Another interesting paper I've discovered these days - published in 2002 - was Internet Research Needs Better Models, by Sally Floyd and Eddie Kohler (Berkeley). In there they conclude that Internet research has a great need for better models, and for better common evaluation of these models. Some of the wrong implicit assumptions that they point down as the cause of the problem are: 1) flows live for a long time and transfer a lot of data, 2) "dumbbell" topologies with one congested link are used, 3) flows on the congested link share a small range of round-trip times, 4) most data traffic across the link is one-way, 5) reverse-path traffic is rarely congested.
In the exact moment that I am specifying in detail my PhD work plan (thinking of source, demand and topology models, evaluation, etc.) it is really important to take the above-mentioned points into consideration.
Tuesday, 30 October 2007
Monday, 29 October 2007
Internet Measurement Conference 2007
The program of the Internet Measurement Conference 2007 was very interesting. The best paper award went to I Tube, You Tube, Everybody Tubes: Analyzing the World's Largest User Generated Content Video System. Mia (that has been around in the Computer Lab for some time), Pablo Rodriguez (from Telefonica) et al presented a very detailed and interesting study on User Generated Content systems, like youtube.
I also enjoyed the article Characterizing Residential Broadband Networks. Some of the results were interesting: 1) packet transmissions over cable suffer high jitter as a result of cable’s time-slotted access policy (which can affect TCP Vegas due to its reliance on RTT), 2) DSL links show large last-hop delays and considerable deployment of active queue management policies such as random early detection (RED), 3) both cable and DSL ISPs use traffic shaping and deploy massive queues that can delay packets for several hundred milliseconds (really bad for things like VoIP).
It was also interesting to know that about 83% of IP packets are all-zero in the Type of Service field, and IP options are virtually not used, along with fragmentation. Oh, and Path MTU discovery rules... :) (check more on Analysis of Internet Backbone Traffic and Header Anomalies observed)
But the program is interesting as a whole and hence worth inspecting in detail.
I also enjoyed the article Characterizing Residential Broadband Networks. Some of the results were interesting: 1) packet transmissions over cable suffer high jitter as a result of cable’s time-slotted access policy (which can affect TCP Vegas due to its reliance on RTT), 2) DSL links show large last-hop delays and considerable deployment of active queue management policies such as random early detection (RED), 3) both cable and DSL ISPs use traffic shaping and deploy massive queues that can delay packets for several hundred milliseconds (really bad for things like VoIP).
It was also interesting to know that about 83% of IP packets are all-zero in the Type of Service field, and IP options are virtually not used, along with fragmentation. Oh, and Path MTU discovery rules... :) (check more on Analysis of Internet Backbone Traffic and Header Anomalies observed)
But the program is interesting as a whole and hence worth inspecting in detail.
Thursday, 18 October 2007
Multicast TE still remains in its preliminary stage
I have just found out a very interesting site on QoS Aware Multicast Management. In there they state that "relevant research on multicast TE still remains in its preliminary stage compared to its unicast counterpart".In fact, "despite the progress for unicast services, traffic engineering for multicast flows remains largely a dark area till now".
They have a specific section on Multicast Traffic Engineering. In there they divide Multicast TE in MPLS Based Multicast Traffic Engineering and IP Based Multicast Traffic Engineering.
In MPLS-based multicast TE point-to-multipoint LSPs are explicitly constructed, and the mathematical problem formulation is often related to the Steiner tree problem for minimising traffic delivery cost. So we need to set up dedicated MPLS tunnels. My PhD proposal is exactly on this issue, and part of it is to develop scalable heuristics for multicast TE.
In IP Based Multicast Traffic Engineering, the basic idea is to convert engineered multicast trees into shortest path trees by optimising link weights. The main advantage in this approach is that legacy IP routers are able to compute multicast trees by applying the Dijkstra’s shortest path algorithm (with the pre-configured link weights).
They have a specific section on Multicast Traffic Engineering. In there they divide Multicast TE in MPLS Based Multicast Traffic Engineering and IP Based Multicast Traffic Engineering.
In MPLS-based multicast TE point-to-multipoint LSPs are explicitly constructed, and the mathematical problem formulation is often related to the Steiner tree problem for minimising traffic delivery cost. So we need to set up dedicated MPLS tunnels. My PhD proposal is exactly on this issue, and part of it is to develop scalable heuristics for multicast TE.
In IP Based Multicast Traffic Engineering, the basic idea is to convert engineered multicast trees into shortest path trees by optimising link weights. The main advantage in this approach is that legacy IP routers are able to compute multicast trees by applying the Dijkstra’s shortest path algorithm (with the pre-configured link weights).
A Machine Learning Approach for Efficient Traffic Classification
Today's talk on the Computer Lab was on "A Machine Learning Approach for Efficient Traffic Classification". The speaker was Wei Li. Wei Li was a PhD student in QMUL but now has moved to the Computer Lab "following [his] supervisor Andrew Moore".
The talk was on the very interesting subject of online traffic classification. Besides being used for network monitoring and intrusion detection, traffic classification can also serve as the input for application modeling. For that reason it could be useful to model the IPTV service, for instance, which would in turn be important as an input to my OPNET simulations.
Wei Li presented a machine-learning approach that accurately classifies internet traffic using C4.5 decision tree. Without inspecting packet payload, their method can identify traffic of different types of applications with 99.8% total accuracy, by collecting 12 features at the start of the flows. But overall it was a very nice talk.
Some questions arose on the features chosen (why those 12 and not others, when 248 were available?) and on the relationship between accuracy and time (can be an important aspect to consider in some applications, like intrusion detection).
The talk was on the very interesting subject of online traffic classification. Besides being used for network monitoring and intrusion detection, traffic classification can also serve as the input for application modeling. For that reason it could be useful to model the IPTV service, for instance, which would in turn be important as an input to my OPNET simulations.
Wei Li presented a machine-learning approach that accurately classifies internet traffic using C4.5 decision tree. Without inspecting packet payload, their method can identify traffic of different types of applications with 99.8% total accuracy, by collecting 12 features at the start of the flows. But overall it was a very nice talk.
Some questions arose on the features chosen (why those 12 and not others, when 248 were available?) and on the relationship between accuracy and time (can be an important aspect to consider in some applications, like intrusion detection).
Tuesday, 9 October 2007
How to read a paper
A big part of a researcher's time is spent reading papers. Either with the aim of keeping current in their field or for a literature survey in a new field, a researcher will read tens (or even tons :) ) of papers monthly. For this reason, it is very important to know how to read a paper.
In July's issue of Computer Communications Review (CCR Volume 37, Number 3 July 2007) S. Keshav (he is the author of a very nice book on communications systems: An Engineering Approach to Computer Networking) wrote a good article on "how to read a paper". I believe a perusal of this short paper is crucial for a new researcher. Paper reading skills are not taught anywhere, so this article is extremely useful.
In July's issue of Computer Communications Review (CCR Volume 37, Number 3 July 2007) S. Keshav (he is the author of a very nice book on communications systems: An Engineering Approach to Computer Networking) wrote a good article on "how to read a paper". I believe a perusal of this short paper is crucial for a new researcher. Paper reading skills are not taught anywhere, so this article is extremely useful.
Wednesday, 3 October 2007
An Introduction
I am a PhD student in the University of Cambridge. I am now starting my second year, and I would like to share all kinds of stuff related with my research work. This was the reason why I've decided to create this blog: to be sort of a logbook of my research.
The objective of my PhD thesis is the design of a GMPLS system for provisioning optical core and access networks for Multicast TV, and so this weblog will be dedicated to topics related - although not exclusively. As perceived by the blog title, I consider all of this "IPTV research" generically. I am pretty sure these topics will eventually be addressed:
1) Multicast
2) Traffic Engineering (TE)
3) Optical Networks
4) Routing
5) Quality of Service
6) IPTV
7) ...
and mixes of all the above (something like "Multicast TE Routing in Optical Networks to provide IPTV with nice QoS" would be a cool topic :)). And more generic topics related to telecommunications, Internet, protocols, next generation networks, etc., etc., will probably appear too.
I will try to bring news, scientific papers (old and new), ideas, results, etc. I will also welcome comments from all of my readers, either directly posted into the site or to my e-mail: fvramos at gmail dot com.
The objective of my PhD thesis is the design of a GMPLS system for provisioning optical core and access networks for Multicast TV, and so this weblog will be dedicated to topics related - although not exclusively. As perceived by the blog title, I consider all of this "IPTV research" generically. I am pretty sure these topics will eventually be addressed:
1) Multicast
2) Traffic Engineering (TE)
3) Optical Networks
4) Routing
5) Quality of Service
6) IPTV
7) ...
and mixes of all the above (something like "Multicast TE Routing in Optical Networks to provide IPTV with nice QoS" would be a cool topic :)). And more generic topics related to telecommunications, Internet, protocols, next generation networks, etc., etc., will probably appear too.
I will try to bring news, scientific papers (old and new), ideas, results, etc. I will also welcome comments from all of my readers, either directly posted into the site or to my e-mail: fvramos at gmail dot com.
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