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DNS prefetching : browser optimisations may cause DNS server overload

Fri, 03/11/2011 - 01:36 by Olivier Bonaventure • Categories:

Recent browser have added an optimisation that enables the browser to resolve all the DNS names that appear inside a visited HTML page while the browser displays the HTML page. This can speed up the retrieval of the next link on which the user will click. Unfortunately, on websites that contain a large number of different hostnames on each page (e.g. pointers to homepages of users who have posted comments), this may lead to a large number of DNS requests for each HTML page retrieved.

Route Flap Damping is back ?

Thu, 03/10/2011 - 23:32 by Olivier Bonaventure • Categories:

One of the problems faced by BGP routers today is the BGP churn, i.e. the number of messages that they have to process. Measurement studies have shown that a small fraction of the prefixes are responsible for a large fraction of the BGP messages that are received by BGP routers. Furthermore other studies have shown that the destination prefixes that carry lots of traffic usually have stable BGP routes.

New TCP timestamps

Thu, 03/10/2011 - 22:10 by Olivier Bonaventure • Categories:

Introduced in RFC1323, the TCP timestamp option enables TCP hosts to better estimate the round-trip time by adding a timestamp to each transmitted TCP segment. These timestamps are also useful for high bandwidth transfer to protect against the reutilisation of the same TCP sequence number for different segments during the same MSL. These timestamps are supported by most TCP implementations today.

The return of T/TCP

Thu, 03/10/2011 - 15:41 by Olivier Bonaventure • Categories:

In the early 1990s, the T/TCP extension to TCP was proposed to allow hosts to exchange data without being forced to wait until the end of the three way handshake. Specifications ( RFC1379 and RFC1644) and implementations were written, but this TCP extension has never been largely used.

Securing BGP

Thu, 03/10/2011 - 15:10 by Olivier Bonaventure • Categories:

BGP is one of the key protocols that are used on the Internet today. Despite of its importance, the security of BGP is still a concern. Several solutions to improve the security of BGP have been proposed by the research community :

TCP crypt

Thu, 03/10/2011 - 15:03 by Olivier Bonaventure • Categories:

Despite its respectable age (the first specification was published in September 1981), TCP is still alive and researches and IETFers continue to develop new extensions to improve the protocol. Multipath TCP received a lot of attention during the last years. Another TCP extension to improve the security of TCP has been submitted for the next IETF meeting. TCP crypt aims at improving the security of TCP by allowing the utilisation of crypto mechanisms to protect the TCP segments.

MPLS autobandwidth

Mon, 03/07/2011 - 15:27 by Olivier Bonaventure • Categories:

Since several years, Cisco routers have included a feature called mpls autobandwidth that allows the router to compute automatically the bandwidth required for an LSP and adjust the reserved bandwidth. This feature seems interesting, but personally I have always feared that it could cause oscillations in a network if the change in reserved bandwidth leads to a change in paths for the concerned LSPs.

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