© 2006 BBN Technologies 1SPINDLE Project Intentional Naming and Deferred Binding in DTN Prithwish...

1SPINDLE Project

© 2006 BBN Technologies

Intentional Naming and Deferred Binding in DTN

Prithwish BasuBBN Technologies

[email protected]

DTNRG meeting, IETF 71Philadelphia, March 13, 2008

2SPINDLE Project


Outline

• Intentional naming• Persistent deferred binding in DTN• Example: Addressing by location and role• DARPA DTN demonstration

3SPINDLE Project


Intentional Naming

• A DTN application registers with its attributes• User node addresses an endpoint by a predicate on

some attributes = intentional destination name• Intentional name needs to get resolved to the

appropriate application(s) now or in future– Delivery to an intentionally named endpoint ~ querying a

distributed database– Name has persistent delivery semantics

• Related work– MIT’s INS, but our focus is on DTN– Berkeley’s P2 system (Declarative Routing)

4SPINDLE Project


Examples of Use Cases

• Heterogeneous network names– DNS name, IP addr, telephone number, etc.– Source can send bundle to “Node with IPv6 address A”

• Descriptive location and role based addressing– Node(s) within 100m of bridge at (Lat,Long)– All soldiers with rank lieutenant or higher in building B

• Authorization based addressing– All personnel with Top Secret clearance

• Node-attribute based addressing– All nodes with at least 100GB of free storage– Sensor nodes reporting temperature > 45 degrees C

5SPINDLE Project


Expressivity of Names

• How expressive should names be?– Basic: aliases– Intermediate: (a1 > v1) ((a2 < v2) (a3 == v3)) – Advanced: Body of a Horn clause in Logic Programs– Semantic Web motivation: OWL Description Logic Programs– Query models: SQL queries, PROLOG goals, SPARQL, etc.

• Delivery Semantics– Unicast: dtn:intent:uni#president(BBN)– Anycast:

dtn:intent:any#within(restaurant,FenwayPark,1km)– Multicast:

dtn:intent:all#within(restaurant,FenwayPark,1km)

6SPINDLE Project


Name Scheme

• Adhere to the <scheme>:<ssp> syntax but define “ssp” further

• Applications register their attribute(value) information– dtn:app#attr1(val1),attr2(val3),attr3(val3)

• Bundle’s destination field has an intentional name– dtn:intent#attr1(val1),attr2(val2)– dtn:intent#attr1(val1);attr1(val2)– dtn:intent#pred1(attr1(val1),attr3(val3))– …

• Semantics: DTN endpoint(s) which can satisfy the query are potential recipients of the bundle

• The predicate query can be complex as long as it can be executed in the network at the appropriate node

7SPINDLE Project


Name Resolution and Persistent Deferred Binding

• Complete resolution may not be possible at source– Source may not know about potential bound endpoint(s)– Source may have stale information

• Hence, perform progressive resolution– Resolve portion of the name that can be resolved with

available information in the local KB– This may not disclose the identity of ultimate endpoint(s)– But may forward the bundle toward a node that can help

make progress (so ultimate binding is deferred)– Persistent: a query can lie dormant in a node until the

predicate evaluates to true at a later time (can happen in mobile scenarios)

• In the general form, this is the semi-join problem in distributed DBs and is hard, especially in DTN– But several scenarios may be more tractable

8SPINDLE Project


dtn:intent#within(role_id(yellow),coord(X,Y),10)

(X,Y)

r = 10

GRAIN: Gradient-based Resolution Algorithm for

Intentional NamesDisseminate GPS

location to neighbors

SGeog-route STEM stage

only coord(X,Y) is resolvedMetadata Ext Block = STEM

Predicate-scoped FLOODrole_id(yellow) is resolved

Metadata Ext Block = FLOOD

Persistent deferred deliveryto descriptively named groupsunder disruption & mobility

9SPINDLE Project


Example: Intentional Names Based on Role and Geographic Attributes

Fort A P Hill, Virginia

sourceDestination = dtn:intent#within(role_id(rifleman),coord(long,lat),radius),policy(geogrouteallnbrs)

10SPINDLE Project


Notional Architecture: Name Attribute Dissemination

11SPINDLE Project


Notional Architecture: Resolution

12SPINDLE Project


Architectural and Algorithmic Issues

• Scalability for the general case– Semi-join problem in DTNs becomes hard as #attrs grows

• Incremental Deployment– All DTN nodes may not be running LB decision plane– We need tunneling with Bundle-in-Bundle encapsulation,

because the original bundle fields such as intentional name cannot be altered

• Security concerns– DOS attack due to multi/anycast feature of names– Made worse due to persistence– Verify that the name resolution was done by a trusted

party

13SPINDLE Project


BACKUPS

14SPINDLE Project


Semi-Join Problem in Distributed DBs

• Consider name dtn:intent#guardian(N,X),student(X,bostonlatin)– N is the main unbound variable = canonical name attribute– Want to deliver to guardians of all students of Boston Latin

• Tables/predicates: guardian, student– Could be base facts: guardian(tom,john),

student(john,bostonlatin)– Or inference rules: guardian(X,Y) :- father(X,Y) ; mother(X,Y)

• Even if rules/ontologies are known, all base facts may not reside on the same node– … so the goal can be evaluated at a resolver only by

performing a semi-join on the tables guardian and student• This is hard to do in the general case, especially in DTN

– So we need techniques for synchronizing fact bases for increasing the probability of successful resolutions

15SPINDLE Project


Expressive Overlap of Description Logic with Logic

Programs

Extracted from Grosof et al., WWWC 2003“Description logic programs: combining logic programs with description logic”

First OrderLogic

DescriptionLogic

Horn LogicPrograms

DescriptionLogic

Programs

LogicPrograms

[Negation asFailure]

[ProceduralAttachments]

© 2006 BBN Technologies 1SPINDLE Project Intentional Naming and Deferred Binding in DTN Prithwish...

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