Transcript 1.1 Introduction

1.1 Introduction
• The Internet and its protocols (IP, TCP, UDP, etc.) were developed
within the ARPANET, a US Department of Defense funded R&D
network.
• Originally the ARPANET was built as a single layer network (Layer 3)
which was assumed to be fairly reliable. A simple Transport-level
protocol (NCP) was used. As the ARPANET developed, several
challenges arose:
* unreliable network components, such as Aloha networks began to
be included;
* LANs began to be attached (reliability & addressing issues)
* overall network management in a multi-network environment.
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• In the late 1970s it was redesigned to use:
* a connectionless Layer 3 protocol to pass between
subnetworks (IP)
* a reliable end-to-end transport protocol (TCP)
1.2 A Brief History
• Basic concepts developed in the mid-1970s.
• In 1973, the Internet Assigned Numbers Authority (IANA,
www.iana.org) was formulated to handle issues related to the
Internet address and other Internet protocol parameters.
• The present form of the major protocols was consolidated 19771979.
• In 1983, the DCA (Defense Communications Agency) split the
ARPANET to form the research-only ARPANET, and the
operational MILNET.
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• In 1983 the Internet Engineering Task Force (IETF,
www.ietf.org) is formulated to handle the Internet
standardization.
• The standards are in the form of Request for Comments (RFC),
followed by a four-digit number, i.e. RFCxxxx
• RFCs can be freely accessed online.
• In 1986 the NSF (National Science Foundation) funded
NSFNET, a long-haul backbone network.
• By 1990, the Internet had expanded to 200,000 computers on
3,000 networks.
1.3 Basic Network Architecture
• The Internet is technologically independent from:
* underlying communications media
* underlying communications protocols
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• Network built on a common connectionless unreliable
packet delivery service.
• A user image of a single network
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• The network is built from:
* Physical networks (AKA subnetworks), which have their
own local delivery mechanisms. E.g. Ethernet, fast
Ethernet, FDDI, ATM, etc.
* Gateways or Routers, which join together the physical
networks. The primary task of Routers is to:
pass Layer 3 (IP) packets from one network to another;
make routing decisions about the destination of the packets
* Hosts with network links, which are workstations,
mainframes, etc. attached to physical networks.
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1.4 Protocol Layering
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• TCP/IP is the main application protocol. A variety of
services can be provided with other related protocols.
• In D E Comer’s view, the Internet can roughly be classified
into 5 layers, compared with the ISO 7 layer structure
(mapping can be found).
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1.5 Internet Address Assignment
• How an IP is assigned to a host computer?
• Two types are available, IPv4 (deployed 1/1/1983) and IPv6 (7/1999).
• IPv4 has 32 bits in “dotted-decimal” form, IPv6 has 128 bits and
hexadecimal form.
Internet Assigned
Numbers Authority
(IANA)
Internet Service
Provider
(ISP)
Regional Internet
Registry
(5 worldwide)
(RIR)
Local Internet
Registry/National
Internet Registry
(LIR/NIR)
End User
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