Chapter 12

Internet Connection Protocols and Technologies in the 90s

The Network Takes Shape

The explosion of the World Wide Web in the 1990s was supported by a solid foundation of communications protocols and a variety of connection technologies that allowed ever-increasing numbers of users to access the global network. Let's take a closer look at these key elements.

12.1 Fundamental Internet Protocols:
The Common Language of the Network

Several standardized protocols allowed computers to communicate over the Internet. Here are the main protagonists:

TCP/IP (Transmission Control Protocol/Internet Protocol): This suite of protocols is the very foundation of the Internet. IP (Internet Protocol): Responsible for addressing (assigning a unique IP address to each connected device) and routing (routing data packets across the network to their destination). IP works at the network layer (Layer 3 of the OSI model). TCP (Transmission Control Protocol): It operates at a higher level (Layer 4 of the OSI model) and is responsible for establishing a reliable connection between two hosts, dividing the data into packets, ensuring that they arrive at their destination in order and without errors, and reassembling them. TCP is connection-oriented. Evolution: TCP/IP has remained the basic protocol of the Internet, evolving over time to support new needs, such as IPv6 for the increase in available addresses.
IP (Internet Protocol): Responsible for addressing (assigning a unique IP address to each connected device) and routing (routing data packets across the network to the destination). IP works at the network layer (Layer 3 of the OSI model).
TCP (Transmission Control Protocol): It operates at a higher level (Layer 4 of the OSI model) and is responsible for establishing a reliable connection between two hosts, dividing the data into packets, ensuring that they arrive at their destination in order and without errors, and reassembling them. TCP is connection-oriented.
Evolution: TCP/IP has remained the basic protocol of the Internet, evolving over time to support new needs, such as IPv6 for the increase in available addresses.
DNS (Domain Name System): This system translates human-readable domain names (e.g. google.com) into the numeric IP addresses (e.g. 172.217.160.142) needed by computers to communicate. A DNS server receives a query with a domain name and responds with the corresponding IP address. The distributed architecture of DNS ensures the scalability and robustness of the system.
HTTP (HyperText Transfer Protocol): The protocol on which the World Wide Web is based. It defines how browsers (HTTP clients) request web pages and other resources from web servers (HTTP servers) and how servers respond to these requests, transferring the data (usually in HTML format). Early versions of HTTP (like HTTP/1.0) were pretty simple, with one request for each resource.
FTP (File Transfer Protocol): Used to transfer files between computers over a TCP/IP network. An FTP client connects to an FTP server and can upload or download files. FTP uses separate connections for control (commands) and data.
SMTP (Simple Mail Transfer Protocol): The standard protocol for sending emails between email servers. A mail client (or server) uses SMTP to send a message to an outgoing mail server, which then forwards it to the destination server.
POP (Post Office Protocol) and IMAP (Internet Message Access Protocol): Protocols used by email clients to retrieve messages from incoming mail servers. POP: Downloads messages to the user's computer and, in the default configuration, deletes them from the server. The most common versions in the 1990s were POP2 and POP3. IMAP: Allows users to access messages directly on the server, keeping them synchronized between different devices. IMAP became increasingly popular in the late 1990s due to its greater flexibility.
POP: Downloads messages to the user's computer and, in the default configuration, deletes them from the server. The most common versions in the 1990s were POP2 and POP3.
IMAP: Allows users to access messages directly on the server, keeping them synchronized between different devices. IMAP became increasingly popular in the late 1990s due to its greater flexibility.

12.2 Internet Connection Technologies in the 1990s:
The Speed Dilemma

In the 1990s, several technologies allowed users to connect to the Internet, each with its own characteristics of speed, cost and availability:

Dial-up (Modem): The most popular technology at the beginning of the decade. An analog modem converted digital computer data into analog signals that could be transmitted across the public switched telephone network (PSTN). Another modem at the end of the ISP server converted the analog signal back to digital data. Speed: Typical speeds ranged from 28.8 kbps to 56 kbps (with the introduction of the V.90 standard in the late 1990s). Operation: It established a temporary connection (circuit-switched) by occupying the telephone line. Evolution: Modems evolved with faster standards, but remained limited by the analog nature of the traditional telephone network.
Speed: Typical speeds ranged from 28.8 kbps to 56 kbps (with the introduction of the V.90 standard in the late 1990s).
Operation: It established a temporary connection (circuit-switched) by occupying the telephone line.
Evolution: Modems evolved with faster standards, but remained limited by the analog nature of the traditional telephone network.
ISDN (Integrated Services Digital Network): A circuit-switched digital network technology. It offered digital channels for data, voice and video transmission. Rate: The most common configuration for Internet access was the Basic Rate Interface (BRI), which provided two "B" channels of 64 kbps each (for a total of 128 kbps) and a "D" channel of 16 kbps for signaling. Operation: Required dedicated ISDN telephone lines and an ISDN modem. Evolution: ISDN offered speeds faster than dial-up and was more reliable, but it was more expensive and its availability was not universal.
Rate: The most common configuration for Internet access was the Basic Rate Interface (BRI), which provided two "B" channels of 64 kbps each (for a total of 128 kbps) and a "D" channel of 16 kbps for signaling.
Operation: Required dedicated ISDN telephone lines and an ISDN modem.
Evolution: ISDN offered speeds faster than dial-up and was more reliable, but it was more expensive and its availability was not universal.
DSL (Digital Subscriber Line): A family of technologies that used ordinary copper telephone lines to transmit digital data at high speeds. ADSL (Asymmetric Digital Subscriber Line): The most common variant for residential access. It was asymmetric, meaning that the download speed (to the user) was significantly faster than the upload speed (from the user). This was ideal for web browsing and downloading content. Early implementations offered download speeds from a few hundred kbps to 1-2 Mbps. SDSL (Symmetric Digital Subscriber Line) and HDSL (High-bit-rate Digital Subscriber Line): Other variants of DSL offered symmetric speeds (equal download and upload) and were more used by companies that needed more upload bandwidth. How it worked: Used different frequencies on the telephone line for voice and data, allowing you to use the telephone and the Internet at the same time. Required a DSL modem. Evolution: DSL technologies have evolved over time, with variants such as ADSL2+ and VDSL offering much faster download speeds.
ADSL (Asymmetric Digital Subscriber Line): The most common variant for residential access. It was asymmetric, meaning that the download speed (to the user) was significantly faster than the upload speed (from the user). This was ideal for web browsing and downloading content. Early implementations offered download speeds from a few hundred kbps to 1-2 Mbps.
SDSL (Symmetric Digital Subscriber Line) and HDSL (High-bit-rate Digital Subscriber Line): Other variants of DSL offered symmetrical speeds (equal download and upload) and were more used by companies that needed more upload bandwidth.
How it worked: Used different frequencies on the telephone line for voice and data, allowing you to use the telephone and the Internet at the same time. Required a DSL modem.
Evolution: DSL technologies have evolved over time, with variants such as ADSL2+ and VDSL offering much faster download speeds.
Cable Internet: Leveraged the existing infrastructure of coaxial cable television networks to provide access to the Internet. Speed: Offered download speeds faster than dial-up and often comparable to or faster than early DSL. Speeds could vary depending on the number of users sharing bandwidth on a given network segment. How it worked: Required a cable modem to connect the computer to the cable network. Evolution: The technology behind wired Internet has evolved with standards such as DOCSIS (Data Over Cable Service Interface Specification) to increase speed and efficiency.
Speed: Offered download speeds faster than dial-up and often comparable to or faster than early DSL. Speeds could vary depending on the number of users sharing bandwidth on a given network segment.
How it worked: Required a cable modem to connect the computer to the cable network.
Evolution: The technology behind wired Internet has evolved with standards such as DOCSIS (Data Over Cable Service Interface Specification) to increase speed and efficiency.
Dedicated Leased Lines: Telephone lines dedicated to a single user, which provided a point-to-point connection with guaranteed bandwidth. They were expensive and used primarily by businesses and organizations that needed reliable, high-capacity connections. T1: A digital circuit that carried data at a speed of 1,544 Mbps. It was a common standard for business connections and Internet service providers. T2: A digital circuit with a capacity of 6,312 Mbps. Less common than T1, it was used by organizations with higher bandwidth needs. T3: A high-capacity digital circuit with a speed of 44,736 Mbps. Used primarily by Internet backbone providers and large institutions. Evolution: These dedicated lines have evolved towards even faster standards, such as the OC (Optical Carrier) series, with speeds reaching Gigabits per second and beyond, using fiber optics.
T1: A digital circuit that carried data at a speed of 1,544 Mbps. It was a common standard for business connections and Internet service providers.
T2: A digital circuit with a capacity of 6,312 Mbps. Less common than T1, it was used by organizations with higher bandwidth needs.
T3: A high-capacity digital circuit with a speed of 44,736 Mbps. Used primarily by Internet backbone providers and large institutions.
Evolution: These dedicated lines have evolved towards even faster standards, such as the OC (Optical Carrier) series, with speeds reaching Gigabits per second and beyond, using fiber optics.

12.3 Evolution over Time:

During the 1990s, there was a progressive transition from slow but ubiquitous dial-up connections to faster technologies such as ISDN, DSL and cable Internet, the availability of which gradually increased. Leased lines remained a solution for businesses with specific bandwidth needs. Connection speeds steadily increased thanks to technological advances and the growing demand for increasingly data-rich online content.

Internet protocols provided the rules for communication, while various connection technologies offered the physical means to access the global network. The 1990s were a time of intense evolution in both fields, with dial-up dominating at the beginning of the decade and the first forms of broadband starting to appear towards the end, setting the stage for the rapid growth and transformation of the Internet in the new millennium.