There are two versions of the time sequence graph, the more straightforward Stevens graph** and the more advanced TCP trace graph.
#CONSTANT TCP RETRANSMISSION WIRESHARK HOW TO#
This article will teach you how to interpret TCP connections using the TCP time-sequence graphs. Wireshark offers a couple of graphs for TCP analysis: RTT, throughput, window scaling, and the time sequence graphs. Having a basic understanding of how Wireshark visualizes packet information in a TCP graph, you can take shortcuts in the analysis workflow and avoid spending many hours looking for patterns that are barely visible in the limited perspective of the packet list. You can bypass limits in Squid by tweaking the configuration, but then again it is an unrealistic test.Why don't you use graphs instead? They are a powerful tool in a packet analyst's craft. Some browsers consider the proxy to be a single host but others also have different limits for the proxy (up to 15 concurrent, too). Actually, a user's browser will limit the connections to a single host to a number between 6 and 12 concurrent (depending on the browser and version). 60 new connections per second from several different hosts is more than OK, but it is unrealistic if they are coming from a single host. If you are trying to simulate user load I'm afraid you're not doing it right. 60 new connection per second from the same host is considered harmful by pretty much every network and security administrator out there and any default settings on a firewall or even on a proxy will start silently dropping your traffic.
The retransmissions you're seeing are probably due to someone else in the network dropping any other SYN packets from you. I see in your capture's screenshot that it has been 2 seconds since you started the process and you've mentioned getting stuck after ~120 connections, which is a good number of new connections in 2 seconds. As symcbean pointed out, it is more efficient and it may be so evident on your example because you're quickly opening lots of new sockets. Reusing TCP ports is not a bad thing per se. Also FIN, ACK and RST received for the earlier request.Īttaching tcp dump screenshot for reference:Ĭan you please let me know why it is using same port for the new request and re-transmitting the packet again? Is there a way to avoid port reuse? During this hanged state, I took tcpdump on server and found that it is showing "TCP port numbers reused" and start sending sync packet with same port which was used earlier and showing "TCP Retransmisson". This URL I have blocked on URL filtering engine.Īfter some requests ~120 wget got hanged in between for exactly 1 min. This URL filtering engine which will allow/block URL according to the rule.įrom client I have run a script which does 500 wget to in a loop continuously. Squid then forwards to a URL Filter which has a list of whitelists and blacklists. I have a squid proxy installed on a unix machine which is sending handling http requests coming from an trusted source. Facing issues due to TCP Port Reuse and Retransmission for HTTP traffic.
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