OpenVPN can run over either the transmission control protocol or user datagram protocol transports. Selecting which one to use is a highly technical problem and one that most VPN services keep hidden behind the scenes. Some virtual private network services, however, prefer to let clients select which connection protocol they prefer.
The reason is that both TCP and UDP provide distinct benefits and weaknesses in each other. Selection depends on what the internet network uses and what matters to users most, such as reliability or speed. Whether your information is transferred and in total depends on which network protocols you use, UDP or TCP. Both TCP or UDP does the same job but in different ways. One is more faster, and the other one is faster.
UDP and TCP are two commonly used network protocols that users interact with daily to determine how information is transferred over the internet. While they are comparable in many ways, their differences make them helpful for different purposes.
In this blog, TechNinjaPro will go over these network protocols and the main differences between them.
Why does OpenVPN use UDP and TCP?
OpenVPN protocols themselves function best over the UDP protocol. And by default, the connection profile that you can download from the Access Server is preprogrammed first to try UDP and if that fails, then try TCP. Unluckily, on some restrictive networks, all internet traffic except very commonly used ports is simply blocked.
What is TCP?
TCP is a connection-oriented protocol that devices use to communicate on the internet. It is one of the main protocols in the TCP/IP protocol suite and offers error detection and correction. Furthermore, TCP guarantees reliable information delivery and ensures that packets will arrive in the same order they were sent.
What is UDP?
UDP is a connection-less protocol that functions much like TCP but without error detection and correction services. Instead, data packets are constantly sent to the recipient, whether they have been received or not. This allows for systems to communicate with one another more efficiently and quickly with less overhead.
How UDP and TCP work?
TCP is the most commonly used network protocol on the internet because it is considered more reliable. Here is what it does to send your information:
- TCP assigns each packet a unique identifier and a sequence number. This lets the receiver identity which data packet was received and which one is arriving next.
- Once the packet is received and if it is in the correct order, the receiver sends an acknowledgment to the sender.
- The sender can now send other data packets.
- If the data packet is lost or sent incorrectly, the receiver stays silent, indicating that the same packet needs to be resent.
Because the information is sent in sequence, it helps with information congestion and flow control and makes it easier to find out and fix any errors. This also means that information sent over TCP is more likely to reach its destination in full. However, it has a downside. There is a lot of back and forth communication between the two parties, so it takes longer to establish a connection and exchange information.
UDP completes the job without the need for unique identifiers or sequence numbers. UDP sends information in a stream and only has a checksum to make sure that the information arrived uncorrupted. It has no error correction, nor does it care about lost packets. UDP is more error-prone, but it sends information much faster than TCP.
TCP
Benefits
- Congestion Control
- Unique Identification
- In Order Delivery
- Error Detection
- Data Re-transmission
Drawbacks
- Image Blocking
- Loss Result of Congestion
- Slow Handshake
- Network Optimization
- Slow Start
UDP
Benefits
- Connection Speed
- Multicast Applications
- Processing Time
- Transmission Delay
- Error Detection
Drawbacks
- Incorrect Order
- No Congestion Control
- Router Support
- Connectionless
- Unreliable
When to use TCP and UDP?
TCP is a perfect choice, and even it has associated overhead. As a result, when most of the overhead is in the connection, your app stays connected for any length of time. UDP is perfect to use with multimedia like Voice over Internet Protocol. You can use TCP sockets when both server and client independently send packets at that time; an occasional delay is acceptable. You should use user UDP if both server and client may separately send packets, and occasional delay is not permitted.
Difference Between UDP and TCP
Now, let’s discuss some of the critical differences between UDP and TCP:
Speed
UDP is more faster than TCP because it has less to do. TCP has to establish a connection and handles error control, and guarantee that data arrive in order. On the other hand, UDP does not guarantee the delivery of transferred data packets and sends data without establishing a network connection.
Congestion and Flow Control
TCP’s congestion and flow control mechanism ensure that a sender does not overwhelm a receiver by quickly transmitting too much information. UDP does not provide congestion and flow control as data packets are received in a continuous sequence or dropped.
Connectionless & Connection-Oriented
TCP is a connection-oriented protocol, whereas UDP is a connectionless protocol. In TCP, a connection is created between a sender and receiver before sending information. When it comes to UDP, it does not need an explicit connection to transmit data.
Reliability
TCP is known for being reliable. When you send information via TCP, it is guaranteed t arrive at your intended destination without errors. Even if the information is corrupted or lost in transit, it will recover and resend it. TCP also tracks if data packets go missing or are in the wrong order.
UDP is an unreliable network protocol and does not guarantee data delivery. Due to this, datagrams might become corrupt or lost during transit. Moreover, UDP does not track packets between the receiver and the sender.
Ordering
With TCP, ordering and sequencing are done to make sure data packets are delivered in the same order in which they were sent. However, UDP sends datagrams in any random order.
Conclusion
Many virtual private network services support OpenVPN in their applications and allow users to choose between the UDP and TCP protocol. It is essential to note that neither of them is better than the other, and the difference is not even noticeable to most end users. Generally, UDP provides better speeds, but it can vary on a scenario-by-scenario basis.
In some situations, either one of the protocols might be required to circumvent a firewall. Both UDP and TCP are able to run on different ports. On the other hand, OpenVPN uses UDP port 1194 by default, and it is common for firewalls to blacklist it. If your connection is blocked, your best way is to switch to TCP, which is more firewall-friendly.
