ITECH1102: Application Layer And Network Protocol
Categories of Interaction in Application Layer
Application Layer is a seventh layer of Open Systems Interconnection model. It consists of several protocols which focuses on the process to process communication across Internet Protocol networks which provide communication to the end users. User applications are able to interact with services and the devices through this layer include: Facebook and search engines.
Categories of Interaction in Application Layer
Client Server Architecture. This involves one computer or process is client while another is a server. Client process or computer requests resources from a dedicated server, while the server offers the client resources by listening to client’s request for example ftp client and ftp server. The advantage of this can be used in provide resource to several computers in the network. Also roles can be distributed in the network.
Peer to Peer Architecture. This involves network device being independent. A computer can act as a both client and server. All the computers in the network shares resources such as printers without a dedicated server. The advantage of this architecture is that it can be set up easily in home network. The disadvantage of this is that administrative roles cannot be manage in a large network
Host Based Architecture. This involves having one powerful computer which have several dumb terminals. The computing power is shared among the dumb terminals include bank transactions such as ATM.
Cloud Based Architecture. Cloud computing offers services such as platform, operating system and software. Customers don’t need to worry about buying hardware or operating system or platforms from vendors, they only subscribe as a service.
Infrastructure as a service. This involves cloud computing manages all the network infrastructure and their purpose is to provide this infrastructure to customers as a service.
Platform as service. The cloud provider offer hardware software and database services to the client. They own this services.
Software as Service. The cloud provider offer wide range of Softwares as a software development environments, email services etc.
Internet Application
- Web browser
Network Applications
- Email Client
- File Transfer Services
Network Protocol
Network application have set standards of rules that enables them to communicate together in the network. Examples of network protocol include:
- HTTP
- FTP
- NTP
- POP
Internet Network Layer
Address Resolution Protocol
The purpose of ARP is to determine MAC address of a machine in the network with a specific IP address.
Role of Network Layer
It deliver network traffic to another host in the network
Internet Protocol
Every device In the Internet Protocol requires Internet protocol address in order to communicate. It involves routers, switch, gateways, computer etc.
Client Server Architecture
Types of IP Address
- IPv4 which is 32 bit long
- IPv6 which is 128 bit long
Computer gets an IP address through static addressing and dynamic addressing. DHCP is used to assign IP address dynamically to devices in the network.
IP settings include
- IP address
- Default Gateway
- Subnet Mask
Network Component of IP Address
Two parts of and IP Address.
- High order bits – Specify IP network of IP address
- Low order bits – Specify unique IP address
Subnet Mask tells what how many bits an IP address is given in a network portion and how many node portion can be given.
Types of IP Addresses
Public Computer can communicate in the internet.
Private only computer can communicate in local area network and not in internet.
Network Address Translation
NAT involves changing a private address of the local area network to that of the router’s ISP address.
Router
The purpose of router is to transfer packets from computer to its destinations. Routers decides on routes to use based on mapping. Each packet contain source and its destination which routers uses it to know its source and destination. Routers are intelligent, communicate with one another and able to learn routes from each other dynamically.
Routing protocol
- Open Shortest Path
- Routing Information Protocol
- Border Gateway Protocol
Internet Assigned Numbers Authority
This is the body which oversees the naming of domains.
Domain Naming System
Resolution of IP and Names are done by the DNS.
Physical Layer
It involves connections of physical devices in the network.
Type of data
- Digital data.They are stored in digital format. It is made up of 0 and 1.
- Analog data.This are transmitted like voice which takes infinites level.
Data Transmission Media
- Cables
- Radio Devices
Point to Point Circuit This involves connections between two devices.
Multipoint Circuit. This involves one media being shared by several devices for example WIFI.
Data Flow
- Simplex This involves sending data in one direction.
- Half Duplex. This involves data moving from both direction but one at a time.
- Full Duplex. This involves data moving in both direction at the same time.
Multiplexing
This involves diving communication channels so that it allow several connection at the same time.
Methods of Multiplexing
- Time Division Stations transmit at different time.
- Frequency Division Different channel transmits using different frequency.
- Wavelength DivisionDifferent wavelength are sent at the same time. For example fiber cables.
Digital Transmission of Data. This involves data being send by a sender to receiver.
Transmission media
- Unshielded Twisted Pair Cable
- Shielded twisted Pair Cable
- Coaxial Cable
- Microwave
- Satellite
- Infrared
Topics Questions
Topic 4
- 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.
- Describe why routers require at least 2 network cards.
Router routes traffics to different networks so it must have two physical or logical network card to handle traffic routing
- Describe when entries are added and removed from the ARP cache.
When there is local traffic new ARP entries are created. 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 the router must know the source and its destination of a packet in order to send a packet
Topic 6
- How many bits are used in a UDP header to store the destination port number?
16 bits
Explain how you arrived at this number.
UDP destination port stores 2 bytes therefore 1 byte = 8 bits hence 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.
Peer to Peer Architecture
Browser tabs uses multiplexing to send data concurrently therefore they cannot be mixed.
- 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.
Flags
If a SYN/ACK segment is sent to a host it responds with RST segment
If a SYN segment is sent to a host it responds with a SYN/ACK if the port is open,
If a SYN segment is sent to a host it responds with a RST if the port closed,
If a SYN segment is sent to a host it doesn’t give a response if the port filtered.
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 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.
Topic 8
- 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 forsends 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 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.
References
Functions of LLC and MAC sub-layers of Data Link Layer | Computer Networking Demystified. (2018). Retrieved from https://computernetworkingsimplified.in/data-link-layer/components-data-link-layer-llc-mac/
An Inside Look at TCP Headers and UDP Headers. (2018). Retrieved from https://www.lifewire.com/tcp-headers-and-udp-headers-explained-817970
Sending data across different browser tabs – Arnelle’s Blog. (2018). Retrieved from https://blog.arnellebalane.com/sending-data-across-different-browser-tabs-6225daac93ec
What is a Three-Way Handshake? – Definition from Techopedia. (2018). Retrieved from https://www.techopedia.com/definition/10339/three-way-handshake
TCP Flow Control. (2018). Retrieved from https://www.brianstorti.com/tcp-flow-control/
What’s the difference between Type 1 and Type 2 hypervisors?. (2018). Retrieved from https://searchservervirtualization.techtarget.com/feature/Whats-the-difference-between-Type-1-and-Type-2-hypervisors
3G, 4G, 4G LTE, 5G – What are these new Technologies Anyway. (2018). Retrieved from https://whatsag.com/
What is cell? – Definition from WhatIs.com. (2018). Retrieved from https://searchmobilecomputing.techtarget.com/definition/cell
How Do Cell Phones Work? – Pong Pulse. (2018). Retrieved from https://pongcase.com/blog/cell-phones-work/
Mobile Phone Base Stations, How do mobile base stations work, Mobile Base Stations in Australia, Cell Tower, Mobile Phone Tower. (2018). Retrieved from https://www.mobilenetworkguide.com.au/mobile_base_stations.html
What is a Mobile Switching Center (MSC)? – Definition from Techopedia. (2018). Retrieved from https://www.techopedia.com/definition/8448/mobile-switching-center-msc