Subject: CSTB report (...RE: [IMRG] Measurement TCPs)

From: "Ayyasamy, Senthilkumar (UMKC-Student)" <[email-masked]>
Date: Mon, 16 Sep 2002 16:30:29 -0500

When i walk through the whole thread, I remember reading same 
concerns from a CSTB report. Even persons outside the Networking 
community accepts such concerns. "Good data outlive bad theory" 
is the most apt quote from the report.

Some of the uses of the archived data, as per the report,
"Archived Internet snapshots could provide an analogous baseline for 
 evaluating the large-scale impact of both evolutionary and revolutionary 
 changes in the Internet. Archived data could also be used by Internet 
 researchers to determine if newly identified traffic phenomena (for 
 example, a future equivalent of heavy-tailed behavior) existed in earlier 
 instantiations of the Internet."

The barrier, as per the report, include:
  - Acquiring representative data points
  - paucity of data
  - routing asymmetry and multipathing makes it hard 
    to get even details about TCP type of flows.
  - business and privacy concerns  

Lets try to see how much we have answered the above barriers:
  A number of test bed initiatives have answered the first barrier. 
Internet2 have some good representative data points accomodating the 
scalability of Internet. Taking representative data from the voluminous 
data set is another important question. An effective passive sampling 
scheme by means of simple functions in a router at line speed is enough
to answer the above concern. Trajectory based sampling and algorithms for
accounting based on sampling are some of the recent initiatives.
 The routing asymmetry and multipath are not a big issue for collecting
data. As ratul mentioned, working around such things are always interesting
and give new insight for even routing assymmetry problems. 

A challenge, which the report poses to the networking community, is:
  "(1) to develop and deploy the technology to make it possible to
       record a day in the life of the Internet, a data set containing 
       the complete traffic, topology, and state across the Internet 
       infrastructure and 
   (2) to take such a snapshot."
Do we all have an answer for the above challenge? 

So, at last, what does the report sees as major problems, which this group
might work on:

- Problem of scalability: A Good sampling mechanism and inference techniques
  are enough to get representative data from the massive trace sets. A better 
  example for inference techniques, where we infer details from incomplete 
  information, is topology inference works using Publicaly available BGP data.

- Measurement infrastructure: Leaving the equally important question of building 
  the infrastructure, the other points which reseachers should mind while working
  around new ideas are, "incorporating self-measurement, analysis, and diagnosis as 
  basic design points of future system elements and protocols.This is particularly 
  critical to providing insight into failures that are masked by higher layers of
  abstraction, as TCP does by intentionally hiding information about packet loss 
  from applications."

- Non-technical factors: Privacy issues. One can work around the problem by means
  of some anonymization techniques like ethan's work on tcpurify.

So, as good researchers, lets not ask the service providers to release their 
sensitive data. But, work more on: 
 1. finding more representative data points in the Internet.
 2. working on passive sampling schemes for collecting representative data sets.
 3. learn to live with partial data by means of inference techniques.
 4. Make sure our future ideas incorporate self-measurement and self-indentifying
    feature.
 5. develop new anonymization techniques.

- Senthil.

PS: All the above ideas/views are from a CSTB report "Looking Over the Fence at 
Networks: A Neighbor's View of Networking Research" with little of my own insight.
For more details :http://www7.nationalacademies.org/cstb/pub_lookingover.html

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