Model OSI Flashcards
What does the Physical Layer of the OSI model do?
It is responsible for the transmission and reception of raw data bits over a physical medium.
Name three types of cables used in the Physical Layer.
Ethernet cables, fiber optic cables, coaxial cables.
What devices operate at the Physical Layer?
Hubs, repeaters, and network interface cards (NICs).
What is the role of the Physical Layer in wireless communication?
It manages the transmission of signals over wireless media like Wi-Fi and Bluetooth.
What is the signal format in the Physical Layer?
Data is transmitted as electrical signals, light pulses, or radio waves.
What is the primary responsibility of the Data Link Layer?
It is responsible for error detection, frame synchronization, and flow control for reliable data transfer over a link.
Name two protocols used in the Data Link Layer.
Ethernet, PPP (Point-to-Point Protocol).
What does the MAC address refer to in the Data Link Layer?
It is a unique identifier assigned to a network interface card (NIC) used for communication on the Data Link Layer.
What is a frame in the context of the Data Link Layer?
A frame is a unit of data that includes both the payload and the necessary addressing information for data transmission.
What is CSMA/CD in the Data Link Layer?
CSMA/CD (Carrier Sense Multiple Access with Collision Detection) is a protocol for managing access to a shared communication medium to avoid collisions.
What is the main role of the Network Layer?
It is responsible for routing data between different networks and devices, ensuring it reaches the correct destination.
What protocol is most commonly associated with the Network Layer?
IP (Internet Protocol).
What is the difference between IPv4 and IPv6?
IPv4 uses 32-bit addresses, while IPv6 uses 128-bit addresses, allowing for a much larger address space.
Name a device that operates at the Network Layer.
Routers.
What is routing in the Network Layer?
Routing is the process of determining the optimal path for data to travel from the source to the destination across multiple networks.
What is the primary function of the Transport Layer?
It ensures reliable data transfer by providing error control, flow control, and data segmentation.
Name two common transport layer protocols.
TCP (Transmission Control Protocol) and UDP (User Datagram Protocol).
What is the difference between TCP and UDP?
TCP provides reliable, connection-oriented communication with error correction, while UDP is connectionless and faster but without error correction.
What are ports used for in the Transport Layer?
Ports are used to identify specific services or applications running on a device, such as HTTP (port 80) or HTTPS (port 443).
What is segmentation in the Transport Layer?
Segmentation is the process of breaking larger data into smaller packets, making it easier to transmit over the network.
What does the Session Layer manage?
It manages sessions between applications, including establishing, maintaining, and terminating communication sessions.
Name one protocol that operates at the Session Layer.
NetBIOS (Network Basic Input/Output System).
What is a session in networking?
A session is a temporary connection established between two devices for communication, typically lasting for the duration of a transfer or session.
How does the Session Layer manage session synchronization?
It uses checkpoints to synchronize the data transfer during long sessions.
What is the role of dialog control in the Session Layer?
Dialog control ensures that communication between devices is orderly, managing whether communication is full-duplex or half-duplex.
What is the function of the Presentation Layer?
It translates, encrypts, and compresses data to ensure it is in a format that the application can process.
Name two examples of data encoding schemes used in the Presentation Layer.
ASCII and EBCDIC.
What is SSL/TLS used for in the Presentation Layer?
SSL/TLS is used for securing communication by encrypting data between two devices.
What is the role of compression in the Presentation Layer?
Compression reduces the size of the data to save bandwidth and improve transmission speed.
Name one format used in the Presentation Layer to represent data.
XML (eXtensible Markup Language).
What is the main role of the Application Layer?
It provides network services directly to end users and applications, such as email, file transfer, and web browsing.
Name three protocols used in the Application Layer.
HTTP, FTP, SMTP.
What is the role of DNS (Domain Name System) in the Application Layer?
DNS translates domain names (like www.example.com) into IP addresses.
Are software applications (e.g., web browsers, email clients) part of the Application Layer?
No, they are not part of the Application Layer, but they depend on the protocols provided by the Application Layer for communication.
Name one example of an email client that relies on the Application Layer for communication.
Outlook or Thunderbird.
Which OSI layer does a Fiber Optic Cable belong to?
Physical Layer.
In which OSI layer do Hubs operate?
Physical Layer.
A Network Interface Card (NIC) operates at which OSI layer?
Physical Layer.
Which OSI layer does Bluetooth belong to?
Physical Layer.
A Repeater operates at which OSI layer?
Physical Layer.
Which OSI layer does the Ethernet protocol belong to?
Data Link Layer.
In which OSI layer does a Switch operate?
Data Link Layer.
What OSI layer does the MAC address work at?
Data Link Layer.
Which OSI layer does PPP (Point-to-Point Protocol) operate in?
Data Link Layer.
In which OSI layer does the ARP (Address Resolution Protocol) work?
Data Link Layer.
Which OSI layer does the Internet Protocol (IP) belong to?
Network Layer.
A Router operates at which OSI layer?
Network Layer.
Which OSI layer does the Routing Information Protocol (RIP) operate in?
Network Layer.
What OSI layer does the ICMP (Internet Control Message Protocol) belong to?
Network Layer.
Which OSI layer is responsible for IP address assignment?
Network Layer.
Which OSI layer does the TCP (Transmission Control Protocol) belong to?
Transport Layer.
A Load Balancer operates at which OSI layer?
Transport Layer.
Which OSI layer does the UDP (User Datagram Protocol) belong to?
Transport Layer.
What OSI layer does the SCTP (Stream Control Transmission Protocol) work at?
Transport Layer.
Which OSI layer is responsible for ensuring end-to-end communication between devices?
Transport Layer.
Which OSI layer does the NetBIOS protocol operate in?
Session Layer.
A Session Border Controller (SBC) works at which OSI layer?
Session Layer.
Which OSI layer manages the establishment, maintenance, and termination of communication sessions?
Session Layer.
Which OSI layer does the RPC (Remote Procedure Call) protocol work at?
Session Layer.
In which OSI layer does data synchronization between two devices occur?
Session Layer.
Which OSI layer does the SSL/TLS protocol operate in?
Presentation Layer.
What OSI layer does the JPEG (Joint Photographic Experts Group) format belong to?
Presentation Layer.
A Data Compression algorithm works at which OSI layer?
Presentation Layer.
Which OSI layer does the ASCII (American Standard Code for Information Interchange) character encoding belong to?
Presentation Layer.
Which OSI layer handles encryption of sensitive data?
Presentation Layer.
Which OSI layer does HTTP (Hypertext Transfer Protocol) belong to?
Application Layer.
In which OSI layer does the SMTP (Simple Mail Transfer Protocol) operate?
Application Layer.
A Web Browser operates at which OSI layer?
Application Layer.
Which OSI layer does the FTP (File Transfer Protocol) belong to?
Application Layer.
Which OSI layer does the DNS (Domain Name System) protocol work in?
Application Layer.
What is the transport unit of the Physical Layer?
Bits. In this layer, data is transmitted as a sequence of bits (ones and zeros) across the physical medium.
What is the transport unit of the Data Link Layer?
Frame. The Data Link Layer groups bits into frames, which are the units of transmission at this layer.
What is the transport unit of the Network Layer?
Packet. The Network Layer divides frames into packets, which are routed across different networks.
What is the transport unit of the Transport Layer?
Segment. In this layer, packets are divided into segments, which are reliably transmitted between devices with error control and flow control.
What is the transport unit of the Session Layer?
Data. The Session Layer manages the data exchange between applications on different machines, but it does not have a specific transport unit as its primary role is to control the session flow.
What is the transport unit of the Presentation Layer?
Data. Similar to the Session Layer, the Presentation Layer deals with data that is formatted, encrypted, or compressed. It does not have a specific transport unit.
What is the transport unit of the Application Layer?
Data. The Application Layer deals with the data generated by applications, which is transported through the lower layers of the network. It does not have a specific transport unit, as it depends on the protocols used by the application.
Wich is the most important routing protocol?
BGP (Border Gateway Protocol)
What type of media does the Physical Layer use for data transmission?
Copper cables (Ethernet), fiber-optic cables, wireless radio waves, etc.
Which devices operate at the Physical Layer?
Hubs, repeaters, network adapters, and cables.
What is the main function of the Physical Layer?
It transmits raw binary data (bits) over a physical medium.
What does the Physical Layer convert data into?
It converts data into electrical signals, light signals, or radio waves, depending on the medium used.
What is the main responsibility of the Physical Layer regarding the transmission of bits?
It defines the transmission method (electrical, optical, or radio signals) and the data rate (how fast the bits are transmitted).
What is the main unit of data used by the Data Link Layer?
Frame. The Data Link Layer encapsulates data into frames for transmission.
What is the function of the Data Link Layer in terms of error control?
It performs error detection and error correction to ensure data integrity.
Which devices operate at the Data Link Layer?
Switches, network interface cards (NICs), bridges.
What does the Data Link Layer do with the packets from the Network Layer?
It encapsulates packets into frames and adds physical addressing information (MAC addresses).
How does the Data Link Layer help with flow control?
It manages data flow between devices to prevent congestion by using techniques like backpressure and windowing.
What is the main unit of data used by the Network Layer?
Packet. The Network Layer takes data from the Data Link Layer and organizes it into packets for routing.
Which devices operate at the Network Layer?
Routers, layer 3 switches.
What is the primary function of the Network Layer?
It is responsible for routing packets across different networks and determining the best path to reach the destination.
What protocol does the Network Layer use for addressing devices on different networks?
IP (Internet Protocol). It assigns unique IP addresses to devices for identification.
What is the purpose of routing in the Network Layer?
Routing determines the best path for data packets to travel across the network, ensuring that they reach their destination.
What is the purpose of DHCP?
DHCP dynamically assigns IP addresses and other network configuration parameters to devices on a network.
What are the key components involved in the DHCP process?
DHCP Discover, DHCP Offer, DHCP Request, and DHCP Acknowledgment.
What port does DHCP use for communication?
DHCP uses UDP ports 67 and 68.
What is the main benefit of using DHCP in a network?
It automates the assignment of IP addresses, making network management easier.
How does DHCP ensure that IP addresses are unique within a network?
DHCP uses a pool of available IP addresses and ensures no two devices are assigned the same address within the lease period.
What is the main function of DNS?
DNS resolves human-readable domain names (like www.example.com) into IP addresses.
What type of DNS record is used to resolve a domain to an IPv4 address?
A (Address) Record.
What is a DNS cache?
A temporary storage location where DNS records are kept to speed up the process of resolving domain names.
What does the “TTL” (Time To Live) field in a DNS record indicate?
It specifies how long the DNS record is valid and can be cached before a new lookup is required.
What is the difference between an authoritative DNS server and a recursive DNS server?
An authoritative server stores the original DNS records for domains, while a recursive server queries DNS records on behalf of clients and caches the results.
What is the main purpose of HTTP?
HTTP is a protocol used for transferring hypertext (web pages) over the internet.
What port does HTTP use?
HTTP uses port 80.
What is the main difference between HTTP and HTTPS?
HTTPS encrypts data with SSL/TLS, while HTTP transmits data in plain text.
What are HTTP methods, and can you name some of them?
HTTP methods define actions for interacting with resources. Common ones include GET, POST, PUT, DELETE, and HEAD.
What is an HTTP status code?
An HTTP status code is a three-digit code returned by the server indicating the result of the request (e.g., 404 Not Found, 200 OK).
What is the main characteristic of TCP?
TCP is a connection-oriented protocol that ensures reliable delivery of data.
What is a TCP segment?
A TCP segment is a unit of data transmitted by the TCP protocol, containing a header and the actual data.
How does TCP establish a connection between devices?
TCP uses a three-way handshake to establish a connection.
What are the three steps in the TCP three-way handshake?
SYN, SYN-ACK, ACK.
What is the purpose of the TCP sliding window mechanism?
It controls the flow of data and ensures that the sender does not overwhelm the receiver.
What is the main characteristic of UDP?
UDP is a connectionless protocol that does not guarantee the delivery of data, making it faster but less reliable than TCP.
What is the advantage of using UDP over TCP?
UDP has lower overhead and faster transmission, making it ideal for real-time applications like streaming.
What port does UDP typically use for DNS queries?
UDP port 53.
How does UDP handle data transmission?
UDP sends data packets without establishing a connection, and it does not perform error checking or correction.
In which situations is UDP typically used?
UDP is used in applications like video streaming, online gaming, and VoIP (Voice over IP).
What is the maximum number of unique addresses in IPv4?
IPv4 can support up to 4.3 billion unique addresses (2^32).
What is the size of an IPv4 address?
An IPv4 address is 32 bits long, usually written as four octets (e.g., 192.168.1.1).
What is the range of IPv4 private addresses?
Private IPv4 addresses include the ranges:
10.0.0.0 – 10.255.255.255
172.16.0.0 – 172.31.255.255
192.168.0.0 – 192.168.255.255
What is the role of a subnet mask in IPv4?
A subnet mask defines the network portion and host portion of an IPv4 address.
What is NAT (Network Address Translation) in IPv4?
NAT allows multiple devices on a private network to share a single public IPv4 address for accessing the internet.
What is the main difference between IPv4 and IPv6?
IPv6 uses a 128-bit address, which allows for a significantly larger address space compared to IPv4’s 32-bit address.
What is the size of an IPv6 address?
An IPv6 address is 128 bits long, typically written in eight groups of four hexadecimal digits.
What is the purpose of IPv6 address notation with colons (e.g., 2001:0db8::1)?
IPv6 addresses are written in hexadecimal format, and leading zeros in each block can be omitted for simplicity, and consecutive zero blocks can be represented with a double colon.
How does IPv6 handle address autoconfiguration?
IPv6 can automatically configure itself using SLAAC (Stateless Address Autoconfiguration).
What is the role of IPv6 in solving IPv4 address exhaustion?
IPv6 provides a much larger address space, ensuring there are enough IP addresses for the growing number of devices connected to the internet.
What is the primary function of ICMP?
ICMP is used for error reporting and diagnostic functions, such as the ping command.
What is an example of an ICMP message?
Echo Request and Echo Reply messages, used for pinging.
What does an ICMP “Destination Unreachable” message indicate?
It indicates that a packet could not reach its destination for various reasons, such as a network or host being unreachable.
What is the ICMP message type for a “time exceeded” error?
The Time Exceeded message is sent when a packet’s TTL (Time to Live) expires.
How does ICMP help with troubleshooting network issues?
ICMP tools like ping and traceroute help identify connectivity problems and network latency.
What is the purpose of ARP?
ARP maps an IP address to a MAC address on a local network.
What does an ARP request contain?
An ARP request contains the sender’s MAC address, sender’s IP address, and the target’s IP address.
What is the role of the ARP table?
The ARP table stores mappings of IP addresses to MAC addresses, helping devices to resolve addresses without broadcasting ARP requests.
What happens when an ARP request cannot find the target MAC address?
The device will typically broadcast an ARP request to all devices on the local network.
What is an ARP cache timeout?
An ARP cache timeout is the duration for which an IP-to-MAC address mapping is stored before it is refreshed.
What is the primary function of RARP?
RARP is used to map a MAC address to an IP address, typically used by diskless devices to obtain an IP address.
Why is RARP considered obsolete today?
RARP has been replaced by BOOTP and DHCP, which provide more functionality and are more efficient.
What type of routing protocol is RIP?
RIP is a distance-vector routing protocol that uses hop count as its metric.
What is the maximum hop count in RIP?
The maximum hop count in RIP is 15, which means any network farther than 15 hops is considered unreachable.
What type of routing protocol is OSPF?
OSPF is a link-state routing protocol that uses a more sophisticated algorithm (Dijkstra) to determine the best path.
What does the subnet mask 255.255.255.0 represent in CIDR notation?
he subnet mask 255.255.255.0 is represented as /24 in CIDR notation, meaning the first 24 bits are used for the network portion.
How can you determine the network address of an IP address using a subnet mask?
Perform a bitwise AND operation between the IP address and the subnet mask to determine the network address.
What is the purpose of the network address in IPv4?
The network address identifies the specific network to which a host belongs, used by routers to determine the path for data transmission.
How does a device use a subnet mask to communicate with another device in the same network?
The device uses the subnet mask to determine if the destination IP address is within the same network; if yes, it sends data directly to the destination device.
What is a broadcast address in IPv4, and how is it determined?
The broadcast address is used to send data to all devices in a subnet. It is determined by setting all the host bits in the IP address to 1.
Given the IP address 192.168.1.1 and subnet mask 255.255.255.0, what is the network address?
The network address is 192.168.1.0.
How do you calculate the number of subnets in an IPv4 network?
The number of subnets can be calculated by using the formula
2^𝑛 , where n is the number of bits borrowed from the host portion of the address for subnetting.
What is a supernet in IPv4?
A supernet is a network created by aggregating multiple smaller networks into a larger network, typically used in classless inter-domain routing (CIDR).
If you have a subnet mask of 255.255.255.192, how many subnets can you create from the original network?
The subnet mask 255.255.255.192 corresponds to /26 in CIDR notation, which allows for 4 subnets (since 2^2=4)
What is the difference between a /24 and a /30 subnet in terms of the number of hosts?
A /24 subnet allows for 254 hosts, while a /30 subnet only allows for 2 hosts (typically used for point-to-point links).
What is the significance of the first and last IP addresses in any subnet?
The first IP address in a subnet is the network address, and the last IP address is the broadcast address. Both cannot be assigned to hosts in the network.
