“Network Coding and Its Implications on Optical Networking”
This was an invited talk by Muriel Médard, from the MIT. Some notes:
1. Multicast capacity can be achieved with network coding. Minimum cost multicast is possible by allowing coding.
2. What about achieving the network coding advantage by coding only a subset of nodes? Cost of doing in every node would be prohibitive…
3. Some interesting paper on this topic: “Information-theoretic framework for network management for recovery from non-ergodic link failures” (Ho, Medard, etc.), “Concept of 1*N protection that uses network coding over p cycles”, Kamal 2006
4. Other interesting paper: Menendez and Gannett, 2008, show that network coding can lead to significant savings in back up resources by allowing coding. Only bitwise XOR is considered as it can be handled in the optical domain (in the electronic domain we don’t have this limitation, but the problem is that we need OEO conversion…).
5. Her group has showed that it’s possible to have benefits of coding even without having all nodes doing it.
6. Finally another paper with an evolutionary approach (Infocom 07) to minimise coding cost (number of coded lambdas).
All this network coding stuff could be of interest for multicast…
“CAPEX and OPEX in Aggregation and Core Networks”
This was yet another invited talk by Claus Gruber, Nokia. Some notes:
1. From the slides: “Video services will drive exponential growth… especially from IPTV”.
2. Revenues and traffic were usually correlated, but they are now being more decoupled. So we have maintained the network costs low… otherwise were done.
3. How to reduce CAPEX? Some examples: a) transport bits on the lowest level – it’s cheaper, b) the network should be automated, by using GMLS as control plane and path computation elements, c) use virtualisation techniques to enable fast cost efficient deployment of new services, d) optimal mix of intermediate grooming and routing and transport bypass.
4. How to reduce OPEX? Reduce energy consumption. Internet technologies represent 1 to 4% of energy consumption today…
5. IP/MPLS routers consume more power (1kW /100Gbps). Next in the list L2 switches, followed by SDH nodes, and finally ROADM nodes…
6. Extend traffic engineering decisions with energy profile info. Try to find paper “Energy profile aware routing”. I think this guy stole my idea in this paper… OK, he was first! :) But making routing “green” seems a good thing, and it’s a hot topic definitely.
“Architectures for Energy-Efficient IPTV Networks”
Jayant Baliga presented a paper with a new energy consumption model of IPTV storage and distribution (IPTV in his talk was VoD). Some notes:
1. Energy becoming an issue – OPEX, greenhouse gases. He focused on video delivery over public internet.
2. Some notes on power consumption: ethernet switch – 9 nJ/b, Broadband net gw (140 nJ/b), router (26 nJ/b). Core net: core router (17 nj/b), optical OXC (0.02 nJ/b). Data center: edge router (26 nJ/b), server (430nJ/b). Etc.
3. Packets traverse an average of 13 hops (3 hops metro + 9 on core + 1 data centre).
4. They check how many data centres they should use. The conclusion is that unpopular movies would stay in few data centers, say 1 or 2, but a very popular one would stay in several – he said 200 was a good number.
5. Optical bypass reduces power consumption.
6. P2P is efficient at low downloads per hour (unpopular content), but for high demand content is not efficient at all (due to upstream speeds being low).
“Power Saving Architectures for Unidirectional WDM Rings”
Another paper by our colleagues from
1. Are multihop architectures able to offer a reduction of OPEX (they reduce CAPEX)?
2. They have analysed power savings… and used ILP for this. These are the values they used (from work published recently): power of electronic interfaces = 197mW, power of optical interfaces = 189mW.
Main problem: it is an ILP formulation, so not scalable. Heuristics needed… maybe we can collaborate with them again? :)