دانلود رایگان مقاله مسیریابی هش کارآمد و تکنیک دامنه خوشه بندی برای شبکه اطلاعات محور

Abstract

Hash-routing is a well-known technique used in server-cluster environments to direct content requests to the responsible servers hosting the requested content. In this work, we look at hash-routing from a different angle and apply the technique to Information-Centric Networking (ICN) environments, where in-network content caches serve as temporary storage for content. In particular, edge-domain routers re-direct requests to in-network caches, more often than not off the shortest path, according to the hash-assignment function. Although the benefits of this off-path in-network caching scheme are significant (e.g., high cache hit rate with minimal co-ordination overhead), the basic scheme comes with disadvantages. That is, in case of very large domains the off-path detour of requests might increase latency to prohibitive levels. In order to deal with extensive detour delays, we investigate nodal/domain clustering techniques, according to which large domains are split in clusters, which in turn apply hash-routing in the subset of nodes of each cluster. We model and evaluate the behaviour of nodal clustering and report significant improvement in delivery latency, which comes at the cost of a slight decrease in cache hit rates (i.e., up to 50% improvement in delivery latency for less than 10% decrease in cache hit rate compared to the original hash-routing scheme applied in the whole domain).

6. Conclusions

The process of resolving requests to in-network caches has concerned the ICN community so far and has resulted in several proposals to deal with this issue. However, the tradeoff between performance (in terms of cache hits) and co-ordination overhead (which raises scalability concerns) is not easy to balance. We believe that hash-routing techniques offer a very easy to implement, efficient and scalable way of assigning content items to network caches and redirecting content requests to the corresponding cache. Our initial results in [10] revealed significant increase in performance, but did not take into account the case of very large networks, where the stretch of the detour path can become very big. In this paper we have extended our previous study to deal with this issue of extensive detour trips indicated by the hash-routing function. Our proposal builds on nodal clustering techniques that limit the number of nodes that a request will have to travel in order to reach the corresponding cache in case of very large networks. We report significant reduction in delivery delay with a slight decrease in cache hit rate. In general hash routing combined with domain partitioning can reduce the average item delivery latency up to 50% depending on the various system parameters (i.e., popularity pattern, cache size, content popularity fluctuations), as well as on the actual topological characteristics of the network itself. The proposed framework requires that ICN architectures adopt hash-routing as their routing mechanism. On the other hand, and in order to maintain the inherent characteristics of the on path content placement with opportunistic request-to-cache routing, the approach presented could be also applied to a partially coordinated caching scheme similar to the one in [63]. In such a scheme, a fraction of each router’s cache could be used to support the proposed hash-routing framework and the rest of the cache capacity could be used opportunistically to cache passing-by items. In this case, an interest packet that heads either towards the router indicated by the hash assignment function or towards the content server, searches at each intermediate router for a matching cached information item. We intend to explore such a hybrid scheme in our future work in this area.