TCP/IP and Subnets | Question and Answer

Running head: TCP/IP AND SUBNETS
TCP/IP and Subnets
Name of the Student
Name of the University
Author Note

1TCP/IP AND SUBNETS
Table of Contents
Question 1..................................................................................................................................2
What is a link-layer frame? A network layer datagram? A transport-layer
segment? And application-layer message?...........................................................2
Question 2..................................................................................................................................3
Is it possible for an application to enjoy reliable data transfer even when the application
runs over UDP? If so, how?...................................................................................................3
Question 3..................................................................................................................................4
Subnet Classification..............................................................................................................4
Question 4..................................................................................................................................5
Use of Protocols.....................................................................................................................5
References..................................................................................................................................6

2TCP/IP AND SUBNETS
Question 1
What is a link-layer frame? A network layer datagram? A
transport-layer segment? And application-layer message?
Link-layer frames are communication units which are found in the data link layer. The
data link layer obtains the data packets sent through network layer and then performs
encapsulation of the packets into frames. When the frame size happens to be larger than
expected, these packets get broken to multiple smaller sized frames. From receiver’s side, the
data link layer picks the signals delivered and assemble the respective frames.
The data link-layer frames have various components and these are the following:
 Frame Header
 Payload Field
 Trailer
 Flag
The frame header stores source and destination addresses of the frames and the control
bytes. The payload field stores message specific data which must get delivered. The trailer
comprises of the error detection as well as error correction bits and is even known as frame
check sequence. Two flags at each end marks the start and end of the frames.
The packets in the IPv4 layer are called datagrams (Gupta, Kumar & Barve, 2017).
Datagrams are variable length packets consisting to main parts. These are the header part and
the data part. The length of the header can vary between 20 to 60 bytes and stores information
that are necessary for routing purposes. The Network layer is a connectionless service and the
packets created by the source host traverse through multiple routers till it reaches the router
whose internal network contains the destination host of the packet.

3TCP/IP AND SUBNETS
Transport layer segment is the second layer of the TCP/IP model and refers to an end
to end layer that can be used for delivering messages to hosts (Byun, Li & Lim, 2019). It is
termed end to end as it provides point to point connections instead of one hop and another.
HTTP, SMTP and FTP are examples of protocols used in the application layer.
Messages based on these protocols are used to deliver data between multiple systems.
Question 2
Is it possible for an application to enjoy reliable data transfer even when the
application runs over UDP? If so, how?
Applications can enjoy reliable data transfer despite making use of the UDP protocol.
This can be ensured by making use of Alternating Bits or Selective Repeat protocols (Li,
Long & Wei, 2018). Although UDP happens to be an unreliable and connectionless protocol
for conducting data transfer. Like TCP, UDP is one of the data transfer protocols which exist
in the transport layer of the TCP/IP architecture.
Alternating Bit Protocol or ABP refers to a connectionless protocol used for
transferring single directional messages among clients and servers. This happens to be the
simplest implementation of sliding window protocol in which the sequence number alternates
among 0 and 1 while the size of the window is 1. In ABP, requests or ACK messages are sent
among clients and server with the AB being either 0 or 1. When the client sends an AB to the
server and gets a response, the AB is flipped and a newer request is sent. Hence, based on the
AB sent by client the server knows if it should send the old packet or a new one.
Selective Repeat Protocol or SRP is another connectionless protocol that can be used
to increase reliability of data transfer however, contrary to ABP this involves servers to send
several number of packets in parallel which happens to be 10 by default for every new
request. After receiving the packets from the server, the sequence of received packets is

4TCP/IP AND SUBNETS
verified by the client and thus gets to know about the missing packets and the process gets
repeated till every packet of the specific request is received.
Question 3
Subnet Classification
Subne
ts
Neede
d IPs
Allocate
d
Address
es
Network
Address
CID
R
Mas
k
Subnet Mask Host IP
Range
Broadcast
Address
Subnet
2
90 126 223.1.17.0 /25 255.255.255.
128
223.1.17.1
-
223.1.17.1
26
223.1.17.1
27
Subnet
1
60 62 223.1.17.1
28
/26 255.255.255.
192
223.1.17.1
29 -
223.1.17.1
90
223.1.17.1
91
Subnet
3
12 14 223.1.17.1
92
/28 255.255.255.
240
223.1.17.1
93 -
223.1.17.2
06
223.1.17.2
07
As can be seen from the IP addressing table above, the detailed subnet information for
all the three subnets are given (Young, 2018). Starting with the largest subnet, for subnet 2,
number of IP address needed is 90 therefore number of borrowed bits is 27. This is because
the minimum subnet allocation for 90 hosts needs to be a subnet with 128 IP addresses where
the starting and the ending IP addresses are reserved for the network and broadcast addresses
which are 223.1.17.0 and 223.1.17.127 respectively (Vegoda, 2017). Thus the number of IP
addresses made available to Subnet 2 is 26 – 2 = 64 - 2 = 62. Similarly, for Subnet 1, the
number of IP addresses required is 60 which is less than the subnet division of 64 and
therefore number of borrowed bits is 26. In this subnet the starting and ending IP addresses
that is the network and broadcast addresses are 223.1.17.128 and 223.1.17.191 respectively.
Lastly for subnet 3, the number of IP addresses required is 12 (Huang & Wang, 2018). This is

5TCP/IP AND SUBNETS
less than the subnet division of 16 IP addresses and therefore number of borrowed bits is 24.
Here the network and broadcast addresses are 223.1.17.192 and 223.1.17.207 respectively.
Based on the borrowed bits, the size of CIDR masks of subnets 2, 1 are determined which are
25, 26 and 28 respectively.
Question 4
Use of Protocols
When trying to enable internet connection to a host machine after booting it and
opening university hosted web page Interact 2, the user needs to ensure the following steps.
Ensure the Ethernet cable from the switching device is connected to the Ethernet port of the
host machine, power the host machine on, when the operating system is booted, the user
should open the network adapter settings and if the configuration needs to be made manually
the user needs to right click on the Ethernet connection, select properties, check TCP/IPv4
and go to properties and then select ‘Use following IP address’ and then enter the specified IP
address, subnet mask and put the subnet default IP address of the university router as the
Default gateway (Komosný, Vozňák & Rehman, 2017). The preferred DNS server should
have the IP address of the server machine through which the DNS services for the web page
Interact 2 are being made available (Al-Fannah, 2017). If the network is to automatically
identify the IP addresses through DHCP the user should not change the radio button obtain IP
addresses automatically and all the required configuration will be acquired immediately.
However, for ensuring DHCP, the university needs to configure the specific settings either
through the router or through a separate server. If the website uses SSL the domain address
should have https:// instead of http:// else host machines if acquire DNS services for the http
protocol may not be able open the web page if non SSL web pages are blocked by firewall
rules.

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References
Al-Fannah, N. M. (2017, October). One leak will sink a ship: WebRTC IP address leaks.
In 2017 International Carnahan Conference on Security Technology (ICCST) (pp. 1-
5). IEEE.
Byun, H., Li, Q., & Lim, H. (2019). Vectored-Bloom Filter for IP Address Lookup:
Algorithm and Hardware Architectures. Applied Sciences, 9(21), 4621.
Gupta, A., Kumar, D., & Barve, A. (2017). Hidden markov model based credit card fraud
detection system with time stamp and IP address. International Journal of Computer
Applications, 166(5), 33-37.
Huang, J. Y., & Wang, P. C. (2018). TCAM-based IP address lookup using longest suffix
split. IEEE/ACM Transactions on Networking, 26(2), 976-989.
Komosný, D., Vozňák, M., & Rehman, S. U. (2017). Location accuracy of commercial IP
address geolocation databases.
Li, G., Long, Z., & Wei, Z. (2018, April). Research of future network with multi-layer IP
address. In AIP Conference Proceedings (Vol. 1955, No. 1, p. 040186). AIP
Publishing LLC.
Vegoda, L. (2017). Updates to Special-Purpose IP Address Registries draft-bchv-rfc6890bis-
07.
Young, A. (2018). Geolocation by IP Address: A Summary.