Packets and Protocols2011 Qu 3 2012 Qu 3 Extra Question

How is data organised for transferral over a network?

•Models of layered protocol architecture can be used to describe the movement of data in a network medium.•A protocol determines the nature of data packets, including

o the construction of the packeto the type of error checking to be usedo the data compression method, if anyo how the sending device will indicate that it has

finished sending a messageo how the receiving device will indicate that it has

received a message.•Protocols can include FTP, SMTP, POP3, and TCP/IP..

Students investigate protocols with particular reference to TCP/IP.

Students use models of layered protocol architecture, such as the TCP/IP model, to discuss movement of data in a network

Lin lives in Kuala Lumpur and plays a multi-user strategy game on the Internet with friends in Australia. All possible paths that data packets can take from Kuala Lumpur to various cities across Australia are shown in the diagram below. The lines between cities indicate the path segments data packets can travel on, and the numbers indicate the time the packets take to travel along each segment.

2011 Question 3 Protocols & Packets

b) (i) Identify the two protocols needed to transfer data, as shown in the diagram on the previous page, and explain the main role of each protocol. Protocol 1: Main role:

Protocol 2: Main role:

(4 marks)

IP (Internet Protocol)

To handle the addressing (routing) of packets

Information IP uses includes:The total length of the packet Time to Live, the number of routers the packet should go through before it is lost. Source IP address and Destination IP address, which may be several routers away.

TCP (Transmission Control Protocol)

To handle splitting of data into packets, sequencing, transmission sessions, error checking, resending lost packets

Information TCP adds includes:Source and destination ports, sequence number, acknowledgement number, checksum, data

(ii) State the network hardware device that decides the best path for data packets to take.

(iii) (1 mark)

(iii) Give an example of the detail, stored inside each data packet, that the network hardware device uses to direct the packets.

(1 mark)

RouterEach router contains a continually updated router table by which decisions are made on where to pass the packet

IP Address of the destination computer such as 192.134.55.12

2012 Question 3 Protocols & Packets Ella studies at university in Brisbane but is currently overseas in Singapore. She needs to access her files, which are stored on a server at her university. The university allows students access to a virtual private network (VPN), which Ella can use to download or upload her files from or to an internal file server.

c (ii) State the protocol that would be used to retrieve the Networks_Homework’ document. (1 mark)

(iii) Ella has selected the ‘Networks_Homework’ document to download from the university server. Describe how TCP/IP prepares Ella’s document for transmission over the Internet. (4 marks)

FTP (File Transfer Protocol) allows for the transmission of files over the internet. This is, however, encapsulated within a TCP/IP framework.

At the Application layer FTP has prepared the document for transmission. TCP then divides the data into packets at the Transport layer, and adds packet info in a header and footer. This includes packet sequence number,, checksum, ack number. IP adds addresses at the Network/Internet layer, also time to live. Further checks are added at the Data Link layer.

(f ) Explain how TCP ensures that Ella’s computer has received the ‘Networks_Homework’ document. (4 marks)

The TCP protocol at the originating computer includes an ack (acknowledgment) number. This is a random number. The receiving computer returns this ack number plus the length of the packet, which is an additional check that nothing has gone wrong.

The originating computer had started a clock when it transmitted the package, and if it doesn’t receive the correct ack number it will resend the packet.

At the destination computer TCP receives the packets at the transport layer and uses sequence numbers to place them in order ready for the application layer. If a packet has not been received then a request would be sent to the host computer for a new copy of the packet.

When all packets are received and placed in order the would be passed onto the application layer to be interpreted by FTP.

Packet/Protocol Question 1. Write a sentence for each of the numbers, explaining that part of the process

2 Explain why items travel in packets when they are downloaded from one website toanother.

(2 marks)

3 State the difference between reliable data transfer and best-effort delivery and which protocol provides is required for each.

4 State the purpose of the following packet components:(i) Originating address.

(ii) The number of packets.

(iii) Packet number.

(3 marks)

size of packets leads to more efficient flow of data or alternative routes increases the chance of the packets arriving if there is a break in the route.

Best effort delivery (IP) routes to a destination, but does not guarantee reception, where reliable data transfer (TCP) uses an acknowledgement process to establish a continued link, and resend any lost packets.

return address for data requested, for resending etcto determine the totality of the file

order of packet assembly to reconstruct data

5 Explain the purpose of the underlined segments of a TCP/IP package

The total length of the packet, which can vary according to the data segment in TCP, and gives an indication of where the end of the packet isTime to Live, which is the number of routers the packet should go through before it is lost. Every time this packet is put through a router, Time to Live decreases by 1.Source IP address Destination IP address, which may be several routers away. Each router contains a continually updated router table by which decisions are made on where to pass the packet.

· Source Port [SP] (16 bits): the port the local machine is using to listen for responses from the destination machine. · Destination Port [DP] (16 bits): the port to be used for the remote machine as a packet is being sent out to its destination. (Initially suggested, but can be modified).

· Sequence Number [SN] (32 bits allows both TCP stacks to know what packets have been received and which ones have not. If a packet with a certain sequence number is missing, it s resent. The sequence number also allows extra security so that other users cannot easily break into the middle of your connection and continue where you left off. Once there is a TCP communication session set up between two machines, the sequence number increases are directly proportional to the number of data bytes that are transmitted (see the following).

· Acknowledgment Number [TL] (32 bits): This works by acknowledging the sequence number as sent by the remote host. It equals the sender’s sequence number plus the Len, or amount of data, at the TCP layer, which allows some error checking. The local host's Acknowledgement Number is a reference to the remote machine's Sequence number, and the local machine's sequence number is related to the remote machine's acknowledgement number. (Also called ACK number, and essential for getting the reliable connection. IP doesn’t have ACK numbers). When the host TCP originates a message, it also starts a clock and if it does not receive the acknowledgement within some specified time, it re sends the same packet. So this way TCP makes sure that no packet gets lost.

· TCP Checksum [TCPCS] (16 bits):covers the header and data portion of a TCP packet to allow the receiving host to verify the integrity of an incoming TCP packet. The TCP/IP stack will detect broken packets.

Networks / Architecture

• 2011 Qu 3 2012 Qu 3 Extra Question How can a network be described?•Key terminology includes LAN, WAN, nodes, peer-to-peer and client–server, transmission media, and address.How can a network be managed?•Key terms include network operating system, access rights and privileges, firewall, and proxy server.How can a user access the services of the Internet?•Key terms include Internet service provider (ISP), point of presence (POP), backbone, email, FTP, forums, messenger, newsgroups, World Wide Web, intranet, and virtual private network (VPN).What are the key aspects of transmitting data over a network?•Bandwidth and speed of transmission.•File types and file transmission.•Security.

Students classify a network and its components.Students learn the roles servers can play in a network.Students learn how a network operating system controls and coordinates the activities on a network.Students consider management and security of programs, files, devices, and users (workgroups), including monitoring, filtering, and external access.Students consider external access to networks and the roles firewalls play in network security.Students learn how to access the Internet and investigate the nature of services a user can access on the Internet. Students investigate internal networks, using web technology.Students describe data transmission, using the terms medium, channel, bandwidth, and routed path.Students describe file type and size, and forms of file compression.Students describe methods of data encryption, and private and public keys.

Lin lives in Kuala Lumpur and plays a multi-user strategy game on the Internet with friends in Australia. All possible paths that data packets can take from Kuala Lumpur to various cities across Australia are shown in the diagram below. The lines between cities indicate the path segments data packets can travel on, and the numbers indicate the time the packets take to travel along each segment.

2011 Question 3 Networks

(a) Computers and communication systems use various communication media, including: • copper cable • satellite microwave signal • optical fibre

• Bluetooth signal. • infrared signal (i) From the media listed above, identify which are not appropriate for use in constructing path segments.

(2 marks)

ii) From the media listed above, explain which is the most appropriate communication

medium to construct the path segment between Kuala Lumpur and Perth. (2 marks)

Neither infrared, nor Bluetooth are suitable, IR (Infrared) signal as line of sight is required. Bluetooth signal is limited to around 10m.

Microwave signals that are transmitted via Satellite or Laser signal that is transmitted via fibre optic cable laid in the ocean. Both offer lots of bandwidth and do not lose data over large distances

(ii) State the network hardware device that decides the best path for data packets to take.

(iii) (1 mark)

(iii) Give an example of the detail, stored inside each data packet, that the network hardware device uses to direct the packets.

(1 mark)

RouterEach router contains a continually updated router table by which decisions are made on where to pass the packet

IP Address of the destination computer such as 192.134.55.12

c) Refer to the diagram on the previous page.

(i) List, in order, the cities that are on the best path that the data packets should take from Kuala Lumpur to Sydney.

(ii) State the best path for the data packets to take if none of the communication media on the direct path segment between Adelaide and Melbourne are available.

Kuala Lumpur – Perth – Adelaide – Melbourne – Sydney : 6+1+1+2=10

KL- Perth Darwin Brisbane Melbourne –Sydney : 6 + 2 + 1 + 1 + + 2 = 12

(iii) Suggest one reason why a communication medium that exists between Adelaide and Melbourne might not be available.

(2 marks)

Externalextreme weather conditions (flood, heat, fire, earthquakes)accidental damage of linesBlackoutsMaintenance work carried out

InternalEquipment failureBlackoutsMaintenance work carried out

2012 Question 3 Networks 3. Ella studies at university in Brisbane but is currently overseas in Singapore. She needs to access her files, which are stored on a server at her university. The university allows students access to a virtual private network (VPN), which Ella can use to download or upload her files from or to an internal file server. (a) (i) Outline three reasons why the university might use this technology to

allow students access. (3 marks)

(

Allow external off-site secure access to her work files. Enables external students to enrol into courses and range of potential clients. Allows policies to define access to the other resources on the network that is protected. Reduces the physical services (people, resources) and after hour services required on site. Encourages students to Bring Your Own Devices (BYOD) to free up computer lab resources.

ii) Describe the processes of the VPN that allow Ella’s computer to connect to the internal file server. (2 marks)

The VPN would request a user name and a password. This would be cheeked against the NOS (Network Operating System) acceptable users list. The NOS would also set the parameters of her access based upon her account and group policies.

A virtual private network (VPN) is a network set up over the Internet using ports dedicated to data transmission (often Layer 2 Tunnelling Protocol (L2TP) using TCP Port 1701) and security (typically Internet Protocol Security (IPSec )). Each node on the VPN uses the same protocols and ports, so no others can get a look in. It is set up by software, not physically, so it is virtual, and its security makes it private.

(c) Ella’s browser displays the resources that she can access while her computer is connected to the VPN, as shown.

(i) Explain the function of the Network Operating System (NOS) when it responds to Ella’s request to download a file. (2 marks)

The VPN would transmit a request for a user name and a password. NOS (Network Operating System) would check the response against an acceptable users list. The NOS would also set the parameters of her access based upon her account and group policies. Ella will not be able to access any other resources on the network outside of the NOS restrictions. If the conditions are met, then the NOS will allow the FTP (File Transfer Protocol) Server to transmit the file to the requesting IP address.

(d) The communication medium between Singapore and Perth is an optical fibre cable that lies on the ocean floor. State another medium that could be used to transmit the packets to Australia.

Satellite technology, uses radio/microwaves to transmit data .

(e) The images on the next slide show the Internet connection while Ella is using the network at the times shown. All the possible paths that data packets can take from Ella’s computer in Singapore to various cities in Australia are shown in the diagram below. The lines between cities indicate the path segments data packets can take, while the numbers indicate the time taken to travel along each segment. Each number represents 100 milliseconds.

(i) Explain why the numbers shown along the path segments are different in the two images shown (2 marks)

The data loads change on network segments every millisecond and therefore the state of the internet is never constant and forever changing. Data trafficking demands cause congestion and load on one segment. Changes in Electromagnetic interference, extreme weather conditions can change response times along copper segments.

(ii) A router in Darwin receives packets at different times, as shown. Outline the factors involved in the router determining the next segment the data packets should take.

(3 marks)The router would use a routing metric to determine the best routes for packets based upon its routing table (map of connected nodes) along with distance-vector routing algorithm protocols, link algorithms and Bandwidth, network delay time form previous sent packets in the routing table, hop count, path cost, load, reliability, communication cost.

During her Information Technology Studies class, Kim connects her laptop computer via wireless to the school’s network.(a) Describe how the network operating system will process Kim’s attempts to log on

to the network. (3 marks)

(b) Describe how the network operating system will process Kim’s attempts to print a file from her laptop computer on a network printer. (2 marks)

(c) Describe how the network operating system will process Kim’s attempts to save her file to a friend’s network folder. (2 marks)

Extra Questions

NOS compares Kim’s UserID & password to list of IDsand allow/deny authentication

NOS checks access rights to printer queues, then assigns file place on permitted queue, stores and sends file to printer in turn

NOS checks permissions (restrictions) on folder If Kim assigned Write permission for that folder NOS will allow the action

Identify and explain two problems with the network shown in the diagram above. (4 marks)

Most obvious 2 problems: Switch and Hub should be reversed

No firewall to Internet

The network diagram shows a local area network. Outline whether the network would be likely to be peer-to-peer or client server. (2 marks)

client server – access to services controlled by NOS on server

A stack of servers is shown in the diagram. Name and outline the use of two of these servers. (4 marks)

e-mail server- manages the transfer of electronic messages from one computer to another

print server – accepts print jobs from client computers and sends data to the appropriate printerfile server – stores files for use by many client machines over a networkproxy server – client computers make requests to the proxy server eg for a web page and the proxy server connects to the specified server on behalf of the client

Social responsibility(Information Systems)

What is the impact of computer-based information systems on society?• Effectiveness, efficiency, and reliability are

relative terms• effectiveness is about whether all outcomes

are successfully achieved• efficiency is about how well desired

outcomes are achieved, by using minimum resources

• reliability is about whether desired outcomes are consistently achieved over time.

What are the issues for managing the elements of a computer-based information system?What careers are there in the information technology industry?

Students consider the impacts and consequences of using computer-based information systemsStudents learn and apply the terms efficiency, reliability, and effectiveness.Students investigate the security, protection, backup, and recovery of data, privacy, ownership, and social and cultural practices and values that relate to the collection and storage of data.Students consider copyright and other intellectual property rights and discuss the human element of computer-based information systems.The development, maintenance, and use of computer-based solutions or software offer a range of career paths for students to investigate, including database developer/administrator, software engineer, systems analyst, technician, and network administrator.

What is the impact of network technology on society?• New technologies include telephony, voice-over-IP (VoIP), videoconference, groupware, global positioning systems (GPS), and collaborative and social software.What are the issues for managing and using networks?What are the ethical considerations for using network technology?

Social responsibility(Computers and Communication Systems)

Students investigate examples of how network technology has changed the way in which individuals, organisations, and communities communicate and conduct business. Examples include Internet banking, shopping, stock trading, virtual learning, remote access, and community meetings.

Students discuss the potential of using new technologies to conduct business and deliver education.

Students discover the importance, and means, of implementing security, protection, and privacy measures, and how to be culturally sensitive.

Students discuss issues such as spam, flaming, phishing, downloading, and uploading, and a range of issues related to forums, chat rooms, and instant messaging.

(d) While Lin is connected to the Internet, she wants to secure both her computer and the data she sends out over the Internet. (i) Identify and explain one method of making Lin’s computer secure from unauthorised access by others over the Internet. Method: Explanation:

(3 marks)

Blocking ports

Only have ports open that are used, for example blocking Telnet: 23. Blocking of IP addresses: Have a Black-list, White-list of IP addresses to ensure no unauthorized access and is secure from source IP addresses that run malicious attacks (Router, Proxy server). Blocking unsolicited packets by rejecting packets arriving to the PC that have not been the result of requests from the PC in the first instance (Firewall)

2011 Question 3

(ii) Identify and explain one method of making Lin’s data secure while it travels through the Internet. Method: Explanation: (3 marks)

Encryption

This involves very large prime numbers that are used to turn the data into code. Sender encrypts, so the receiver can decrypt the message. The security depends more on the short time the encryption is used than the complexity of the key.

(e) A friend of Lin has warned her to be careful of spam and phishing on the Internet.

(i) Outline one similarity and one difference between spam and phishing.Similarity: Difference:

(2 marks) (ii) Explain why spam and phishing are issues for Internet users.

(2 marks)

Almost all Spam occurs via emails. Phishing can occur via email, but can also be website postings. Spam is un-solicited and un-wanted email, as well as junk postings made on websites (newsgroups/forums). Phishing uses the concept of fishing. Is deceptive email (mainly) designed to get personal details/information from the user/system without authorization. Usually contains a link to an online form seeking details. Phishing will ask for a response but Spam generally does not.

They are an issue for users, as they are annoying, and dangerous in giving out personal information that can be used against them (key issues: fraud, confidentiality, identity theft, loss of money, defaming).Issue because it cannot actually be stopped. They are an issue for the Internet, as they cause the greatest congestion, traffic flow problems globally.

2012 Question 3 (Soc Resp)Ella studies at university in Brisbane but is currently overseas in Singapore. She needs to access her files, which are stored on a server at her university. The university allows students access to a virtual private network (VPN), which Ella can use to download or upload her files from or to an internal file server. (a) (i) Outline three reasons why the university might use this technology to allow students access.

Allow external off-site secure access to her work files. Enables external students to enrol into courses and range of potential clients. Allows policies to define access to the other resources on the network that is protected. Reduces the physical services (people, resources) and after hour services required on site. Encourages students to Bring Your Own Devices (BYOD) to free up computer lab resources.

(b) (i) While Ella’s computer is connected to the VPN, a phone call interrupts her and she leaves her computer for a time. When she returns to access the VPN, she finds that her computer has been disconnected from it. Identify what has caused the disconnection. (1 mark)

(ii) State the advantage to Ella of her computer becoming disconnected from the VPN.(1 mark)

(iii) Outline two other likely advantages to Ella of being able to access the internal file server through the VPN. (2 marks)

The connection to the VPN is no longer active as the connection-based protocols has timed her session out due to inactivity. The VPN closes the session if the connection is inactive for a specified amount of time.

The closing of the session act as a security measure to prevent other users hacking into her access. This procedure also reduces the work load of the VPN with open and dormant connections and prevents her home computer using data to ping empty packets to the university server to keep the connection alive and therefore reduces her internet usage.

Allows possible access to other resources such as shared folders, printers and databases. The resources act the same way as if she was logged on at uni without being there. Allows Ella to work from anywhere with an internet connection and she does not need to wait for the computer labs to be open to access her files on the network.

2011-4. A new business has opened, with branches across Australia. The business must meet legal requirements to protect the personal information that it holds about customers against:• loss • unauthorised access • unauthorised changes • unauthorised distribution of customer details • other forms of misuse. Discuss how the business can manage an information system to meet each of these requirements.

Loss is covered by a comprehensive back-up plan. (eg grandparent – parent child, monthly-weekly- daily). Partial backups are undertaken frequently, and complete backups are taken at regular intervals. The backup medium should be robust, eg DVD, tape, portable drive) and secured off site. Backup software should be used to enable restoration in a logical mannerUnauthorised access controlled by limiting access. This can be physical, eg locks, siting the servers in hard to access rooms. More importantly, access should be by user id and password,sufficiently complex to make it unlikely they can be guessed.Unauthorised changes can be controlled using rights and privileges. Only those with the authority should have the access privilege to write or modify.Unauthorised distribution can also be governed to a certain extent by the system logic – eg proxy servers, firewalls to prevent unauthorised emails, file transfer. It can also be managed by business policy, and monitoring staff to ensure policy is adhered to. Shredding of unwanted data in physical form ensures the information can not be shared.

2012-4 A business is considering whether to stop using tapes and local servers and start using ‘cloud computing’ as a storage solution. Discuss how this change may affect employees and the business. (8 marks)

Note to students: Identify, Explain, Give Example in context.

Employees:•Access files anytime anywhere with an active internet connection•Cost of Software can be free to use for example DropBox•Employees can purchase more space if needed and therefore offsetting the running costs of the system•Enables employees to work from home – less sick days and office space.•Allow staff to have more time to work on new projects.•Can set up shared file areas with invited users

Company:•Less physical backup storage and management required at the business.•Removes/reduces backing-up from the business network.•Data backup is the vendor’s responsibility and up time of servers.•Requires more internet to upload and download the data.•Business can focus on internet distribution rather then archiving materials•Offset the money saved on servers and hard drives to improve the internet connection

Hardware Software Data Procedures People

DesignDetermine hardware

specifications.

Select off-the-shelf programs.

Design alterations and custom programs as necessary.

Design system and

related structures.

Design user and operations

procedures.

Develop user and operations job descriptions.

Implementation Obtain, install and test hardware.

License and install off-the-shelf

programs. Write alterations and

custom programs. Test programs.

Create system. Fill with data. Test data.

Document procedures. Create training programs.

Review and test procedures.

Hire and train personnel.

Integrated Test and Conversion

Design and Implementation for the Five Components of an Information System

p 262 Experiencing MIS Kroenke, Bunker, Wilson) (2010) Pearson Australia modified

SDLC: System Maintenance Phase (maintenance means fix or adapt)

SystemDefinition

SystemMaintenance

Problem or Need for Change Users

Record requests for change: Failures EnhancementsPrioritise requestsFix failures Patches Service packs New releases

p 263 Experiencing MIS Kroenke, Bunker, Wilson) (2010) Pearson Australia

SECURITY SAFEGUARDS AS THEY RELATE TO THE FIVE COMPONENTS

Hardware

Software Data Procedures

People

Technical Safeguards

Identification andauthorisation

Encryption Firewalls

Malware protection Application design

Data SafeguardsData rights and

responsibilities Passwords EncryptionBackup and recovery

Physical security

Human SafeguardsHiringTrainingEducationProcedure designAdministrationAssessmentComplianceAccountability

Job Positions in the Information Systems IndustryP 276, Experiencing MIS Kroenke, Bunker, Wilson) (2010) Pearson Australia (modified)

Title Element(approx) Responsibilities Knowledge, Skill and Characteristics

Requirements

2008 Australian

Salary range - : -

System analyst All

Work with users to determine system requirements, design and develop job descriptions and procedures, help determine system test plans.

Strong interpersonal and communications skills. Knowledge of both business and technology. Adaptable.

$70 000-$110 000

Programmer Software Design and write computer programs.

Logical thinking and design skills, knowledge of one or more programming languages.

$50 000-$70.000

PQA test engineer Software

Develop test plans, design and write automated test scripts, perform testing.

Logical thinking, basic programming, superb organisational skills, eye for detail.

$40 000 - $105 000

Technical writer

Software Procedures

people

Write program documentation, help-text, procedures, job descriptions, training materials.

Quick learner, clear writing skills, high verbal communications skills.

$70 000-$85 000

User support representative

Software procedures

people

Help users solve problems, provide training.

Communications and people skills. Product knowledge. Patience.

$35 000-$55 000

Job Positions in the Information Systems IndustryP 276, Experiencing MIS Kroenke, Bunker, Wilson) (2010) Pearson Australia (modified)

Title Element(approx) Responsibilities Knowledge, Skill and Characteristics

Requirements

2008 Australian

Salary range:

Computer technician

HardwareSoftware

Install software, repair computer equipment and networks. Associate degree,diagnostic skills. $30 000-$75

000

Network administrator

HardwareSoftware

Monitor, maintain, fix and tune computer networks.

Diagnostic skills, in-depth knowledge of communications technologies and products.

$65 000 -$120 000

Consultant All

Wide range of activities: programming, testing, database design, communications and networks, project management, security and risk management, strategic planning.

Quick learner, entrepreneurial attitude, communications and people skills. Respond well to pressure. Particular knowledge depends on work.

e.g. EAP Consultant$90 000-$120 000

Salesperson AllSell software, network, communications and consulting services.

Quick learner, knowledge of product, superb professional sales skills.

$70 000-$ 170 000

Small-scale project manager

Data People

Procedures

Initiate, plan, manage, monitor and close down projects.

Management and people skills, technology knowledge. Highly organised.

$85 000-$ 120 000

Job Positions in the Information Systems IndustryP 276, Experiencing MIS Kroenke, Bunker, Wilson) (2010) Pearson Australia (modified)

Title Element(approx) Responsibilities Knowledge, Skill and Characteristics

Requirements

2008 Australian

Salary range:

Large-scale project manager

Data People

Procedures

Initiate, plan, monitor and close down complex projects.

Executive and management skills. Deep project management knowledge.

$100 000-$ 150 000

Database administrator

DataSoftware

Procedures

Manage and protect database (see Chapter 12).

Diplomatic skills, database technology knowledge.

$80 000-$ 105 000

Chief technology officer (CTO)

AllAdvise CIO, executive group and project managers on emerging technologies.

Quick learner, good communication skills, deep knowledge of IT.

$95 000-$ 120 000

Chief information officer (CIO)

DataPeople

Procedures

Manage IT department, communicate with executive staff on IT- and IS-related matters. Member of the executive group.

Superb management skills, deep knowledge of business and good business judgment. Good communicator. Balanced and unflappable.

$160 000-$250 000executive benefits and privileges.

BONUS QUESTION

• For each of these layers suggest an appropriate protocol.

• Application: • Transport: • Network:

BONUS QUSTION_2k9

• (i) The packets arrive out of order. Identify the layer in which the packets are reassembled.

• (ii) Explain how the packets are reassembled to construct the entire web page that was requested by the user.