[Docs] [txt|pdf] [Tracker] [Email] [Nits]

Versions: 00

INTERNET-DRAFT                                               H. Kitamura
<draft-kitamura-ipv6-record-route-00.txt>                NEC Corporation
Expires in six months                                   17 November 2000

                      Record Route for IPv6 (RR6)
                      Hop-by-Hop Option Extension

               <draft-kitamura-ipv6-record-route-00.txt>

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   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.

Abstract


   This document proposes a "Record Route for IPv6 (RR6)" mechanism.  It
   is composed of one new IPv6 hop-by-hop option (RR6 option) extension.

   The RR6 mechanism is redesigned to establish an optimized record
   route mechanism for IPv6. Two types of new features are introduced.

   1. In order to prevent scalability problems and to make the mechanism
   flexible, the beginning and ending points of the data recording range
   are controlled by using their specifiers.

   2. In order to record long IPv6 addresses efficiently, a simple
   address compression method is introduced. Since the compression is
   achieved by utilizing characteristics of recorded IPv6 addresses
   effectively, the mechanism is efficient and optimized for IPv6.




H. Kitamura                                                    [Page 1]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


1. Introduction

   This document proposes a "Record Route for IPv6 (RR6)" mechanism.  It
   is composed of one new IPv6 Hop-by-Hop option (RR6 option) extension.

   In the IPv6 specifications [IPv6], no record route function is
   defined, and the record route function for IPv4 is less flexible and
   has scalability problems.

   The RR6 mechanism is redesigned to establish an optimized record
   route mechanism for IPv6 and fix the problems of the record route
   function for IPv4. Two types of new features are introduced to
   achieve this goal.

   1. In order to prevent scalability problems and to make the mechanism
   flexible, the beginning and ending points of the data recording range
   are controlled by using their specifiers.

   2. In order to record long IPv6 addresses efficiently, a simple
   address compression method is introduced. Since the compression is
   achieved by utilizing characteristics of recorded IPv6 addresses
   effectively, the mechanism is efficient and optimized for IPv6.


2. Design of the Record Route for IPv6 (RR6) Mechanism

   Since a record route operation runs on each node along a
   communication path, it is appropriate to achieve the record route
   operation as a hop-by-hop option operation. One IPv6 hop-by-hop
   option (RR6 option) is introduced to establish the RR6 mechanism.


2.1 Roles of the RR6 Option Operations

   The RR6 option has the following roles.

   1. Provide Data Storing Space

      A Data Space is prepared in the RR6 option header. All of the data
      recorded by the RR6 option operation is written into the Data
      Space in the RR6 option header.

      Changing the length of the packet on an intermediate node makes
      the mechanism complex, so that the length of the Data Space is not
      changed by the RR6 address data recording operations on each node.
      When the packet in which the RR6 option is set is prepared for
      sending, the Data Space is preallocated in it.




H. Kitamura                                                    [Page 2]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


      (Since the length of the Data Space is limited, the data recording
      or carrying capacity of one packet in which the RR6 option is set
      is limited. This scalability issue is discussed in Section 2.2)

   2. Record Address Information

      When a packet in which the RR6 option is set passes through nodes
      along the communication path, the RR6 option operation routine on
      each node records (incoming interface's) address information of
      the node. The address information is written into the Data Space
      in the RR6 option header.

      Exception:
      On the source node, outgoing interface's address information of
      the source node is recorded.

   3. Carry the Recorded Data

      The recorded data is carried by packets in which the RR6 option is
      set. This is easy to achieve, because the Data Space exists in the
      RR6 option header.

      (Since recorded data is normally analyzed on a source node that
      issues the packet in which RR6 option is set, the recorded data
      must be carried back to the source node. Namely, the RR6 option
      must be set to the packet that returns to the source node. This
      issue is discussed in Section 2.4)

2.2 Data Recording Range Control

   Since the length of the Data Space is limited, the data recording or
   carrying capacity of one packet in which the RR6 option is set is
   limited.

   To prevent scalability problems and to make the mechanism flexible,
   the beginning and ending points (nodes) of data recording range are
   controlled by using their specifiers.

   When a packet in which the RR6 option is set can not record or carry
   all of address information of nodes along the communication path
   (because the number of nodes is larger than the capacity), an
   additional packet(s) whose data recording beginning point specifier
   is set appropriately is issued and the remaining address information
   is recorded and carried by it.

   This RR6 mechanism does not cause any scalability problems. Details
   of the data recording range control are explained in Section 3.3.




H. Kitamura                                                    [Page 3]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


2.3 Address Recording with Compression

   The maximum length of one hop-by-hop option is 255 octets, and the
   IPv6 address is long in length (16 octets). If address information is
   recorded as a plain (non-compressed) address format, one hop-by-hop
   option can record and carry only 15 record entries.

   When the RR6 mechanism is applied to a large-scale network
   environment, 15 entries are insufficient. Thus, it is necessary to
   provide a compressed address recording method.

   It is requested that a compressed address recording method of the RR6
   mechanism must be sufficiently simple and efficient, because the RR6
   mechanism is achieved as a hop-by-hop option operation that runs on
   each node along the communication path. A complex and heavy operation
   is not suitable for the compressed address recording method.

   A series of recorded addresses is composed of successive neighbor
   addresses, and is not a series of random numbers. It is strongly
   assumed that each address is correlated with its previous or
   succeeding address in the series. In other words, two neighboring
   addresses will have the same leading part (prefix). This special
   characteristic can be used for a simple and efficient address
   compression method.

   Generally speaking, compression methods are categorized into two
   types, intra-compression and inter-compression.

   Since inter-compression methods work efficiently for a series of
   successive neighbor addresses, the RR6 mechanism adopts one of the
   inter-compression methods to achieve a compressed address recording
   mechanism. Details are explained in Section 3.3,

2.4 Loop Communication Path

   Since recorded data is normally analyzed on a source node that issues
   a packet in which the RR6 option is set, the recorded data must be
   carried back to the source node. Namely, the RR6 option must be set
   to the packet that returns to the source node.

   There are two ways of making a loop communication path.

   One is to utilize an ICMPv6 Echo Request/Reply (ping6) mechanism.

      In order to run the RR6 mechanism appropriately on the ping6
      mechanism, the following two operations must be implemented on the
      ping6's target node.




H. Kitamura                                                    [Page 4]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


      1. All of the RR6 option fields must be copied from
         an Echo Request message to an Echo Reply message.

      2. The Hop Limit field of the IPv6 header of these messages
         must be copied as a continuous sequence.


   The other is to prepare a packet in which a Route option is set.

      The source node must be set to the final destination of the Route
      option, and the target node must be set to one of the intermediate
      nodes that are specified in the Route option.

      No special operations are required to run the RR6 mechanism in
      this method.


3. Record Route for IPv6 (RR6) Option Format: IPv6 Hop-by-Hop Option


     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Option Type  |  Opt Data Len |    RR6_Type   |  Rec_Pointer  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Begin_Hop_L  |   End_Hop_L   |    Reserved   |               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
     |                                                               |
     |                                                               |
     |                           Data Space                          |
     |                                                               |
     |                                                               |

   Option Type:    8-bit.
                   Identifier of the type of option (RR6 option)
                   Value is 001xxxxx. 0x20+TBA
                   (Tentatively 0x23)

                   RR6 Option Type must be started as 00 to avoid
                   discarding the packet at the RR6 feature disabled
                   node, and the third bit must be set to 1 to record
                   data into the [Data Space].
                   [see Section 4.2 of RFC2460]

   Opt Data Len:   8-bit unsigned integer.
                   Length of the [Option Data] field of this option
                   Max: 255
                   Depends on the length of [Data Space]





H. Kitamura                                                    [Page 5]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


   RR6_Type:       8-bit.
                   Identifier of the data recording type

                   =0 Plain (non-compressed) address record type
                   [see Section 3.2]
                   =1 Compressed address record type
                   [see Section 3.3]

   Rec_Pointer:    8-bit unsigned integer.
                   Pointer that shows next data recording point
                   in the [Data Space] in octet

                   Initial: 0
                   Data recording status can be checked by Rec_Pointer
                   (=0 means that no data has been recorded yet)

   Begin_Hop_L:    8-bit unsigned integer.
                   Data recording beginning point specifier
                   (In a model case, it shows Hop Limit value of
                    the node that begins the data recording on the path)

                   default: 255
                   [see Section 3.1]

   End_Hop_L:      8-bit unsigned integer.
                   Data recording ending point specifier
                   (In a model case, it shows Hop Limit value of
                    the node that ends the data recording on the path)

                   default: 0

                   End_Hop_L has another role to indicate that
                   [Data Space] is filled on the communication path.

                   When it is detected that [Data Space] is fully filled
                   and there is no space left to record new data,
                   [End_Hop_L] is set with the Hop Limit value of the
                   last data record node.
                   [see Section 3.1]

   Reserved:       8-bit. (Reserved Octet)
                   Reserved octet for future use.

   Data Space:     [Opt Data Len]-5 octets
                   Buffer space to record the address information data.

                   Length of [Data Space] must be longer than or
                   equal to 17 (length of one fixed length record).



H. Kitamura                                                    [Page 6]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


3.1 Procedure of Data Recording Range Control

   As described in Section 2.2, the data recording range can be
   controlled by specifying the data recording beginning and ending
   points. Begin_Hop_L and End_Hop_L are used to specify these points.

   When a packet the RR6 option is set passes through a node, the
   current Hop Limit value (Hop_L) of the node is initially compared
   with Begin_Hop_L and End_Hop_L. If Hop_L is located between them, an
   address recording operation is started.

   End_Hop_L has another role. If the Data Space is fully filled on an
   intermediate node on the communication path, End_Hop_L is set with
   the Hop Limit value of the last data record node to indicate its
   location.

   The following describes an algorithm of data recording range control.

    while (Begin_Hop_L >= Hop_L && Hop_L >= End_Hop_L) {
      Prepare a data record to write into the Data Space;
      // Check the remaining space in the Data Space
      if (there is enough space to record address information) {
        Record the prepared data record into the Data Space;
        if (Data Space has been fully filled without odd remains) {
            End_Hop_L is set by the Hop Limit value of the current node;
        }
      } else { // there is no space left to record new data
         End_Hop_L is set with the Hop Limit value of
         the last (previous) data record node;
         // End_Hop_L = Prev_Rec_HopL;
         // in the compressed address record type [see Section 3.3]
      }
    }

3.1.1 Example of Data Recording Range Control

   Examples of data recording range control behavior are shown here.

    INI: Hop Limit value of the source node that issues a packet
                    [Source]-[Node1]-[Node2]-[Node3]-[Node4]-[Node5]-...
    Hop Limit value     INI   INI-1   INI-2   INI-3   INI-4   INI-5  ...
    (ex. INI=64)         64      63      62      61      60      59  ...
    default (w/o Cont.)   x       x       x       x       x       x  ...
    (Begin=(64=INI))
    w/ Record Range Cont. -       -       -       x       x       x  ...
    (ex. Begin=61)
    w/ Record Range Cont. -       -       x       x       x       -  ...
    (ex. Begin=62, End=60)



H. Kitamura                                                    [Page 7]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


3.2 Plain (Non-Compressed) Address Record Type

   In this section, a plain (non-compressed) address record type is
   explained.

   When [RR6_Type] = 0, a plain (non-compressed) address record type is
   used to record address information.

   This record type is the simplest method to record address information
   into the [Data Space]. Address information of a node is recorded as
   plain format (without compression).

   Each node provides one data record that contains address information.
   The length of the data record is fixed (17 octets). When a packet in
   which the RR6 option is set passes through a node, one data record
   space is consumed in the [Data Space].

   The following is the format of one fixed-length data record.

                                                     +-+-+-+-+-+-+-+-+
                                                     |   Hop_Lim_A   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                Address of Node A  (16 octets)                 |
     |                            (Hop_Lim_A= Hop Limit of Node A)   |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   One fixed-length data record comprises the Hop Limit (1 octet) and
   the (incoming interface's) address (16 octets) information of the
   node.

   Hop Limit information of the node is used to identify the location on
   the communication path.


   Exception:

   If [Begin_Hop_L] >= Hop Limit value of the source node, the source
   node must record its address information. Since there is no incoming
   operation on the source node, outgoing interface's address
   information is recorded into the [Address of Node] field instead of
   incoming interface's address information.








H. Kitamura                                                    [Page 8]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


   3.2.1 Example of Data-Filled Format (Plain Address Record Type)

   The following shows an example of how the [Data Space] is filled with
   fixed-length data records.

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Option Type  |  Opt Data Len |   RR6_Type=0  |  Rec_Pointer  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Begin_Hop_L  |  Max_Records  |    Reserved   |   Hop_Lim_A   |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                Address of Node A  (16 octets)                 |
     |                            (Hop_Lim_A= Hop Limit of Node A)   |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Hop_Lim_B   |                                               |
     +-+-+-+-+-+-+-+-+                                               |
     |                Address of Node B  (16 octets)                 |
     |                            (Hop_Lim_B= Hop Limit of Node B)   |
     |               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               |   Hop_Lim_C   |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
     |                Address of Node C  (16 octets)                 |
     |                            (Hop_Lim_C= Hop Limit of Node C)   |
     |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               |   Hop_Lim_D   |               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
     |                Address of Node D  (16 octets)                 |
     |                            (Hop_Lim_D= Hop Limit of Node D)   |
     |                                               +-+-+-+-+-+-+-+-+
     |                                               |               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               +
     |                                                               |
     |                                                               |

   Some nodes on the communication path do not record address
   information for some reason (e.g., not implementing or intentionally
   disabling the RR6 feature).

   Thus, Node A, B, C, D, ... are not always successive neighbor nodes,
   and Hop_Lim_A, Hop_Lim_B, Hop_Lim_C, Hop_Lim_D, ...  are not always
   consecutive descending numbers.









H. Kitamura                                                    [Page 9]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


3.3 Compressed Address Record Type

   In this section, a compressed address record type is explained.

   (This document defines one simple and efficient compressed address
   record type. Since there are various address compression methods,
   other compressed address record types may be proposed in other
   documents in future).

   When [RR6_Type] = 1, a compressed address record type is used to
   record address information.

   Address information of a node is recorded into the [Data Space] as a
   compressed format. Each node provides one data record. Since address
   information is compressed, the length of the record is variable (max
   17 octets). When the packet in which the RR6 option is set passes
   through a node, its RR6 operation consumes one variable-length data
   record space in the [Data Space].

3.3.1 Compression Method

   Series of recorded addresses have a special characteristic. It is
   composed of successive neighbor addresses. It is strongly assumed
   that each address is correlated with its previous or succeeding
   address in the series. Specifically, it is assumed that two
   neighboring addresses have the same leading part (prefix).

   By omitting the same leading part, address information can be
   compressed. This simple compression method utilizes the special
   characteristic efficiently, and it is adopted for this record type.

   (This method is categorized into inter-compression methods. In order
   to simplify the mechanism, intra-compression methods are not used in
   this record type.)


   To establish a simplified compression mechanism, the same leading
   part is omitted in octet unit (not bit unit).

   The compression is composed of the following operations.

   1. Compare current address with previous address.

   2. Find the same leading part between them in octet

   3. Omit the same leading part in octet, and calculate the length
      of the remaining part of the current address information.




H. Kitamura                                                   [Page 10]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


3.3.2 Data Space Format Extension for Compressed Address Record Type

   In order to compare current and previous information, the leading 17
   octets of the [Data Space] are used to keep Hop Limit and Address
   information of the previous (last data recorded) node.

   The following format is used in the compressed address record type.
   (This format is an upper compatible format from the basic RR6 format)

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Option Type  |  Opt Data Len |   RR6_Type=1  |  Rec_Pointer  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Begin_Hop_L  |   End_Hop_L   |    Reserved   | Prev_Rec_HopL |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                Previous Record Address                        |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                Data Space (for Variable Length Data Records)  |
     |                                                               |


   Prev_Rec_HopL:  8-bit unsigned integer.
                   Hop Limit value of the previous (last data recorded)
                   node

   Previous Record Address: 16-octet
                   (Incoming interface's) address of the previous
                   (last data recorded) node

   (If [Begin_Hop_L] >= Hop Limit value of the source node, the source
   node fills [Prev_Rec_HopL] with Hop Limit value of the source node,
   fills [Previous Record Address] with outgoing interface's address
   information of the source node, and sets [Rec_Pointer] with 17)


3.3.3 Variable Length Data Record Format

   The following is a format of one variable-length data record.

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...
     | DHop  |  Len  |     Compressed Address
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-...

     (Maximum length: 17 octets)




H. Kitamura                                                   [Page 11]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


   DHop:           4bit.
                   Hop difference that is calculated by the following
                   formula   [Prev_Rec_HopL] - [Current Hop Limit]
                   (=0 means more than 15 hop difference)

   Len:            4bit.
                   Length of the following [Compressed Address]
                   (=0 means 16)

   Compressed Address:
                   Compressed current address
                   (The same leading part in octet is omitted)

                   (Max length 16)

   Note:

   In usual cases (hop differences are smaller than 16), [DHop] can show
   accurate hop difference. Only when some hop difference on the path is
   larger than 15, a situation ([DHop] = 0) appears in the [Data Space],
   and this causes a Hop Limit counting ambiguity.

   If the situation ([DHop] = 0) appears only once in the [Data Space],
   such an ambiguity can be cleared by checking the initial Hop Limit
   value and the Hop Limit value of the received packet.

   If the situation ([DHop] = 0) appears more than once in the [Data
   Space], such ambiguities are not cleared in the compressed address
   record type. If it is necessary to count Hop Limit values of nodes
   accurately, the plain (non-compressed) address record type
   accompanied with appropriate data recording range control is used.


3.3.4 Operation Steps at Each Node

   1. Prepare a variable-length data record
      Calculate "DHop", "Compressed Address" and "Len"

   2. Write the data record into [Data Space (for Variable Length
      Data Records)].  Writing start point in [Data Space] is
      indicated by [Rec_Pointer]

   3. Update [Rec_Pointer]    ([Rec_Pointer] += (1+[Len]))

   4. Update [Prev_Rec_HopL] with Hop Limit value of current node

   5. Update [Previous Record Address] with address information
      of current node



H. Kitamura                                                   [Page 12]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


   Note:

   Only step 4 and 5 are executed on an initial data record node, and no
   data is recoded into [Data Space (for Variable Length Data Records)].



3.3.5 Example of Data-Filled Format (Compressed Address Record Type)

   The followings show an example how the [Data Space] is filled with
   variable-length data records.

     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Option Type  |  Opt Data Len |   RR6_Type=1  |  Rec_Pointer  |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Begin_Hop_L  |   End_Hop_L   |    Reserved   | Prev_Rec_HopL |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     |                Previous Record Address  (16 octets)           |
     |                                                               |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | DHop_A| Len=13|                                               |
     +-+-+-+-+-+-+-+-+                                               |
     |                   Compressed Address A  (13 octets)           |
     |                               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                               | DHop_B| Len=12|               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+               |
     |                   Compressed Address B  (12 octets)           |
     |                                               +-+-+-+-+-+-+-+-+
     |                                               | DHop_C| Len=9 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                   Compressed Address C   (9 octets)           |
     |                                                               |
     |               +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |               | DHop_D| Len=10|                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               |
     |                   Compressed Address D  (10 octets)           |
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |










H. Kitamura                                                   [Page 13]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


4. IANA Considerations

   The RR6 mechanism has introduced one IPv6 Hop-by-Hop option. In order
   to implement the RR6 mechanism, one IPv6 Hop-by-Hop option type value
   is tentatively assigned from unassigned spaces as follows.

      IPv6 Hop-by-Hop Option: RR6 Type:    0x23 (Tentatively)

   This number must be assigned by IANA officially.


5. Security Considerations

   Since address information is not secret information of nodes, the
   Record Route for IPv6 (RR6) mechanism not have any direct impact on
   Internet infrastructure security.





Appendix A. Recorded Hop Limit value of the Node

   A node deals with two Hop Limit values on it. One is set to receiving
   packets; the other is set to transmitting packets. The timing when
   Hop Limit value is changed (decremented) on the node is not clearly
   defined. It is necessary that which values is appropriate to be
   recorded by the RR6 option operations.

   Since the recorded Hop Limit value of the node is used to identify
   its location on the communication path, it must be unique and
   different from Hop Limit values of other nodes on the path.

   The initial Hop Limit value is not decremented on the source node, so
   that the initial Hop Limit value is adopted for the recorded Hop
   Limit value of the source node. Thus, the first node (succeeding node
   from the source node on the path) can not use the initial Hop Limit
   value, and the decremented initial Hop Limit value is adopted for the
   recorded Hop Limit value of the first node.

   Therefore, the rule is inductively defined. The recorded Hop Limit
   value of the node is the Hop Limit value that is set to transmitting
   (outgoing) packets. In other words, the decremented Hop Limit value
   that is set to receiving (incoming) packets is used for the recorded
   Hop Limit value of the node.






H. Kitamura                                                   [Page 14]


INTERNET-DRAFT         Record Route for IPv6 (RR6)         November 2000


Appendix B. RR6 Implementation

   The main RR6 operations are implemented at incoming operations (e.g.,
   ip6_input()). Some RR6 operations, however, are implemented at
   outgoing operations (e.g., ip6_output()), because the RR6 mechanism
   must run on the source node.



References

   [IPv6]    S. Deering, R. Hinden, "Internet Protocol, Version 6 (IPv6)
             Specification," RFC2460, December 1998.

   [ICMPv6]  A. Conta, S. Deering, "Internet Control Message Protocol
             (ICMPv6) for the Internet Protocol Version 6 (IPv6)
             Specification," RFC2463, December 1998.


Author's Address:

   Hiroshi Kitamura
   NEC Corporation
   Development Laboratories
   (Igarashi Building 4F) 11-5, Shibaura 2-Chome,
   Minato-Ku, Tokyo 108-8557, JAPAN

   Phone: +81 (3) 5476-1071
   Fax:   +81 (3) 5476-1005
   Email: kitamura@da.jp.nec.com





















H. Kitamura                                                   [Page 15]


Html markup produced by rfcmarkup 1.129b, available from https://tools.ietf.org/tools/rfcmarkup/