COMIT: Active Content Management at Internet Scale

互联网目前在终端主机之间被动地推送比特，无论是服务器、固定或移动用户设备，还是传感器。网络不“理解”正在传输的内容，也就是说，它不知道内容。这种不可知的操作模式影响了它的几个关键功能，例如高效的内容分发和内容感知流量工程。因此，网络不能很好地应对近年来构成主要使用模式的呈指数级增长的多媒体内容访问。固定和移动网络提供商不断升级其基础设施，但由于利润率不断下降，这种情况已变得不可持续。迫切需要在主动内容管理的保护伞下重新思考流量管理，而不是被动的内容传输，使互联网服务提供商能够更好地控制流量，并为其网络的长期发展实现可持续的模式。在这种背景下，以信息为中心的网络(ICN)已成为当前主机到主机通信模式的替代方案，并建议在用户应用程序和内容本身之间进行直接通信，将实际信息或内容放在最前面，而不考虑位置。在ICN中，网络传输单独的、可识别的内容块，而不是具有不透明数据的数据容器，即分组。内容按名称标识，相关分组包含内容块的一部分；后者可以从托管服务器或网络内路由器缓存中检索，因为网络内缓存是ICN范例的一个关键方面。流行内容往往会在网络缓存中停留更长时间，而基于内容名称的“选播路由”会检索到与用户最接近的副本。这极大地增加了流量本地化，避免了闪烁的人群效应，并使网络提供商能够控制传输的信息，允许他们根据对命名内容的实际需求来设计他们的网络。尽管到目前为止，研究界已经在基于内容名称的位置无关的路由方面投入了大量的努力，但还没有找到一个被广泛接受和可扩展的解决方案。任何命名方案都必须能够容纳10**12个或更多对象，并且仅基于内容名称的内容解析和路由引起了严重的可扩展性问题。此外，当前基于IP的互联网代表着一个庞大的基础设施，不能轻易被新的、全新的设计所取代。考虑到这一点，并考虑到我们在ICN领域的大量研究经验，我们相信有可能在没有激进的ICN方法的情况下实现ICN的流量本地化和可持续网络演进的好处，而是通过在因特网体系结构中以渐进的方式引入将在当前网络层之上和传输层(即层3.5)之下运行的“内容层”。该层将截取通信，将为所请求的内容产生与位置无关的唯一名称，并将根据复杂的高速缓存策略将后者存储在网络中。内容将使用ICN操作方式以任播方式访问，但覆盖在IP上，利用基于IP的可扩展路由的存在，保持完全的向后兼容性并保护当前投资。此外，拥塞控制将在内容层内以逐跳而不是端到端的方式处理，同时保持与当前端到端操作的兼容性，同时最大限度地利用可用的网络资源，提高用户体验质量，并为未来具有严格实时要求的互联网应用铺平道路。

The Internet is currently passively pushing bits between end-host machines, be it servers, fixed or mobile user devices, or sensors. The network does not "understand" what is being transferred, i.e., it is not content-aware. This agnostic mode of operation affects several of its key functionalities, for example, efficient content distribution and content-aware traffic engineering. As a result, the network is not able to cope well with the exponentially increasing amounts of multimedia content access which constitute the major mode of use in recent years. Fixed and mobile network providers keep continuously upgrading their infrastructures but the situation has become unsustainable due to their eroding profit margins. There is an urgent need to rethink traffic management under the umbrella of active content management, rather than passive content transfer, allowing ISPs to control traffic better and achieve a sustainable model for the long-term evolution of their networks. New approaches that maximise traffic localisation are essential for long-term global network sustainability.In this context, Information-Centric Networking (ICN) has emerged as an alternative to the current host-to-host communication paradigm and proposes direct communication between user applications and the content itself, putting the actual information or content in the forefront and disregarding location. In ICN, the network transfers individual, identifiable content chunks, instead of data containers, i.e. packets, with opaque data. Contents are identified by name and relevant packets contain a part of a content chunk; the latter can be retrieved from the hosting server or from an in-network router cache, given that in-network caching is a key aspect of the ICN paradigm. Popular content tends to stay longer in network caches and "anycast routing" based on content names retrieves the closest copy to the user. This increases dramatically traffic localisation, avoids flash crowd effects and gives to network providers control over the information transferred, allowing them to engineer their networks based on the actual demand for named content.Despite the considerable amount of effort that has been invested to date by the research community in location-independent routing based on content names, a widely acceptable and scalable solution is yet to be found. Any naming scheme would have to be able to accommodate 10**12 or more objects and content resolution and routing based solely on content names raises serious scalability concerns. In addition, the current IP-based Internet represents a massive infrastructure that cannot be easily replaced by a new, clean slate design. Having this in mind, and given our considerable research experience in the ICN area, we believe it is possible to achieve the ICN benefits of traffic localisation and sustainable network evolution without radical ICN approaches but by introducing, in an evolutionary manner, a "content layer" in the Internet architecture which will operate above the current network layer and below the transport layer, i.e. layer 3.5.This layer will intercept communication, will produce unique location-independent names for requested content and will store the latter within the network according to sophisticated caching policies. Content will be accessed in an anycast fashion using ICN style of operation but overlaid over IP, exploiting the existence of scalable IP-based routing, maintaining full backwards compatibility and protecting current investment. In addition, congestion control will be dealt with in a hop-by-hop rather than an end-to-end basis within the content layer, maintaining at the same time compatibility with current end-to-end operation while maximizing the use of available network resources, increasing user quality of experience and paving the way for future Internet applications with stringent real-time requirements.