Wednesday, March 23, 2011


On February 3, 2011, ICANN/IANA announced, Available Pool of Unallocated IPv4 Internet Addresses Now Completely Emptied. The problem of IPv4 address exhaustion makes support for IPv6 a necessity, however there are significant challenges in supporting IPv6.

The article, There is no Plan B: why the IPv4-to-IPv6 transition will be ugly, provides a good introduction to some of the challenges. Critically, IPv6 is not backward compatible with IPv4, requiring a complex mixture of dual stack, NAT and tunneling strategies to maintain connectivity between IPv6 and IPv4 hosts:
In order to help network vendors and service providers test their IPv6 transition solutions, the Internet Society (ISOC) has organized World IPv6 Day for July 8th, 2011.

Visibility into network traffic provides vital information needed to manage IPv6 deployments. Even if an organization has no immediate plans to support IPv6, it is very likely that there is already IPv6 traffic present on the network since IPv6 support is enabled by default on many operating systems. Serious performance and security problems can result if IPv6 traffic isn't carefully monitored and managed.

The sFlow standard fully supports IPv6 monitoring. Most switch vendors include sFlow monitoring within their switch hardware, providing the visibility needed to manage the transition to IPv6, reporting on all IPv4 and IPv6 traffic as well as the different encapsulation and tunneling protocols for IPv6 transition. Switches supporting sFlow don't need to be upgraded in order to report on IPv6 traffic, the sFlow data exported by the switches contains packet header information that allows an sFlow analyzer to report on all different types of traffic on the network. The end-to-end visibility provided by sFlow ensures that traffic can be monitored and problems identified wherever they occur in the network.

For example, Amsterdam Internet Exchange (AMS-IX) uses sFlow to track the growth in IPv6 traffic on their network. The following chart trends IPv6 traffic over the last year:

Enabling sFlow monitoring in the network is a critical first step toward managing a smooth transition to IPv6. Proactive deployment of sFlow monitoring ensures that the data is available to troubleshoot and avoid problems as systems are transitioned to an IPv6 world.


  1. Hi,

    I have a question related to IPv6 data obtained from SFLOW that is enabled on our 'Top of Rack' switches. IPv6 data is relatively small compared to IPv4 and we see a lot of variance in the number of measurements we get every five minutes from SFLOW. It is very less in one 5 minute interval but is significant in the next 5 minutes (say 11 -> 350 measurements in 5 minutes).
    Is this expected ? Is there a way to overcome this ?

    1. If isn't much IPv6 traffic then there won't be many sFlow samples - this is expected. You can measure over longer periods to get more accurate results - see Scalability and accuracy of packet sampling