Why do we need a network ?
- Share resources
- Communicate: emails, chat, voIP
- Control and monitor for security
- Entertainment: video games, social media, etc.
Physical elements of a network
Hosts or “end devices”:
- Clients
- Servers(DNS, DHCP, NAT)
- Devices(printer, phones, etc.)
- External storage: NAS, SAN, etc.
Interconnection equipment:
- Router, switch, etc.
- Transmission media: network cables, optic fibber, radios
Local Area Network (LAN)
Often used by a small or medium business(business network or home network). Links computer, server and devices, usually in the same building. Shares common resources: files, folders, media, etc.
Metropolitan Network MAN
Usually Intermediate sized network. Can be used in large cities, to connect multiple cities or towns or a large area with several buildings. A MAN is larger than a LAN but smaller than a WAN.
Wide Area Network WAN
A very large network, like the internet(Inter Networking), the most popular WAN. A network of networks that allows communication with one another.
Client/Server?
Client:
- The client is the one asking for “service”
- The client sends a request to the server
- The client requests are directed to network ports: FTP(21), HTTP(80), HTTPS(443)
Server:
- The server is the one distributing the services.
- The server is listening for incoming requests
- The services can be a website, access to files and folders, etc.
- The server listens on ports
What is a Windows Domain?
- A sort of kingdom which is managed by the king(domain controller)
- Allows to centralize the users, computer accounts with the help of an contact list service such as Active Directory.
- Allows to control privileges for the domain users.
Virtualisation
- A network can also rely on virtualisation servers
- A physical service can host many virtual machines
- There are many known hypervisors such as Microsoft Hyper-V, VMware, VirtualBox, etc
Advantages :
- Allow the use of full potential on physical resources; RAM,CPU, etc.
- A lot of power and resources saving
- Allow the attribution several dedicated servers to a single task
- Allows to implement secondary servers
Disadvantages:
- A virtual server is not a powerful as a physical server
- If the host or the virtualisation server fails, the who network fails
- Certain specific related problems to the virtualisation itself
to be continued next class….
Network Interface Card (NIC)
- The NIC allows communication between a computer and the transmission equipment(cable, wifi, etc)
- Every host needs a NIC to communicate
- The NIC allows to send and receive
- Can be integrated within the motherboard or added via PCI express ports
NIC : physical address vs logical address
A NIC needs 2 addresses to communicate:
Physical Address:
- MAC Address (Media Access Control), is unique for every single device. Ex : 7Y-D5-2G-93-7H-76
- This address is given by the manufacturer, usually not editable
- Used for local communication
Logical Address:
- The IPv4 or IPv6 which can be configured on the NIC. Easy to change. Ex: 172.16.0.50
- Allows to move from a network to another, change network or for internet browsing.
- Can be dynamic or static
For the network to function properly a NIC need the following configs:
- IP address
- Subnet Mask
- Default Gateway address
- At least one DNS address
NIC: static or dynamic?
- By default, a NIC is set to dynamic
- The computer which the NIC is set to dynamic will receive it’s IP from the DHCP server(Dynamic Host Configuration Protocol)
- The server distributes the IP to it’s client from it’s “pool”
- This address will change by itself
- If no DHCP available, the computer will take a random address starting with 169.254.X.X
- We can give a static configuration ourself. This config will never change as long as we don’t edit it
Transmission speed(negotiation)
A NIC can support many transmission speeds:
- 10 Mbps(Ethernet or 10BASE-T)
- 100mpbs(Fast Ethernet or 100BASE-T)
- 1gbps(Gigabit Ethernet or 1000BASE-T)
- 10gbps(10 gigabits Ethernet or 10GBASE-T)
Two modes
Full-Duplex:
- Can send and receive at the same time.
- A cable connection is usually Full-Duplex
Half-Duplex:
- The NIC can only send or only receive.
- Wifi is usually Half-Duplex