以内容为中心的新型网络架构设计与缓存机制研究

发布时间：2018-12-21 14:34

【摘要】：随着网络中内容分发需求的日益增长,传统TCP/IP网络在以内容分发为主的网络环境中的弊端日益突显,因此信息中心网络(Information-Centric Networking,ICN)得以提出和发展。ICN实现了从以主机为中心的IP架构到以内容数据为中心的架构演变,通过网内缓存机制使得中间路由节点可以缓存和提供内容副本,从而提高了内容分发效率。此外,ICN基于内容名路由,以无连接的方式来进行通信,天然的支持移动性。然而,目前基于ICN的网络架构方案都是完全替代IP网络式的方案,这存在两个方面的问题:一是全局网络问题,即路由性能、IP兼容性等方面的问题导致架构可行性不足,在可预见时间内难以部署实施,但是对于以内容分发为主的网络环境,TCP/IP网络存在较大的弊端;二是边缘网络移动性问题,即ICN移动性方案要求用户在切换后重新发送请求,导致切换中断时延较大。同时,由于ICN节点缓存空间有限,需要部署高效的缓存机制来优化架构的缓存性能。然而现有的反应式缓存方案存在缓存冗余性等问题,导致缓存命中率较低,并且无法解决移动用户重传请求产生的切换等待时延问题。因此,本文针对上述网络架构和缓存机制存在的问题,提出了新型架构方案和对应架构场景的缓存机制。本文主要贡献如下:(1)针对目前ICN架构研究中的全局可行性问题,本文提出和实现了一种基于IP网络的网内缓存架构方案CAIP(Caching Anywhere in IP networks)。CAIP方案通过定义携带内容标识的IP选项和新型路由节点,在IP网络中实现了网内缓存机制。该方案提出了 IP路由和缓存索引查找相结合的路由方案,以及逐跳确认和转发分离的新型可靠传输方案,从而一方面可以兼容TCP/IP协议,另一方面高效可靠得实现了网内缓存。最后,基于Linux内核开发的系统平台,验证了 CAIP架构可以有效提高内容分发效率。(2)针对CAIP架构存在的缓存性能问题,本文设计了一种反应式协同缓存方案。该方案通过让路由节点与其邻居节点之间交互缓存信息,减少了缓存冗余性。当节点缓存空间不足时,首先以最大化本地缓存内容价值为目标进行本地内容更新;其次结合邻居节点的缓存空间因素、邻居节点路径因素和内容价值因素,将本地替换出的内容分配至邻居节点,充分利用了节点的缓存资源。最后,通过仿真验证了该缓存方案可以有效提升缓存性能和减少内容获取时延。(3)针对CAIP架构存在的边缘移动性问题,本文提出了一种CAIP与SDN技术结合的无线缓存网络架构,即利用SDN技术对CAIP架构的边缘无线局域网进行集中化管理。SDN控制器维护了无线接入点的内容缓存和用户的二层信息,从而实现了 CAIP架构对边缘移动性的支持。同时,基于CAIP-SDN架构提出了一种主动式移动增强型缓存方案,该方案预先缓存用户的二层流表信息和获取的内容数据。最后,仿真验证了基于CAIP-SDN架构的主动式缓存方案可以明显减少移动用户的切换时延。
[Abstract]:With the increasing demand of content distribution in the network, the disadvantages of the traditional TCP/ IP network in the network environment based on content distribution are becoming more and more prominent, so the information center network (ICN) can be put forward and developed. ICN realizes the evolution of the architecture from the host-centric IP architecture to the content data-centric architecture, enabling the intermediate routing node to cache and provide a copy of the content through the intra-network caching mechanism, thereby increasing the content distribution efficiency. In addition, the ICN communicates in a connectionless manner based on the content name route, and natural support mobility. However, the currently ICN-based network architecture scheme is a completely alternative IP network scheme, which has two problems: one is the problem of global network, that is, the problems of routing performance, IP compatibility and the like lead to the insufficient architecture feasibility, and can be difficult to deploy and implement in the foreseeable time, However, for the network environment based on the content distribution, the TCP/ IP network has a great disadvantage; 2 is the edge network mobility problem, that is, the ICN mobility scheme requires the user to re-send the request after the handover, resulting in a large switching interrupt time delay. At the same time, due to the limited cache space of the ICN node, an efficient caching mechanism is required to optimize the cache performance of the architecture. However, the existing reactive caching scheme has the problems of cache redundancy and the like, resulting in lower cache hit rate, and can not solve the problem of waiting time delay caused by the mobile user re-transmission request. Therefore, in view of the problems existing in the above-mentioned network architecture and the caching mechanism, the new architecture scheme and the caching mechanism of the corresponding architecture scene are put forward. The main contributions of this paper are as follows: (1) In view of the global feasibility problem in the current ICN architecture research, this paper proposes and implements an IP (Cached Anywhere in IP networks) based on IP network. In the IP network, the IP option and the new routing node carrying the content identification are defined, and the intra-network caching mechanism is implemented in the IP network. In this scheme, a routing scheme combining IP routing and cache index lookup is proposed, and a new and reliable transmission scheme for confirming and forwarding separation on a hop-by-hop basis is proposed, so that the TCP/ IP protocol can be compatible on the one hand, and on the other hand, the buffer in the network can be efficiently and reliably realized. Finally, based on the system platform developed by Linux kernel, it is verified that the CAIP architecture can effectively improve the content distribution efficiency. (2) In view of the problem of the cache performance existing in the CAIP architecture, this paper designs a kind of reactive cooperative caching scheme. The scheme reduces the cache redundancy by making the way of the interaction buffer information between the node and its neighbor node. when the cache space of the node is insufficient, the local content updating is firstly carried out with the aim of maximizing the value of the local cache content; secondly, the local content is distributed to the neighbor node according to the cache space factor, the neighbor node path factor and the content value factor of the neighbor node, and the cache resources of the nodes are fully utilized. Finally, the simulation verifies that the cache scheme can effectively improve the cache performance and reduce the content acquisition time delay. (3) Aiming at the problem of edge mobility existing in the CAIP architecture, this paper presents a wireless buffer network architecture combined with the technology of CAIP and SDN, that is, the SDN technology is used to centralize the edge wireless local area network of the CAIP architecture. The SDN controller maintains the content cache of the wireless access point and the two-layer information of the user, thereby realizing the support of the CAIP architecture for edge mobility. At the same time, based on the CAIP-SDN architecture, an active mobile enhanced caching scheme is proposed, which pre-caches the user's two-layer flow table information and the acquired content data. Finally, the simulation verifies that the active caching scheme based on the CAIP-SDN architecture can significantly reduce the switching time delay of the mobile user.
【学位授予单位】：中国科学技术大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TP393.02

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