pcap file format

https://wiki.wireshark.org/Development/LibpcapFileFormat Libpcap File Format magic_number: used to detect the file format itself and the byte ordering. The writing application writes 0xa1b2c3d4 with it’s native byte ordering format into this field. The reading application will read either 0xa1b2c3d4 (identical) or 0xd4c3b2a1 (swapped). If the reading application reads the swapped 0xd4c3b2a1 value, it knows that all the… Continue reading pcap file format

NAT Traversal Practices for Client-Server SIP

https://tools.ietf.org/html/rfc6314 NAT Traversal Practices for Client-Server SIP ALGs have limitations (as per RFC 4787 [RFC4787] Section 7, RFC 3424 [RFC3424], and [RFC5245] Section 18.6), and experience shows they can have an adverse impact on the functionality of SIP. This includes problems such as requiring the media and signaling to traverse the same device and not… Continue reading NAT Traversal Practices for Client-Server SIP

Troubleshooting link up/down and autonegotiation

http://etherealmind.com/ethernet-autonegotiation-works-why-how-standard-should-be-set/ http://www.cisco.com/c/en/us/support/docs/switches/catalyst-6500-series-switches/17053-46.html Recommended Port Configuration (Autonegotiation or Manual Configuration) There are many opinions on the subject of autonegotiation. Previously, many engineers advised customers not to use autonegotiation with any switch-connected device. However, improvements in the interoperation of autonegotiation and the maturity of the technology has recently changed the view of autonegotiation and its use. In… Continue reading Troubleshooting link up/down and autonegotiation

Tcp Zero Window

https://www.wireshark.org/docs/wsug_html_chunked/ChAdvReassemblySection.htmlhttps://blog.apnic.net/2014/12/15/ip-mtu-and-tcp-mss-missmatch-an-evil-for-network-performance/https://wiki.wireshark.org/TCP%20ZeroWindow http://wesmorgan.blogspot.jp/2011/03/tcp-zero-windows-and-why-they-can-be.html TCP Zero Windows – and Why They Can Be VERY Bad TCP zero windows FIN says “i finished talking to you, but i’ll still listen to everything you have to say until you’re done” RST says “there is no conversation. i won’t say anything and i won’t listen to anything you say” –… Continue reading Tcp Zero Window


http://comp.unix.solaris.narkive.com/AhC8mF5S/solaris-9-tcpattemptfails $ ndd -get /dev/tcp tcp_time_wait_interval 60000 $ ndd -get /dev/tcp tcp_fin_wait_2_flush_interval 16000 $ ndd -get /dev/tcp tcp_rexmit_interval_max 10000 $ ndd -get /dev/tcp tcp_ip_abort_interval 60000 $ ndd -get /dev/tcp tcp_keepalive_interval 90000 $ ndd -get /dev/tcp tcp_conn_req_max_q 16384 $ ndd -get /dev/tcp tcp_conn_req_max_q0 16384 $ ndd -get /dev/tcp tcp_xmit_hiwat 131072 $ ndd -get /dev/tcp tcp_recv_hiwat 131072… Continue reading tcpattemptfails

Spanning Tree Protocol and PortFast

What is Spanning Tree and Portfast, and how can they affect my Altiris environment? During the execution of the Spanning-Tree Algorithm, Spanning-Tree will force the ports to go into five different states: Blocked Listen Learn Forward Disabled The transitioning period from state to state takes the following times by default: From blocking to listening: 20… Continue reading Spanning Tree Protocol and PortFast

Heartbeat and multicast in redhat HA add-on

https://access.redhat.com/solutions/165433 How do I configure cluster nodes to use a dedicated heartbeat interface? https://access.redhat.com/articles/40051 Red Hat Enterprise Linux Cluster, High Availability, and GFS Deployment Recommended Practices It is highly recommended to separate the private network for cluster heartbeat from the application network. This should be done wherever possible. Red Hat Clustering in Red Hat Enterprise… Continue reading Heartbeat and multicast in redhat HA add-on