Basic Networking Concepts 1. 2. 3. 4. Introduction Protocols Protocol Layers Network Interconnection/Internet 1
1. Introduction -A network can be defined as a group of computers and other devices connected in some ways so as to be able to exchange data. -Each of the devices on the network can be thought of as a node; each node has a unique address. -Addresses are numeric quantities that are easy for computers to work with, but not for humans to remember. Example: 126.96.36.199 -Some networks also provide names that humans can more easily remember than numbers. Example: www.javasoft.com, corresponding to the above numeric address. … NIC addr1 NIC addr2 NIC addrN 2
Addressing Internet address Consists of 4 bytes separated by periods Example: 188.8.131.52 -The R first bytes (R= 1,2,3) correspond to the network address; -The remaining H bytes (H = 3,2,1) are used for the host machine. -InterNIC Register: organization in charge of the allocation of the address ranges corresponding to networks. -Criteria considered: → Geographical area (country) → Organization, enterprise → Department → Host Domain Name System (DNS) -Mnemonic textual addresses are provided to facilitate the manipulation of internet addresses. -DNS servers are responsible for translating mnemonic textual Internet 3 addresses into hard numeric Internet addresses.
Ports -An IP address identifies a host machine on the Internet. -An IP port will identify a specific application running on an Internet host machine. -A port is identified by a number, the port number. -The number of ports is not functionally limited, in contrast to serial communications where only 4 ports are allowed. -There are some port numbers which are dedicated for specific applications. Applications Port numbers HTTP 80 FTP 20 and 21 Gopher 70 SMTP (e-mail) 25 POP3 (e-mail) 110 Telnet 23 Finger 79 4