985 and 1995.
Technical plan - This is specifically intended to provide “interconnected networks” for commercial business communication. It drove the
development of all kinds of Internet Business Model service prior to the Internet adopted the IBM IN Business Model.
Business plan - yes, see above.
The Internet switched from NCP to TCP/IP.
Prodigy began its online service as a pre ISP Internet service provider. It was a joint venture between IBM and Sears. It followed a prior
joint venture between IBM Sears and CBS. Like the France Videotex , it allowed subscribers to search for information and do other
activity such as banking and shopping.
Technical plan - This was another Internet type service provider that existed prior to the Internet.
Business plan - Was specific to provide online commercial network services prior to Internet.
InfoExepress, a formal IBM Electronic Customer Support expansion push was announced. It was a further activity to exploit IBM’s ECS
activity and drive the global network architecture and strategy.
Technical plan - This is specifically intended to stimulate “interconnected networks” for commercial business communication. It drove
the development of all kinds of Internet type service prior to the Internet.
Business plan - see above.
TCP/IP researchers began work to get Al Gore to support funding for new TCP/IP network to be able to compete with the IBM Information
Network Business Model. TCP/IP owes it's existence to Al Gore and the other legislators who approved spending to further develop
An operating network invention disclosure was published. That Invention disclosure described an intelligent network that allowed any
point to be an origination point, intermediate point or a destination point. Throughout the network, the components would share
information about other locations. The address schema was similar to the phone company address schema in that it had levels that
were separated by “-“. For example, an address might be abc-xyz-1234. The intent was to allow a virtually unlimited address capability.
The purpose of that address schema was to eliminate the potential problems with other transmission protocols. The overall invention
disclosure intent was to have a flat structure without any hierarchy and one that allowed any point to be a server, router or client. The
invention disclosure eluded to the natural extension of the system throughout the network resulting in the elimination of distinction
between system and network. Since the Invention disclosure was rated publish, it became public domain which made it available for
use my anybody without tracking.
Technical plan - None. It was a statement outlining a requirement for a technical plan.
Business plan - NONE.
Computer shorthand invention disclosure was published. Computer shorthand is the use of each bit to represent a complete word or
meaning. One bit can represent a full screen or a name to be inserted in a field in a full screen.
Technical plan - None. It was a statement outlining a requirement for a technical plan.
Business plan - NONE.
TCP/IP researchers said TCP/IP was seriously inhibited by not using the Commercial Business Model. They recognized that TCP/IP
was on a path to demise if it didn't build a new TCP/IP and that is must adopt the open any to any commercial business model instead
of the closed Arpanet restrictions.
Al Gore and other legislators assisted in getting approval to allow the government research network to adopt the commercial Business
Model. If TCP/IP had not been allowed to participate in the existing larger commercial business, the Business Model would have
continued without using TCP/IP.
NSF issued a contract for IBM, MCI and Merrit Systems to build the NSF Internet to replace the NSFs Arpanet. The new NSF Internet had
the same fair use rules that specifically excluded all business that the ISP Internet is know for today. In 1988 when the NSF issued the
contract, there were thousands of public and private networks. We have already seen that the Arpanet didn’t lend anything to the
networking service world. The 26 year old Arpanet was an insignificant government funded network for government, academic and
research. Statistically, based on user population and lines, it barely existed and would have been lumped in a category of all others. The
NSF or it’s military Arpanet experienced people didn’t have an architecture or strategy to deliver what we know of today’s Internet.
As long as the fair use rules exist, the government NSF Internet couldn’t become part of the global network. The significance of the NSF
Internet contract is the addition of IP and the name “Internet”for the already functional huge commercial global networks.
When the government funded NSF Internet was first available, in many ways it was a much better information source. The fair use rules
kept the business activity out. When I did a search, I found good information because it wasn’t filtered with the answers sorted based
on business interests. Now when we do searches, there are hundreds or even millions of answers and they are filled with business
interests. By the time the government NSF Internet was delivered by the contacted companies, the breadth and scope of activity of the
existing huge commercial networks well underway but without the unifying name “Internet: and different protocols were used. Fair use
rules were the closest thing to an architecture and they were specifically in opposition to the ultimate function of the later ISP provided
Technical plan - built on military Arpanet historical requirements.
Business plan - didn’t build toward eventual Internet. It was specific as a closed to government, academic and research.
If the fair use rules had been enforces instead of unofficially ignored, this network would have been one of the lesser also ran networks.
NSF Internet Fair use rules were officially - unofficially ignored. That is an anecdotal event. All users were officially required to read and
comply with the fair use rules. This unofficially ignoring of the fair use rules was necessary to prevent the NSF provided Internet from
remaining the closes and limited network like the military Arpanets had been for 29 years. That was in part because prospective users
of the government’s new NSF provided Internet were already connected to the Global network or to BITNET or other commercial
providers. The biggest problem with the NSFs provided Internet was it’s poor performance, lack of reliability and lack of security. IP was
the least robust language or protocol for “interconnecting networks”. It’s design was for closed use within an enterprise instead of open
use across enterprises “interconnected networks”. Other protocols were much more robust since they were intended for cross
enterprise use. Also, anecdotally, the NSF’s Internet was in part made up of routers in universities where students could view and alter
any traffic that went through the university router. Users didn’t send confidential information. Anecdotally users sent the same stuff three
times with hope that one of the three would arrive at the other end. The NSF Internet couldn’t possible become a widely used or
generally accepted service even though the anecdotal wink about the lack of enforcement of the fair use rules did stimulate it’s growth.
Without the government contract, for the NSF funded Internet, the function and capability of the ISP Internet did already and would have
continued to exist with the same scope and scale.
Technical plan - built on military Arpanet. Was an acceptable technology for closed or restricted communications within the government
Business plan - Was specifically for closed and fair use restricted use. Did NOT officially adopt the Business Model.
However; when the fair use rules were anecdotal official unofficially ignoring, the NSF Internet had tacitly adopted the IBM Global
Network Business Model or architecture and strategy. While it officially remained closed to government, academic and research, it
unofficially followed or embraced the prior existing commercial Business Model.
3 Protocol consolidation and conversion 1995 to1996, and
Existing network services providers began a transition from other protocols to IP and they became know of as Internet Services
Providers. The NSF Internet went away and it was replaced by the ISP provided Internet. The ISP Internet had a few major changes
from the NSF funded Internet. The new ISP Internet was a commercially delivered service that used the Internet Protocol. As a
commercial business venture, it didn’t have the all the security problems of the short lived NSF Internet. Sure, traffics to universities
went through their gateway but that wasn’t as much of an issue outside the universities. Reliability and performance significantly
improved because it was a business instead of a research project. The fair use rules didn’t exist. This major step meant the entire
Electronic Customer Support or Global Network architecture and strategy for business to business, along with business to consumer
and private individual to private individual could be conducted.
Technical plan - Used public techniques such as telephone type address abc-xyz-1234. Used computer shorthand bit to name
substitution. Used flat network approach with each point equal as origin, router or destination. Used intelligent network information
sharing. All those key aspects were in the public domain.
Business plan - It adopted the core component of the network business model that had existed since 1980. It specifically included the
philosophy that any user on any network would be able to communicate with any user on any network. It was up to non-IP networks to
provide their own gateway to IP. It unofficially didn’t have any of the historical fair use rules. The ISP Internet business model exactly
matches the results specified in the Global Network Architecture and Strategy.
4 Natural growth 1996 to today.
This phase is simply a continuation of the architecture and strategy that was defined in 1980. By the mid 1990s, basically, the business
world was already doing business to business communications. Service providers and their customers conducted their migration to the
Internet Protocol. There was some additional business connection growth but all of the major US companies and many of the major
worldwide companies were already connected for e business so business networking growth slowed. They were already connected to
their service provider. They just needed to change to IP. While there were hundreds of thousands of businesses and hundreds of
millions of users already connected to pre-Internet service providers, there were hundreds of millions of individual users who were new
business. There was a low cost wide array of network services available to attract individual users. The field was open for new
businesses to emerged with a ready made customer base eager to use new capabilities That meant new service opportunities were to
be created. The philosophy of “anything that can be recorded electronically can be delivered electronically” had finally been realized.
Some things like school friends and class reunion communication weren’t a surprise. Online auctions were a surprise but were part of
the any thing recorded electronically can be delivered electronically philosophy. E-mail was already being fully exploited by business.
The people at work wanted to forget computers at home but they still liked the E-mail capability idea for use with friends and family. So
they helped stimulate other individual users to sign up for E-mail and other online services. Technology existed for new age conversion
from things like passing notes in class to text messages in class.
Since 1999, some people rationalize the slowing growth of the Internet user population. It has basically reached the maturity phase
defined in the 1980 architecture and strategy. Just because the individual users to individual users phase was the final stage of the
strategy by 1999, it doesn’t end the growth opportunity. We just need a new architecture and strategy to drive new requirements and
What is the true story of where the Internet came from?
It came from years of growth from competition between commercial system and network component and service providers. Then they
all agreed to convert to the use of a common language.
If there is one first day for the ISP Internet we know today, it is that day when the Commercial Internet Service Providers began delivering
service on the ISP Internet that is strictly a full function commercial service. The debt of thanks for the ISP Internet goes to all the work by
millions of people in hundreds or thousands of companies who made some small and some very large contributions from 1960 to
today. A small thanks is proper for the US Air Force for initiating the military project that led to the contribution of the Internet name.
Those in the military path were just a few of the millions who made contributions.
The Internet generically retro-applies back through the military path and should or does also retro-apply to the much larger older
commercial path that gave us 50 years of commercial online and network services.
any network to communicate with any user or user on any other network to perform electronic business and
do social networking. It is based on the statement that: anything that can be recorded electronically can be
What is IP. It is the protocol that all network managers adopted. IP is like concrete on a highway. Any road
surface or technology can work on the highway.
Who invented the Internet?
The answer has two parts, Many people invented the technologies, One person invented the business
model of a shared online network to allow any to any to any. There were millions of users on hundreds of
thousands of networks while IP was being developed. In 1980, all the existing networks were isolated. That
is when the Business Model for connecting all networks was invented. All network providers adopted the
business model while IP was being invented. The Internet protocol was invented as a technology for closed
government networks. Eventually, the managers of the closed government networks adopted the existing
open commercial business model.
The Internet business model began as the Electronic Customer Support Architecture and Strategy. The IBM
Information Network Marketing Guide included the business model as a marketing approach years before IP
was made available for commercial use.
See scanned pages from the 1985 IBM Information Network Marketing Guide showing the ECS business
See scanned pages from announcements and news letter articles showing the success of the ECS model
In an article called “What Is The Internet (And What Makes It Work) - December, 1999 By Robert E. Kahn
and Vinton G. Cerf” they write:
For a long time, the federal government did not allow organizations to connect to the Internet to carry out
commercial activities. By 1988, it was becoming apparent, however, that the Internet's growth and use in the
business sector might be seriously inhibited by this restriction.
When the Internet Business Model was 8 years old and in place, it was adopted by the developers of IP.
How to have a Secure Internet
We can not have good security if we do not know who is supposed to do what. That means, great security begins with a
detailed registration process to provide comprehensive information about each user and the connections they approve.
In the past, there were different communication methods or languages for the many Value Added networks. They all adopted
a common communication language and became Internet Service Providers. They did not adopt a common network
management structure. There is a new Internet Secure Internet Architecture that provides a common network management
structure that all ISPs can adopt.