ICN Management Considerations

This section addresses management considerations regarding specific ICN deployments and scenarios, by analyzing the opportunities, requirements and possibilities for management deployment therein. This analysis starts with the proposal of a NDN-based face management framework, followed by considerations from video adaptation, content management and network policies scenarios.

The Named Data Networking ICN architecture provides a new communication framework built on named data. Like other ICN counterparts, such as , and , NDN intrinsically supports security, routing/forwarding, reliability, caching and even mobility, aiming at scalable and more efficient content-distribution than today's IP-based approaches. Fostered by an open-source implementation , NDN has been at the heart of an active topic with several research contributions evaluating its deployment feasibility and performance in a number of scenarios . NDN relies on a hierarchical, human-readable namespace to address named data objects, where the naming scheme is simultaneously used to both name information and to route it. It relies on content requesters sending an Interest packet with a Content Name, where the prefix can provide information for global and organizational routing, while the suffix indicates versioning and segmentation details. When a node receives an Interest packet asking for content which matches what is already available at the node, it responds with a matching Data packet carrying back the content. Each NDN node comes with a set of supporting data structures which enable the coordination between the transmission of Interest packets with the reception of the corresponding Data packets. These structures include: Content Store: maintains an indication of locally available content, according to name, and is used for Interest packet matching. If the content is available at the node, the Interest packet is consumed, and a Data packet with the respective content is sent towards the request origin. Pending Interest Table (PIT): keeps track of Interest packets seen previously by the node, on their way to locate matching content. Interest packets in the PIT were not matched to content available in the node. Basically, PIT maintains a degree of state regarding Interest packets, mapping them to a corresponding egress network interface. Forward Information Base (FIB): associates named data to potential holders of the content. A routing protocol can populate the FIB (although this is outside the scope of NDN) or it can be populated through registration in a local NDN store. NDN introduces the concept of a Strategy Layer, which can control Interest packet forwarding behavior. It basically determines which is the best interface (or set of interfaces) to send an Interest packet. The "strategy" component establishes a pre-configured algorithm for tackling Interest packet decisions, ranging from sending it sequentially on each interface until a Data packet is received, to evaluating which interfaces provide better performance (i.e., lower average RTT) in retrieving certain content (as discussed in ). It is important to keep in mind that NDN replaces the commonly used term "interface" with the term "face", since packets can be forwarded over hardware network interfaces as well as between application interfaces, further acknowledging the information dissemination capabilities of ICN. This aspect is considered in and , where programs can be associated to the NDN governing structures (like the FIB), defining configurations such as "sendToAll" and "sendToBest" with respect to managing the content reaching process. Corujo et al. exploit these concepts enabling management mechanisms to be deployed, and steer network operations and NDN operation, as described in the following section.

An important aspect supporting network management procedures is the interaction of network information residing at the network side with information about the network from the perspective of clients connected to it. The former includes, for instance, information stored in the network operator core about user profiles, associated policies, or data collected by the access network equipment, such as current and past traffic load levels, active flows, and maintenance information. Today, such information can be retrieved for management and operation support through dedicated signaling protocols (e.g., , ), or Operation Support Services (OSS) web services. The client point of view of the network includes information that, for example, a wireless terminal can provide, indicating wireless link quality, average return-trip times (RTT) or perceived Quality of Experience (QoE). Both types of information can be capitalized upon allowing, for example, the network to coordinate network management procedures, considering as input information obtained from other network elements as well as from user nodes. One way to generate management information in network entities and at client nodes, as well as to consume and act upon it (i.e., using the management information exchange as a control channel) is to couple NDN nodes with Management Agent (MA) entities. Fig. 1 (redrawn here from for convenience) illustrates how a MA can be deployed in both network and client entities, interfacing with different operational aspects and protocol layers of an NDN node. By using NDN content reaching and disseminating mechanisms, management information can be consumed by the MA to steer not only the behavior of application processes and network interfaces, but also to interface with NDN supporting structures (i.e. Content Store, FIB, PIT). Effectively, different kinds of information can be conveyed to a network node responsible for managing the network (under different perspectives and processes), and resubmitted back towards client nodes, affecting the way applications interface with network interfaces and the NDN fabric.

|WLAN | | +------------^-+ +-+----+ +---+ | +------+ | +---------+| | Face 1 | | +--------------+ +------+ +---+ | +------+ | |Pending <--------+| | | <---->|LTE | | |Interest Table| +------+ +---+ | +------+ | +--------------+ | | | Face i | | +------+ +---+ | +------+ | +--------------+ | | | | <---->| MA | | |Forward | +------+ +---+ | +------+ | |Information <---------+| | Face j | | |Base | +-+----+ +---+ | +------+ | +--------------+ | <---->|VoIP | | +---+ | |Video | +------------------------------------------+ +------+ ]]> Figure 1. NDN Management Framework MA can interface with the PIT and FIB structures, acting as a dynamic, application- and/or network-controlled interface to the strategy layer. This could also be used to direct how to forward NDN Interest and Data packets, in a configurable manner. Regarding network interfaces, the MA can interface with them not only to control (i.e., initiate wireless access scanning procedures), but also to collect information (i.e., an informational event regarding detected access points). Finally, the MA can also interface with application processes, drawing out information about the perceived QoS/QoE (e.g., lost packets or delay from a real-time video feed) and also to execute commands, such as selecting a better video codec when the network commands the video flow to be accessed from a different wireless access interface. Conversely, MA entities residing in network equipment can provide informational events as well, but related to network-side link layer characteristics (such as number of attached nodes or load), as well as accepting commands from the network (i.e., activate maintenance procedures). Management processes residing in the network core can leverage information collected from applications, client terminals and network equipment, to drive optimization procedures. Such optimization procedures can also tap into other entities, containing complementary information such as policies and subscription information, and use it to produce an overall network decision, which can then be forwarded to multiple client nodes, in a policy enforcing way. An important consideration from the NDN architecture, is the hierarchical namespace, allowing nodes to request and convey management data, by simply using an appropriate prefix (e.g., ccn://domain/management/ME). By leveraging the NDN information-centric dissemination mechanisms to convey management information and commands as content, these management extensions inherit the intrinsic capabilities of the NDN architecture, including security and reliability, which are fundamental for management procedures.

In order to implement management operations, besides the interfacing capabilities of the MA entity mentioned in the previous section, a management framework needs other supporting mechanisms in order to provide the envisioned management capabilities, while maintaining the inherent NDN capabilities. Concretely, when nodes connect to the network, the management entities need to become aware of the management capabilities of the newly-connected node. In addition, an asynchronous information exchange capability needs to be provided, allowing not only the request of management information, but also the ability to push information towards a remote node (i.e., sending a command or an informational event).

The discovery procedure is illustrated in Fig. 2 (redrawn from ), and borrows for the procedures described in . The procedure starts with the newly connected User Equipment (UE) broadcasting an Interest packet (Fig. 2:1) perhaps with a well-known content name (e.g., ccn://domain/management/mgmt-case/ME) to its local network.

| | | |(2) DATA | |<-/domain/management/mgmtm-case/ME------------------| |(Signature, ME-publisher-id, key locator | | DATA:supported security mechanisms) | | | |(3) INTEREST | |-/domain/management/mgmt-case/ME/MA-published-id/ ->| |(encrypted with ME's PK:security-mechanism, SKey) | | | |(4) DATA | |<-/domain/management/mgmt-case/ME/MA-publisher-id/--| |(encrypted with ME's PK:security-mechanism, SKey) | | DATA: Session Key received | | | |(5) INTEREST | |<-/domain/management/mgmt-case/MA-publisher-id/-----| | /nonce (encrypted) | | | |(6) DATA | |-/domain/management/mgmt-case/MA-publisher-id/----->| | /nonce (encrypted) | | DATA: Encrypted nonce received | ]]> Figure 2. Secure Management Session Establishment The "mgmt-case" part of the name can be used to select different aspects of management capabilities allowed by a Management Entity (ME) (i.e., a management decision point in the network). The ME then replies to this Interest with a Data packet (Fig. 2:2), providing its shorthand identifier (i.e., ME-publisher-key) and a key locator, indicating how to retrieve its public key (assuming it is authorized by another key trusted by the UE). In this way, the MA at the UE recognizes the ME as a valid signer (and provider) of management content. A session key, Ks, is generated by the MA, considering an encryption algorithm from the ones indicated by the ME in the Data packet. The MA then expresses its desire to receive (and reply to) Interests matching a specific NDN name associated with the management service (e.g., ccn://domain/management/mgmt-case/ME/MA-publisher-id), where MA-publisher-id uniquely and globally identifies the MA, through a cryptographic digest of its public key. After this, the MA sends an Interest packet (Fig. 2:3) to retrieve management Data from the ME containing the short-hand identifier of the MA (MA-publisher-id), the chosen encryption algorithm and session key (Ks), both encrypted with the public key of the ME. In this way, the confidentiality of the content exchanged between the ME and the MA is guaranteed. The ME responds with a Data packet (Fig. 2:4) signaling the reception of the session Key. Before the actual exchange of management data begins, the ME generates a challenge (i.e., a nonce) which is sent via an Interest packet (Fig. 2:5) to the MA, indicating through a named data name that it requests the reception of the response to this challenge, sent by the MA using a Data packet (Fig. 2:6). This allows the ME, after verifying the signature of the Data packet, to verify that the encryption algorithm and the session key are valid for the MA, making it ready to exchange information for coordinating management procedures in the network.

After the discovery and security establishment procedures have been finalized, the framework provides the capability for both the MA and the ME to securely obtain management content from one another. In order to push unsolicited content, a dual Interest/Data procedure can maintain compatibility with the Interest and Data exchange/consumption of the NDN architecture. Fig. 3 (redrawn from Fig.2 of ) illustrates the procedure which is initiated by the MA. In this case, the MA intends to push management information to the ME. It does so via an Interest packet manifesting its interest in receiving management content with a local sequence number. This sequencing allows the recovery of new content over cached content. If the ME is interested in retrieving content from the MA, it answers back with a Data packet, where it indicates that it is willing to receive management content. Then, the ME sends an Interest packet to retrieve the management data with the sequence number provided by the MA, which responds with a Data packet containing the information it wanted to push into the ME.

As a proof-of-concept, a software prototype of the management framework, was developed for , using the CCNx Java API . At this early stage, it includes the implementation of an ME and an MA as NDN applications, supporting the NDN management operations outlined in Fig. 3. Thus, the ME and the MA can push unsolicited content to each other, related with management operations. To validate this basic prototype, considered a specific use case supported by the framework, i.e., face management. This entails configuring and selecting an appropriate face in a UE to retrieve a given content. Based on the CCNx, an evaluation test-bed was deployed including an NDN UE (featuring an MA and a set of network interfaces), a content server and a network node (featuring an ME). These entities are interconnected by a set of NDN routers. The purpose of the evaluation scenario is to demonstrate feasibility for the protocol exchanges mentioned earlier. Note that the code has been tested in a small-scale environment where the ME is topology-aware and keeps track of conditions of the access networks that are available to the UE. Thus, the ME can provide the MA with management information reporting the appropriate face for content retrieval, or an alternative point of access that could be used to improve the performance. The MA uses the management information to reconfigure the FIB (and possibly the network interfaces) in the UE, setting the appropriate face to forward subsequent Interests. For validation purposes, a local application was also implemented at the NDN UE that works similarly to a ping utility, generating periodic Interests that match a given prefix (served by the content server), and computing the Round Trip Time of each Interest/Data exchange. The RTT values obtained by this application in , indicate that the performance of the NDN management framework in the considered evaluation scenario is satisfactory, given the early stage of this work. Further development and testing is ongoing.

This section investigates ICN management considerations for the delivery of video data, and especially the adaptive delivery of video. From a content perspective, multimedia is omnipresent in the Internet, e.g., producing 62% of the total Internet traffic in North America's fixed access networks . Video, and multimedia content in general, is has specific characteristics, which have to be considered and where network management consideration are necessary. The consumption of multimedia content comes along with timing requirements for the delivery of the content, for both, live and on-demand consumption. Long startup delays, buffering periods or poor quality, etc. should be avoided to achieve a good Quality of Experience of the consumer of the content. Of course, these requirements are heavily influenced by routing decision and caching, which are central parts of ICN, and which may be leveraged more efficiently by an intelligent network management.

Today's dominant streaming systems are based on the common approach of leveraging HTTP-based Internet infrastructures, which are consequently based on the Transmission Control Protocol (TCP) and the Internet Protocol (IP). Especially the adaptive multimedia streaming (AMS) via HTTP is gaining more and more momentum and resulted in the standardization of MPEG-DASH , which stands for Dynamic Adaptive Streaming over HTTP. The basic idea of AHS is to split up the media file into segments of equal length, which can be encoded at different resolutions, bitrates, etc. The segments are stored on conventional HTTP Web server and can be accessed through HTTP GET requests from the client. Due to this, the streaming system is pull based and the entire streaming logic is on the client side. This means that the client fully controls the bitrate of the streaming media on a per-segment basis, which has several advantages, e.g., the client knows its bandwidth requirements and capabilities best. As one can see, ICN and adaptive multimedia streaming have several elements in common, such as the client-initiated pull approach, the content being dealt with in pieces as well as the support of efficient replication and distribution of content pieces within the network. As ICN is a promising candidate for the Future Internet (FI) architecture, it is useful to investigate its suitability in combination with AMS systems and standards like MPEG-DASH as shown in , as well as the possibilities and benefits of intelligent network management to improve the performance of AMS in ICN as well as the resulting QoE at the client. One of the most promising aspects in this context is the possibility of ICN to consume content from different origin nodes as well as over different network links in parallel, which can be seen as an intrinsic error resilience feature w.r.t. the network. This is a useful feature of ICN for adaptive multimedia streaming within mobile environments since most mobile devices are equipped with multiple network links. Here, a focus of ICN management could be in the load balancing of such traffic between the available links. This would increase the effective media throughput of the multimedia content, however, it could potentially lead to high variations of the resulting bandwidth which is available to the client. As DASH is designed for environments with dynamic bandwidth conditions, they can be compensated in general. However, more conservative adaptation algorithms may prevent too frequent switching between the content's bitrate representations as well as compensate short-term bandwidth drops caused by network link switches more smoothly.

An ICN network aims by definition to facilitate access to and delivery of information objects (content and services). An ICN network can certainly do more, as it has been discussed in earlier sections. However, as content (in particular, video) access and delivery seems to be the dominant use case in current host-based networks, ICN networking carries content delivery as a minimum requirement. Indeed, virtually all ICN approaches so far include content delivery as a premise. In that respect, from the perspective of a content owner or provider, an ICN network functions essentially as a content delivery network. This creates a set of extra requirements for ICN. Not surprisingly, content providers and end users alike should be able to Read (consume) a content object available on the ICN network. But, in addition, a content provider needs the ability to Create (publish), Update, and Delete content. In this way, these three operations (Create, Update, and Delete) stand as the core aspects whose implications on ICN have to be considered. For example, it's not obvious how content can be deleted from an ICN network that makes extensive use of in-network caching. In addition, Accounting, which is typical required by any service provider, also needs to be tackled.

Early-phase work in NetInf management discussed a two-fold problem. The first question that arises is whether it is possible by adopting a new set of network primitives and in-network storage to usher a new type of network management. In other words, can network management become information-centric while handling often host-centric data? The second question is whether an information-centric network is more suitable for self-management mechanisms than IP-based networks are. In particular with respect to the later, introduced some design considerations for adding self-management mechanisms in NetInf. Of interest from this early work are two examples where network management can play a new role. First, network management can get involved in decisions about caching and (re)distribution of content, and not only whether an (inter)face is on or off, or what traffic limits should be enforced. Moreover, network policies can be distributed securely in the same way as other content in the network, removing the need for centralized management, and enabling improved recovery procedures. Second, network management can get involved in more intricate processes such as controlling multiaccess support, intermediating for content adaptation when deemed appropriate, and enabling richer tools for traffic engineering.