Lesson 1
The OSI model (Open System Inter-connect): this is a 7 layered model which covers all the aspects in the environment of computing, the steps are as follows:
- Physical Layer - Media, signal and binary transmission (can also be the hub or repeater)
- Data Link - Physical addressing (The switch would fit in here)
- Network - Path determination and logical addressing (the router would fit in here)
- Transport - end to end connections and reliability
- Session - Interhost communication
- Presentation - data representation and encryption
- Application - network process to application
1 - 3 are physical (hardware) and 4 - 7 are logical (software, services)
The OSI model would work in order of sent i.e. the sending device would send in order of 1 to 7 and the receiving device would receive as 7 to 1.
Here is some terminology that we learnt and need to know:
- Networks - To communicate and share resources which could be files, printers and email
- Network components -
- Device - any hardware
- Media - connects devices to the network and carries the data between
- Network adapter - hardware that translates the data between network and device
- Network operating system - (NOS) - software that controls traffic and resources
- Protocol - set of rules for communications
Servers
Server is a network computer which shares resources with and responds to requests from other network computers.
Clients
Also known as a node or peer, this is a network computer which utilises the resources of other network computers. This client computer has its own processor, memory and storage.
Peers
Self sufficient computer which acts as both a server and client to similar computers on its network.
They have decentralised security and will have a DOS running (like XP) and not a NOS (Server 2003/8)
Host Computers
A powerful centralised computer system such as a mainframe computer that performs data storage and processing on behalf of clients.
TCP/IP
TCP/IP is routable (routers can and need to be used and not switches) The router recognises, for leaving the network to get to the www.
Terminals
Terminals have a chip on the network card which is called a PROM (Programmable Read Only Memory) It is a specialised network device on a host-based network that transmits the data entered by the user to to the host for processing and then displays the result ( like a bank teller) - these terminals are often called "dumb".
Authentication
This is network security measures to gain access to the network resources
- Username and passwords - usernames are usually public info and are often available, the password is secret and should be protected at all costs.
Network Directory Services
A network Directory is a a centralised hierarchical database which stores and organises data about network users and resources - we will be using MS Active Directory (all control is here)
Some important notes to remember:
- DOS, like XP is Disc operating system
- NOS, like server 2003 is Network operating system
- Persons have permissions and resources have rights
- SMTP - simple mail transfer protocol
- TCP/IP - transmission control protocol / Internet protocol
- 802.3 - ethernet
- 802.5 - token, ring environment
- 802.11 - Wireless
- Server client - provides better security and is centralised
- Peer to Peer - less security and is decentralised
- HUB or Repeater - broadcasts to everyone on the network
- Switch - has some intelligence and will remember the MAC address of computers in its network
- Router - uses TCP/IP and not MAC
There are two types of servers:
- Member servers - provide resources such as databases (SQL, sequel server)
- Domain Controller - Authenticates users, contains the directory services (Active Directory) which contains all users, rights and permissions
Servers need to provide:
- ACCESS
- FAULT TOLERANCE
- SECURITY
- HIGH AVAILABILITY
So, the morning was a bit early but this meant that the skies were still 
