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Tuesday, February 14, 2012

Top 10 Requirements for Future Networks (Towards an Omni-Present Internet)

Over the next ten-to-fifteen years, it is anticipated that significant qualitative changes to the Internet will be driven by the rapid proliferation of mobile and wireless computing devices.Wireless devices on the Internet will include laptop computers, personal digital assistants, cell phones, portable media players, and so on, along with embedded sensors used to sense and control real-world objects and events. As mobile computing devices and wireless sensors are deployed in large numbers, the Internet will increasingly serve as the interface between people moving around and the physical world that surrounds them. Emerging capabilities for opportunistic collaboration with other people nearby or for interacting with physical-world objects and machines via the Internet will result in new applications that will influence the way people live and work. 

The potential impact of the future wireless Internet is very significant because the network combines the power of cloud computation, search engines, and databases in the background with the immediacy of information from mobile users and sensors in the foreground. The data flows and interactions between mobile users, sensors, and their computing support infrastructure are clearly very different from that of today’s popular applications such as email, instant messaging, or the World Wide Web.
Considering the wide range of future wireless network usage scenarios (4G cellular/mobile, WLAN, mesh, P2P, DTN, sensor networks, vehicular networks, sensor/pervasive systems), it is important to extract a set of common requirements general enough to meet these needs, as well as those of future applications that cannot easily be predicted today.

It is important to note that these requirements should apply to future access networks and the Internet protocol stack as a whole in view of the increasingly predominant role of wireless end-user devices. The current approach of designing specialized networking solutions for cellular systems, ad hoc nets, sensor applications, and so on leads to undesirable fragmentation (and hence poor scalability, lack of interoperability, inefficiencies in application development, etc.) among different parts of the network, and needs to be replaced by a unified end-to-end protocol architecture that supports emerging requirements of both wired and wireless networks.

To elaborate further, basic transport services of future Internet protocols should reflect intrinsic radio properties such as spectrum use, mobility, varying link quality, heterogeneous PHY, diversity/MIMO, multihop, multicast, and so on, and the capabilities of emerging radio technologies such as LTE, nextgeneration WLAN, Bluetooth, Zigbee, vehicular standards such as 802.11p, and of course, cognitive software-defined radio (SDR). In addition, Internet protocol service capabilities should be designed to serve emerging uses of wireless technology, not only for conventional mobile communications, but also for content delivery, cloud computing, sensing, M2M control, and various other pervasive system applications. Below are some key requirements for future networks designed to support the range of wireless usage scenarios;

1. Dynamic spectrum coordination capability: Historically, network protocols have been designed to support resource management in terms of wired network concepts such as link bandwidth and buffer storage. As radios become an increasingly important part of the network, it will be useful to be able to specify and control radio resources within the networking protocol itself. For example, control protocols should be able to support dynamic assignment of spectrum to avoid conflicts between multiple radio devices within the network. Just as current IP networks incorporate protocols such as dynamic host control protocol (DHCP) for address assignment, future networks could incorporate a distributed repository of spectrum usage information that could then be used to assign nonconflicting spectrum to radio devices when they join the network.

2. Dynamic mobility for end-users and routers: As more and more end-user devices become wireless, networks will need to be designed to support mobility as a normal mode of operation rather than as a special case. This means that end-user devices should be able to attach to any point in the network (i.e., global roaming), with the network providing for fast authentication and address assignment at a very large scale. Currently available mechanisms such as DHCP and mobile IP represent a first in this direction, but a more general solution could involve a clean separation of naming and addressing where each device would have a unique name, but would only be assigned a routable address local to the network with which it is currently associated (and this routable address may be as general as a geographic location, i.e., geo-address). The main challenge is to provide a distributed global name resolution and address assignment service that scales to the level of billions of mobile devices. Because wireless devices may also serve as routers in some of the ad hoc environments discussed earlier, the network should be able to support dynamic migration of subnetworks. In addition, dynamic handoff of traffic from one point of attachment to another may be required for certain connection-oriented services.

3. Fast discovery and ad hoc routing: Because several wireless usage scenarios involve ad hoc associations and continuously changing network topology, it is important for the network to support fast discovery of neighboring network elements. Discovery protocols for ad hoc networks should support efficient topology formation in multihop wireless environments taking into account both connectivity requirements and radio resources. Multihop wireless scenarios further require efficient ad hoc routing between network elements with dynamically changing topologies and radio link quality. The ad hoc routing protocol used in wireless access networks should seamlessly integrate with the global routing protocol used for end-to-end connectivity.

4. Cross-layer protocol stack for adaptive networks: Routing in multihop wireless networks requires a greater awareness of radio link layer parameters to achieve high network throughput and low delay. This means that the network’s control plane should include information about radio link parameters to be used for algorithms that support topology discovery and routing. A key architectural issue is that of determining the appropriate granularity and degree of aggregation with which this cross-layer information is exchanged across different parts of the network (i.e., access, regional, core, etc.).

5. Incentive mechanisms for cooperation: Ad hoc mobile networking scenarios typically involve cooperation among independent wireless devices. It will be important for future Internet protocols to include protocols that enable such cooperation, first by advertising resources and capabilities to neighboring radios and second by providing mechanisms for exchange of credits or barter of resources in return for services such as relaying or multihop forwarding.

6. Routing protocols for intermittent disconnection: Today’s Internet routing and transport protocols are designed under the assumption of continuous connectivity. However, this assumption is no longer valid for mobile devices that frequently experience disconnection due to radio signal fading and/or service unavailability. Future protocols should be designed for robustness in presence of occasional disconnection. In order to achieve this, the network generally needs to be able to store in-transit data during periods of disruption, while forwarding messages opportunistically when a path becomes available.

7. Transport protocols for time-varying link quality: Reliable delivery of data on the Internet is currently accomplished using transport control protocol (TCP) for end-to-end flow control and error control. TCP is known to perform poorly in wireless access networks that are characterized by higher packet error rates than wired links, along with time-varying bandwidth caused by variations in radio channel quality and medium access control (MAC) layer contention. Future transport layer protocols should be designed to work efficiently in presence of packet errors and varying end-to-end bandwidth – this will require the ability to distinguish between congestion in the network and channel quality variations.

8. Efficient multicasting and multipath routing: The wireless channel has inherent multicast capabilities, that is, a single packet sent by a radio is simultaneously received by all receivers within the transmission range. This property can be exploited to improve network performance in various scenarios, but the routing and transport protocols have to be enhanced to support multicast operation as a core capability. Radio multicast also opens up the possibility of multipath routing in which multiple independent paths are used for routing a single packet to improve end-to-end reliability and delay.

9. Location awareness and geographic routing: As discussed earlier, emerging pervasive computing applications (i.e., vehicular, sensor, M2M) often require the ability to delivery packets to an entire geographic region rather than to a specific IP address. Also, for mobility services, knowledge of the current geographic location is central to providing various new services such as navigation and geographic search. This means that future networks should provide location information as a basic control plane capability. In addition, it would be desirable to optionally offer geographic multicast and routing modes by which packets can be delivered to a specified geographic region.

10. Content- and context-awareness: A number of future network service scenarios involve content addressability or content routing. For example, an M2M application might involve a query for a particular functionality (such as “printer”), and it would thus be useful if the network protocol can resolve a content query to one or more specific network addresses. Another network capability to be considered is that of content routing by which network routers forward traffic based on content attributes of the data being carried.

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