User applications enabled us to interact with thousands of application and devices on the internet. This applications uses network in order to communicate include Facebook, Twitter, Youtube and many others. Sneaker net. This involve transporting data using floppy disk from the source to the destination.
Categories of Interaction
Client Server Architectures
- Client request resources from a dedicated host server for example email client, web client like browser.
Role of Server
- Server waits for the client to request for resources then response with specific resource. The server may requires authentication while others may not requires.
Peer to Peer Architectures
- In this type of architecture the each machine can act as a client and server. All machines can share resources and also can access shared resources for example home network.
Pro’s and cons of Client/server vs peer to peer
- Peer to Peer networks work well in home networks
- Distributed administrative roles of each peers
- Peer to Peer network does not support large networks
- In Client/server there is a strong distinction between roles of network administrators and users
Host Based Architecture
- In this architecture a dumb terminal is attached to a powerful mainframe computer. The mainframe only process the task and output results in the terminals.
Cloud Based Architecture
- This involves providing remote services such as computing platform, operating system and software to customers. Customers does not need to buy hardware or network infrastructure but only subscribe for the resources used.
Infrastructure as a Services IAAS
- Cloud provider manages hardware, Softwares, storage and all the network components.
- Client no longer provide hardware’s to be used.
Platform as a service
- The cloud provider offers the hardware, operating system and database or any other Softwares to the customer.
This allows the organization to build their own custom applications without the need to worry about the operating system, database system or hardware.
Software as a Service
- Cloud provide everything including the software which customers will used to customize the service to suit their needs.
Other Network Applications
- File transfers from FTP sites
This are set standard rules which network application must adhere in order to communicate in the network. For example Web application uses Hypertexts Transfer Protocol.
Role of Application Layer Protocol
- Establish consistent rules between sender and receiver
- Specify how data inside messages is structured and types of messages that are send between source and destinations.
- Handle message dialogue by determining which entity communicate first and its response.
Aims of the network
- Ensures that message is delivered intact without any lose.
Network data exchanges the use of all the layers.
As data passes through protocol stack protocol headers are added at each layer include: The transport layer normally adds a TCP header. The network layer adds an IP header. The Data Link layer add an Ethernet header. This information in the headers inform the destination about the destination and other important information.
Address Resolution Protocol
ARP determines the MAC address of a machine on the local network with a specific IP address.
ARP Entries Added
When there is a successful ARP Commands ARP entries is added into the ARP Cache. New IP address and Mac address is added into the ARP Cache as an entry.
ARP Entries Deleted
ARP entry age out after a certain period of time which is determine by the operating system.
Role of Network Layer
- It deliver network traffic from one host to another
Types of IP
- IPv4 address They are 32 bit long e.g 10001101 10000100 11000100 00011010
- IPv6 address They are 128 bits long e.g FE80:0000:0000:0000:ACC1:44F9:91B5:AC1B
Computer get IP address through manual Administration assignment or Automatic Administration (dynamic host controller which allocate IP address to machines).
Other important IP settings
- IP Address
- Local Router Address(Gateway)
- Subnet Mask
Component of IP Address
- Higher Order Bits – Specify IP Network of IP Address
- Low Order Bits – Specify unique of part of IP
- It applies to all the machines in the network. A series of binary 1 bits (indicating the network portion) followed byA series of binary 0 bits (indicating the node portion).
Expressing the number of Network Bits of IP Address
- If we replace all node bits of an IP address with zeros we get that IP addresses network address.
- If we do a bitwise AND of the IP address with the subnet mask we also get the IP addresses network address.
- CIDR – Classless inter-Domain routing
Type of IP Address
- Public IP Address - Communicate on the internet.
- Private IP Address – Communicate on a local network and discarded by the router on exit.
Network Address Translation
Natting involves changing IP address of a local IP addressing requesting a resource from internet to The IP address of ISP router. The IP port number will be used to distinguish the requests by the router.
Role of Router
Move a network packet forward 1 step towards its destination. Routers work in a similar fashion, moving packets forward 1 step at a time. The route can change from packet to packet. Routers have routing table which specifies route for packet to exit through. Router is an intelligent device which communicate with one another so in case of routes change it get updated.
- OSPF (Open shortest Path First) [used on the Mt Helen campus network]
- RIP (Routing Information Protocol) [older protocol mostly replaced by OSPF]
- BGP (Border Gateway Protocol) [used on the Internet]
Internet Assigned Numbers Authority
Body which oversees the naming of domains. They work is to delegates naming of different geographical regions of the world to other authorities.
Domain Name System
Name resolution is the process of looking up the IP address of an Internet name, or for reverse lookups, determining the host name of a particular IP address. Name resolution of internet is handled by the DNS.
This is the connection of computers in the network
Type of Data
- Digital Data - stores information in digital format.
- Analog Data – This are information being recorded and outputted.
Digital and Analog Transmissions
- Radio Devices
- Microwave Devices
Point to Point Circuit
This is a direct connection between two devices and media is not shared to any other devices.
It shares connections with multiple devices for example WI-FI
- Simplex – Sends data in one direction only.
- Half Duplex – System allows data flow in both direction but one at a time can send data.
- Full Duplex – Allows data to flows in both directions.
Multiplexing is used to divide up a communications channel so the channel can transmit multiple conversations at the one time.
Methods of Multiplexing
- Time division Multiplexing (TDM) - Different stations get to transmit at different times. Bandwidth can be wasted. A variation called Statistical TDM can allocate more access to devices that require it. This reduces waste in the channel bandwidth.
- Frequency division multiplexing (FDM) - Different channels transmit on a different frequency
- Wavelength division Multiplexing (WDM) – This is used in Fibre optic cables. Instead of one light beam being transmitted down the fibre, multiple colours of light (different wavelengths) are sent at the same time, each carrying different data.
Digital transmission of Data
Transmission occurs between sender and receiver. During transmissions data is being encoded so that both the sender and receiver understand each other. Encoding is done on the Ethernet. Encoding is a way of representing binary data that is 1s and 0s in the network.
Encoding binary will ensures that the sender and receiver stays at a synchronization.
- Unshielded twisted pair - Cheap, Easy to work with, low data rate, short range, higher attenuation
- Shielded twisted pair – metal braid or sheathing that reduces interference, higher data rate, more expensive, harder to handle (thick, heavy)
- Coaxial cable - Consists of two conductors, inner and outer Outer conductor is braided shield Inner conductor is solid metal Separated by insulating material
- Optical Fibre - Greater capacity data rates of hundreds of Gbpsover tens of kilometers, Smaller size & weight, lighter than UTP and cable, considerable advantage in laying, Lower attenuation, Electromagnetic isolation, Greater repeater spacing
- Terrestrial Microwave - It requires fewer repeaters but needs line of sight visibility
- Satellite Microwave
- The LLC is sometimes described as providing a multiplexed service to upper layer protocols. Describe what this statement means and try to give an example of this in action.
LLC receives the frames from the physical Layer below and hand over the datagram to L3 protocol at the network layer above. It allows IPv4, IPv6, IPX and other protocol transactions concurrently.
- Describe why routers require at least 2 network cards.
One of router NIC is connected to the local area network while the other one is connected to the other networks.
- Describe when entries are added and removed from the ARP cache.
When there is local traffic new ARP entries are created so IP Address and Mac address are added as an entry. ARP entries are removed from cache when the period has expired. Expiry period of ARP cache varies from different Operating System
- As a Data Link frame moves through an internetwork, the Ethernet frame header is modified at each step. Describe why this must happen at each router.
Because next hope must know the packet details such as source, destination and type of data to be exchange between the sender and receiver.
- How many bits are used in a UDP header to store the destination port number?
Explain how you arrived at this number.
UDP destination port stores 2 bytes therefore 1 byte = 8 bits so 8 *2 = 16 bits
- It is commonplace for two tabs on a browser to be concurrently connected to the same web server. Discuss how the data meant for one browser tab is never mixed up with that of the other tab.
Each browser tab have unique port number which will be used to combine the host IP address and a unique port number for every request to be made.
- Describe the 3-way handshake process. Your description should make it clear the Flags that are exchanged at each step and the meaning of each of those flags.
- SYN segment is sent to a host it responds with a SYN/ACK if the port is open.
- SYN/ACK segment is sent to a host it responds with RST segment
Client sends a SYN packet data to server through internet protocol. If the server has an open port then it accept the connection and acknowledge the client that it has accepted through a SYN/ACK packet data. Then client respond back to the server with ACK data packet acknowledging that the connection has been initiated.
- Describe how flow control is achieved in a TCP connection.
TCP uses sender buffer to store packets needed to be send and TCP receiver will use receiver buffer to extract all the packets. Receiver packer controls the packet being receive by advertising it’s receive window to the sender buffer that there is more space available.
- Describe the differences between type 1 and type 2 Virtualization.
Type 1 run directly on a hardware while Type 2 run on the operating system.
- The switching technologies used for mobile communications has changed throughout the mobile phone technologies 1G through to 4G. Describe the changes that have occurred.
1G only supported voice. 2G Supported Voice and Simple data such text messages, speed was less than 0.5Mbps. 3G supported Web browsing, email, video downloading, picture sharing and speed were 2Mbps. 4G speed range between 100Mbps and 1Gbps.
- Describe the roles of the following elements of the mobile phone network:
- Cell is responsible for transmitting and receiving signal.
- Base station is responsible for sends and receives radio signals and is responsible for forming the cell area.
- Mobile switching center. This is where call set up and switching for mobile takes place.
- Describe the roles of the Base station and the Mobile switching center as a mobile phone moves from one cell to another.
Base station which the phone is connected to and its signal is weakening as the mobile phone moves toward another cell signal is responsible for handing over a mobile phone to another base station. Mobile switching is responsible for call set up and switching and routing mobile phone to another route of new base station.
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