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Versions: 00 01 02 03 04 05                                             
Mobile Ad Hoc Networking Working Group                        Namhi Kang
INTERNET DRAFT                                       DASAN Networks Inc.
2 March 2006                                                Younghan Kim
                                           University of Soongsil, Korea


                    Quality of Service Extension to
                Dynamic MANET OnDemand Routing Protocol
                       draft-kang-dymoqos-01.txt


Status of This Memo

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Copyright Notice

   Copyright (C) The Internet Society (2006).






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Abstract

   This document describes extensions to the Dynamic MANET On-demand
   (DYMO) routing protocol in order to enable mobile nodes to discover
   and maintain QoS routes.  DYMO is a reactive (on-demand) routing
   protocol designed for use by mobile nodes in multi-hop wireless ad
   hoc networks.  Extensions of this document include the necessary
   additions to the routing table and the DYMO message element.


Table of Contents

   1. Introduction                                                     3
   2. Routing Table Entries for Qos Routing                            4
   3. Extensions to DYMO Message Elements                              5
      3.1. QoS Routing Element (QRE)                                   5
      3.2. QoS Route Error (QERR)                                     10
   4. QoS DYMO Operations                                             12
      4.1. QoS Route Discovery                                        12
      4.2. QoS Route Maintenance                                      13
   5. Security Considerations                                         14
   6. Revision of the Draft                                           15
   References                                                         16
   Author's Address                                                   16
   Intellectual Property Statement                                    17
   Disclaimer of Validity                                             17
   Copyright Statement                                                17


















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1. Introduction

   The DYMO routing protocol specifies a reactive means to discover a
   route to the destination for MANET nodes.  A source node disseminates
   RREQ message toward the destination node to discover a route to the
   node.  Once the RREQ message arrives at the destination node, it
   responds RREP message back to the source node over the discovered
   path by unicasting.  During such a route discovery process,
   intermediate nodes (i.e. nodes that relay the RREQ and RREP message)
   update its routing table based on the routing information that is
   present in those two messages for each direction.  DYMO also offers
   adaptation to changing network topology, which can be occurred by the
   mobility of nodes as the main cause, by means of the route
   maintenance mechanisms [1].

   In order to provide MANET nodes with QoS routes, extensions to DYMO
   message elements are required.  These extensions specify the service
   requirements (say maximum tolerable delay, maximum tolerable jitter,
   and/or minimum bandwidth limitation) that must be guaranteed by nodes
   along a route from a source to the destination.

   This document presents which extensions are required for support QoS
   in routing, how service guarantees are achieved by using the defined
   extensions without high impacts on the existing DYMO operations and
   how QoS routes are discovered and maintained are also briefly
   described.

   The extensions of this document conform to the DYMO routing protocol
   (i.e. the extentions to DYMO data structure specified in [1]).

   In this document, the extension to routing table is first described
   and then two message element extensions, QoS Route Element (QRE) and
   QoS Route Error (QRERR), are presented for supporting QoS routing.

   The keywords "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 [2].








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2. Routing Table Entries for QoS Routing

   In QoS routing, routing table entries can be defined differently
   according to the type of QoS model; per-flow based model (say IntServ
   model [3]) or per-class based model (say DiffServ model [4]).

   In case of the per-flow based mechanism, the following entries may be
   added to the routing table of each DYMO router on the path.  A
   routing table entry is defined for each flow to specify QoS
   requirements requested by the source (requestor) of the particular
   flow, where a flow can be identified by the pair of IP address and
   port number.

      - Maximum Tolerable Delay

      - Maximum Tolerable Jitter

      - Minimum Available Bandwidth

      - List of Sources Identifier Requesting Delay Guarantees

      - List of Sources Identifier Requesting Jitter Guarantees

      - List of Sources Identifier Requesting Bandwidth Guarantees,
      where the Source Identifier consists of IPSourceAddress and Port
      number.

   In case of the class-based model, on the other hand, the following
   fields may be added to the routing table of a DYMO router.  Each
   routing table entry is defined for each pre-specified class, where a
   packet belonging to each class can be distinguished by DSCP (DiffServ
   Code Point) as specified in [5].

      - Maximum Tolerable Delay

      - Maximum Tolerable Jitter

      - Minimum Available Bandwidth

      - List of Classes

      - List of Sources Identifier Belonging to Each Class



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3. Extensions to DYMO Message Elements

   In this section, we present two extensions to DYMO message element
   for support QoS route.  The work especially considers the compact
   representation for use by mobile nodes in using of limited capacity,
   the future extensions for covering various QoS parameters and the
   support of the per-flow based mechanism and the per-class based
   mechanism as well.

3.1 QoS Routing Element (QRE)

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |          Len          |    TTL    |I|A|S| Res |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                   NotifyAddress (QoS Requestor)               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                         TargetAddress                         :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         TargetSeqNum                          |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                                                               :
   :                   QoS Information Block (QIB)                 :
   :                                                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                                                               :
   :                QoS State Information Block (QSIB)             :
   :                                                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |  THopCnt  |Res|                                               :
   +-+-+-+-+-+-+-+-+                                               :
   :                                                               :
   :                    Routing Blocks (RBlocks)                   :
   :                                                               :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                    Figure 1. QoS Routing Element (QRE)

   QoS Routing Element (QRE) is an extension to the DYMO Routing Element
   (RE) in order to enable a source to discover a path that is able to
   guarantee the QoS requirements.  The QoS requirements of the source



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   are specified in the QIB (QoS Information Block) field.

   Element Type (Type)

      The Type field identifies that this element is QRE.  The field
      also specifies how the QRE is handled in case where nodes do not
      implement or understand such QoS extensions.  The data structure
      of the Type is as follows.

              0                          0
              0 1 2 3 4 5 6 7 8          0 1 2 3 4 5 6 7 8
              +-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+
              |     Type      |     =    |M| H |         |
              +-+-+-+-+-+-+-+-+          +-+-+-+-+-+-+-+-+

                                Figure 2. Type

      In QRE, M bit MUST be set to one (1) in order to indicate that QRE
      requires notification via an UERR when QRE is not understood or
      handled by a node on the path.  Therefore QRE MUST convey Noti-
      fyAddress field to which UERR is sent.  As well as the H bits in
      the Type field MUST set to (11) in order to force a node which
      does not support QRE to drop the QRE packet without processing any
      other QoS DYMO elements.

   NotifyAddress (QoS Requestor)

      IP address of the source that have originally generated this QRE
      to request a particular service.

   Most of fields conform to the DYMO message element specified in [1]
   except the newly defined two information block fields (i.e. QoS
   Information Block (QIB) and QoS State Information Block (QSIB)).
   Those two blocks are defined as follows.

   QoS Information Block (QIB)

      This field can be used differently according to the type of ele-
      ment message (i.e. whether a route request or a route reply ele-
      ment with QoS extensions).  In QRREQ message, on one hand, the QIB
      field indicates the service requirements that must be met at nodes
      along a route to the destination.  On the other hand, in QRREP



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      message, the destination uses this field to inform the route's
      resources available for the QoS requestor.  The route's resources
      are gathered or updated by intermediate nodes and contained within
      the QSIB field during the route discovery process.  The data
      structure of QIB field is described in Figure 3.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |U|QPCnt|QoS PM |Res|Traffic Cls|      QoS Param Value 1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |QoS Param Value N(if presented)|   Padding Bits (if needed)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                   Figure 3. QoS Information Block (QIB)

   U-bit (U)

      1-bit selector to indicate whether the route discovery process to
      be continued.  This bit is coupled with S bit of QRE.  If S-bit is
      set to one (1) in the QRE, then a reporting message SHOULD be sent
      to the previous hop within UNICAST_MESSAGE_SENT_TIMEOUT as speci-
      fied in [1].  At this time the two nodes (i.e. previous hop and
      QRE receiver) can detect whether the link between two nodes is
      bidirectional or unidirectional.  If U-bit is also set to one (1)
      and the link is unidirectional, then the QRE receiver is forced to
      stop the route discovery process.

   QoS Parameter Count (QPCnt)

      The most significant 3 bits, QPCnt bits, indicate the number of
      QoS parameters being presented within the QIB field.

   QoS Parameter Mark (QoS PM)

      The 5 bits marker of QoS PM field specifies which parameter is
      present in QIB to specify the service requirements.  This field
      consists of the following bit marker.

                      0                  0
                      4 5 6 7 8          4 5 6 7 8
                      +-+-+-+-+          +-+-+-+-+



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                      |QoS PM |     =    |B|D|J|R|
                      +-+-+-+-+          +-+-+-+-+

                  Figure 4. QoS Parameter Marker (QoS PM)

   B-bit (B)

      1-bit marker to indicate whether the minimum bandwidth is speci-
      fied as one of the service requirements within QIB.

   D-bit (D)

      1-bit marker to indicate whether the maximum delay (end to end
      delay) is specified as one of the service requirements within QIB.

   J-bit (J)

      1-bit marker to indicate whether the maximum jitter (end to end
      jitter) is specified as one of the service requirements within
      QIB.

   R-bit (R)

      Reserved 1 bit for the future extensions (i.e. for other QoS
      parameters such as power of a node).  Typically, this bit is set
      to zero (0) and ignored in any processing.

   Reserved (Res)

      Reserved 2 bits for the future extensions.  Typically, these bits
      are set to zero (0) and ignored in any processing.  In addition to
      these 2 bits, there exists one more reserved bit described above
      (in QoS PM field).  These three reserved bits are conceptually
      distinguished in order to support easy to implement, i.e. byte-
      oriented allocation of variable in conventional programming lan-
      guage such as C.

   Traffic Class (Traffic Cls)

      The Traffic Cls field allows mobile nodes to employ the per-class
      based mechanism (say DiffServ).  This field is specified by using
      6-bits code, called DSCP (Differentiated Services Code Points)



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      that indicate a particular class [5].

   QoS parameter value (QoS Param Value)

      The number and the type of QoS parameters depend on the first 16
      bytes of QIB as addressed above.  If B and D bit are set to one
      (1), for example, there MUST exist two parameter value fields so
      that the padding field does not needed.  QoS Param Value fields
      are defined as follows.

      - Minimum Bandwidth Requirement
         16-bit number, measured in kbits/second (kbps). The maximum
         value is about 131 Mbps (2^17 - 1 kbps).  If the required band-
         width is less than 1kbps, the value is set to one (1).  That
         is, the least bandwidth requirement the source requires is 1
         Kbps.

      - Maximum End to End Delay Requirement
         16-bit number, measured in milliseconds (ms)

      - Maximum End to End Jitter Requirement
         16-bit number, measured in milliseconds (ms)

   Padding Bits

      The Padding field of QIB is used to confirm to DYMO message ele-
      ment.  If QoS PCnt is even number then these bits are set to zero
      (0).

   QoS State Information Block (QSIB)

      In QoS routing, intermediate nodes along a path to the destination
      should inform the destination about its current state of resources
      in order that the destination is able to decide the optimal route
      among route candidates.  The number and the type of QoS State Val-
      ues depend on the QIB field.  For example, if a source specifies a
      delay parameter as a QoS requirement (i.e. D bit in QoS PM field
      is set to one (1)), there MUST exist a QoS state value in QSIB for
      presenting a delay value on candidate paths.  In this case, all
      intermediate nodes MUST accumulate its measured delay.  The data
      structure of the QSIB is illustrated in figure 5.




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   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |       QoS State Value 1       |QoS State Value N(if presented)|
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |QoS State Value N(if presented)|   Padding Bits (if needed)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

              Figure 5. QoS State Information Block (QoS SIB)

3.2 QoS Route Error (QRERR)

   QoS Route Error (QRERR) is an extension to the DYMO RERR message ele-
   ment.  QRERR message element is generated when an intermediate node
   realizes a lack of capability to maintain the QoS guarantees for a
   specific route.  The data structure of this element is as follows.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |     Type      |          Len          |    TTL    |I|Reserved |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :                         QUNodeAddress1                        :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                         QUNodeSeqNum1                         |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                           UQParam1                            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   :               Additional QUNodeAddressN (if needed)           :
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |               Additional QUNodeSeqNumN (if needed)            |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                     Figure 6. QoS Route Error (QRERR)

   QoS Unsupported Node Address (QUNodeAddress)

      The IP address of the node that cannot guarantee QoS any more.

   QoS Unsupported Node Sequence Number (QUNodeSeqNum)

      The sequence number of the node that cannot guarantee QoS, if



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      known; otherwise this field set to zero (0).

   Unsupported QoS Parameter (UQParam)

      The main difference between RERR and QRERR is the UQParam (Unsup-
      ported QoS Parameter) field which is used to inform the QoS
      requestor about which QoS parameter is no longer available for the
      originally specified QoS requirements.  Once the QoS requestor
      receives the QRERR, it re-builds a QoS route process based on the
      unavailable QoS parameters if it still has packets to deliver.
      This field is illustrated in figure 7.

   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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |QPCnt| QoS PM  |Res|Traffic Cls|      QoS Param Value 1        |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |QoS Param Value N(if presented)|   Padding Bits (if needed)    |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                          Figure 7. UQParam field

   All fields are equivalent to the fields of QIB in the QRE message
   element but differently used.  QoS PCnt indicates the number of
   scarce resource and each of their kinds are marked in QoS PM filed to
   identify the next fields (i.e. which parameter(s) is (are) present in
   UQParam field).

   QoS Parameter Value

      The QoS Parameter Value field reports the measured QoS parame-
      ter(s) that fails to meet the originally requested QoS.  If a par-
      ticular node is aware of higher delay than the maximum permissible
      delay, the measured delay is reported to the QoS requestor.

   The QRERR message MUST be delivered to all QoS requestors potentially
   affected by the change in the QoS parameter.








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4. QoS DYMO Operations

4.1 QoS Route Discovery

   Like DYMO routing procedures, a QoS route is also discovered by means
   of two way handshaking consisting of a route request and route reply
   cycle.  Instead of DYMO RREQ, the source (QoS requestor) disseminates
   QRREQ (RREQ with a QoS extension) to the destination.  QRREQ message
   elements therefore should contain required QoS parameters as well as
   the QoS reporting information on the path that the message has been
   experienced.  Thereafter, the destination node decides a correct
   route that can meet the QoS requirements and then sends QRREP (RREP
   with a QoS extension) to the source.

   Ahead of re-broadcasting a QRREQ message by an intermediate node, the
   node must check its resources whether it is available for the QoS
   requirements contained within the QRREQ message during the route dis-
   covery process.  Thereafter, if resources are enough to meet service
   requirements, the intermediate node updates QoS information that is
   present in the QRREQ message to inform the destination about the cur-
   rent QoS states related to the path.

   That is, QRREQ should contain two different fields.  One is used to
   specify the QoS requirements of the source (i.e. QoS requestor) that
   must be met at nodes through the path.  The other field is used to
   inform both the QoS requestor and the destination that selects a
   proper QoS route the current network conditions such as delay, jit-
   ter, and/or bandwidth.

   In case of delay and jitter, intermediate nodes accumulate each of
   their measured delay and jitter value to the corresponding value of
   the received QRREQ message.  For this reason, the destination can be
   aware of the end to end delay and jitter along the path.

   In case of bandwidth (i.e. capacity to transmit), the node compares
   its measured value with the value of QSIB field in the received QRREQ
   message.  If the measured value is smaller than the value of the mes-
   sage, the field is updated to the measured one.  This field allows
   the destination to be aware of the actual minimum bandwidth over a
   route from the source to the destination since the value of QSIB is
   always bigger than the minimum value that the QoS requestor requires.
   If it is not the case, a node MUST drop the QRREQ message since there



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   is not enough bandwidth to guarantee the required one.  Such a way
   allows the QoS requestor to be able to increase the minimum bandwidth
   requirement according to the network condition dynamically.

   In QoS enabled DYMO, M-bit MUST be set to one (1) and H-bits MUST be
   set to (11).  Therefore, if the QoS extended element is not supported
   or handled by the processing node, the node MUST send a UERR to the
   NotifyAddress (QoS requestor) and drop the message to prevent that
   unsupported message is not propagated further.

   In DYMO, I bit of RE message indicates whether the element has been
   ignored by some intermediate nodes.  Therefore, in QoS DYMO, if the I
   bit is (1), the QRE message MUST be dropped.

   The recent revision of DYMO specifies S-bit to allow the previous hop
   to ensure that the link traversed in not unidirectional.  It may be
   useful to detect a unidirectional link(s) along a path in the process
   of QoS route discovery.  The existence of a unidirectional link may
   not be a problem in some QoS applications such as stock quote stream-
   ing.  However, others require fully directional link on the path from
   a source to the destination(s).  Examples include multimedia confer-
   encing, IP telephony and most of RTP based QoS applications.  There-
   fore, it is necessary to inform how each of cases is handled at nodes
   along path.

   When a node ensures the link is unidirectional then the node performs
   the route discovery process based on the U-bit coupled with S-bit.
   If U-bit and S-bit in QRE are both set to one (1), then the QRE
   receiver is forced to stop the route discovery process.

4.2 QoS Route Maintenance

   In order to react to changes in the network resources, nodes monitor
   their links under the aspect of QoS.  When a node is aware of the
   fact that resources of its link is no longer available for the QoS
   requestor, a QoS-Route Error (QRERR) is sent to the QoS requestor to
   inform the current unavailable QoS parameters of the route. Once the
   requestor receives the QRERR, it re-builds a QoS route process based
   on the unavailable QoS parameters if it still has packets to deliver.






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5. Security Considerations

   This document does not discuss any special security concerns in
   detail.  The protocol of this document is built on the assumption
   that all participating nodes are trusted each other as well as there
   is no adversary who modifies/injects false route elements to corrupt
   the QoS routes.

   However, support of secure routing protocol is prerequisite for
   launching a secure communication in the presence of adversaries.  In
   such an environment, most of all MANET routing protocols including
   DYMO are vulnerable to many kinds of attacks.  It is fairly easy to
   inject fake routing messages or modify legitimate ones so that net-
   work operation would be heavily disturbed (e.g., by creating loops or
   disconnecting the network).  Therefore, it is necessary to find a
   means to authenticate/verify control messages to discover and main-
   tain a proper route.  Especially, QRE message MUST be authenticated
   to enable nodes participating in QoS DYMO routing protocol to assure
   the origin of the QRE message.


























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6. Revision of the Draft

   Version 1 of the draft has been revised as follows.

      - This section was been appended.

      - Several TYPOs was been corrected.

      - Some work was done to allow the draft to be compatible to the
      last revision of DYMO draft such that

         o Inserting S-bit into QoS Routing Element (QRE)

         o Inserting U-bit into QoS Information Block (QIB)

         o Modifying QoS Parameter Marker field

         o Adding the description how the U-Bit is handled in section
         3.1 and section 4.1


























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References


[1]  I. Chakeres, E. Belding-Royer and C. Perkins. Dynamic MANET On-
     demand (DYMO) Routing. IETF Internet Draft draft-ietf-manet-
     dymo-03 June 2005. Work in Progress.

[2]  S. Bradner. Key words for use in RFCs to Indicate Requirement Lev-
     els.  Internet RFC 2119, March 1997.

[3]  R. Braden, D. Clark, and S. Shenker, Integrated Services in the
     Internet Architecture: an Overview, Internet RFC 1633, June 1994.

[4]  S. Blake, D. Black, M. Carlson, E. Davies, Z. Wang, and W. Weiss,
     An Architecture for Differentiated Services Internet RFC 2475,
     Decem- ber 1998.

[5]  Nichols, K., Blake, S., Baker, F. and D. Black. Definition of the
     Differentiated Services Field (DS Field) in the IPv4 and IPv6 Head-
     ers, Internet RFC 2474, December 1998.


Author's Addresses

   Questions about this memo can be directed to:

   Namhi Kang
   Ubiquitous Network Research Center
   DASAN Networks Inc.
   3F FineVenture Bldg. 345-1, YaTap-Dong,
   BunDang-Gu, SeongNam-Si, KyongGi-Do, 463-070
   Korea
   +82 2 814 0151
   nalnal@dcn.ssu.ac.kr

   Younghan Kim
   University of Soongsil in Seoul
   11F Hyungnam Engineering Bldg. 317, Sangdo-Dong,
   Dongjak-Gu, Seoul 156-743
   Korea
   +82 2 820 0904
   yhkim@dcn.ssu.ac.kr



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Disclaimer of Validity

   This document and the information contained herein are provided on an
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Copyright Statement

   Copyright (C) The Internet Society (2006).  This document is subject
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Kang, Kim               Expires September 1, 2006              [Page 17]