ISP and Egress Path Selection for Multihomed Networks

Mon, 03/17/2008 - 11:32 by Damien Saucez • Categories:

The paper "ISP and Egress Path Selection for Multihomed Networks" written by Dhamdhere and Dovrolis and presented at IEEE INFOCOM'06 discusses a solution to select the best ISPs for multihommed stub depending on traffic patterns of the stub.

The idea is simple, first, determine the traffic top X prefixes of the stub. Determine the possible ISPs for the stub and use stochastic techniques to detemine the subset of ISP to subscribe to and how to perform the best egress path selection.

Bandwidth estimation: metrics, measurement techniques, and tools

Mon, 03/17/2008 - 11:04 by Damien Saucez • Categories:

The paper titeled "Bandwidth estimation: metrics, measurement techniques, and tools" (R Prasad, C Dovrolis, M Murray, K Claffy - Network, IEEE, 2003) is divided in three main chapters. First, it defines the three following metrics:
- Capacity: the maximum possible IP layer transfer rate.
- Available bandwidth: the unused, or spare, capacity of a link during a certain time period.
- Bulk Transfer Capacity (BTC): the maximum throuhput obtainable by a single TCP connection (depends on many factor like rtt, window size, TCP implementation).

XEN: CentOS 5.1 guest on a CentOS 5.1 host mini howto

Fri, 03/14/2008 - 13:15 by Damien Saucez • Categories:


In this small tutorial, we present how to setup CentOS guests with the standard tools proposed by CentOS.

By default, CentOS gives good tools to rapidly create networked guests, see by yourself:

Host preparation

  • Configure Xen for private networking:
    1. Virtual networks can be configured in /etc/libvirt/qemu/networks/autostart/default.xml. The default configuration is good enough for us but feel free to modify it:

BGP misconfigurations strike back in Pakistan and affect Youtube

Tue, 02/26/2008 - 01:46 by Olivier Bonaventure • Categories:

All network engineers who are working with the interdomain routing protocol used on the Interned named BGP know that BGP is not 100% secure and that misconfigurations or attacks could cause problems on the Internet. The key problem is that BGP does not have mechanisms to verify the validity of a received route advertisement. From time to time, misconfigurations happen and are discussed on operators mailing lists such as nanog. Yesterday, youtube was affected by such a misconfiguration.

The 14 engineering challenges for the 21st century

Fri, 02/22/2008 - 14:48 by Olivier Bonaventure • Categories:

The NSF has issued a report listing the 14 engineering challenges that need to be solved to ensure progress of the world. See

The US National Academy of Engineering also published an interesting web site with the great achievements of the 20th centruy.

Communications of the ACM is changing... at last

Fri, 02/15/2008 - 12:33 by Olivier Bonaventure • Categories:

Communications of the ACM is the magazine sent to all members of the Association for Computing Machinery the worlwide association of computing scientists. During the last years, the magazine has been focussing on the management of information systems and was less interesting for the average computer scientist. This is changing as ACM is updating Communications of the ACM starting in 2008 with a redesigned magazine that will contain detailed breakthrough research papers.

IPv4 addresses for sale ?

Thu, 02/14/2008 - 01:45 by Olivier Bonaventure • Categories:

The Internet community is seeing both a growth in the allocation of IPv4 addresses and also the end of the IPv4 addressing space. According to the latests predictions, the IPv4 addressing space will be exhausted in 2011-2012. Instead of focussing on the development of IPv6, ARIN is considering to allow owners of IPv4 addresses to sell them to anyone instead of giving them back for free to ARIN when they are not used anymore.

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