Bus architecture and performance Network (and other) interfaces attach to the motherboard using some kind of interconnect. Typically a motherboard has a couple of ...

Wireshark Wireshark is a packet capture/analysis tool, similar to tcpdump but much more elaborate. It has a graphical user interface (GUI) which allows "drilling ...

OS Specific Configuration Hints: BSD Variants Performance tuning By default, earlier BSD versions use very modest buffer sizes and don't enable Window Scaling by ...

SIFTR Statistical Information for TCP Research Written by James Healy and Lawrence Stewart from Swinburne University in 2007, SIFTR is a kernel module for FreeBSD ...

IP Performance Metrics (IPPM) Working Group An IETF Working Group that has been chartered in 1997 to define metrics for network performance. Over the years, the group ...

Quick Start TCP Quick Start TCP was codified in an Experimental RFC (RFC 4782) in 2007. Based on explicit feedback from the network, it can use a large Initial Window ...

High Speed TCP Variants There have been numerous ideas for improving TCP over the years. Some of those ideas have been adopted by mainstream operations (after thorough ...

Troubleshooting Procedures PERT Troubleshooting Procedures, as used in the earlier centralised PERT in GN2 (2004 2008), are laid down in GN2 Deliverable DS3.5.2 (see ...

Large Send Offload (LSO) This feature is also known as "Segmentation Offload", "TCP Segmentation Offload (TSO)", " TCP Multidata Transmit (MDT), or "TCP Large Send ...

Network Adapters Demultiplexing to Multiple Threads Over the past years, multi threaded and multi core machines have become dominant, not just in the high performance ...

Network Adapter and Driver Issues One aspect that causes many performance problems is adapater and NIC compatability issues (full vs half duplex as an example. The ...

Latest News Efforts to increase TCP's initial congestion window The 78th IETF meeting is taking place in Maastricht this week, and one of the many topics being discussed ...

TCP's Initial Congestion Window (ICW or IW) The initial version of TCP Congestion Control specified that the congestion window should start at the maximum segment ...

TCP Flow Control Note: This topic describes the Reno enhancement of classical "Van Jacobson" or Tahoe congestion control. There have been many suggestions for improving ...

Statistics for PERTKB Web Month: Topic views: Topic saves: File uploads: Most popular topic views: Top contributors for topic save and ...

Serialization Delay (or Transmission Delay ) Serialization delay is the time it takes for a unit of data, such as a packet, to be serialized for transmission on a ...

Interrupt Coalescence (also called Interrupt Moderation , Interrupt Blanking , or Interrupt Throttling ) A common bottleneck for high speed data transfers is the ...

Secure Shell (SSH) SSH is a widely used protocol for remote terminal access with secure authentication and data encryption. It is also used for file transfers, using ...

Path MTU The Path MTU is the Maximum Transmission Unit (MTU) supported by a network path. It is the minimum of the MTUs of the links (segments) that make up the path ...

TCP Vegas TCP Vegas uses variations in measured throughput as an indication of congestion, in addition to packet loss. It also uses finer timer granularity compared ...

Web100 Linux Kernel Extensions The Web100 project was established to close the " wizard gap" between what performance should be possible on modern research networks ...

Multicast Traceroute ( mtrace ) The original traceroute idea of sending probe packets with increasing TTLs and evaluating the generated ICMP "destination unreachable ...

ICSI Netalyzr Netalyzr is a java applet developed by ICSI which will let you do a whole bunch of Internet connectivity tests. This can be used to determine the Internet ...

Welcome to the home of PERTKB. This is a web based collaboration area for collecting the knowledge base of the eduPERT. If you're looking for topics to work on, check ...

Windows TCP Analyzer The Microsoft Windows SDK also contains a tool that can read the so called ESTATS of an open TCP connection. When running, you get a listing of ...

Windows Network Monitor Microsoft Research has developed its own Wireshark variant called the Network Monitor. It's current version at time of writing is V3.3 which ...

OS Specific Configuration Hints: Solaris (Sun Microsystems) Planned Features Pluggable Congestion Control for TCP and SCTP A proposed OpenSolaris project foresees ...

News Archive (2008) For current news, check out the LatestNews section Recordings and other Materials from eduPERT Training Event now available In late November 2008 ...

TCP Westwood An improvement on TCP Westwood, which adds a bandwidth estimation algorithm that "provides a measure of used bandwidth that is not aliased" (from an ...

HighSpeed TCP HighSpeed TCP is a modification to TCP congestion control mechanism, proposed by Sally Floyd from ICIR (The ICSI Center for Internet Research). The main ...

TODO The PERT Knowledge Base is a Wiki, so it can be edited by anyone after a simple registration procedure. Here are a few suggestions for further developing the ...

Automatic Tuning of TCP Buffers Note: This mechanism is sometimes referred to as "Dynamic Right Sizing" (DRS). The issues mentioned under "Large TCP Windows" are ...

The window scaling problem Many firewalls check that a TCP segment falls within the expected window. If window scaling is in use but the firewall does not support ...

CUBIC An enhancement of BIC, this was added to the BIC implementation in Linux 2.6.16, and became the default algorithm in 2.6.19. In Linux 2.6.26, the algorithm ...

tcpdump (examples) Here are some more tcpdump examples for some more advanced use cases. For simple usage examples, see the main tcpdump topic. Filter on protocol ...

tcpdump One of the early diagnostic tools for TCP/IP that was written by Van Jacobson, Craig Leres, and Steven McCanne. Tcpdump can be used to capture and decode ...

TCP (Transmission Control Protocol) The Transmission Control Protocol (TCP) is the prevalent transport protocol used on the Internet today. It uses window based transmission ...

TCP Acknowledgements In TCP's sliding window scheme, the receiver acknowledges the data it receives, so that the sender can advance the window and send new data ...

TCP Reno TCP Reno builds upon TCP Tahoe's congestion control, adding the Fast Recovery mechanism described in RFC 2001. With this mechanism, isolated packet losses ...

Support for Large Frames/Packets ("Jumbo MTU") On current research networks (and most other parts of the Internet), end nodes (hosts) are restricted to a 1500 byte ...

Why Latency Is Important Traditionally, the metric of focus in networking has been bandwidth . As more and more parts of the Internet have their capacity upgraded ...

Windows Specific Host Tuning Next Generation TCP/IP Stack in Windows Vista / Windows Server 2008 / Windows 7 According to http://www.microsoft.com/technet/community ...

DTrace DTrace is a dynamic tracing framework developed by Sun for their Solaris and OpenSolaris operating systems. It allows tracing many aspects of execution across ...

Host and Application Measurement Tools Network performance is only one part of a distrbuted system's perfomance. An equally important part is the performance od the ...

SNMP The Simple Network Management Protocol was standardized by the IETF and is mostly used by operators to monitor various types of network equipment, as well as ...

Management Information Base (MIB) This term describes the set of management information accessible through a network management protocol such as SNMP. SNMP uses a ...

SNMP Counter Wrap Many of the variables accessible through SNMP are counters . Counters in SNMP are never reset, and they don't have a defined starting value. So ...

Low Priority for SNMP Handling Devices such as routers often give low priority to the SNMP, which handles SNMP requests, compared to other tasks that are deemed more ...

Sizing of Network Buffers Where temporary congestion cannot be avoided, some buffering in network nodes is required (in routers and other packet forwarding devices ...

SNMP Update Lag When accessing management variables such as traffic counters over SNMP, you should be aware of the following: The SNMP agent on a managed device ...