Section: Information System Operations, Maintenance and Support
Explanation/Reference:
The NOT keyword is used in the question. You need to find out a protocol which does not work at
application layer. TCP protocol works at transport layer of a TCP/IP models.
For your exam you should know below information about TCP/IP model:
Network Models
Layer 4. Application Layer
Application layer is the top most layer of four layer TCP/IP model. Application layer is present on the top of
the Transport layer. Application layer defines TCP/IP application protocols and how host programs interface
with Transport layer services to use the network.
Application layer includes all the higher-level protocols like DNS (Domain Naming System), HTTP
(Hypertext Transfer Protocol), Telnet, SSH, FTP (File Transfer Protocol), TFTP (Trivial File Transfer
Protocol), SNMP (Simple Network Management Protocol), SMTP (Simple Mail Transfer Protocol) , DHCP
(Dynamic Host Configuration Protocol), X Windows, RDP (Remote Desktop Protocol) etc.
Layer 3. Transport Layer
Transport Layer is the third layer of the four layer TCP/IP model. The position of the Transport layer is
between Application layer and Internet layer. The purpose of Transport layer is to permit devices on the
source and destination hosts to carry on a conversation. Transport layer defines the level of service and
status of the connection used when transporting data.
The main protocols included at Transport layer are TCP (Transmission Control Protocol) and UDP (User
Datagram Protocol).
Layer 2. Internet Layer
Internet Layer is the second layer of the four layer TCP/IP model. The position of Internet layer is between
Network Access Layer and Transport layer. Internet layer pack data into data packets known as IP
datagram's, which contain source and destination address (logical address or IP address) information that
is used to forward the datagram's between hosts and across networks. The Internet layer is also
responsible for routing of IP datagram's.
Packet switching network depends upon a connectionless internetwork layer. This layer is known as
Internet layer. Its job is to allow hosts to insert packets into any network and have them to deliver
independently to the destination. At the destination side data packets may appear in a different order than
they were sent. It is the job of the higher layers to rearrange them in order to deliver them to proper network
applications operating at the Application layer.
The main protocols included at Internet layer are IP (Internet Protocol), ICMP (Internet Control Message
Protocol), ARP (Address Resolution Protocol), RARP (Reverse Address Resolution Protocol) and IGMP
(Internet Group Management Protocol).
Layer 1. Network Access Layer
Network Access Layer is the first layer of the four layer TCP/IP model. Network Access Layer defines
details of how data is physically sent through the network, including how bits are electrically or optically
signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical
fiber, or twisted pair copper wire.
The protocols included in Network Access Layer are Ethernet, Token Ring, FDDI, X.25, Frame Relay etc.
The most popular LAN architecture among those listed above is Ethernet. Ethernet uses an Access
Method called CSMA/CD (Carrier Sense Multiple Access/Collision Detection) to access the media, when
Ethernet operates in a shared media. An Access Method determines how a host will place data on the
medium.
IN CSMA/CD Access Method, every host has equal access to the medium and can place data on the wire
when the wire is free from network traffic. When a host wants to place data on the wire, it will check the
wire to find whether another host is already using the medium. If there is traffic already in the medium, the
host will wait and if there is no traffic, it will place the data in the medium. But, if two systems place data on
the medium at the same instance, they will collide with each other, destroying the data. If the data is
destroyed during transmission, the data will need to be retransmitted. After collision, each host will wait for
a small interval of time and again the data will be retransmitted.
Protocol Data Unit (PDU):
Protocol Data Unit - PDU
The following answers are incorrect:
HTTP, FTP and NTP protocols works at application layer in TCP/IP model.
The following reference(s) were/was used to create this question:
CISA review manual 2014 page number 272
