Ch. 4 Network Layer
On your home computer, what is the IP address reported by ipconfig /all (Windows) or ifconfig (MAC/ Linux)?
192.169.1.3 (example)
13. What decimal number does the binary number 10001101 represent? 11011001?
10001101 represents 128 + 8 + 4 + 1 = 141 11011001 represents 128 + 64 + 16 + 8 + 1 = 217
12. How would you represent 217 in binary? 168?
217 = 1*128 + 1*64 + 0*32 + 1*16 + 1*8 + 0*4 + 0*2 + 1*1. Therefore 21710 = (11011001)B2. 168 = 1*128 + 0*64 + 1*32 + 0*16 + 1*8 + 0*4 + 0*2 + 0*1. Therefore 16810 = (10101000)B2. B = Base
What is the need for a computer address at the IP layer when computers also have a MAC address?
MAC addresses are local to a network, but IP addresses are global identifiers. The use of two different addresses enables technology independence so that the MAC technology can change without any change in IP. If IP addresses were also used at the data link layer, a change in IP would require a change in all data link layer technologies as well.
From your home computer, go to www.whatismyip.com and make a note of your IP address. Type this address into the search box at www.arin.net. Who is the owner of that address block?
My IP address was 68.238.65.12. (will vary) ARIN reports that Verizon Online LLC (VRIS) is the owner of this IP address. Verizon is my network service provider.
1. Briefly describe routing — the primary function of the network layer.
Routing is the process of selecting a path on the Internet which can be used to deliver data to a destination. Routing is performed using devices called routers. Routers exchange network information with each other to be automatically informed about the network's layout. Routers save this information as a routing table. When a packet arrives at a router, the device uses its routing table to determine the most suitable neighboring router to pass the packet. Through this process, the packet eventually reaches its destination.
You wish to assign unique labels to 200 objects using binary numbers. What is the minimum number of bits needed?
Since 2^7 = 128 and 2^8 = 256, we need at least 8 bits to have enough labels to uniquely label 200 items.
14. What is dotted decimal notation?
The dotted decimal notation is the standard manner in which IP addresses are written for the convenience of end users. For convenience of representation, the 32 bit IP addresses are broken down into 4 blocks of 8-bits each. Each of these 8-bit blocks is called an octet. For user display, each octet is converted to decimal and the 4 decimal numbers are separated by dots. An example IP address in dotted decimal notation is 192.169.3.4.
15. What information is conveyed by each part of a two-part IP address?
The left-most part identifies the network in which the address is located and the right-most part identifies the individual host within the network. This partition is done to facilitate the delivery of data packets. The network part identifies the network to which the address belongs. The remaining bits of the IP address identify the computer within this network.
How are IP addresses similar to MAC addresses? In what ways are the two addresses different?
The two addresses are similar in that both IP addresses and MAC addresses are used to address hosts on the network. Also, both addresses have multiple parts. The differences include the fact that the left-most part of a MAC address identifies its manufacturer whereas the left-most part of an IP addresses identifies the network where the address is located. MAC addresses are assigned by the manufacturer, whereas IP addresses are assigned by the network administrator.
16. How are the 32 bits of an IP address organized in a typical large network?
Within a large network, the host part of the IP address is split into two sub-parts. The first of these is the subnet ID and the second is the host ID. The subnet ID is used to route packets within the network.
