What is TCP; where is it used in TR7?

Short answer

TCP (Transmission Control Protocol, RFC 9293) is the transport protocol that delivers data by establishing a connection, in order and without loss: the two ends first open a connection with the three-way handshake, lost segments are retransmitted and the data is delivered in the order it was sent. Most services, such as HTTP/1.1, HTTP/2, SSH, SMTP, LDAP and database connections, run over TCP. In TR7, TCP is selected or monitored in several places: HTTP and L7 TCP vServices accept the TCP connection on TR7; in a Network vService, TCP - L4 is selected as the Protocol; in health checks, the TCP type checks whether a connection to the port can be established; in Firewall rules, TCP is selected as the Protocol and a Destination Port is entered. The state of the open TCP connections is monitored on the vService Sessions screen and in the TCP panels on the Network tab of the home page.

Where It Is Used in TR7

Where	Field / label	What for
vService type	HTTP, L7 TCP	Terminating the TCP connection on TR7 and processing the application traffic
Network vService form	Protocol = TCP - L4	Balancing TCP at the IP and port level without terminating the connection
Load Balancer → Profiles → Health Checks	Check Type = TCP, TCPS	Checking whether a connection can be established to the server's port (and, optionally, the response with TCP scenario steps)
Network → Firewall → Add	Protocol = TCP → Destination Port	Applying the rule to TCP traffic and to specific ports
vService → Logs & Tracking → vService Sessions	The Status Code column (e.g. TCP_ESTABLISHED)	Monitoring the TCP state of the open connections
Home → Network tab	TCP Connection States, TCP Active Connections, TCP Connection Problems	Device-wide TCP connection counts and state distribution
The L4 DDoS Management screen of the route table	The TCP band (SYN flood, connection and flag rules)	Rules against TCP-based L4 attacks
WEB-CLI	sys-cmd ss (ss), sys-cmd telnet (telnet)	Listing the TCP sockets; testing the connection to a TCP port

• The difference between L7 TCP and Network (TCP - L4): What is the difference between L7 TCP and Network (TCP - L4); aren't they both TCP?
• The difference between a TCP health check and an HTTP health check: What is the difference between a TCP port check and an HTTP check; which should I choose?
• The meaning of the connection states: What do TCP connection states (such as ESTABLISHED and TIME_WAIT) mean?

Common Misconceptions

• "TCP and HTTP are the same thing." HTTP/1.1 and HTTP/2 are application protocols carried over a TCP connection; HTTP/3, on the other hand, uses QUIC over UDP instead of TCP (What are HTTP/3 and QUIC?).
• "A TCP health check proves that the application is working." A TCP check with no scenario step defined shows only that the port accepts connections; it counts as successful even if the application returns an error.
• "L7 TCP is the same thing as TCP - L4." L7 TCP terminates the connection on TR7; TCP - L4 in a Network vService forwards the connection without terminating it.

How it is done in the documentation

• Network vService · Protocol
• Health Checks · TCP
• Firewall · Protocol
• Home · Network · TCP Connection States

Related questions

• Should I use an HTTP vService or an L7 TCP vService for my HTTPS site?
• What is the difference between L7 TCP and Network (TCP - L4); aren't they both TCP?
• What is the difference between a TCP port check and an HTTP check; which should I choose?
• Is it possible to reject or silently drop a connection at the TCP level (TCP Connection Management)?