Internet DRAFT - draft-ahn-manet-dsr-crri

draft-ahn-manet-dsr-crri



MANET Working Group                                         Sanghyun Ahn 
Internet Draft                                       University of Seoul
Expires: May 23, 2018                                  November 30, 2017 

                                     
   DSR Extensions for the Resolution of Cached Route Reply Implosion
                   draft-ahn-manet-dsr-crri-02.txt 

Status of this Memo

   This Internet-Draft is submitted to IETF in full conformance with the
   provisions of BCP 78 and BCP 79.  This document may not be modified,
   and derivative works of it may not be created, except to format it
   for publication as an RFC or to translate it into languages other
   than English.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF), its areas, and its working groups.  Note that
   other groups may also distribute working documents as Internet-
   Drafts.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   The list of current Internet-Drafts can be accessed at
   http://www.ietf.org/ietf/1id-abstracts.txt.

   The list of Internet-Draft Shadow Directories can be accessed at
   http://www.ietf.org/shadow.html.

   This Internet-Draft will expire on May 23, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents (http://trustee.ietf.org/
   license-info) in effect on the date of publication of this document.
   Please review these documents carefully, as they describe your rights
   and restrictions with respect to this document.







Ahn                      Expires May 23, 2018                   [Page 1]

Internet-Draft DSR Extensions for the Resolution of Cached November 2017

Abstract

   In DSR, a node can generate a route reply in response to a received
   route request if it has a fresh route to the destination in its
   route cache. However, this can incur the cached route reply
   implosion problem and DSR just tries to mitigate this problem
   by reducing the possibility of cached route reply collisions.
   This document describes how DSR can be extended for the resolution
   of the cached route reply problem. 


Table of Contents

   1.  Requirements notation  . . . . . . . . . . . . . . . . . . . .  3 
   2.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Extensions on DSR Route Request Option . . . . . . . . . . . .  3
   4.  Operations Related to C Flag . . . . . . . . . . . . . . . . .  5
   5.  Other Considerations . . . . . . . . . . . . . . . . . . . . .  6
   References . . . . . . . . . . . . . . . . . . . . . . . . . . . .  6
   Author's Address . . . . . . . . . . . . . . . . . . . . . . . . .  6  































Ahn                     Expires May 23, 2018                    [Page 2]

Internet-Draft DSR Extensions for the Resolution of Cached November 2017


1.  Requirements notation

   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 [RFC2119].

   
2.  Introduction

   The DSR protocol [1] works based on the source routing mechanism
   and support multiple routes between a source and destination node
   pair by maintaining several routes in the route cache at the source.
   However, in DSR, the route reply storm problem can happen
   because of route replies generated by intermediate nodes with fresh
   routes to the destination in their own route caches (i.e., cached
   route replies). DSR tries to solve this route reply storm problem
   by reducing the possibility of route reply collisions with adding
   a short jitter delay before the broadcast of a route reply.
   However, DSR does not try to resolve the cause of the route reply
   storm problem.

   The main reason of the route reply storm is uncontrolled
   generation of route replies at intermediate nodes, i.e., cached
   route replies. Therefore, a mechanism to control the generation of
   route replies at intermediate nodes is required for the effective
   operation of DSR. However,for the support of multipath routing,
   too tight restriction (control) on route reply generation may not be
   desirable. Therefore, when controlling the generation of route
   replies, both of these aspects need to be considered. In this draft,
   we describe how DSR Options header has to be extended to support
   the control of generation route replies.


3.  Extensions on DSR Route Request Option

   In DSR, there is no way to control the generation of cached route
   replies, so a C (Cached route reply) bit is inserted in the DSR
   Route Request option, To do that, the size of the Identification
   field is reduced to 12 bits from 16 bits.

   The Route Request option in the DSR Options header is extended as
   follows:








Ahn                     Expires May 23, 2018                    [Page 3]

Internet-Draft DSR Extensions for the Resolution of Cached November 2017


 0                   1                   2                   3
 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|  Option Type  |  Opt Data Len |     Identification    |C| Resv|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                         Target Address                        |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Address[1]                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Address[2]                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                              ...                              |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|                           Address[n]                          |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   IP fields
      The same as described in [2].

   Route Request fields
      The same as described in [2] except for the Identification field,
      the C bit and the Resv field.

   Identification
      The definition of this field is the same as that in [2].
      Only the size of this field is reduced to 12 bits.

   C
      C bit is used to indicate whether cached route replies are
      allowed or not. C bit is set to 1 if the cached route reply
      is allowed. The intermediate nodes can generate cached route
      replies only when the C bit of the received Route Request option
      is 1. Otherwise, only the destination node can generate
      route replies.

   Resv
      The reserved field for further extensions on DSR Route Request
      option.











Ahn                     Expires May 23, 2018                    [Page 4]

Internet-Draft DSR Extensions for the Resolution of Cached November 2017


4.  Operations Related to C Flag

   If a source node has to find a route to a destination, it first
   checks CRR(i), the ratio of the CRREP messages to the RREP messages
   received during previous route requests which can be computed by
   using the exponential weight moving average (EWMA).

   CRR(i) = alpha * (N_CRREP(i) / N_RREP(i)) + (1-alpha) * CRR(i-1)  (1)

   Here, CRR(i) is the CRR value of the ith route request and and
   alpha is a weight between 0 and 1. NCRREP(i) and NRREP(i) are the
   number of cached RREP messages received and the number of RREP
   messages received for the ith route request, respectively.
   If CRR(i) is greater than the given threshold CRR_TH, it broadcasts
   an RREQ message with C = 0 to discover a route to the destination
   with the adaptive CRREP generation capability.

   If a node, which is not the destination, receives an RREQ message
   with C = 0 and has the route information to the destination
   specified in the RREQ message, it decides the generation of a
   CRREP message probabilistically.
   If an intermediate node n receives an RREQ message with C = 0 and
   satisfies the condition of delta_n^'>= delta_TH^', it generates the
   corresponding cached RREP message based on the probability P_n:

   delta_n^' = delta_n - 2                                           (2)

   P_n = (delta_TH^' + 1) / (delta_n^' + 1)                          (3)

   In the above equations, delta_n is the number of 1-hop neighbors
   (i.e., the node density) of the node n and delta_TH is the threshold
   of the number of 1-hop neighbors and P_n is the probability of
   generating the cached RREP message of n. In Equation (2), the reason
   for subtracting 2 is to get the number of the neighbor nodes of n,
   delta_n^', which may generate cached RREP messages. Here, 2 reflects
   those two nodes which are the previous-hop node having sent the RREQ
   message and the next-hop node on the route. delta_TH^' is the
   threshold for an intermediate node to generate a cached RREP message
   according to P_n when it receives an RREQ message with C = 0 and
   delta_n^' is greater than or equal to delta_TH^'. In the case of
   delta_n^' = delta_TH^', with P_n = 1, the number of cached RREP
   messages generated is (delta_n^' + 1) at most. That is,
   if delta_n^' = delta_TH^', the maximum number of cached RREP
   messages generated by the node n and its 1-hop neighbors is
   (delta_TH^' + 1).

  



Ahn                     Expires May 23, 2018                    [Page 5]

Internet-Draft DSR Extensions for the Resolution of Cached November 2017


5.  Other Considerations

   TBD.


References

   [1] D. Johnson, Y. Hu and D. Maltz, "The Dynamic Source Routing
       Protocol," RFC 4728, February 2007.
              

Author's Address

   Sanghyun Ahn 
   University of Seoul 
   90, Cheonnong-dong, Tongdaemun-gu 
   Seoul 130-743
   Korea 
   Email: ahn@uos.ac.kr































Ahn                      Expires May 23, 2018                   [Page 6]