A content can be replicated in more than one node, in Information Centric Networks (ICNs). Thus, more than one path can be followed to reach the same content, and it is necessary to decide the interface(s) to be selected in every network node to forward content requests towards such multiple content containers. A multipath forwarding strategy defines how to perform this choice. In this paper we propose a general analytical model to evaluate the effect of multipath forwarding strategies on the performance of an ICN content delivery, whose congestion control follows a receiver driven, loss-based AIMD scheme. We use the model to understand the behavior of ICN multipath forwarding strategies proposed in the literature so far, and to devise and evaluate a novel strategy. The considered multipath forwarding strategies are also evaluated in a realistic network setting, by using the PlanetLab testbed.
- The exploitation of in-network multipath requires to discover internal network paths and to control the forwarding of traffic inside the network. Consequently, the path discovery and multipath forwarding mechanisms must be necessarily executed by the IP network layer We are not considering the possibility of using the source routing IP option since practically is not supported , thus involving network nodes. Instead, congestion control mechanism can remain above IP, at the communication end-points. However, as shown in fig. , this division of multipath functionality in two different layers creates inter operation issues, of which a crucial one is packet reordering. In fact, if a per-packet strategy were used by IP routers, it would cause out of order packet delivery (as different paths may have different delays) and TCP-based congestion control would wrongly reduce the send-rate, even in absence of congestion @cite_16 . Conversely, out-of-order delivery does not occur in the case of per-flow multipath forwarding strategies. Thus, per-flow strategies are the safest approach in TCP IP networks, to exploit in-network multipath.
@cite_16
1898772099
In this paper, we investigate TCP performance over a multipath routing protocol. Multipath routing can improve the path availability in mobile environment. Thus, it has a great potential to improve TCP performance in ad hoc networks under mobility. Previous research on multipath routing mostly used UDP traffic for performance evaluation. When TCP is used, we find that most times, using multiple paths simultaneously may actually degrade TCP performance. This is partly due to frequent out-of-order packet delivery via different paths. We then test another multipath routing strategy called backup path routing. Under the backup path routing scheme, TCP is able to gain improvements against mobility. We then further study related issues to backup path routing, which can affect TCP performance. Some important discoveries are reported in the paper and simulation results show that by careful selection of the multipath routing strategies, we can improve TCP performance by more than 30 even under very high mobility.