Tagged: FQDN

FQDN vs PQDN: What is the difference?

When navigating the complexities of networking and IT, it’s essential to grasp various domain naming conventions, notably the distinction between Fully Qualified Domain Names (FQDN) and Partially Qualified Domain Names (PQDN). This blog post delves into the FQDN vs PQDN debate, aiming to clarify these crucial concepts for both professionals and enthusiasts.

FQDN Explained

A Fully Qualified Domain Name (FQDN) is the complete and absolute address of a host on the Internet, encompassing all domain levels, including the top-level domain (TLD) and any subdomains, right up to the host name. An FQDN is hierarchically structured from the most general (rightmost) to the most specific (leftmost) component.

Characteristics of FQDN:

  • Uniqueness: An FQDN is distinct across the internet.
  • Structure: It comprises the hostname and all domain levels, culminating in a top-level domain.
  • Example: For instance, server.example.com is an FQDN where server is the hostname, example is the second-level domain, and .com is the top-level domain.
  • DNS Resolution: FQDNs are pivotal in DNS lookups to resolve specific IP addresses.

Understanding PQDN

In contrast to FQDN, a Partially Qualified Domain Name (PQDN) is a domain name that isn’t entirely specified. It finds frequent use in local networks, where the context implicitly fills in the missing parts of the address.

Characteristics of PQDN:

  • Context-Dependent: PQDNs hinge on the context of the local network.
  • Incomplete: These names do not encompass all hierarchical domain levels.
  • Example: A PQDN could be as simple as server within a local network, where the rest of the domain (example.com) is implied.
  • Usage: PQDNs are typically employed in internal networks for easy communication within a limited scope.

FQDN vs PQDN: The Core Differences

  1. Completeness: FQDNs are exhaustive and fully specify a host’s position in the domain name system, whereas PQDNs are partial and rely on contextual understanding.
  2. Application Scope: FQDNs are essential for unique identification on the internet, crucial for web services and external communications. PQDNs are mainly used within local networks, where they rely on the network’s implicit context.
  3. DNS Resolution: Any DNS server on the internet can resolve an FQDN, while PQDNs require specific network contexts for resolution.
  4. Practical Examples: An FQDN like mail.google.com globally identifies a specific host (mail) within the google.com domain. Conversely, a PQDN like mailserver might be employed within a company’s intranet to denote its internal mail server.


Grasping the FQDN vs PQDN distinction is pivotal for network administrators, IT professionals, and those involved in network system management or setup. FQDNs ensure a globally unique and complete address, vital for internet-based communication, while PQDNs provide a shorthand for host identification within localized networks. Recognizing the appropriate usage of each can enhance network communication efficiency and prevent potential miscommunication.

TTL (Time to Live): Meaning, Purpose & Usage

Understanding Time to Live (TTL) is essential for efficient and reliable internet data management. In this blog post, we will explore TTL’s meaning, purpose, and usage, including its history, benefits, and common misconceptions. Learn how TTL can improve your data transmission and get the most out of this essential networking protocol.

Definition & Overview of TTL

Time to Live is a concept that defines a certain number of seconds for a specific data packet to live on the internet. TTL is a timer associated with every DNS record, including website address and email address. This timer allows a limit to be set for how long the data packet will be available and accessible to any requestor. Time to Live provides for data to be updated more regularly than if it had to be manually updated. It provides an additional layer of control over which nodes on the internet can access the data that is hosted on a particular website. As the time value specified by the TTL reaches zero, the data stored by the website can be discarded. However, it is essential to note that the Time to Live enables data to be live on the internet and avoid having to be reached over and over.

History of TTL

Time to Live has been in use since the early days of the internet and has evolved. Initially, the TTL was only used in terms of name resolution, converting a fully qualified domain name (FQDN) into an IP address. Eventually, the concept of Time to Live became expanded to include all types of communication between nodes. This was to control better how long data was available and allow data to be discarded after the time value was reached. Over time, major revisions and optimizations to the TTL protocol have been released, allowing it to be used in more applications than just name resolution. The ability to discard data after a particular set time has allowed for more efficient and effective data management, making the internet a much more reliable network overall.

How TTL is used in TCP/IP and DNS Protocols

Time to Live is used to control various aspects of data transmission between nodes in a network. In particular, Time to Live can be used with the Transmission Control Protocol (TCP) and the Domain Name System (DNS) protocol. In the case of TCP, TTL defines the ‘time-out’ period for any data transmissions from a node. This helps ensure that data is not lost or forgotten after a certain period of time. Regarding DNS, TTL controls how long the address data stored on a DNS server will remain valid. When an address change occurs, the TTL will tell the DNS server how often to update its records (like A record and MX record). 

Another important use of TTL can be found in email services. By controlling the TTL for messages, mail delivery systems can impose certain restrictions to where messages can go and how long they stay valid. This can prevent spam messages from being sent out indefinitely and allows for greater control over how emails travel across the internet. Overall, the use of Time to Live can make communication and data management within networks more efficient and reliable.

Considerations when Setting Time to Live

When specifying a TTL value, it is crucial to consider a few key points: 

  • Only short Time to live values can lead to nodes being able to access data as they cannot cache the packets. 
  • Excessively high TTL values may lead to data needing to be updated more quickly.
  • Set the TTL to an appropriate value for the data being sent. 
  • Monitor the impact of any changes to ensure it is not affecting overall performance in an undesired way.


Time to Live is a critical component of ensuring efficient and reliable data transmission and management on the internet. By understanding its purpose, history, and usage, you’ll be able to get the most out of the TTL protocol. With this knowledge, you’ll be able to make sure that data is up-to-date and accessible, as well as prevent problems associated with unchecked TTL settings.