Networking Material taken mainly from HowStuffWorks.com The Internet A network of networks Computers Servers and clients routers switches Ethernet Network
Material taken mainly from HowStuffWorks.com
The original Ethernet described communication over a single cable shared by all devices on the network. Once a device attached to this cable, it had the ability to communicate with any other attached device.
Each Ethernet devices has a unique address.
The Ethernet protocol specifies a set of rules for communication.
The computer gives the NIC a message for another networked device and the NIC formats that message for transport over the Ethernet. The reverse is also true, the NIC receives messages from the network and reformats them so that the computer can understand.
A switch creates a series of instant networks that contain only the two devices communicating with each other at that particular moment.
Switches maintain their own Medium Access Control (MAC) look-up tables. These table indicate which network device is at which port on the switch. The look-up tables are constantly updated. When a switch is newly installed, it will construct its table via an Address Resolution Protocol (ARP) broadcast.
Routers are devices that let messages flow between networks
Most switches operate at the Data layer (Layer 2) of the OSI Reference Model, while routers operate at the Network layer (Layer 3)
When a router receives a packet, it looks at the Layer 3 source and destination addresses to determine the path the packet should take. A standard switch relies on the MAC addresses to determine the source and destination of a packet, which is Layer 2 (Data) networking.
Layer 7: Application - Layer that interacts with the operating system or application whenever the user chooses to transfer files, read messages or perform other network-related activities.
Layer 6: Presentation - Takes the data provided by the Application layer and converts it into a standard format that the other layers can understand.
Layer 5: Session - Establishes, maintains and ends communication with the receiving device.
Layer 4: Transport - Maintains flow control of data and provides for error checking and recovery of data between the devices.
Layer 3: Network - Logical routing and addressing are handled here.
Layer 2: Data – Assigns the appropriate physical address.
Layer 1: Physical - This is the level of the actual hardware.
The philosopher-translator-secretary architecture.
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Any server machine makes its services available to the Internet using numbered ports, one for each service that is available on the server.
Logical port numbers correspond to application layer programs.
These port numbers are included in the address information of a packet.
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