CCNA OSI Layer Exam Quiz

Explanation
1.1 Application layer: Provides a means for the user to access information on the network through an application. This layer is the main interface for the user to interact with the application and therefore the network.
The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer.

Explanation
1.4. Transport layer: Responsible for reliable transmission of data and service specification between hosts. The major responsibility of this layer is data integrity--that data transmitted between hosts is reliable and timely. Upper layer data grams are broken down into network-sized data grams if needed and then implemented using appropriate transmission control. The transport layer creates one or more than one network connection, depending on conditions. This layer also handles what type of connection will be created. Two major transport protocols are the TCP (Transmission Control Protocol) and the UDP (User Data gram Protocol).

Important features of Transport layer:

Transport layer ensures reliable service.
Breaks the message (from sessions layer) into smaller packets, assigns sequence number and sends them.
Reliable transport connections are built on top of X.25 or IP.
In case IP, lost packets arriving out of order must be reordered.
Important features of TCP/UDP:

TCP/IP Widely used for network/transport layer (UNIX).
TCP: (Transport Control Protocol) This is a connection oriented protocol.
UDP (Universal Data gram Protocol): This is a connectionless transport layer protocol.
Application programs that do not need connection-oriented protocol generally use UDP.

Explanation
The Internet Control Message Protocol (ICMP) is one of the core protocols of the Internet Protocol Suite. It is chiefly used by networked computers' operating systems to send error messages—indicating, for instance, that a requested service is not available or that a host or router could not be reached.
ICMP [1] relies on IP to perform its tasks, and it is an integral part of IP. It differs in purpose from transport protocols such as TCP and UDP in that it is typically not used to send and receive data between end systems. It is usually not used directly by user network applications, with some notable exceptions being the ping tool and traceroute.
ICMP for Internet Protocol version 4 (IPv4) is also known as ICMPv4. IPv6 has a similar protocol, ICMPv6

Explanation
WANs are all about exchanging information across wide geographic areas. They are also, as you can probably gather from reading about the Internet, about scalability—the ability to grow to accommodate the number of users on the network, as well as to accommodate the demands those users place on network facilities. Although the nature of a WAN—a network reliant on communications for covering sometimes vast distances—generally dictates slower throughput, longer delays, and a greater number of errors than typically occur on a LAN, a WAN is also the fastest, most effective means of transferring computer-based information currently available.
An X.25 WAN consists of packet-switching exchange

ATM is a connection-oriented, unreliable (does not acknowledge the receipt of cells sent), virtual circuit packet switching technology. Unlike most connectionless networking protocols, ATM is a deterministic networking system — it provides predictable, guaranteed quality of service. From end to end, every component in an ATM network provides a high level of control. ATM technology includes:

Explanation
Internet Protocol Security (IPsec) is a protocol suite for securing Internet Protocol (IP) communications by authenticating and encrypting each IP packet of a data stream. IPsec also includes protocols for establishing mutual authentication between agents at the beginning of the session and negotiation of cryptographic keys to be used during the session. IPsec can be used to protect data flows between a pair of hosts (e.g. computer users or servers), between a pair of security gateways (e.g. routers or firewalls), or between a security gateway and a host.

Explanation
Network Layer
This layer addresses the data. It adds an IP address which allows our data to flow across networks. The protocols involved in this layer are IP and IPX.

Explanation
Simple Network Management Protocol (SNMP) is used in network management systems to monitor network-attached devices for conditions that warrant administrative attention. SNMP is a component of the Internet Protocol Suite as defined by the Internet Engineering Task Force (IETF). It consists of a set of standards for network management, including an application layer protocol, a database schema, and a set of data objects.
Overview and basic concepts

In typical SNMP use, one or more administrative computers have the task of monitoring or managing a group of hosts or devices on a computer network. Each managed system executes, at all times, a software component called an agent (see below) which reports information via SNMP to the managing systems.
Essentially, SNMP agents expose management data on the managed systems as variables (such as "free memory", "system name", "number of running processes", "default route"). But the protocol also permits active management tasks, such as modifying and applying a new configuration. The managing system can retrieve the information through the GET, GETNEXT and GETBULK protocol operations or the agent will send data without being asked using TRAP or INFORM protocol operations. SNMPv3 INFORM messages are valuable because they provide a reliable way for this data to be acknowledged by the management system, which is important because SNMP is a UDP-based protocol. Management systems can also send configuration updates or controlling requests through the SET protocol operation to actively manage a system. Configuration and control operations are used only when changes are needed to the network infrastructure. The monitoring operations are usually performed on a regular basis.
The variables accessible via SNMP are organized in hierarchies. These hierarchies, and other metadata (such as type and description of the variable), are described by Management Information Bases (MIBs).
[edit]Basic components
An SNMP-managed network consists of three key components:
Managed device
Agent
Network management system (NMS)
A managed device is a network node that contains an SNMP agent and that resides on a managed network. Managed devices collect and store management information and make this information available to NMSs using SNMP. Managed devices, sometimes called network elements, can be any type of device including, but not limited to, routers, access servers, switches, bridges, hubs, IP telephones, computer hosts, and printers.
An agent is a network-management software module that resides in a managed device. An agent has local knowledge of management information and translates that information into a form compatible with SNMP.
A network management system (NMS) executes applications that monitor and control managed devices. NMSs provide the bulk of the processing and memory resources required for network management. One or more NMSs may exist on any managed network.

Explanation
he Cisco Discovery Protocol (CDP) is a proprietary layer 2 network protocol developed by Cisco Systems that runs on most Cisco equipment and is used to share information about other directly connected Cisco equipment such as the operating system version and IP address. CDP can also be used for On-Demand Routing (ODR), which is a method of including routing information in CDP announcements so that dynamic routing protocols do not need to be used in simple networks.
Cisco devices send CDP announcements to the multicast destination address 01-00-0c-cc-cc-cc (also used for other Cisco proprietary protocols such as VTP). CDP announcements (if supported and configured in IOS) are sent by default every 60 seconds on interfaces that support Subnetwork Access Protocol (SNAP) headers, including Ethernet, Frame Relay and ATM. Each Cisco device that supports CDP stores the information received from other devices in a table that can be viewed using the show cdp neighbors command. The CDP table's information is refreshed each time an announcement is received, and the holdtime for that entry is reset. The holdtime specifies how long an entry in the table will be kept - if no announcements are received from a device and the holdtime timer expires for that entry, the device's information is discarded (default 180 seconds).
The information contained in CDP announcements varies by the type of device and the version of the operating system running on it. Information contained includes the operating system version, hostname, every address for every protocol configured on the port where CDP frame is sent eg. IP address, the port identifier from which the announcement was sent, device type and model, duplex setting, VTP domain, native VLAN, power draw (for Power over Ethernet devices), and other device specific information. The details contained in these announcements is easily extended due to the use of the type-length-value (TLV) frame format. See external links for a technical definition.
HP removed support for sending CDP from HP Procurve products shipping after February 2006 and all future software upgrades. Receiving CDP and showing neighbor information is still supported. CDP support was replaced with Link Layer Discovery Protocol. [1]

Explanation
Network File System (NFS) is a network file system protocol originally developed by Sun Microsystems in 1984,[1] allowing a user on a client computer to access files over a network in a manner similar to how local storage is accessed. NFS, like many other protocols, builds on the Open Network Computing Remote Procedure Call (ONC RPC) system. The Network File System is an open standard defined in RFCs, allowing anyone to implement the protocol

SQL (Structured Query Language) (pronounced /ˌɛskjuːˈɛl/)[1] is a database computer language designed for managing data in relational database management systems (RDBMS). Its scope includes data query and update, schema creation and modification, and data access control. SQL was one of the first languages for Edgar F. Codd's relational model in his influential paper, "A Relational Model of Data for Large Shared Data Banks".[2] and became the most widely used language for relational databases

Explanation
ARP (Address Resolution Protocol) and RARP (Reverse Address Resolution Protocol) are indeed Data-Link Layer protocols. ARP is used to map an IP address to a physical (MAC) address on a local network, while RARP performs the reverse, mapping a MAC address to an IP address. These protocols operate at the Data-Link Layer of the OSI model, which is responsible for the reliable transmission of data frames over a physical link. Therefore, the correct answer is Data-Link Layer.

Explanation
The correct answer is Transport Layer. The OSI model is a conceptual framework that standardizes the functions of a communication system into seven different layers. The Transport Layer, which is the fourth layer in the OSI model, is responsible for establishing a reliable connection between two devices and ensuring the error-free delivery of data packets. The Sequence Package Exchange (SPX) protocol is a connection-oriented protocol that operates at the Transport Layer, making it the correct answer.

Explanation
Encryption would take place on the Presentation layer of the OSI model. This layer is responsible for the formatting and encryption of data before it is transmitted. Encryption ensures that the data is secure and cannot be accessed by unauthorized parties. By encrypting the data on the Presentation layer, it can be safely transmitted over the network and decrypted by the receiving device on the other end.

Explanation
PPP (Point-to-Point Protocol) is a data link layer protocol that is commonly used for establishing a direct connection between two nodes in a network. It is responsible for encapsulating network layer packets and transmitting them over a physical medium. Therefore, PPP would reside on the Data-Link layer of the OSI model.

Explanation
LAPB (Link Access Procedure, Balanced) is a data link layer protocol used for reliable data transmission between two nodes in a network. The data link layer is responsible for the reliable transfer of data between adjacent network nodes. Therefore, LAPB would reside on the Data-Link Layer of the OSI model.

Explanation
HSSI (High-Speed Serial Interface) is a physical layer protocol used for high-speed data communication. It provides a physical connection between devices and is responsible for transmitting raw bitstream over a physical medium. Therefore, HSSI would reside on the Physical Layer of the OSI model, which is responsible for the actual transmission and reception of data bits.

Explanation
Rlogin is the correct answer because it is a remote login protocol that operates at the Application layer of the OSI model, not the Presentation layer. The Presentation layer is responsible for data formatting and conversion, while Rlogin is used for establishing a remote login session between hosts. ASCII and EBCDIC are character encoding standards that can be used at the Presentation layer. JPEG and GIF are image file formats that are typically handled at the Application layer.

Explanation
UDP (User Datagram Protocol) is a connectionless, unreliable, and best-effort protocol used for sending datagrams over an IP network. It does not guarantee the delivery or order of packets, making it suitable for applications that prioritize speed and efficiency over reliability. The Transport Layer of the OSI model is responsible for managing end-to-end communication between hosts and ensuring the reliable delivery of data. Therefore, UDP is found on the Transport Layer of the OSI model.

Explanation
BGP, or Border Gateway Protocol, is an external protocol used for routing data between different autonomous systems (AS) on the internet. It operates at the Application Layer of the OSI model because it uses TCP/IP to establish connections and exchange routing information. The Application Layer is responsible for providing network services to applications and users, making it the appropriate layer for BGP.

Explanation
OSPF, RIP, and Net BEUI are network layer protocols. The network layer is responsible for addressing, routing, and delivering data packets across different networks. These protocols operate at this layer to ensure efficient and reliable communication between devices on a network. They handle tasks such as determining the best path for data transmission, managing network congestion, and providing error detection and correction. Therefore, the correct answer is Network Layer.

Explanation
HDLC (High-Level Data Link Control) is a protocol that operates at the Data-Link layer of the OSI model. This layer is responsible for the reliable transmission of data between two directly connected nodes over a physical link. HDLC provides error detection and correction, flow control, and framing of data packets. Therefore, the correct answer is Data-Link layer.

Explanation
HTML would reside on the Application Layer of the OSI model. The Application Layer is responsible for providing network services to user applications. HTML is a markup language used for creating web pages and is typically interpreted by web browsers, which are considered user applications. Therefore, HTML would be processed and rendered at the Application Layer.