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¨ Publish/Subscribe Internet Routing Paradigm (PSIRP) (Trossen et al., 2008) and its successor, PURSUIT (Trossen and Parisis, 2012).
¨ Objects in PURSUIT are higher level, more closely related to what applications, services, or users might require.
¤ Similar to DONA or TRIAD objects.
¤ Object names are valid within a PURSUIT scope.
n They are called RIDs – Rendezvous Identifiers
¨ The creator of an object publishes it by sending a message to a scope and requesting that it assign a RID to the object
ICN: PSIRP/PURSUIT
34
¨ A scope is implemented as a set of rendezvous servers that hold a mapping between each RID in that scope and one or more lower-level network
addresses by means of which the object can be retrieved.
¤ Scopes themselves are named using a form of RID.
¨ The name of an object is a sequence of RIDs: <top-level RID, second-level RID, …, final RID>
¨ Subscriptions express interest in receiving the object.
¨ Scopes also contain a topology manager (TM), which is responsible for keeping track of where copies are stored.
¤ When a subscribe request is received by the scope, the rendezvous server contact the TM, which determines how to deliver the content to the requesting subscriber.
ICN: Network of information (Netinf)
35
¨ (Dannewitz et al. 2013)
¨ Netinf, like DONA used flat, globally unique names to identify data objects.
¨ The name of an object is defined as the hash of its contents.
¨ Netinf, like NDN, defines a standard format for the data object (in this case a MIME representation).
¨ The Netinf retrieval model is similar to DONA: a get message is
routed using the ID of the object to a site where the object is found, at which point a transport connection is opened to deliver the object.
ICN: Network of information (Netinf)
36
¨ The Netinf designers contemplate a system with regional diversity, as discussed above, and discuss two approaches to realizing this:
¤ either state is established at region boundaries as the get is forwarded so that subsequent transport connections can be linked together through that boundary point to deliver the object, or
¤ some sort of return source route is assembled in the get message to allow a response to be returned.
ICN: Network of information (Netinf)
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¨ Two modes of ID-based routing:
¤ One is a system of Name Resolution Servers (NRS), organized as a hierarchy
¤ direct routing on IDs in the routers in the system, perhaps in a local region of the network.
ICN: Discussion
38
¨ The challenge for such schemes is whether a routing scheme can be devised that can meet the scale requirements of the architecture.
¤ They are not defined as part of the architecture.
¨ Difference among them: the extent to which the data naming is embedded within the actual network architecture.
¤ NDN depends entirely on the data names and has no concept of a routable network-level address.
¤ TRIAD and DONA requires a subset of the routers to understand data names.
¤ The names in PURSUIT are used not to forward packets but only as the basis for a query to a rendezvous server.
Requirement: Architecting for Change
39
¨ How to design an architecture so that if survives over time.
¨ Expressive Internet architecture (XIA):
¤ Allow the network to use a variety of means to deliver the packet to the intended destination and to provide a range of services in the network.
¤ Packets can carry several forms of addresses at once:
n CID – content identifier
n SID – identifier of a service hosting that data
n HID – host where the service is located
n AD – administrative domain in which the CID is known.
¤ Fallback forwarding
XIA: specific features
40
¨ The various identifiers, collectively called XIDs, are specified to be self-certifying
¨ XIA gives the end-point options for bypassing or routing around points of failure in the network by cleverly using the multiaddress destination field in the packet.
¨ The scalability, control, and isolation on next-generation networks (SCION) system (part of XIA) provide a structure to break up the overall network into that are called trust domains
¤ Which allow a variety of end-point controls over routing.
Requirement: Intermittent and High-Latency Connectivity
41
¨ Delay/disruption Tolerant Networks (DTNs) were crafted to deal with these challenging requirements
¨ DTN objective is to provide a useful data delivery service in the context of vey long delays and unreliable communication channels.
¨ Forwarding must be based on reliable intermediate storage points rather than direct best-effort end-to-end forwarding.
¨ The unit of storage is not the packet, but a higher-level entity which they call a bundle.
DTN
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¨ It is similar in some respects to proposals such as Metanet, Plutarch or FII.
¨ DTN assumes devices at region boundaries that terminate transport connections, receive and reassemble bundles, and potentially store
those bundles for long periods of time until onward transfer is possible.
¨ The names for DTN bundles are of the form <region-name, entity-name>, where the region names are globally meaningful, and the entity names are only routable within the region.
¤ each of the names is a variable-length text string, rather than any sort of flat self-certifying ID.
DTN
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¨ The basic communication paradigm of the DTN architecture resembles Internet email, with (presumed reliable) Mail Transfer Agents and no architected end-to-end confirmation of delivery.
¨ Since store-and-forward nodes will have finite storage, DTNs raise complex flow control issues.
¨ DTN depends on a routing scheme that is not specified as part of the architecture but must be realized.
¤ The DTN paper proposes a framework in which routes are composed of a set of time-dependent contacts, which are assembled by a routing algorithm.
Requirement: Shaping Industry Structure
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¨ One of the requirements I listed for an architecture was its economic viability and the industry structure it induced.
¨ Proposals (from industry) for a National Information Infrastructure (NII):
¤ CSPP – Computer Systems Policy Project (now the Technology CEO Council):
n (Computer Systems Policy Project, 1994)
n High-level vision document: contains a list of requirements (access, first amendment, privacy, security, confidentiality, affordability, protection of intellectual property, new technologies, interoperability, competition, and freedom from carrier liability).
¤ XIWT – Cross-Industry Working Team
n convened by Robert Kahn at the Corporation for National Research Initiatives
n Dug deeper into the potential architecture of an NII.
XIWT – Cross-Industry Working Team
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¨ They described a functional services framework and a reference architecture model.
¨ Requirements: sharability, ubiquity, integrity, ease of use, cost effectiveness, standards, and openness.
¨ They emphasized two interfaces that were not well-defined in the Internet:
¤ the Network-Network interface (the data and control interface that defines how ISPs interconnect) and
¤ the Network Service Control Point to Network interface, which would allow for
intelligent control of the network, perhaps supporting the ability of third parties to control the behavior of the network.
Shaping Industry Structure: Discussion
46
¨ These documents did not have much influence on the technical community developing the Internet.
¨ The proposal for a NNI was not inconsistent with the current Internet
¤ It just brought a focus on an aspect that was underdeveloped at the time
¨ The proposal for a network service control point was less compatible with the current Internet.
¤ Reminiscent of the intelligent network interface being contemplated by the telephone system to allow the control of advanced services.
¤ Perhaps we see an early glimmer of software-defined networking (SDN).
Requirement: Mobility
47
¨ Key requirements for an architecture that supports mobility:
¤ separation of location from identity,
¤ accommodating intermittent connectivity and variable performance
¤ the ability to track the location of moving devices, networks and data.
¨ MobilityFirst (MF) was motivated by the desire to deal with issues raised by mobile end nodes
¤ movement of devices from one network to another and
¤ transient outages when devices become unreachable.
MobilityFirst
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¨ Two levels of binding between name and address:
¤ Naming services (NSs), map from a host, service, sensor, data, or context to a flat ID, a global unique indentifier (GUID)
¤ Global Name Service (GNS), that maps from a GUID to its current location, which is a network address, or NA.
¨ Both the destination GUID and the destination NA are included in the header of a packet
¤ Allows rapid forwarding based on the NA but also allows routers to deal with mobility and redirections by making dynamic queries to the GNS as data is moving through the network.
MobilityFirst
49
¨ Routers can store data in transit at intermediate points if the destination is temporarily unavailable
¨ Stored data is identified by its GUID until de router can determine a new destination NA.
¨ To enhance security, both the GUID and NA are public keys
¤ So anyone in possession of a GUID or NA can confirm that the binding is valid.
MobilityFirst: Discussion
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¨ GNS is a specific approach for a stable service that remembers the current location of the mobile element.
¤ The mobile end point (or mobile network) must report its current location to that service as it moves.
¤ End points that want to contact that mobile point must know how to reach that service.
¨ Dealing with mobile endpoints:
¤ MF takes a very ambitious approach: allowing for the redirection of a packet to a new point of attachment while the packet is in transit.
¤ A simpler approach would be to drop a packet if a GUID is not found at the destination NA, generate an error message, and the sender would have to determine the current valid NA.
MobilityFirst: Discussion
51
¨ GNS potential security issue:
¤ Anyone could query GNS for a given GUID and track its current location.
¨ Mobile end nodes that want to be reachable by anyone would still register their location in a public mapping service,
¤ But end node that have more restricted communication patterns might use a more private mapping service that is only available to selected
communicating parties.
Requirement: Cross-layer optimization
52
¨ There is not a specific architectural proposal that illustrates this goal.
¨ But, designers of wireless networks for highly challenging conditions (e.g. tactical battlefield networks), argue that it is necessary to
abandon the layer abstraction.
¨ Wireless technology has some powerful technology-specific features (e.g. broadcast), as well as some technology-specific limitations (e.g.
highly variable signal quality and interference levels).
Requirement: Cross-layer optimization
53
¨ The higher service layers and applications need to be designed taking into account these specific considerations, exploiting the features to
compensate for the limitations.
¨ This approach would preclude the inclusion of these networks in either an overlay or conversion internet architecture…
Requirement: Minimize the Need for Globally Unique Identifiers
54
¨ Many of the schemes depend on globally unique identifiers (for data, services, or end points).
¨ Global uniqueness can be assured in a number of ways:
¤ Hierarchical identifiers: few top-level unique prefixes (e.g. in PURSUIT)
¤ Very large identifiers: e.g. ids created using cryptographic hashes (e.g., SHA-3 produces values ranging from 28 to 64 bytes.
¨ An alternative approach is to try to avoid any need for global identifiers in addressing.
¤ E.g. NewArch’s FARA