Back to the Basics — Networking: TCP/IP and Internet — Where did it start?
Many years ago, Transmission control Protocol/Internet Protocol(TCP/IP) was known primarily as the protocol of the internet. The biggest challenge of getting LAN connected to the internet was figuring out how to mesh TCP/IP with the proprietary protocols that were the basis of the LANs.
Eventually, both IPX/SPX and NetBIOS gave way to TCP/IP as the basis for local area networking, eliminating the challenge of translating IPX/SPX to NetBEUI to TCP/IP. As a result, TCP/IP is not just the protocol of the internet now, but also the protocol of most LANs are based.
What is the Internet?
The Internet is a network of networks. It consists of hundreds of thousands of separate computer networks, all interlinked, so that the user of any of those networks can reach out and potentially touch a user on any other networks.
- Loosely organized — No single organization has authority over the Internet.
- International — Nearly 200 countries are represented on the Internet
- Collaboration — It exists because many different organizations cooperate to provide services and support needed to sustain it.
- Autonomous — The internet community respects that organizations that join the internet are free to make their own decisions about how they configure and operate their networks
- Interconnected — The whole key to the internet is the concept f interconnections which uses standard protocols that enable networks to communicate with each other.
- Networks — The internet would be completely unmanageable, it consisted of half a billion individual users all interconnected.
TCP/IP Standards and RFCs
The TCP.IP protocol standards that define how the internet works are managed by the IETF. However, IETF doesn’t impose standards. Instead, it simply oversees the process by which ideas are developed into agreed upon standards
An Internet standard is published in the Request for Comments(RFC) document. When a document is accepted for publication. it is asssigned an RFC number by the IETF. The RFC is then published. If the standard is enhanced, the enhancement is covered in a separate RFC.
Proposed Standard — Generally stable, have resolved known design choices, are believed it to be well understood
Draft Standard — Well understood and known to be quite stable. At least two interoperable implementation must exist, developed independently from separate code bases.
Internet Standard — Have been fully accepted by the internet community as highly mature and useful standards
The TCP/IP Protocol Framework
Like the seven layer OSI Reference Model, TCP/IP protocols are based on a layered framework. TCP/IP has 4 layers. These layers are shown in the diagram.
Network Interface Layer
The lowest level of TCP/IP architecture is the network interface layer. It corresponds toe the OSI physical and data link layers. You can use many different TCP/IP protocols at the network interface layers including Ethernet and token ring for LANs and protocols such as X.25, Frame Relay and ATM for wide area networks (WANs)
The network interface layer is assumed to be unreliable
Network Layer
the network layer is where data is addressed, packaged and routed among networks. Several important Internet Protocols operate at the network layer:
- Internet Protocol — A routable protocol that uses IP addresses to deliver packets to the network devices. IP is an internationally unreliable protocol, so it does not guarentee delivery of information
- Address Resolution Protocol(ARP) — Resolves IP addresses to hardware Media Access Control (MAC) addresses, which uniquely identify hardware devices.
- Internet Control Message Protocol(ICMP) — Send and receives diagnostic messages. ICMP is the basis of ubiquitous ping command
- Internet Group Management protocol(IGMP) — Used to multicast messages to multiple IP addresses at once.
Transport Layer
The transport layer is where sessions are established and data packets are exchanged between hosts. Two core protocols are found at this layer:
- Transmission Control Protocol(TCP) — Provides reliable connection-oriented transmission between two hosts. TCP establishes a session between hosts and then ensures delivery of packets between the hosts
- User Datagram Protocol(UDP) — Provides connectionless, unreliable, one-to-one or one-to-many delivery
Application Layer
The application layer of the TCP/IP model corresponds to the session, presentation and application layers of the OSI Reference model. A few of the most popular application layer protocols are
- Hypertext Transfer Protocol(HTTP) — the core protocol of the World Wide Web
- File Transfer Protocol(FTP) — A protocol that enables a client to send and receive complete files from a server
- Telnet — the Protocol that lets you connect to another computer on the internet in a terminal emulation mode
- Simple Mail Transfer Protocol(SMTP) — One of several key protocols that are used to provide email services
- Domain Name System(DNS) — the protocol that allows you to refer to other host computers by using names rather than numbers.
More about OSI Layer —
Happy Learning!!
