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Industrial Ethernet S7-300/400 CPs -- Product information -- System description (protocols)
How are the communication resources assigned in the S7-300?
How do you load the 3D, CAx and ePLAN data for the SIMATIC products?
What are the differences between OPEN MODBUS / TCP Redundant V1 and OPEN MODBUS / TCP Redundant V2?
What should you watch out for when you enable the "SNMP" function in the configuration of the security module?
Which security modules support the DNS function?
What should you watch out for when enabling and using the security functions of CP343-1 Advanced and CP443-1 Advanced?
What should you watch out for when upgrading from previous modules to the successor module CP443-1 or CP443-1 Advanced?
How do you verify the authenticity of the Siemens modules CP343-1 and CP443-1?
What should you watch out for when operating a port of CP343-1, 6GK7343-1CX10-0XE0 and 6GK7343-1EX30-0XE0 with firmware V2.1 or higher, with 10 Mbit/s half duplex?
Which IO controllers and IO devices support the following functions: IRT, prioritized startup, MRP, PROFIenergy, Shared device, I device and clock-synchronized mode?
Where do you procure the firmware extension for the CP 343-1 ERPC for database connection?
Which SIMATIC S7-300/S7-400 modules support the NTP time-of-day message and how do you activate this kind of time synchronization?
Which modules can you use when implementing software redundancy?
Which types of connection/protocols do the S7-300/400 CPUs and the CPs support by default?
Which PROFINET nodes support automatic commissioning (device replacement without interchangeable medium) in the case of topological configuration and device replacement without topological configuration?
Which PROFINET nodes support the extended PN diagnostics and what do you have to configure?
Using C-PLUG with network components and SIMATIC CPs
What properties have the communication services and protocols that can be used in the Industrial Ethernet network?
Behavior of the communication processors during data transfer via TCP connections without RFC 1006
What should you watch out for with the ICMP Redirect (Internet control message protocol) function regarding the IP address of the router used for Industrial Ethernet CPs?
What should you pay attention to with the autonegotiation function for negotiating the LAN mode in Industrial Ethernet CPs?
What is the connection between subnet masks and IP addresses with regard to subnetting and supernetting (Classless Inter Domain Routing CIDR)?
Which modules support the S7 routing function?
In the case of open TCP/IP communication via Industrial Ethernet using T blocks with IE CPs and CPUs, why are different amounts of messages sent when the maximum length of 1452 bytes of user data is transferred?
What properties, advantages and special features does the ISO protocol offer?
What properties, advantages and special features does the UDP protocol offer?
What properties, advantages and special features does the ISO-on-TCP protocol offer?
What properties, advantages and special features does the S7 protocol offer?
What properties, advantages and special features does the TCP protocol offer?
What are the requirements for disabling the PROFINET CBA interface for CP443-1EX40?
"Time Wait" with TCP connection setup
What are the different data block lengths for the various protocols of Send/Receive communication?
What is RFC1006 and what do I need this service for?
Meaning and function of the "Keep Alive" in TCP connections
"Time Wait" with TCP connection setup
Part number:

QUESTION:
Why with TCP connections do I have to wait five seconds after setup until I can initiate connection setup again?

ANSWER:
This behavior is due to the interaction of the RFCs describing the TCP/IP.
RFC 793 describes the TCP protocol with its mechanisms; the connection setup is also defined in it.

A detailed definition of this mechanism is also available in RFC 1337, which deals specifically with the "TIME-WAIT" time factor.
The calculations and the proposed values for this factor are described in this RFC.

The time factor is intended to prevent messages - which are theoretically still in the network and transferred late to the node via the router - from interfering with the connection clear-down and setup.

In RFC 1337 the time factor is assigned some of the proposed values ranging from 2 minutes to 4.55 hours.
In order to avoid such time periods, a fixed value of 5 seconds has be set in the CP firmware.

During this time it is not possible to set up a new connection via a port whose connection has just been cleared down or receive a message. Such messages are acknowledged with the last acknowledge message that closed the connection.

Keywords:
Connection setup after connection interrupt


 Entry ID:18619393   Date:2004-03-12 
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