Networking Introduction

These are simply some notes I took while reading the textbook Computer Networking, J. Kunrose and K. Ross, Pearson 2012.

The Internet

End systems are connected together by a network of commmunication links and packet switches. A packet switch takes a packet arriving on one of its incoming communication links and forwards that packet on one of its outgoing communication links. End systems access the Internet through Internet Service Providers (ISPs), which is essentially a network itself.

End systems, packet switches and other pieces of the Internet run protocols that control the sending and receiving of information within the Internet.

The Internet can also be described as an infrastructure that provides services to applications, applications which are running on the end systems. End systems attached to the Internet provide a socket interface which is essentially a set of rules that the sending program must follow so that the Internet can deliver the data to the destination program. Using different socket interfaces the application are able to exploit different services provided by the Internet.

Protocols

A network protocol is similar to a human protocol and all the activities in the Internet involve two or more communicating entities are governed py protocols. The entities, in order to communicate with each other, must run the same protocol to accomplish the task. Different protocols sre used to accomplish different communication tasks.

Thus a protocol defines the format and the order of messages exchanged between two or more communicating entities, as well as the actions taken on the transmission and/or receipt of a message or other event.

The network edge

The Internet's end system are typically desktop computers, servers, mobile devices and an increasingly growing number of devices related to the IOT upcoming world. End systems are usually referred to as hosts because they host application programs. Hosts are further divided into two categories:

• clients
• servers

Informally clients tend to be PCs, smartphones and so on, while servers tend to be more powerful machines that store and distribute web pages. stream video, and so on.

Access networks

Access networks are essentially the network that physically connects an end system to the first router (edge router) on the path to the receiver end system. The most common type of access networks are:

• DSL (Digital Subscriber Line): this type of connection uses the existing telephone wire connection (twisted-pair copper wire) to connect to the Internet, the speed connection is quite low, an example of transmission rate is of 55Mbps downstream and 15 Mbps upstream.
• Cable Internet acces: it makes use of the television cable infrastructure, it provides a shared broadcast medium and the typical rates are up to 43 Mbps downstream and 31Mbps upstream.
• Fiber to the home (FTTH): it provides an optical fiber connection to the provider central office, the connection is then spitted into different optical fibers reaching the single houses; there are two possible network architectures to perform this splitting: active optical networks (AONs) and passive optical networks (PONs) (which exploits an optical spitter). This type of connection is very fast and it can provide speed rates up to Gbps.
• Satellite link

Usually inside of institutions (but even of houses) the local area network (LAN) makes use of ethernet connections, while in case of wireless connections the wireless area network (WLAN) are based on the WiFi technology.

Just as a side note the most important network categories are:

• Personal area network (PAN)
• Local area network (LAN)
• Metropolitan area network (MAN)
• Wide area network (WAN)
• Global area network (GAN)

If the connection is wireless you usually add wireless in front of these names (i.e. wireless personal area network (WPAN))