BA 479 Final Exam Study Guide

What are the Port ID's for.. HHTP DNS DHCP ?

# IS PORT ID HTTP: 80 DNS: 53 DHCP: 67

Address resolution refers to the process of ? (2 parts)

(1) Translating an application layer address (or domain name) into a network layer address (2) Translating network layer address into a data link layer address.

What is Subnet mask?

(Part of Routing) Using subnet mask, and subnet mask algorithm, IP determines if next computer enroute is on the same subnet as client.

An ISP would typically use static addressing to temporarily assign IP addresses to computers used by its subscribers. TRUE/FALSE

FALSE

Purpose of subnet mask? Why is it important?

*Helps determine if sender and receiver are on same subnet. *Helps determine max # of computers per subnet and helps determine max # of subnets *Can take values other than 0 or 255

Why TCP/IP?

*Most widely used protocol on the internet *Estimated 70-80% of LAN,MAN, and backbone networks use TCP/IP *Reliable protocol *TCP/IP does some error detection/correction functions

What is the minimum information needed by a computer in a TCP/IP Network?

1-Computers IP address 2-A subnet mask address 3-IP address of DNS Server 4-IP address of Router/Gateway that connects the computer outside its subnet (for static routing). If dynamic routing is used, then appropriate routing software/ access to routing tables would be needed

(5) APPLICATION LAYER

1. Protocol operating at this layer: HYPER TEXT TRANSFER PROTOCOL (HTTP). 2. AL will pass a web page request (user data) to the TL of the sender with Hyper Text Transfer Protocol (HTTP) header or HTTP Protocol Data Unit (PDU). 3. After the webpage request has passed through the five layers the AL will receive a webpage from the destination server.

What are 2 popular Transport/Network layer protocols

1. TCP/IP and UDP/IP 2. IPX-(Internet Packet Exchange)/SPX-(Sequenced Packet Exchange)

(4) TRANSPORT LAYER

1. The Protocol operating at this layer is TRANSMISSION CONTROL PROTOCOL (TCP). 2. TCP will do a 3-way handshake to start a session. 3. TCP will then packetize information by splitting the message into multiple packets and numbering those packets. 4. For each packet TCP will prepare a TCP header or PDU. The TCP header or PDU will include a PACKET#, and SOURCE + DESTINATION PORT ADDRESSES. The destination port address specified in a TCP header or PDU is 80. 5. TCP will now have a "packet group" (or frame) which contains (TCP+HTTP+Userdata) . This packet group is then sent to the Network layer. also. UDP/ User Datagram Protocol ( non-confirmation )

(2) DATA LINK LAYER

1. The Protocol operating at this layer: ETHERNET. 2. Functions of Ethernet - Ethernet performs: -Media Access Control (called Carrier Sense Multiple Access with Collision Detection (CSMA/CD)) -Error Detection (called Cyclic Redundancy Check (CRC)) -Error Correction (called Automatic Repeat Request (ARQ)) -Message Delineation Ethernet does message delineation by specifying (in the Ethernet header or PDU) the length of the packet group. 3. Ethernet prepares Ethernet header or PDU for each packet group received from IP. Sample contents of Ethernet header or PDU include: • Source MAC. The MAC address. • Destination MAC. • CRC related remainder • Length of the packet. The Ethernet header or PDU is then appended to the packet group. (Ethernet+IP+TCP+HTTP+User data) is sent through the physical layer.

(3) NETWORK LAYER

1. The Protocol operating at this layer: INTERNET PROTOCOL (IP). 2. IP PERFORM ADDRESSING + ROUTING - It will determine the source IP address (from configuration file assuming IP has already been assigned to A or from DHCP if IP not yet assigned). -It will determine the destination IP address (from cached address in address table or from DNS if destination's IP is not cached) -It will determine the source MAC address (from configuration file) -It will determine destination MAC address (from cached address or using ARP). -It will pass the source MAC address and destination MAC address information to the Data Link Layer. 2. IP PERFORM ALSO PERFORMS ROUTING - It will determine the next hop (with the help of routing table perhaps developed using the subnet mask algorithm and routing algorithm used by routing protocol). 3. IP WILL PREPARE AN IP HEADER FOR THE PACKET GROUP RECEIVED FROM TCP Contents of the IP PDU include source IP, destination IP and next hop information: • Source IP Address is the IP address of A. • Destination IP Address is the IP address of B. • Next hop is: Router R. The IP header or PDU is then appended to the packet group. This packet group (IP+TCP+HTTP+User data) is then passed to the Data Link Layer.

Assume that the source, interim and final destination computers have agreed upon the maximum frame size allowed by traditional Ethernet, which is 1492 bytes, and that all of them use 8-bit ASCII code. Assume Ethernet header size is 26 bytes. Assume that the HTTP header is 10 bytes, TCP header size is 192 bits, and IP header size is 192 bits. Based on the above information, the maximum # of information bytes (non-overhead bytes) in each frame would be:

1408 Bytes

Given the application address (e.g., www.google.com) of a destination computer, the following is helpful in determining the IP address of that destination computer. a. DNS b. DHCP c. ARP

A. DNS

The following were identified in class as subnet mask applications/benefits:

ALL 'Help determine if sender and receiver are in the same subnet' AND 'Help determine maximum # of subnets' AND 'Help determine maximum # of computers (devices) in each subnet' are correct

APPN

Advanced Peer to Peer Networking

Given a Class C IP address, with a subnet mask of 255.255.255.224, compute the number of subnets. Same assumptions for previous question hold true for this question.

Answer: 2^3 = 8 subnets (Formula: 2^y where y denotes # of 1's in binary version of host part of subnet mask; the # of 1's are counted as per the algorithm we used in class). Class C address is of the type: Network.Network.Network.Host

Given a Class B IP address, with a subnet mask of 255.255.254.0, compute the max number of computers per subnet. Ignore restrictions. Examples of restrictions include loop back and broadcast addresses. If your final answer is incorrect, you can obtain partial credit if you show the formula used in the class lecture and explain the symbol(s) used in the formula to determine the max # of computers per subnet.

Answer: 2^9 = 512 computers per subnet. (Formula: 2^x where x denotes # of 0's in binary version of host part of subnet mask; the # of 0's are counted as per the algorithm we used in class). Class B address is of the type: Network.Network.Host.Host

ICANN does what??

Approves IP addresses that can be used by an organization for its computers that participate on the Internet. Internet Corporation for Assigned Names and Numbers (ICANN

Routing Protocols - ASN

Autonomous System of Networks: Interior Routing Protocols: protocols used inside autonomous system Exterior: protocols used outside autonomous system

This server helps with leasing IP addresses to computers that want to participate on the Internet, and don't have an IP address assigned as yet. a. DNS b. DHCP c. ARP

B. DHCP

Primary functions of transport/network layer include:

BOTH 'Packetizing and session management' AND 'Addressing and routing' are correct

Types of Routing

Centralized: All routing decisions are made by one central computer. Decentralized: Computers/routers in network make their own routing decisions following a formal routing protocol, which could be capable of self-adjusting, and adapting to changes in the network configurations

Connection vs Connection-less Routing

Connectionless: different packets of same message take different routes Connection-Oriented: VC (virtual circuit) is set up between sender, receiver

255.0.0.0 would be an example of a Class A IP address. TRUE/FALSE

FALSE

ARP is typically used to determine IP address of next computer on the route. TRUE/FALSE

FALSE

What does DORA mean?

DORA is an acronym used to help remember the correct response order from DHCP Discover Offer Request Acknowledgement

DDOS

Distributed Denial of Service

DNS Server

Domain Name System (or Service) Server

DHCP Server

Dynamic Host Configuration (or Control) Protocol Server

DHCP? Acronym

Dynamic Host Control Protocol

Assume a client requests IP address from DHCP server(s) in a network. Assume the DHCP server(s) respond(s) to this request. The correct order of this request/response process can be outlined as: "DHCP Request, DHCP Discover, DHCP Offer and DHCP Acknowledgement." TRUE/FALSE

FALSE

IP uses a 4-way handshake to finish a session between two computers. TRUE/FALSE

FALSE

IPX/SPX was originally developed by IBM for the mainframe environment. TRUE/FALSE

FALSE

The 3-way handshake (also known as commencement of session management or end-to-end messaging) is a function of IP. IPv4 addresses use dotted decimal notation. TRUE/FALSE

FALSE

The Ethernet card (or NIC) address of a computer is typically expressed in decimal notation. TRUE/FALSE

FALSE

The Ethernet header at the beginning of a frame usually includes IP address information. TRUE/FALSE

FALSE

To send a broadcast message inside the subnet 128.193.0.0, the destination IP (in the IP header) must be 128.193.5.5. TRUE/FALSE

FALSE

The default subnet mask for a Class C IPv4 address would be 255.255.225.0. TRUE/FALSE

FALSE - see the 225?

(1) PHYSICAL LAYER

Governs transmission between adjacent devices connected by a transmission medium. BUS Topology RING Topology STAR Topology

What are the different versions of IP? What does an IP header contain?

IPv4- Dotted decimal notation. ex--> 192.16.224.254 IPv6 IP header contains (among other overhead information) a SOURCE and a DESTINATION address!

Assume handshake process is completed to begin a session. As per BA479 class discussion, in a TCP/IP network, during the transmission of a request (for a web page) from Client A to Web Server B, TCP is directly invoked:

In both Client A and Web Server B, but not in any of the devices enroute

Essay Section on the BA479 Final Exam and a Sample Essay: Assumption: Assume that computer A requests web page from B through router R. Question: Describe the data flow across different layers from computer A to computer B through router R. In the exam, you may have a different example.

In the exam, you will be given most of the essay and will be asked to fill in the blanks where the essay is left partially incomplete. Examples of fill in the blank questions on the partially complete essay on the final exam could include: • What protocol operates at each layer? • What are the major functions of each layer? • What are the sample contents of each Protocol Data Unit (PDU) or header? • What is the source IP address? What is the destination IP address? • What is the packet size when TCP does packetizing? Given a message size, and a packet size, how many packets in a message? How does TCP start a session? How does it end a session? • What is the difference between each layer's role at the sender, and each layer's role at the destination?

What's a disadvantage to Static Addressing?

Inefficient IP/subnet address management - not an efficient way of adding/deleting/changing IP/subnet mask addresses of computers in network. (Solution to this problem is dynamic addressing)

ICANN? Acronym and what do they do?

Internet Corporation for Assigned Names and Numbers IP Addresses are approved by ICANN or one of several private companies authorized by ICANN

Formula for max # of computers per subnet? Formula for # of subnets?

Max # of Computers(hosts)= 2^x (where x = # of 0's in host) # of subnets= 2^y (where y = # of 1's in host)

What router or server allows hosts to participate on the Internet, although these hosts use private IP addresses that are not approved by ICANN?

NAT Router (Network Address Translation Router)

NAT

Network Address Translation or Translator

What does a NAT router stand for?

Network Address Translation router

What is Static Addressing? Would static addressing be better for clients or servers?

Network staff manually assigns each computer on network an IP address when installing TCP/IP. Servers because chances are servers are going to be on 24/7/365, and can get requests from clients anytime. They are likely to need to have an IP all the time.

Routing Protocol Acronyms: OSPF BGP

OSPF - Open shortest Path First - Link state dynamic routing BGP - Border Gateway Protocol - Distance vector dynamic routing

RIP - Acronym

Routing Information Protocol

TCP/IP - Routing

Routing: Path taken by message from sender to final destination Routing Table: Devices that perform routing typically use a routing table that specifies route to different destinations

Sample contents of TCP header include:

Source and Destination MAC addresses

Quality of Service (QoS) Routing

Special type of connection-oriented dynamic routing protocol, different packets assigned different priorities

Decentralized Routing Disadvantage: requires more processing power, compromises network capacity

Static Routing: Table is developed by network manager. Changes made only when computers added or removed from network. Dynamic Routing: Used when there are multiple routes. Network manager can develop route, but can change along the way. - Distance Vector Routing: Routing decisions made based off of number of "hops" along the way - Link State Routing: Decisions made from number of hops in each route, speed of circuits, route conditions, route reliability

SNA

System Network Architecture

The following is/are example(s) of transport/network layer protocols:

TCP/IP and IPX/SPX

An IPv4 address is 32 bits in length. TRUE/FALSE

TRUE

Assume Computers A and B are operating in an older version of Microsoft Windows based network environment which accepts the subnet mask address below. (Hint: Carefully apply the termination criteria of subnet mask algorithm). Question: Computer A (IP: 200.100.50.25; subnet mask: 255.255.255.193) is on the same subnet as Computer B (IP: 200.100.50.26) TRUE/FALSE

TRUE

DHCP and DNS queries use User Datagram Protocol (UDP) on ports 67 and 53 respectively. TRUE/FALSE

TRUE

IPv4 addresses use dotted decimal notation. TRUE/FALSE

TRUE

Vinton Cerf and Bob Kahn are usually referred to as Fathers of TCP/IP. TRUE/FALSE

TRUE

Address Resolution Protocol (ARP)

The ARP and RARP protocols perform the translation between IP addresses and MAC layer addresses

Static Addressing: In each computer, which file typically stores the IP address and subnet mask addresses associated with that computer?

The network layer address and subnet mask value associated with a computer can be obtained from a configuration file. Use IP Config or IP Config/all to determine computer's addresses.

What does the TCP/IP acronym stand for? and what are the major functions of TCP, IP, respectively?

Transmission Control Protocol/ Internet Protocol Major Functions of TCP: segmenting or packetizing, session management linking ApplicationLayer to NetworkLayer (**It only operates at the sender and final destination!**) IP's main functions: Addressing and routing (**Operates at Sender, Final Destination and each intervening computer involved in the message transmission**)

Unicast Broadcast

Unicast: From one sender to one final destination. Broadcast: - Subnet Broadcast - Network Broadcast

Routing Protocols

Used to exchange route status information among computers to enable them to maintain and build their routing tables.

UDP

User Datagram Protocol

Who are the 2 fathers of the internet and what did they invent?

Vinton Cerf and Robert Khan Inventing TCP/IP becoming the fathers of the internet.

What is dynamic addressing?

With this approach, a server is designated to supply a network layer (IP) address automatically to a computer each time the computer connects to the network. This server is called a DHCP server. *Dynamic Addressing greatly simplifies network address management. Next time a client (which has been moved to another subnet) requests an IP address, the new changed IP address will be automatically assigned to the client by DHCP server

IP address classes. What are the different types , how do they differentiate and what are the default subnet masks for the first 3 classes?

classes A, B,C, and D/E. A B and C are used for commercial purposes. D/E are reserved for multicasting(D) and experimental/research(E) (first octet decimal range followed by dotted decimal notation) **Network is always assigned/approved by ICANN Class A: [1 - 126] 255.0.0.0 ---------> Network.Host.Host.Host Class B: [128 - 191] 255.255.0.0 ---------> Network.Network.Host.Host Class C: [192 - 223] 255.255.255.0 ---------> Network.Network.Network.Host (Restrictions for Host address: IP address cannot end in 0 or 255)

TCP is a protocol that operates at the ____________ layer and directly interfaces with _____________ and __________________ layers:

transport; application and network