swaks primary design goal is to be a flexible, scriptable, transaction-oriented SMTP test tool. It handles SMTP features and extensions such as TLS, authentication, and pipelining; multiple version of the SMTP protocol including SMTP, ESMTP, and LMTP; and multiple transport methods including unix-domain sockets, internet-domain sockets, and pipes to spawned processes. Options can be specified in environment variables, configuration files, and the command line allowing maximum configurability and ease of use for operators and scripters.
Tuesday, August 1. 2017
swaks - Swiss Army Knife SMTP - the all-purpose smtp transaction tester
Network Diagnostics
Built in to iproute2:
~$ ip tcp_metrics 192.168.4.2 age 336273.112sec source 192.168.4.1 10.151.0.10 age 17668.708sec cwnd 10 rtt 969us rttvar 788us source 10.9.2.21 10.152.0.10 age 8.368sec source 10.9.2.21
sysstat package (edit /etc/default/sysstat and change ENABLED from false to true, and change /etc/cron.d/sysstat to a different interval)
- to look into:
- sysstat package: sar
netstat
netstat -s|grep -i retran 19448 segments retransmitted 161 times recovered from packet loss due to fast retransmit Detected reordering 3 times using reno fast retransmit 1 timeouts after reno fast retransmit 303 fast retransmits 1 retransmits in slow start TCPRetransFail: 167 TCPSynRetrans: 13966
More stats than you can shake a stick at: ss -ti
Papers on TCP:
- TCP Congestion Control on RTP Media Streams: using ffmpeg, tcptrace, mininet, wanem
- TCP Tuning Techniques for High-Speed Wide-Area Networks: presentation
- Identification of Hostile TCP Traffic Using Support Vector Machines
- SLAC Network Monitoring Tools: large list of curated tools
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