ITECH1102 Assignment template Sur-Names H to Z Student Name Student ID# Tutor Name Campus PRAMOD MAADHAM 30350645 ATMC - Melbourne Summary of Topic 3 (Application Layer) Summary of Topic 5 (Internet (Network) Layer) Summary of Topic 7 (Physical Layer) Problem sheet from Topic 4 (Data Link Layer) Q5 Q7 Q19 Q20 Problem sheet from Topic 6 (Transport Layer) Q5 Q8 Q14 Q15 Problem sheet from Topic 8 (Cloud Mobile) Q5 Q8 Q9 Q10 ITECH1102 Networking and Security Topic 3 – The Application Layer (Layer 5) Last week Last week we looked at: • • • • • • • • • The difference between Circuit Switched networks and Packet Switched networks. The origins of packet switched networks The Arpanet We saw how packet switching can lead to lost packets, duplicate packets and out of order network packets. The role of network interface cards How Hubs, Switches and Routers work We introduced 3 reference networks. Home network, Campus network & the Internet. Introduced the 5 layer Internet (TCP/IP) model of networking. Introduced the 7 layer OSI model of networking ITECH1102 Networking & Security 2 This week – overview of content Introduction to the Application Layer of the Internet Model. Application architectures including: • • • • Client/Server Peer to peer Host based Cloud architectures How simple networked applications work (Web Browser & FTP client) Internet Services can be a source of considerable monetary value The role of Network protocols Common Application layer protocols How data travels through a network & protocol headers ITECH1102 Networking & Security 3 The Application Layer (User Applications) User applications give us the ability to interact with thousands of services and devices on the Internet and on our local network. These applications are enabled though their ability to use networks. Internet services include: • • • • • Facebook Google search engine Google Maps FTP file download sites Domino’s pizza ordering online app • There are thousands of others ITECH1102 Networking & Security 4 The Application Layer (Local user applications) At the local level networks allow: • • • • Access to printers Access to network faxes Access to Network attached storage Shared resources from other local machines Prior to the prevalence of computer networks users would transport data locally by carrying the data on removable media (Floppy disks) to the destination. This approach is commonly referred to as “sneaker net”, so called because everyone at the time wore a type of footwear called sneakers. ITECH1102 Networking & Security 5 Categories of interaction Client/Server Architecture In this type of network the user’s application is described as a client. Common clients include: • • • email clients web clients FTP clients etc. Clients request services of Severs. For example a Web client will request web pages from web servers. Files are requested from File servers. Information from Database severs. ITECH1102 Networking & Security 6 Client/Server Architectures (continued) The role of Servers In client/server networks a server waits for client requests and responds to those requests. Some servers require authentication (Students J drive). Others do not (Eg. Most web servers). In client/server networks the server runs as a service (on Windows) or as a server Daemon (on Linux or Unix). In either case server processes listen for requests from client applications, and upon request respond to those requests. ITECH1102 Networking & Security 7 Strict distinction in roles In Client/Server networking there is a strict distinction between the roles of the client and the server. The client is a Consumer of services. The Server is a Provider of web, file, email or other services. The server program code is totally different from the client code. Example: Common web client software is Firefox, Chrome, Safari etc. Common web server software is IIS on Windows or Apache on Linux/Unix. ITECH1102 Networking & Security 8 Peer to Peer Architectures In peer-to-peer networking each machine in the network can act as both a server and a client (simultaneously if required). All machines (peers) can share resources (file and printers) and can also access any shared resource. Peer to peer networks do not require a dedicated server because the server role can be shared amongst many peers. Home networks that share files or printers to other computers on the network are a good example of a peer to peer network. ITECH1102 Networking & Security 9 Pro’s and cons of Client/server vs peer to peer. Peer to peer can work well in small networks like home network and small businesses. Administrative duties are distributed between the administrators of each peer, because any peer can act as a server. In larger networks (like Fed Uni campus network) network administration cannot be distributed as with peer to peer networks. Client/Server networking requires strong distinction between the roles of Network Administrators and network users. Network administrators control the network and its applications. Network users are only given the minimum access required to complete their day to day roles. ITECH1102 Networking & Security 10 Host based architectures Host based architectures were popular is the early days of computing and still have a strong presence today. Early system used a Mainframe with many attached dumb user terminals. The mainframe performed all the processing. Today Mainframes are used for high volume transaction processing functions like point or sale processing (Woolworths, Coles checkouts), Bank transactions, Airline transactions, Insurance company transactions etc. Some of the processing role has shifted to the point of sale or other terminals but the general processing architecture distinctions still exist. Microsoft Windows also supports a host based architecture to thin clients with its Citrix Metaframe product. (Most processing is done on the server). Users only require thin clients (low powered systems) because they are only required to render the graphical screen updates from the central Citrix server. ITECH1102 Networking & Security 11 Cloud based Architectures Cloud based Architectures are becoming increasingly important in modern computing. Cloud computing providers can supply a range of services to organisations including the computing platform, operating systems and software. This can be attractive to organisations because they no longer require in house hardware/software support for such systems or the associated costs of maintaining servers and associated infrastructure. Cloud services do come at considerable cost. ITECH1102 Networking & Security 12 Infrastructure as a Service (IAAS) The cloud provider manages all hardware, including servers, storage and networking components. The organisation is responsible for all software, including the Operating System/s, applications and associated data. The organisation is also responsible for virtualization software as required. Such architectures have the advantage that the organisation no longer has the responsibility of providing hardware, associated air conditioning of server rooms, power supply issues and associated uninterruptable power backup systems. ITECH1102 Networking & Security 13 Platform as a service (PaaS) The cloud provider offers the hardware, the operating system and base database or other software. The organisation’s programmers can code database or other applications in any language they like. They also have control over their own data. PaaS is not restricted to database infrastructure. This allows the organisation to build their own custom applications without the need to worry about the operating system, database system or hardware. ITECH1102 Networking & Security 14 Software as a Service (SaaS) Here the cloud provider provides everything including the software. User’s access the software from the Internet and are able to customise their user interface. Commonly email is outsourced by organisations to cloud providers. ITECH1102 Networking & Security 15 Common Internet Application Web Browser • • Allow us to view web pages Complete order forms over the Internet • • • • • • Pizza order Census online Download programs and other files from the web Search for information Run web applications from the browser (Eg. draw.io) Microsoft Office online ITECH1102 Networking & Security 16 Other network enabled applications Email client • • Compose and send email Read email File transfer services • Many Internet sites allow downloading of all sorts of files Phone apps • • Weather forecasting applications Banking apps Considerable business value can be gained by developing popular web services (Examples: Facebook, Google, Twitter, Whatsapp etc.) ITECH1102 Networking & Security 17 A close look a some web applications Application 1: Web browser query to Google 1. Open Browser to www.google.com (This is a request to display the Google search page dialog) 2. Submit a query (outbound request) 3. Web server replies with a list of suggested web sites (inbound) • The browser renders the suggested links 4. You select one of the options (outbound request) 5. That web page is displayed on your browser screen ITECH1102 Networking & Security 18 File transfer from an FTP site Application 2 – Download a file using an FTP application • • • • • • • • Run the local FTP client program (Installed by default in Windows) The FTP program asks for the Internet address of the FTP server User enters the address (Eg ftp.novell.com) FTP client requests a connection to the FTP server Server requests a username User responds with valid credentials FTP server provides access to available downloadable files User requests file download ITECH1102 Networking & Security 19 Network protocols All networked applications, including those described above must adhere to a strict set of rules (called protocols) for network communication to succeed. For Web applications the application layer transfer protocol is HTTP (Hypertext Transfer Protocol). For FTP file transfers the FTP client and server applications must comply with the application layer File Transfer Protocol. ITECH1102 Networking & Security 20 Other Application Layer protocols There are many other Application Layer protocols in the TCP/IP protocol suite. Some familiar ones include: • BitTorrent • NTP (Network Time Protocol) • POP (Post Office Protocol) • SMB (Server Message Block) • SSH (Secure Shell) Each of these protocols define the rules that applications and associated server programs must comply with for successful communications between one another. ITECH1102 Networking & Security 21 The role of application layer protocols Communications protocols do the following: • Establish consistent rules between sender and receiver. • Specify how data inside messages is structured and the types of messages that are sent between source and destination. • Handle message dialogue, for instance which entity communicates first and how the response should be handled. ITECH1102 Networking & Security 22 Basic aim of networking As a rule one party in a network transaction makes a request of the other party according to the rules of the appropriate application protocol. We require the network to ensure that the data sent in either direction arrives intact. For instance in the FTP example above we require: • • The username and password entered at the client to arrive unchanged at the FTP server. We require client requested files sent from the server to be exactly the same at the client as they originated on the server. ITECH1102 Networking & Security 23 How do the client and server applications interact Lets start with an FTP client program on your PC and a remote FTP server User Program (FTP client Application) Application Layer Other layers Client’s Networking software Servers Networking software ITECH1102 Networking & Security FTP Server (FTP program) Application Layer Other layers Login and other FTP protocol details are handled at the Data Transfers occur between client and server application the FTP client application and layers. the FTP application. The twoserver application layers must exchange usernames, passwords etc.must to implement All transfers use the the FTP protocol. physical network. 24 Network data exchanges use all layers Client program data must pass through all underlying network layers to reach the Physical Network. So FTP data must traverse the following layers in turn: • • • Transport layer Network Layer Data Link Layer Data being sent traverses down through the software layers of the protocol stack to the physical network. Received data rises up though the layers from the physical network. ITECH1102 Networking & Security 25 Protocol Headers As data passes through the protocol stack, Protocol headers are added at each layer. • • • The transport layer normally adds a TCP header. The network layer adds an IP header. The Data Link layer add an Ethernet header. The headers supply information to the associated layer of the destination machine. The information in these headers informs the destination where the data came from and other essential details. ITECH1102 Networking & Security 26 Visualization of client HTTP request from Firefox. User Program (Firefox) Application Transport Network Data Link Step 3: Step 1: The processStep 4: User opens browser continues. The reverse process occurs at the Ethernet information and enters URL toisa IP information isthe Data Link server addedend. atweb site. at the Headers added are removed at each Layer. Step 2: layer HTTP request is Network layer. as the data moves up through the Thenrequest the resulting frame HTTP is passed to created at the network layers. that sent to thelayer. network theisApplication Transport layer. media. Transport layer information (TCP) is added. Physical ITECH1102 Networking & Security 27 What happens at layers 2,3 & 4. As we progress through the course we will discuss the details concerning each of the other layers. ➢ Topic 4 - Data Link layer ➢ Topic 5 - Network layer ➢ Topic 6 - Transport layer ➢ Topic 7 - Physical layer ITECH1102 Networking & Security 28 Next Week The Data Link Layer Local delivery of network traffic ITECH1102 Networking & Security 29 Commonwealth of Australia Copyright Act 1968 Notice for paragraph 135ZXA (a) of the Copyright Act 1968 Warning This material has been reproduced and communicated to you by or on behalf of Federation University Australia under Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Faculty of Science & Technology Topic 4 – Problem sheet Q1. Which of the following best describes the role of the Data Link layer: (Choose 1) (i) (ii) (iii) (iv) (v) It deletes entries in the ARP cache It uses sockets to identify running applications It provides communication between locally networked devices It uses sequence numbers to maintain reliability It is layer 3 of the TCP/IP model of networking [ 1 mark ] Q2. Which of the following statements about the Data Link layer are incorrect: (Choose the one or more incorrect statements) (i) (ii) (iii) (iv) The Data Link layer is the interface between the network layer and the physical media. The Data Link interface to the network is the Network Interface card. The Data Link layer provides multiplexing of multiple upper layer conversations to the physical media The Data Link uses the IP address for all communications. [ 1 mark ] Q3. Define the following Data Link acronyms: LLC ……………………………………………………………………………………….. MAC ……………………………………………………………………………………….. [ ½ + ½ = 1 mark ] Q4. Describe the main role of the Data Link LLC. [ 1 mark ] Q5. 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. [ 2 marks ] CRICOS Provider No. 00103D Page 1 of 4 Faculty of Science & Technology Q6. What is the main role of the Media Access Control component of the Data Link Layer? [ 1 mark ] Q7. Describe why routers require at least 2 network cards. [ 1 mark ] Q8. How many binary bits constitute a MAC address? …………………………… [ 1 mark ] Q9. Describe the two constituent parts of a MAC address. [ 1 mark ] Q10. What Windows command will display the MAC address of your computers Ethernet network interface card? [ 1 mark ] Q11. What Linux command will display the MAC address of your computers Ethernet network interface card? [ 1 mark ] Q12. Network cards are said to be smart devices. Justify this statement. [ 1 mark ] Q13. Describe the process that leads to the detection of corrupted frame at the Data Link layer. [ 2 marks ] CRICOS Provider No. 00103D Page 2 of 4 Faculty of Science & Technology Q14. An Ethernet frame can contain each of the following: CRC Source MAC address FTP header IP header TCP header Destination MAC address Protocol Type Place the numbers 1 to 7 beside each part to show its order within the frame. Number 1 should indicate the first field in the frame. [ 2 marks for all correct ] Q15. How many bytes constitute the Source MAC address in an Ethernet frame? [ 1 mark ] Q16. How many Hexadecimal digits are required to specify an Ethernet broadcast address? …………………………………. Write that address in the space below. ……………………………………………….. [ 2 marks ] Q17. The following protocols can be categorised as either Controlled access or contention based access. Specify the category of each protocol. FDDI ………………………………………………….. Token Ring ………………………………………………….. WiFi ………………………………………………….. Ethernet ………………………………………………….. [ 2 marks ] CRICOS Provider No. 00103D Page 3 of 4 Faculty of Science & Technology Q18. Describe how each of the following work: The CSMA/CD protocol of Etherenet The CSMA/CA protocol used in WiFi Token Ring (Note – use the internet to investigate each as required) [ 4 marks ] Q19. Describe when entries are added and removed from the ARP cache. [ 2 marks ] Q20. 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. [ 2 marks ] Q21. The number of entries in the ARP cache changes with time. Describe the events that lead to the addition of entries to the cache and events that lead to the removal of ARP cache entries. You discussion should also describe how a ping to a remote address (eg. www.google.com) will affect the arp cache and why. [ 2 marks ] Q22. Describe how to generate an ARP request and reply from your Linux Lite machine. [ 1 mark ] Q23. Generate and capture an ARP request and associated reply. From these packets determine the following: The contents of the Target MAC address field in the ARP request. The contents of the Target MAC address field in the ARP reply. The contents of the Senders MAC address field in the ARP reply. [ 1 mark ] Q24. If your computer determines the destination address of a network packet is to a remote network. What does the Data Link layer software do with that packet? [ 1 mark ] CRICOS Provider No. 00103D Page 4 of 4 ITECH1102 Networking and Security Topic 5 – The Internet (Network) layer Last week Last week we: • • • • • • • • • • Investigated the Data Link layer Data Link sends and receives data from network media The Network Interface Card (NIC) is responsible for Media Access NICs have a globally unique 48 bit MAC address NICs filter traffic (only broadcast and station traffic are passed to the operating system) Data Link frames encapsulate all upper layer protocols (ULP) Broadcast addresses ( FF FF FF FF FF FF ) are processed by all computers. Two media access methods are CSMA/CD & CSMA/CA ARP (Address Resolution Protocol) is used to determine local MAC addresses (We will investigate this a bit more this week) Frame headers change after crossing a router ITECH1102 Networking & Security 2 More about ARP (Address Resolution Protocol) Last week we introduced ARP. ARP determines the MAC address of a machine on the local network with a specific IP address. ARP sends a broadcast asking the question, Who has IP Address 192.168.12.123 (or other IP address) If the targeted machine responds, the MAC address is known and is entered in the ARP cache. ITECH1102 Networking & Security 3 ARP commands (in Windows) To observe the ARP cache contents: arp –a To delete an entry: arp –d < ip address > Eg. arp –d 141.132.196.22 To delete all arp entries: arp –d * Note – some entries will remain (router, multicasts etc.) Some of these functions require administrative privilege and so will not work on lab machines. You can try this on your home machine if you like. Linux syntax is slightly different –a is not required to look at arp cache. ITECH1102 Networking & Security 4 When are entries added and deleted. A successful ARP command will result in a new entry being added to the arp cache. This will be a new local MAC address/IP address pair. New entries are only added as the result of local traffic, packets to remote locations exit via the local router and so will not result in a new entry in the arp cache. ARP entries age out after a set period of time. (The time varies depending on the Operating System) ITECH1102 Networking & Security 5 Arp on Linux This screenshot shows an ARP entry being to the One entry added in the ARP cache prior to pinging a arp cache as a result of a local ping local machine Ping 141.132.196.59 (which is a local machine) New entry in the arp table results ITECH1102 Networking & Security 6 What we can see in Wireshark Enough Let’s have a ITECH1102 Networking & Security Notice that the ARP request is a broadcast (FF:FF:FF:FF:FF:FF) discussion of ARP. and The target MAC address review of the Data Link is blank (00:00:00:00:00:00) Layer 7 What did the Data Link ever do for us? The Router is also on this network. Solution!!! Therefore it can data also to communicate So we can deliver any machine withonany device on the local thethe local network. Send the packet to local router and network let it handle the remote delivery of Yippee network traffic.!!!!!! The problem Data Link implements The next solve is!!how to That is the function oftoRouters communication between communicate with a remote machine? machines the (Oneany thattwo is on anotheron network) local network. It uses the source and destination MAC addresses to address each device. ITECH1102 Networking & Security 8 How do we decide when to send to the Router? But How is this done? Eachofnetwork It is done with the help the on the Internet has a Network (Internet) layer!!! network ID. If the destination and source networks are different (Remote transmission). Send the packet to the Router!!! ITECH1102 Networking & Security the source and EachIf time your computer is about to on the senddestination a network are packet it first determines same and network. if the source destination are on the Send to thenetworks. samedirectly or different destination’s MAC address. 9 Role of the Network Layer Client Application The Network Layer’s role is to deliver network traffic from one Host to another. HOST to HOST Transport Network Data Link Physical ITECH1102 Networking & Security The two hosts are often separated by long distances. Eg. Your home and a eBay server in the USA. The Network layer is all about IP addressing and associated Routing. 10 IP (Internet Protocol) addressing Each device on an IP network requires an IP address. There are two types of IP address: 1. IPv4 address 2. IPv6 address For now we will just consider IPv4 addressing. The IP address of a machine must uniquely identify that machine from all others on the Internet. ITECH1102 Networking & Security 11 Structure of an IPv4 address IPv4 addresses are 32 bits long. Example: 10001101 10000100 11000100 00011010 To make it easy for us humans, we normally separate the 32 bits into 4 lots of 8 (called Octets) and express each octet as a decimal number (between 0 – 255) The above IP address is expressed as follows: 141.132.196.26 ITECH1102 Networking & Security 12 How do computers get an IP address? The Operating System holds a machine’s IP address. It can be configured manually or automatically. Manual administration (static addressing) A user enters the IP settings into the machine’s OS. Automatic administration (dynamic addressing) A DHCP (Dynamic Host Configuration Protocol) server allocates IP settings to the machine. When the machine boots it sends a broadcast requesting IP settings. The networks local DHCP server responds with associated IP address, subnet mask and other settings. ITECH1102 Networking & Security 13 Other important IP settings To communicate on an IP network a machine requires: 1. 2. 3. An IP address Local router’s address - Called Default Gateway on Windows - Called Default Router on Linux Subnet mask The 4th setting which is not essential but particularly useful is the DNS (Domain Name System Server) IP address. DNS servers are responsible for converting IP addresses to names. (Example 172.217.26.4 < --- > www.google.com) ITECH1102 Networking & Security 14 Network / Node components of an IP address An IP address consists of two parts: • High order bits specify the IP network of the IP address. • Low order bits specify the unique part of the IP address. The network bits are common to all hosts on an IP network. The node bits specify a particular host on that network. ITECH1102 Networking & Security 15 Subnet mask A subnet mask applies to all machines (hosts) on an IP network. The format of a subnet masks is: • A series of binary 1 bits (indicating the network portion) followed by • A series of binary 0 bits (indicating the node portion) Hence a subnet mask tells us how many bits of an IP address is devoted to the network portion and how many to the node portion. ITECH1102 Networking & Security 16 Determining the network address of an IP address. Two ways: 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. ITECH1102 Networking & Security 17 CIDR – Classless inter-Domain routing Another way to express the number of network bits of an IP address is to use CIDR notation. Example: 192.168.22.56 /24 The number following the / is the number of network bits. The IP address above therefore has 24 bits devoted to its network address. It is equivalent to a subnet mask of 255.255.255.0 ITECH1102 Networking & Security 18 How this all helps Your computer wants to communicate with another machine. It knows its own IP address and that of the destination. It can determine (with the help of the subnet mask) the network address of the source and the destination. If they are equal -----> Local communication (So send directly to the destination machine) If they are different -----> Remote communication. (So send the packet to the network’s router) ITECH1102 Networking & Security 19 Types of IP addresses Public Public IP addresses can communicate on the Internet. Private Private IP addresses are discarded by routers. They cannot travel on the Internet. Private ranges are: 10.0.0.0/8 – 10.255.255.255 172.16.0.0/12 – 172.31.255.255 192.168.0.0/16 – 192.168.255.255 ITECH1102 Networking & Security 20 Network Address Translation (NAT) The computers (hosts) on most home networks use private IP addresses (allocated by the DHCP server in the router). Home network routers use NAT to provide Internet access to those hosts. This is achieved by changing the IP address of requests to that of the IP address on the ISP side of the router. IP ports (discussed in Topic 6) are used by the NAT router to distinguish the traffic from different hosts on the home network. ITECH1102 Networking & Security 21 The role of routers!!! The path between your computer and a distance web or other server could be many router hops away. For example. Traffic from my office PC to www.google.com traverses 13 routers. The role of a router is to: Move a network packet forward 1 step towards its destination. Analogy Like a game of netball. The GD (goal defence) makes a decision as to the best player to pass the ball to and then does it. That player decides the next player to pass the ball to and does it. Etc. etc. Routers work in a similar fashion, moving packets forward 1 step at a time. The route can change from packet to packet. ITECH1102 Networking & Security 22 How do Routers decide which route to use? Routers require a MAP of the internetwork. The map is called a routing table. Network address Interface Next Hop 141.132.64.0 141.132.64.1 141.132.64.1 141.132.192.0 141.132.64.1 141.132.64.3 141.132.128 141.132.64.2 141.132.64.2 141.132.192 141.132.64.1 141.132.64.3 When a packet arrives, the router determines the destination and source of the frame and sends the packet on its way. The routing table specifies the interface on which packets should exit and also the address of the next router’s address. ITECH1102 Networking & Security 23 What if the network configuration changes? Routers communicate with one another to ensue all routers know about network changes, for instance: • • • A router is offline A particular route is overloaded New routes added or removed Common Routing Protocols include: • 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] Routing protocols update routing table entries as required. ITECH1102 Networking & Security 24 Source IP address and Destination IP addresses are there for obvious reasons. The information in the source IP provides information The IHL fieldheader specifies the header size into routers and the(4destination host multiples of 32 bits bytes). about the network packet. Header sizes can be between 20–60 bytes. Important fields include: Sourcecirculating Address around Time to Live stops packets the Internet forever.Destination The sourceaddress sets the value (header size) [ 20-60bytes] (often to 128 IHL or 64). At each router the value Timethe to Live is decremented. When TTL value Header checksumby the reaches zero the packet is discarded router. Format of IPv4 header The options field is seldom used, so most IP headers are 20 bytes in length. ITECH1102 Networking & Security 25 Naming of Internet hosts Companies and organisations require a block of Public IP addresses to name their servers on the Internet. The block of addresses are associated with the organisations Domain Name. For example: Federation University’s Domain (federation.edu.au) has the IP range 141.132.x.x allocated to it. (65536 IP addresses) The University’s address range was purchased many years ago. ITECH1102 Networking & Security 26 Internet Assigned Numbers Authority (IANA) IANA is the overseeing body for the naming of Internet domains. IANA delegates naming for different geographical regions of the world to other naming authorities. For instance APNIC (Asia Pacific Network Information Centre) for the Asia Pacific region. ISP’s hold blocks of IP addresses and can allocate small IP ranges to their customers. Once an organisation has their domain name and associated IP addresses their server/s can be found on the Internet. ITECH1102 Networking & Security 27 DNS (Domain Name System) Name resolution of Internet names is handled by DNS. 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. Resolution of names is handled by your local DNS server or that of your ISP’s DNS server. If the local DNS server cannot resolve a name, it requests the help of DNS servers that form part of the worldwide DNS server hierarchy. Name resolution is required each time you enter Internet names (eg. www.apple.com) into web browsers because IP addresses are required for network communication to take place. ITECH1102 Networking & Security 28 IPv6 (IP version 6) IPv6 is the most recent version of the Internet Protocol. It was developed by the Internet Engineering Task Force (IETF) to deal with IPv4 address exhaustion. In time IPv6 is meant to replace IPv4. Each IPv6 address is 128 bits in length which gives IPv6 an enormous addressing range. • 2128 possible different addresses • 3.402 * 1038 • 4.5X1015 addresses for every observable start in the universe. ITECH1102 Networking & Security 29 We use Hexadecimal to express IPv6 addresses Because IPv6 addresses are so large we use hexadecimal to express them in 8 lots of 4. Example: FE80:0000:0000:0000:ACC1:44F9:91B5:AC1B Most of the Internet only supports IPv4 and so transitions mechanisms are required. The most important is tunnelling. ITECH1102 Networking & Security 30 Tool Talk A closer look at IP settings on Windows and Linux • • Windows Linux Linux command line: • • • cd ls . .. ~ notations Wireshark: • • • • • ARP (Local address resolution) DHCP DNS (name resolution) Capture filters Display filters ------- Demonstration ------- ITECH1102 Networking & Security 31 Next Week The Transport layer: • TCP • • • Virtual Circuits 3 way handshake Sequence numbers and acknowledgements • UDP ITECH1102 Networking & Security 32 Commonwealth of Australia Copyright Act 1968 Notice for paragraph 135ZXA (a) of the Copyright Act 1968 Warning This material has been reproduced and communicated to you by or on behalf of Federation University Australia under Part VB of the Copyright Act 1968 (the Act). The material in this communication may be subject to copyright under the Act. Any further reproduction or communication of this material by you may be the subject of copyright protection under the Act. Do not remove this notice. Faculty of Science & Technology Topic 6: Transport layer problem sheet Q. We can characterise the addressing at the Data Link layer as MAC addresses. What type of addressing is used at the following layers? Network: …………………………………………… Transport …………………………………………… What entity is being addressed in each case? Q. Network: …………………………………………… Transport …………………………………………… The data unit (called Protocol Data Unit (PDU)) is called different names at the different layers of the TCP/IP model. What are the PDU’s called at each of the following layers? Data Link: ……………….frame …………………. Network Layer: …………………………………………….. Transport (TCP) ……………………………………………. Transport (UDP) ……………………………………………. Physical layer: …………………………………………… Q. Describe Multiplexing as it relates to the Transport layer. Q. What constitutes a Socket? How do server sockets and client sockets differ? Q. How many bits are used in a UDP header to store the destination port number? Explain how you arrived at this number. CRICOS Provider No. 00103D Page 1 of 3 Faculty of Science & Technology Q. What range of port numbers are reserved for server applications and what is this range of port numbers called? Q. What server port numbers are normally used for the following applications? Q. FTP-Data ……………………….. FTP-Control ……………………….. SSH ……………………….. HTTP ……………………….. It is common place 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. Q. Which of the following fields are parts of a UDP header? Source IP address Destination port number Source MAC address Flags Destination MAC address Q. Describe the difference between a stateless protocol and a stateful protocol. Q. Which of the following fields are parts of a TCP header? Source IP address Destination port number Sequence Number Flags Destination MAC address CRICOS Provider No. 00103D Page 2 of 3 Faculty of Science & Technology Q. Describe the role of TCP Timers Q. Define the meaning of the following TCP Flags: FIN ACK SYN Q. 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. Q. Describe how flow control is achieved in a TCP connection. CRICOS Provider No. 00103D Page 3 of 3
Purchase answer to see full attachment