4.3 Supporting Mobility in a Clean-slate ICN Architecture
4.3.1 Framework overview
The framework proposed in this section aims to enhance the ETArch architecture with IEEE 802.21 mechanisms, providing the ETArch controlling entity (i.e., the DTSAs) with context information about the link layer of both underlying network entities and MNs as well as with mechanisms to facilitate and optimize handover procedures. In doing so, ETArch can target a whole new set of network management scenarios, enabled and supported by the context information and mechanisms provided by IEEE 802.21. The specificities of the content being delivered, the number of users requesting the same content (i.e., subscribed to the same workspace), and the link conditions of wired and wireless networks are factors that can help to enhance content-reaching procedures ensuring that the content is sent to the subscribers through the most optimal path. For example, by leveraging context information of the link-layer, the DTSA becomes aware of the link conditions of MNs connected to the network under its domain, as well as neighbor PoAs detected by the MN, including their link parameters and conditions, which can then be used to control and optimize handover procedures of the MNs. Likewise, the DTSA can use this context information to (re)configure the flows across the whole network by using OpenFlow capabilities, aiming to optimize the usage of the network resources.
An overview of the proposed framework merging both ETArch and IEEE 802.21 mechanisms is presented in Figure 4.10.
The DTSA (i.e., the controlling entity) is the central entity responsible for the registration of DTS entities and management of DTS workspace. As such, it communicates with network entities via OpenFlow so it can (re)configure the DTS workspaces via OFPT FLOW MOD messages. As in the previous section, the proposed framework in this section also envisages the configuration of OpenFlow flows up to the network side endpoint, such as wireless network point of attachments (e.g. WLAN Access Point). This is required because DTS workspace configuration needs to be configured in every equipment in the path between endpoints, including the PoAs. Finally, DTS-enabled clients, which are represented in Figure 4.10 as the MNs, communicate via ETCP protocol with the DTSA.
Figure 4.10: Proposed IEEE 802.21-enabled ETArch framework
and core network entities via the MIH protocol of the IEEE 802.21 standard, allowing it to acquire context information about their link layer. In addition, using the MIH protocol, the DTSA is able to communicate with MNs to also acquire context information about their link layer (e.g., current signal strength and detected PoAs) but it is also able to assist MNs in the handover procedures. The technology-abstraction of IEEE 802.21 enables the proposed framework to be applied to different access technologies, both wireless (such as, WLAN, LTE and WiMAX) and wired (such as, Ethernet) technologies.
With these extensions, the DTSA becomes able to dynamically and preemptively extend DTS workspaces towards the handover candidates (i.e., PoAs) detected by the MN while it moves, mitigating the effects of the handover procedure.
The proposed framework is composed by three main entities: (i) DTSA; (ii) EDOBRA switch (i.e., an edge or core switch); and (iii) MNs. Next, each of these entities is described individually.
22.214.171.124 Domain Title Service Agent
The DTSA is the controlling entity of the proposed framework, acting as an OpenFlow Controller for implementing the DTS workspaces in the network, and as a PoS for acquiring link-layer information of the entities under its domain and for assisting in the handover procedure of MNs. Its internal architecture is depicted in Figure 4.11,
4.3. Supporting Mobility in a Clean-slate ICN Architecture 115 on which the dashed modules are the ones developed under the scope of this work and the remaining modules corresponding to the base implementation of the DTSA.
Figure 4.11: DTSA internal architecture
In what concerns its base operation, the DTSA is responsible for storing information about registered DTS entities (via Entity Manager module) and DTS workspaces (via Workspace Manager module), acting as an OpenFlow Controller to (re)configure the forwarding tables of the EDOBRA switches so that DTS workspaces are implemented in the underlying network. Regarding the extension to support mobility, it acts as an PoS (via Mobility Manager module) responsible for handling and controlling the mobility procedures of registered MNs, and to acquire context information from the link-layer of the network entities and MNs under its domain. These functions are interfaced by a central module (NetConnector Manager module) responsible for forwarding messages between the managers and the corresponding resource adaptors. The OpenFlow Resource Adaptor handles OpenFlow messages, while the MIH Resource Adaptor handles messages from the MIH protocol. Finally, it features a MIHF for exchanging MIH protocol messages with remote IEEE802.21-enabled entities, namely network entities (e.g., core switches and PoAs) and MNs.
126.96.36.199 EDOBRA Switch
The EDOBRA Switch (depicted in Figure 4.12) is an extension of a standard OpenFlow switch enhanced with IEEE 802.21 capabilities.
Besides storing information on how packets of each DTS workspace should be treated (in the form of flow entries) and executing data packet forwarding operations regarding its operation as an OpenFlow switch, the EDOBRA Switch uses IEEE 802.21 mechanisms for controlling and monitoring the link layer of its network interfaces. It incorporates a Link SAP for each network interface, which abstracts the upper layers on the specificities of each link technology in what concerns the control and monitor
Figure 4.12: EDOBRA Switch internal architecture
operations of the corresponding interface. For example, whenever a new MN connects or disconnects from a given access network, the Link SAP of the corresponding interface generates an event towards entities that subscribed that event. The Link SAPs are locally interfaced by an MIHF that enables its interaction with remote entities, such as the MN and the DTSA. If the EDOBRA Switch is on the edge of the network, as part of its operation over the ETArch architecture, it is responsible for (de)encapsulating ETCP messages into OpenFlow messages. More specifically, incoming ETCP messages from DTS-enabled clients are encapsulated into OFPT PACKET IN messages and forwarded towards the DTSA, and ETCP messages originated in the DTSA are extracted from the OFPT PACKET OUT messages and forwarded towards the DTS- enabled clients.
188.8.131.52 Mobile Node
The MN (depicted in Figure 4.13) represents a mobile DTS-enabled client that establishes connection with the network.
The MN may be equipped with one or more access technologies, either wired (e.g., Ethernet) or wireless (e.g., WLAN or 3G). The MN is coupled with a Mobility Manager module responsible for handling and assisting the handover procedures. An MIHF is deployed in the MN, allowing higher-layer entities in the device itself (e.g., Mobility Manager module) or external network entities (e.g., DTSA) to control the links and to retrieve context information in an abstract way. Each Link SAPs is responsible for controlling and monitoring a specific network interface, abstracting the upper layers from the specificities of each link technology. Thus, the MN is able to e.g. retrieve the link conditions related with its current connection or provide information about other PoAs on its range. Regarding DTS procedures (e.g., entity registration, workspace creation and workspace (de)attachment), the MN contains a DTS Enabler (i.e., DTS
4.3. Supporting Mobility in a Clean-slate ICN Architecture 117
Figure 4.13: Mobile Node internal architecture
socket implementation) that allows it to exchange ETCP protocol messages with the DTSA and to send/receive messages to/from subscribed workspaces.