The term "TTL" refers to "Time to Live", which is a value in an Internet Protocol (IP) packet header that tells a network router whether or not the packet has been in the network too long, and should be discarded. The TTL is set by the sender of the packet and is decremented by one every time the packet passes through a router.

In IP networking, the TTL is used to prevent a packet from circulating indefinitely in the network in case of a routing loop, where the packet keeps being sent from one router to another without ever reaching its destination. When the TTL value of a packet reaches zero, the router discards the packet and sends an ICMP (Internet Control Message Protocol) "Time Exceeded" message back to the sender, indicating that the packet was not delivered because it exceeded the maximum time it was allowed to spend in the network.

The TTL value can also be used to limit the scope of a network broadcast or multicast, or to restrict the number of network hops that a packet can traverse before being discarded.

Here are some links that may be helpful in learning more about TTL:

- Wikipedia page on Time to Live (TTL) in computer networking: https://en.wikipedia.org/wiki/Time_to_live

- Networking Tutorials: Understanding Time to Live (TTL): https://www.guru99.com/time-to-live-ttl.html

- TTL: Understanding the Concept and Its Significance in IP Networks: https://www.cisco.com/c/en/us/support/docs/ip/time-to-live-ttl/13753-understand-ttl.html

- TTL and Traceroute: https://www.cloudflare.com/learning/ddos/glossary/ttl-and-traceroute/

- Understanding TTL (Time To Live) in IP packets: https://www.reddit.com/r/networking/comments/2ukgjt/understanding_ttl_time_to_live_in_ip_packets/

https://www.youtube.com/watch?v=D5YgYXYKm1A

The Domain Name System (DNS) is a decentralized naming system for Internet resources such as websites, mail servers, and other resources that use the Internet Protocol (IP). It translates domain names, which are easy for humans to remember, into IP addresses, which are numerical labels that are assigned to every device connected to the Internet.

In essence, the DNS acts like a giant phone book that maps domain names to IP addresses. When a user types a domain name into their web browser, the browser queries the DNS servers to resolve the domain name into an IP address. The DNS then returns the IP address to the browser, which then uses the IP address to request the website's content from the corresponding web server.

Here are a few resources for further information about the DNS:

DNS basics: https://en.wikipedia.org/wiki/Domain_Name_System#DNS_resolution_process

How the DNS works: https://howdns.works/

ICANN (Internet Corporation for Assigned Names and Numbers), the organization that oversees the DNS: https://www.icann.org/resources/pages/dns-sec-2013-09-19-en

DNS performance and security: https://www.dnsperf.com/

I hope this information helps!

https://www.youtube.com/watch?v=mpQZVYPuDGU

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