Posts Tagged ‘RLT
DTN Without Bundling
A possible objection to this architecture is that it departs from the Internet model, which is defined by the end-to-end use of IP rather than Bundling. In this section we consider the development of supporting infrastructure that would enable UDP/IP to function in much the sameway as Bundling. Such infrastructure would enable the deployment of DTN (Delay-Tolerant Networking) built on familiar Internet capabilities with no protocol modification.
We recall that IP itself is an overlay network protocol that mediates between different link layer protocols. Suppose one built a “reliable link” system that used TCP/IP tunnels, and suppose one then built IP virtual interfaces to this TCP/IP reliable link tunnel (RLT) system, and also to CFDP-RP and other systems that we have called regional protocols. This would give IP the end-to-end reliability over heterogeneous links that characterizes Bundling (Fig. 1).
Figure 1. An example of data flow in an Interplanetary Internet based on tunneling and RLI.
Tiered naming and addressing, including the late binding of names to addresses at the destination(rather than source) router, is possibly the most challenging Bundling capability to replicate within the Internet model without protocol modification. The approach considered here is to carry regional destination identifiers as URLs in HTTP 1.1 layered on top of UDP/IP. If DTN gateway nodes’ IP addresses are kept relatively stable so that they can be, in effect, usedas region identifiers, URL resolution at the HTTP layer of the destination region’s gateway node can determine the IP address of the final destination; the HTTP service can then accomplish the final intraregional hop of the end-to-end route.
Other Bundling functions could be performedat the link layer, by either the new virtual interfaces or a new reliable link infrastructure (RLI) whose capabilities would be provided to them. RLI capabilities would include:
- Management of nonvolatile storage, which would enable deferred transmission by the virtual interfaces and thus tiered forwarding.
- Custodial retransmission, giving us tiered ARQ.
- Mutual suspicion functions, yielding tiered security.
- Support for deferred delivery and service agent reanimation by virtual interfaces,yielding resilient delivery.
- Postal service notifications, informed by RLI’s custody awareness. These notifications, together with the proposed differentiated services capabilities of the Internet, would give us postal service levels.
The scope of delay tolerance in the Internet would grow as the new virtual interfaces and supporting RLI were added to hosts and routers.