1. Show the subnet address, subnet mask in slash notation, broadcast address, nu
ID: 3544940 • Letter: 1
Question
1. Show the subnet address, subnet mask in slash notation, broadcast address, number of addresses, first valid host address, and the last valid host address for the subnet address of the host with IP v4 address: 192.16.10.5 255.255.248.0
2. An IPv4 header bytes in Hex notation is given: 45 00 05 dc fd 2b 20 00 80 11 95 ca c0 a8 00 64 c0 a8 00 66. Answer the following questions about the header: Are options being used? What type of higher-level protocol is this datagram carrying? Is there a fragmentation? If yes, is this a first, last, or middle fragment? What are source and destination IP addresses for the IPv4 header?
3. A client sends 16 bytes of data to a server using TCP protocol. Calculate the efficiency of this transmission at the TCP level (ratio of data excluding header to the total bytes transmitted). Calculate the efficiency of transmission at the IP level. Assume no options for the header and no errors. Calculate the efficiency of transmission at the data link layer. Assume no options for IP header and Ethernet-II format are used at the data link layer.
4. Using 7-bit sequence numbers, what are the maximum sizes of the send and receive windows for each of the following protocols: Stop-and Wait ARQ, Go-back-N ARQ, and Selective-Repeat ARQ?
5. A block of 200 ASCII characters (with 1-bit even parity) is to be transmitted over a serial link. Calculate the number of bits transmitted and the efficiency of the link if the asynchronous link uses 2 stop bits. What is the efficiency of the link?
Explanation / Answer
1)
IP mask numbers are used to divide internet addresses into blocks called subnets. The mask number represents the number of 1s in the binary of the address that is 'masked" against the address so that it ignores the last bits which are for the group of IP addresses in the masked address.
The first address of a subnet block (all 0s) is called the network address or network ID. The last address (all 1s) is the broadcast address of the network. Typically the network address +1 or the broadcast address -1 is the gateway to the internet. The 'slash' notation (ie /24) is known as CIDR format, while the more conventional 255.255.255.0 notation is considered a subnet mask.
n example of an IP address that is using a zero subnet is 10.1.0.1 with a subnet mask of 255.255.255.0. Earlier this was a kind of network id but today, this IP address is perfectly legal when it comes to subnetting. Thus, if I had an IP address of 10.1.0.0 with a 255.255.0.0 subnet mask is the network ID and if we subnet it, we could actually get 255 valid networks out of it by using the 0 subnet.
Net bits
Subnet mask total-addresses per subnet
/20 255.255.240.0 4096
/21 255.255.248.0 2048
/22 255.255.252.0 1024
/23 255.255.254.0 512
/24 255.255.255.0 256
/25 255.255.255.128 128
/26 255.255.255.192 64
/27 255.255.255.224 32
/28 255.255.255.240 16
/29 255.255.255.248 8
/30 255.255.255.252 4
2)
45 00 05 dc
source will be MAC
yes there is fragmentation
middle fragmentation
transmission efficiency = number of information bits / total number of bits transmitted
number of information bits = 16 bytes * 8 bits/byte = 128 bits
total number of bits transmitted = total number of information bits +
total number of overhead bits
total number of overhead bits = bits in header + bits in trailer
= 0 bytes * 8 bits/byte + 0 bytes * 8 bits/ byte
= 0 bits
transmission efficiency = 128 / ( 128
4)
5)
total bits transmitted = 200*7*(8/4) = 2800 bits
efficiency = 4/8 = 1/2 = 0.5 = 50%
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