Computer Networking Fundamentals

The Application Layer in the TCP/IP model is responsible for facilitating communication between applications running on different devices, by providing protocols that handle data formatting, encryption, and application-specific tasks.

In a client-server model, the client requests services from the server, and the server provides those services.

DNS is the Domain Name System, and its primary role is to translate human-readable domain names into IP addresses, which are the numerical addresses used by computers to communicate.

When a DNS server can't find the IP address for a requested domain name within its database, it will try to find the answer by forwarding the request to another DNS server that might have the information.

The root-level domain in DNS is the highest level in the hierarchy and includes the commonly used domain names like .com, .net, .org, and .edu.

DHCP, or Dynamic Host Configuration Protocol, allows devices on a network to automatically obtain their IP addresses and other network configuration settings.

When a DHCP client joins a network, it first sends a DHCP Discover broadcast to locate a DHCP server.

In response to a DHCP Discover message, the server sends a DHCP Offer message, which proposes an IP address to the client.

After receiving a DHCP Offer, the client sends a DHCP Request message to the server, confirming its acceptance of the offered IP address.

A DHCP Acknowledgment (DHCP ACK) message is sent by the server to the client to confirm the IP address lease, ensuring the client can use the IP address.

While DHCP for IPv4 provides a default gateway in addition to an IP address, DHCP for IPv6 does not provide a default gateway. The client needs to find this information separately.

In File Transfer Protocol (FTP), port 21 is used specifically for control traffic, which handles commands like login, file listing, and data transfer requests between the client and server.

FTP establishes two separate connections for transferring files: one connection (port 21) for sending commands, and another connection (port 20) for transferring the actual file data.

The Server Message Block (SMB) protocol is designed to enable file sharing and printer sharing between computers on a network.

SMB allows clients to access network drives and resources as though they were part of their own local system, unlike FTP, which requires clients to use a separate application to manage connections.

Converting data into packets for transmission is a primary function of the Network Layer, not the Application Layer. The Application Layer focuses on higher-level application interactions.

IMAP (Internet Message Access Protocol) allows emails to remain on the server while the user accesses them, while POP (Post Office Protocol) downloads and deletes emails from the server.

The "A" record in DNS is a type of resource record that maps a hostname to an IPv4 address.

If a DNS request times out during an NS lookup, it usually indicates that the DNS server couldn't resolve the request.

The "authority" section in a DNS response provides the authoritative name servers for the queried domain, indicating the servers that are responsible for that domain's DNS records.

A second-level domain is a domain name immediately below a top-level domain (like .com, .net, .org), such as "google.com" or "cisco.com".

The Application Layer of the TCP/IP model is responsible for handling higher-level application-specific communication, including data formatting, encryption, and application-specific data exchange.

FTP uses port 20 for data transfer, which handles the actual transmission of files between the client and server.

DNS is a hierarchical system that organizes domain names into various levels, starting with the root level at the top and branching down to more specific domains.

When a DHCP server receives a DHCP Request message, it responds with a DHCP Acknowledgment (DHCP ACK) message to confirm the client's IP address lease.

The "A" record in DNS maps a specific host name to its corresponding IPv4 address.

DHCP allows devices on a network to obtain an IP address without manual configuration, making network administration easier.

The responsibility of converting human-readable domain names into IP addresses falls under the Application Layer in the TCP/IP model, as part of the Application Layer's role in facilitating communication between applications.

The Network Layer is responsible for routing data packets across the network, while the Application Layer focuses on application-specific communication.

DNS servers work together to create and maintain a distributed database that holds information about domain names and their corresponding IP addresses.

SMB allows for the security of shared resources, offering a secure way to access files and printers on the network.