Teardown tcp connection что означает
teardown connection
закрытие соединения
завершение соединения
—
[Л.Г.Суменко. Англо-русский словарь по информационным технологиям. М.: ГП ЦНИИС, 2003.]
Тематики
Синонимы
Смотреть что такое «teardown connection» в других словарях:
закрытие соединения — завершение соединения — [Л.Г.Суменко. Англо русский словарь по информационным технологиям. М.: ГП ЦНИИС, 2003.] Тематики информационные технологии в целом Синонимы завершение соединения EN teardown connectionconnection release … Справочник технического переводчика
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ASA FAQ: How do you interpret the syslogs generated by the ASA when it builds or tears down connections?
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Contents
Introduction
This document describes how to interpret the generation for the Transmission Control Protocol (TCP)/User Datagram Protocol (UDP) syslog on the Adaptive Security Appliance (ASA) device when it builds and tears down connections.
How do you interpret the syslogs generated by the ASA when it builds or tears down connections?
All the syslogs discussed in this document are based on the network topologies shown here.
Network Topology
Scenario 1: Management traffic to the ASA inside interface (identity) is sourced from the inside host
Scenario 2: Traffic through the ASA is sourced from the inside host and is destined to the outside host
Scenario 3: Management traffic to the ASA outside interface (identity) is sourced from the outside host
Scenario 4: Traffic through the ASA is sourced from the outside host and is destined to the inside host
Network Topology (Same-Security Interfaces)
Scenario 1: Traffic through the ASA is sourced from the inside host and is destined to the outside host
Scenario 2: Traffic through the ASA is sourced from the outside host to the inside host
*Where 10.1.2.5 is the Static Nat IP for 10.1.1.2
ASA TCP Connection Flags (Connection Build-Up and Teardown)
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Contents
Introduction
This document provides information about Adaptive Security Appliance (ASA) TCP connection flags.
Prerequisites
Requirements
Cisco recommends that you have knowledge of these topics:
Basic knowledge of the TCP Communications Protocol
Basic knowledge of the ASA CLI
Components Used
The information in this document is based on ASA version 8.4.
The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.
ASA TCP Connection Flags
When you troubleshoot TCP connections through the Adaptive Security Appliance (ASA), the connection flags shown for each TCP connection provide a wealth of information about the state of TCP connections to the ASA. This information can be used to troubleshoot problems with the ASA, as well as problems elsewhere in the network.
Here is the output of the show conn protocol tcp command, which shows the state of all TCP connections through the ASA. These connections can also be seen with the show conn command.
The next picture shows the ASA TCP Connection flags at different stages of the TCP state machine. The connection flags can be seen with the show conn command on the ASA.
TCP Connection Flag Values
Additionally, in order to view all of the possible connection flags issue the show connection detail command on the command-line:
TOPIC:
what’s teardown meaning in «sh log» 16 years 2 months ago #10328
Re: what’s teardown meaning in «sh log» 16 years 2 months ago #10329
Re: what’s teardown meaning in «sh log» 16 years 2 months ago #10387
I’ll take jwj’s explanation a step further for you.
TCP has a 3-way connection establishment handshake, and a pair of 2-way close handshakes.
The PIX, like many other professional firewalls, is a stateful firewall. Essentially, this means that the PIX actively monitors all connection oriented traffic (mainly TCP), and builds a connection table (or database) that it uses to keep track of active sessions. Depending on where you set your buffer logging, you can see both the building and teardown of TCP connections that traverse the firewall. For example, you may have a user opening up an FTP session from the inside of your network out to the internet somewhere. In this case, you will see the PIX log a message like:
Built outbound tcp connection for IP address/sourceport to IP Address/21. (word order not exact, but you get the idea)
This log message indicates the start of the 3-way handshake process (it does not mean that it worked, however. )
You can now do a «show conn» on the PIX command line, and you should see a line in there for this particular TCP session. The destination port would be 21, since this is an FTP. Also, there are some flags at the end of the line. If the connection was successful, you will see a capital U (for Up, meaning the 3-way handshake was successful). If you have any a’s or s’s (small or upper case), then something didn’t work, and you are most likely in a SYN-Sent state, waiting for the remote Ack-SYN. That’s a whole other conversation though.
There are about 3 or 4 types of teardown messages that can be logged (if memory serves me). At the very end of the log entry there is a reason. Some of them are:
FINs
TCP-Reset-O
TCP-Reset-I
Conn-Timeout
Deny
There may be others, but you’d have to check the PIX docs to see (if it’s even in there. )
I know you’re going to ask, so here is what each one means:
Lastly, there is ‘Deny’. This one is seldomly observed. Generally, you would see it if a connection that was being application inspected (via the fixup’s, like FTP or http, for example), violated the fixup rulebase. The PIX would clear the connection and log the deny as the reason in the teardown message. I’ve seen really old FTP servers do this.
Re: what’s teardown meaning in «sh log» 16 years 4 weeks ago #11301
For every Built Connection, there’ll always be a teardown. Now there are not few but many reasons of a teardown when you ‘specifically’ talk about a Pix firewall log. Here are a few reasons:
Conn-timeout
Connection ended because it was idle longer than the configured idle timeout.
Deny Terminate
Flow was terminated by application inspection.
FIN Timeout
Force termination after 10 minutes awaiting the last ACK or after half-closed timeout.
Flow closed by inspection
Flow was terminated by inspection feature.
Flow terminated by IPS
Flow was terminated by IPS.
Flow reset by IPS
Flow was reset by IPS.
Invalid SYN
SYN packet not valid.
Idle Timeout
Connection timed out because it was idle longer than timeout value.
IPS fail-close
Flow was terminated due to IPS card down.
SYN Control
Back channel initiation from wrong side.
SYN Timeout
Force termination after two minutes awaiting three-way handshake completion.
TCP bad retransmission
Connection terminated because of bad TCP retransmission.
TCP FINs
Normal close down sequence.
TCP Invalid SYN
Invalid TCP SYN packet.
TCP Reset-I
Reset was from the inside (high security).
TCP Reset-O
Reset was from the outside (low security).
TCP segment partial overlap
Detected a partially overlapping segment.
TCP unexpected window size variation
Connection terminated due to variation in the TCP window size.
Tunnel has been torn down
Flow terminated because tunnel is down.
Unauth Deny
Denied by URL filter.
Unknown
Catch-all error.
Xlate Clear
Command-line removal
Hope that makes the reason crystal.
TOPIC:
what’s teardown meaning in «sh log» 16 years 2 months ago #10328
Re: what’s teardown meaning in «sh log» 16 years 2 months ago #10329
Re: what’s teardown meaning in «sh log» 16 years 2 months ago #10387
I’ll take jwj’s explanation a step further for you.
TCP has a 3-way connection establishment handshake, and a pair of 2-way close handshakes.
The PIX, like many other professional firewalls, is a stateful firewall. Essentially, this means that the PIX actively monitors all connection oriented traffic (mainly TCP), and builds a connection table (or database) that it uses to keep track of active sessions. Depending on where you set your buffer logging, you can see both the building and teardown of TCP connections that traverse the firewall. For example, you may have a user opening up an FTP session from the inside of your network out to the internet somewhere. In this case, you will see the PIX log a message like:
Built outbound tcp connection for IP address/sourceport to IP Address/21. (word order not exact, but you get the idea)
This log message indicates the start of the 3-way handshake process (it does not mean that it worked, however. )
You can now do a «show conn» on the PIX command line, and you should see a line in there for this particular TCP session. The destination port would be 21, since this is an FTP. Also, there are some flags at the end of the line. If the connection was successful, you will see a capital U (for Up, meaning the 3-way handshake was successful). If you have any a’s or s’s (small or upper case), then something didn’t work, and you are most likely in a SYN-Sent state, waiting for the remote Ack-SYN. That’s a whole other conversation though.
There are about 3 or 4 types of teardown messages that can be logged (if memory serves me). At the very end of the log entry there is a reason. Some of them are:
FINs
TCP-Reset-O
TCP-Reset-I
Conn-Timeout
Deny
There may be others, but you’d have to check the PIX docs to see (if it’s even in there. )
I know you’re going to ask, so here is what each one means:
Lastly, there is ‘Deny’. This one is seldomly observed. Generally, you would see it if a connection that was being application inspected (via the fixup’s, like FTP or http, for example), violated the fixup rulebase. The PIX would clear the connection and log the deny as the reason in the teardown message. I’ve seen really old FTP servers do this.
Re: what’s teardown meaning in «sh log» 16 years 4 weeks ago #11301
For every Built Connection, there’ll always be a teardown. Now there are not few but many reasons of a teardown when you ‘specifically’ talk about a Pix firewall log. Here are a few reasons:
Conn-timeout
Connection ended because it was idle longer than the configured idle timeout.
Deny Terminate
Flow was terminated by application inspection.
FIN Timeout
Force termination after 10 minutes awaiting the last ACK or after half-closed timeout.
Flow closed by inspection
Flow was terminated by inspection feature.
Flow terminated by IPS
Flow was terminated by IPS.
Flow reset by IPS
Flow was reset by IPS.
Invalid SYN
SYN packet not valid.
Idle Timeout
Connection timed out because it was idle longer than timeout value.
IPS fail-close
Flow was terminated due to IPS card down.
SYN Control
Back channel initiation from wrong side.
SYN Timeout
Force termination after two minutes awaiting three-way handshake completion.
TCP bad retransmission
Connection terminated because of bad TCP retransmission.
TCP FINs
Normal close down sequence.
TCP Invalid SYN
Invalid TCP SYN packet.
TCP Reset-I
Reset was from the inside (high security).
TCP Reset-O
Reset was from the outside (low security).
TCP segment partial overlap
Detected a partially overlapping segment.
TCP unexpected window size variation
Connection terminated due to variation in the TCP window size.
Tunnel has been torn down
Flow terminated because tunnel is down.
Unauth Deny
Denied by URL filter.
Unknown
Catch-all error.
Xlate Clear
Command-line removal
Hope that makes the reason crystal.