Delay-Tolerant Networking Y. W. Chung
Internet-Draft M. W. Kang
Intended status: Informational Y. Kim
Expires: May 17, 2018 Soongsil University
November 15, 2017
Extension of Probabilistic Routing Protocol using History of
Encounters and Transitivity for Information Centric Network
draft-chung-dtn-extension-prophet-icn-00.txt
Abstract
This document proposes extension of probabilistic routing protocol
using history of encounters and transitivity (PRoPHET) for
information centric network.
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Table of Contents
1. Introduction ................................................. 2
2. Conventions and Terminology .................................. 3
2.1. Conventions ............................................. 3
2.2. Terminology ............................................. 3
3. Forwarding of Interest and Data for ICN ...................... 3
3.1. Delivery predictability of PRoPHET ...................... 3
3.2. Extension for Interest forwarding ....................... 4
3.3. Extension for Data forwarding ........................... 5
3.4. Operation of the proposed extension ..................... 6
4. Security Considerations ...................................... 6
5. IANA Considerations .......................................... 6
6. References ................................................... 7
6.1. Normative References .................................... 7
6.2. Informative References .................................. 7
1. Introduction
In Information centric network (ICN), a node requests Data by
sending Interest packet and this Interest packet is forwarded
through ICN routers. A router with the requested Data replies to the
Interest to the requester and the Interest is delivered through a
reverse path of the forwarded Interest. ICN router manages content
store (CS), pending interest table (PIT), and forwarding information
base (FIB) [George2014]. In CS, cached data is stored for future use.
In PIT, the information of Interest, the incoming and outgoing faces
of the Interest are stored, and this information is used to deliver
Data to the requester using the reverse path of forwarded Interest.
FIB is used to forward Interest to appropriate faces.
ICN is considered important for communication of urgent messages in
disaster situations [Edo2014]. In disaster situations, communication
infrastructure is destroyed and networks are fragmented. In
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fragmented networks where connectivity between the nodes at
different fragmented networks is not possible, opportunistic network
such as delay tolerant networks (DTN) can be used to deliver
messages. In DTN, a message is delivered to a destination node via
opportunistic contacts between intermediate nodes in a store-carry-
forward way.
Since forwarding of Interest and Data should be carried out
opportunistically using DTN in fragmented networks, forwarding
schemes of Interest and Data in connected ICN networks should be
extended to accommodate the disruptive characteristics of DTN. In
this draft, we consider probabilistic routing protocol using history
of encounters and transitivity (PRoPHET)[RFC6693] for extension.
Then, we propose forwarding schemes for Interest and Data of ICN.
2. Conventions and Terminology
2.1. Conventions
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
2.2. Terminology
TBD
3. Forwarding of Interest and Data for ICN
3.1. Delivery predictability of PRoPHET
In PRoPHET, delivery predictability is defined between any two nodes.
The delivery predictability between node A and node B i.e., P(A,B),
increases whenever node A and node B contact as follows:
P(A,B)=P(A,B)_old+(1-delta-P(A,B)_old)*P_encounter,(1)
where delta sets an upper bound for P(A,B) and P_encounter is a
scaling factor to control the rate of increase [RFC6693].
Also, it decreases as time elapses since the last contact as
follows:
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P(A,B)=P(A,B)_old*gamma^K,(2)
where 0<=gamma<=1 is an aging constant and K is the elapsed time.
Finally, the delivery predictability has a transitive property,
i.e., if node A and B encounter frequently, and node B and node C
encounter frequently, then node A probably encounters node C.
3.2. Extension for Interest forwarding
Conventional DTN routing protocol is based on push model and the
destination of a message is a specific node. However, pull model is
used in ICN and Interest is forwarded based on content name, rather
than node ID. In order to forward Interest to appropriate nodes
which have the requested Data in its CS, the delivery predictability
of a node A for the Interest i corresponding to the requested Data
is defined as P(A,N(d_i)), similar to Eq. (1) as follows:
P(A,N(d_i))
=P(A,N(d_i))_old+(1-delta-P(A,N(d_i)_old)*P_encounter,(3)
where N(d_i) represents a set of nodes with the Data corresponding
to Interest i in its CS.
In Eq. (3), P(A,N(d_i)) increases whenever node A contacts another
node which has d_i in its CS, where the number of nodes having Data
d_i is generally larger than 1, since d_i can be cached in multiple
nodes by adopting the ICN approach. Similar to Eq. (2), the delivery
predictability of a node to a node set N(d_i) decreases as time
elapses since the last contact. We note that if node A has Data d_i,
P(A,N(d_i))=1.
When node A and node B contact, Interest i stored in node A is
forwarded to node B, if P(A,N(d_i)) < P(B,N(d_i)), since node B is a
more probable node to deliver Interest i to a node having d_i than
node A. In this case, the information of requester nodes for
Interest i is also delivered to node B. The information of requester
nodes for the same Interest i stored in both node A and node B is
shared, irrespective of the comparison of delivery predictabilities.
For example, if node A has Interest i with requester R1 and if node
B has Interest i with requester R2, both node A and node B have
information of requesters R1 and R2 for Interest i after contact.
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3.3. Extension for Data forwarding
For the delivery of Data in DTN, there is no known reverse path like
the one using PIT in ICN. Therefore, Data also should be delivered
using DTN routing protocol, too. In the proposed extension, the
information of requesters for the considered Data is used to forward
the Data. If the number of requesters for the Data corresponding to
Interest i is only one, the forwarding scheme of conventional
PRoPHET can be applied directly since the destination of the Data is
a requester node and forwarding is carried out based on node ID.
That is, if P(B,R(d_i)) is larger than P(A,R(d_i)), the Data d_i is
forwarded to node B, where R(d_i) is defined as the requester node
for the Data corresponding to Interest i.
If there are multiple requesters for the Data corresponding to
Interest i, current forwarding scheme of PRoPHET should be extended,
too, based on the delivery predictability relationship of two
contact nodes for each requester. In this draft, three forwarding
schemes for multiple requesters are presented in as examples. If
node A and B contact and node A has Data with multiple requesters,
the Data can be forwarded to node B if any of the following
condition is met depending on the selected policy:
1) if the delivery predictability between node B and a requester is
larger than that between node A and the corresponding requester for
any requester,
2) if the delivery predictability between node B and a requester is
larger than that between node A and the corresponding requester for
all requesters,
3) if the average of the delivery predictabilities of node B and
requesters are larger than that between node A and the corresponding
requesters.
For example, if node A has Data d_i with requesters R1 and R2 and if
node B does not have Data d_i already when node A and node B contact,
Data d_i in node A will be forwarded to node B depending on a Data
forwarding policy as follows:
1) if P(A,R1(d_i))