Good things come to those who (can) wait: or how to handle Delay Tolerant traffic and make peace on the Internet

Nikolaos Laoutaris and Pablo Rodriguez
Proc. of ACM HotNets-VII

This paper talks about time shifting Delay Tolerant (DT) traffic in order to reduce bills for ISPs. Two schemes are posited

  • User incentives – users are encouraged to delay downloading with a reward scheme

  • Internet Post Offices (IPOs) – storage for store-and-forward relays for DT traffic.

The authors identify a significant opportunity to reduce bills for ISPs by finding traffic which can be moved in time and hence smooth the traffic flow. The key is to provide incentives for users to move their flow from busy periods (which contributes to the 95th percentile price charged by ISPs) and to less busy periods. A second important component is to identify those flows which are delay tolerant. This must be done while keeping the flat-rate charging scheme.

The incentives are provided by a scheme which gives the users higher than advertised bandwidth during off-peak hours – this bandwidth will typically cost the providing ISP nothing. This scheme assumes that the typical user will be allowed access at rate U throughout the day. A user participating in the incentive scheme will be allowed access at rate U_n  < U during the B busy hours and U_r > U during off peak hours. The r in U_r stands for reward and the n in U_n for nice. If U_n B + U_r (24-B) gg U.24 then the average rate of transfer for the user is much higher than the non-participating user. The authors suggest that the scheme can be modified by having several more levels during the day.

Internet Post Offices (IPOs) collect the DT traffic from end users in an opaque way. In once scenario a local ISP operates a local IPO. In another they are insalled and operated by CDN-like businesses which specialise in DT traffic. In scenareio one the IPOs are co-located at the ISP access providing data transfer at rates limited only by the access network. The user who wishes to send large amounts of data sends it out to the IPO immediately and it is sent on to the final destination from the IPO off-peak saving money for the ISP. The user is incentivised to do this by the scheme above. In the CDN approach the CDN operators use store and forward to transmit delay tolerant traffic in the off-peak.

Potential gains for the schemes are tested by looking at data from real traffic traces from transit ISPs.

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