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INTAREA                                                        R. Bonica
Internet-Draft                                                 R. Thomas
Updates: RFC 4884 (if approved)                         Juniper Networks
Intended status: Standards Track                              J. Linkova
Expires: January 17, 2018                                         Google
                                                               C. Lenart
                                                                 Verizon
                                                            M. Boucadair
                                                                  Orange
                                                           July 16, 2017


                PROBE: A Utility For Probing Interfaces
                      draft-ietf-intarea-probe-01

Abstract

   This document describes a network diagnostic tool called PROBE.
   PROBE is similar to PING, in that it can be used to test the status
   of a probed interface.  It differs from PING in that it does not
   require bidirectional connectivity between the probing and probed
   interfaces.  Alternatively, PROBE requires bidirectional connectivity
   between the probing interface and a proxy interface.  The proxy
   interface can reside on the same node as the probed interface or it
   can reside on a node to which the probed interface is directly
   connected.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   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."

   This Internet-Draft will expire on January 17, 2018.








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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.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   4
     1.2.  Requirements Language . . . . . . . . . . . . . . . . . .   4
   2.  ICMP Extended Echo Request  . . . . . . . . . . . . . . . . .   4
     2.1.  Interface Identification Object . . . . . . . . . . . . .   6
   3.  ICMP Extended Echo Reply  . . . . . . . . . . . . . . . . . .   7
   4.  ICMP Message Processing . . . . . . . . . . . . . . . . . . .   8
     4.1.  Code Field Processing . . . . . . . . . . . . . . . . . .  10
   5.  Use-Cases . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   6.  Updates to RFC 4884 . . . . . . . . . . . . . . . . . . . . .  11
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  11
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  14
   Appendix A.  The PROBE Application  . . . . . . . . . . . . . . .  14
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  16

1.  Introduction

   Network operators use PING [RFC2151] to test bidirectional
   connectivity between two interfaces.  For the purposes of this
   document, we will call these interfaces the probing and probed
   interfaces.  PING sends an ICMP [RFC0792] [RFC4443] Echo message from
   the probing interface to the probed interface.  The probing interface
   resides on a probing node while the probed interface resides on a
   probed node.

   If the probed interface receives the ICMP Echo message, it returns an
   ICMP Echo Reply.  When the probing interface receives the ICMP Echo



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   Reply, it has verified bidirectional connectivity between the probing
   and probed interfaces.  Specifically, it has verified that:

   o  The probing node can reach the probed interface

   o  The probed interface is active

   o  The probed node can reach the probing interface

   o  The probing interface is active

   This document describes a network diagnostic tool called PROBE.
   PROBE is similar to PING, in that it can be used to test the status
   of a probed interface.  It differs from PING in that it does not
   require bidirectional connectivity between the probing and probed
   interfaces.  Alternatively, PROBE requires bidirectional connectivity
   between the probing interface and a proxy interface.  The proxy
   interface can reside on the same node as the probed interface or it
   can reside on a node to which the probed interface is directly
   connected.  Section 5 of this document describes scenarios in which
   this characteristic is useful.

   Like PING, PROBE executes on a probing node.  It sends an ICMP
   Extended Echo message from a local interface, called the probing
   interface, to a proxy interface.  The proxy interface resides on a
   probed node.

   The ICMP Extended Echo Request contains an ICMP Extension Structure
   and the ICMP Extension Structure contains an Interface Identification
   Object.  The Interface Identification Object identifies the probed
   interface.  The probed interface can reside on the probed node or it
   can be directly connected to the probed node.

   When the proxy interface receives the ICMP Extended Echo Request, it
   executes access control procedures.  If access is granted, the probed
   node determines the status of the probed interface and returns an
   ICMP Extended Echo Reply Message.  The ICMP Extended Echo Reply
   indicates the status of the probed interface.

   If the probed interface resides on the probed node, PROBE determines
   the status of the probed interface as it would determine its MIB-II
   [RFC2863] ifOperStatus.  If ifOperStatus is equal to up (1), PROBE
   reports that the probed interface is active.  Otherwise, PROBE
   reports that the probed interface is inactive.

   If the probed interface resides on a node that is directly connected
   to the probed node, PROBE reports that the interface is up if it
   appears in the IPv4 Address Resolution Protocol (ARP) table or the



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   IPv6 Neighbor Cache.  Otherwise, it reports that the interface does
   not exist.

1.1.  Terminology

   This document uses the following terms:

   o  Probing node - The node upon which PROBE executes

   o  Probing interface - The interface from which an ICMP Extended Echo
      originates

   o  Proxy interface - The interface to which the ICMP Extended Echo
      message is sent

   o  Probed node - The node upon which the proxy interface resides

   o  Probed interface - The interface whose status is being queried

1.2.  Requirements Language

   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.  ICMP Extended Echo Request

   The ICMP Extended Echo Request message is defined for both ICMPv4 and
   ICMPv6.  Like any ICMP message, the ICMP Extended Echo Request
   message is encapsulated in an IP header.  The ICMPv4 version of the
   Extended Echo Request message is encapsulated in an IPv4 header,
   while the ICMPv6 version is encapsulated in an IPv6 header.

   Figure 1 depicts the ICMP Extended Echo Request message.

       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      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Identifier          |Sequence Number|   Reserved  |L|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |   ICMP Extension Structure




               Figure 1: ICMP Extended Echo Request Message



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   IP Header fields:

   o  Source Address: The Source Address identifies the probing
      interface.  It MUST be valid IPv4 or IPv6 unicast address.

   o  Destination Address: The Destination Address identifies the proxy
      interface.  It can be a unicast, multicast or anycast address.

   ICMP fields:

   o  Type: Extended Echo Request.  The value for ICMPv4 is TBD by IANA.
      The value for ICMPv6 is also TBD by IANA.

   o  Code: 0

   o  Checksum: For ICMPv4, see RFC 792.  For ICMPv6, see RFC 4443.

   o  Identifier: An identifier to aid in matching Extended Echo Replies
      to Extended Echo Requests.  May be zero.

   o  Sequence Number: A sequence number to aid in matching Extended
      Echo Replies to Extended Echo Requests.  May be zero.

   o  Reserved: This field MUST be set to zero and ignored upon receipt.

   o  L (local) - The L-bit is set of the probed interface resides on
      the probed node.  The L-bit is clear if the probed interface is
      directly connected to the probed node.

   o  ICMP Extension Structure: The ICMP Extension Structure identifies
      the probed interface.

   Section 7 of [RFC4884] defines the ICMP Extension Structure.  As per
   RFC 4884, the Extension Structure contains exactly one Extension
   Header followed by one or more objects.  When applied to the ICMP
   Extended Echo Request message, the ICMP Extension Structure MUST
   contain one or two instances of the Interface Identification Object
   (Section 2.1).

   In most cases, a single instance of the Interface Identification
   Object identifies the probed interface.  However, in some cases, a
   second instance is required for disambiguation.

   If the L-bit is set, the Interface Identification Object identifies
   the probed interface by name, index or address.  It the L-bit is
   clear, the Interface Identification Object identifies the probed
   interface by address.




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   If the Interface Identification Object identifies the probed
   interface by address, that address can be a member of any address
   family.  For example, an ICMPv4 Extended Echo Request message can
   carry an Interface Identification Object that identifies the probed
   interface by IPv4, IPv6 or IEEE 802 address.  Likewise, an ICMPv6
   Extended Echo Request message can carry an Interface Identification
   Object that identifies the probed interface by IPv4, IPv6 or IEEE 802
   address.

2.1.  Interface Identification Object

   The Interface Identification Object identifies the probed interface
   by name, index, or address.  Like any other ICMP Extension Object, it
   contains an Object Header and Object Payload.  The Object Header
   contains the following fields:

   o  Class-Num: Interface Identification Object.  Value is TBD by IANA

   o  C-type: Values are: (1) Identifies Interface By Name, (2)
      Identifies Interface By Index, and (3) Identifies Interface By
      Address

   o  Length: Length of the object, measured in octets, including the
      object header and object payload.

   If the Interface Identification Object identifies the probed
   interface by name, the object payload contains the human-readable
   interface name.  The interface name SHOULD be the full MIB-II ifName,
   if less than 255 octets, or the first 255 octets of the ifName, if
   the ifName is longer.  The interface name MAY be some other human-
   meaningful name of the interface.  The interface name MUST be
   represented in the UTF-8 charset [RFC3629] using the Default Language
   [RFC2277].

   If the Interface Identification Object identifies the probed
   interface by index, the length is equal to 8 and the payload contains
   the MIB-II ifIndex [RFC 2863].

   If the Interface Identification Object identifies the probed
   interface by address, the payload is as depicted in Figure 2.











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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
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |            AFI                |        Reserved               |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |                Address   ....




       Figure 2: Interface Identification Object - C-type 3 Payload

   Payload fields are defined as follows:

   o  Address Family Identifier (AFI): This 16-bit field identifies the
      type of address represented by the Address field.  All values
      found in the IANA registry of Address Family Numbers (available
      from <https://www.iana.org/assignments/address-family-numbers/
      address-family-numbers.xhtml>) are valid in this field.

   o  Reserved: This field MUST be set to zero and ignored upon receipt.

   o  Address: This variable-length field represents an address
      associated with the probed interface.

3.  ICMP Extended Echo Reply

   The ICMP Extended Echo Reply message is defined for both ICMPv4 and
   ICMPv6.  Like any ICMP message, the ICMP Extended Echo Reply message
   is encapsulated in an IP header.  The ICMPv4 version of the Extended
   Echo Reply message is encapsulated in an IPv4 header, while the
   ICMPv6 version is encapsulated in an IPv6 header.

   Figure 3 depicts the ICMP Extended Echo Reply message.

       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      |     Code      |          Checksum             |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |           Identifier          |Sequence Number| Resvd |A|F|S|E|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+





                 Figure 3: ICMP Extened Echo Reply Message



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   IP Header fields:

   o  Source address: Copied from the Destination Address field of the
      invoking Extended Echo Request message

   o  Destination address: Copied from the Source Address field of the
      invoking Extended Echo Request message

   ICMP fields:

   o  Type: Extended Echo Reply.  The value for ICMPv4 is TBD by IANA.
      The value for ICMPv6 is also TBD by IANA

   o  Code: (0) No Error, (1) Malformed Query, (2) No Such Interface,
      (3) Multiple Interfaces Satisfy Query

   o  Checksum: For ICMPv4, see RFC 792.  For ICMPv6, see RFC 4443

   o  Identifier: Copied from the Identifier field of the invoking
      Extended Echo Request packet

   o  Sequence Number: Copied from the Sequence Number field of the
      invoking Extended Echo Request packet

   o  Resvd - This field MUST be set to zero and ignored upon receipt

   o  A (Active) - The A-bit is set if Code is equal to zero and the
      probed interface is active.  Otherwise, the A-bit is clear.

   o  F (IPv4) - The F-bit is set if the A-bit is also set and IPv4 is
      running on the probed interface.  Otherwise, the F-bit is clear.

   o  S (IPv6) - The S-bit is set if the A-bit is also set and IPv6 is
      running on the probed interface.  Otherwise, the S-bit is clear.

   o  E (Ethernet) - The E-bit is set if the A-bit is also set and IPv4
      is running on the probed interface.  Otherwise, the E-bit is
      clear.

4.  ICMP Message Processing

   When a node receives an ICMP Extended Echo Request message and any of
   the following conditions apply, the node MUST silently discard the
   incoming message:

   o  The node does not recognize ICMP Extended Echo Request messages





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   o  The node has not explicitly enabled ICMP Extended Echo
      functionality

   o  The incoming ICMP Extend Echo Request carries a source address
      that is not explicitly authorized for the incoming ICMP Extended
      Echo Request L-bit setting

   o  The incoming ICMP Extend Echo Request carries a source address
      that is not explicitly authorized for the incoming ICMP Extended
      Echo Request type (i.e., by ifName, by IfIndex, by Address)

   o  The Source Address of the incoming messages is not a unicast
      address

   Otherwise, when a node receives an ICMPv4 Extended Echo Request, it
   MUST format an ICMP Extended Echo Reply as follows:

   o  Don't Fragment flag (DF) is 1

   o  More Fragments flag is 0

   o  Fragment Offset is 0

   o  TTL is 255

   o  Protocol is ICMP

   When a node receives an ICMPv6 Extended Echo Request, it MUST format
   an ICMPv6 Extended Echo Reply as follows:

   o  Hop Limit is 255

   o  Next Header is ICMPv6

   In either case, the responding node MUST:

   o  Copy the source address from the Extended Echo Request message to
      the destination address of the Extended Echo Reply

   o  Copy the destination address from the Extended Echo Request
      message to the source address of the Extended Echo Reply

   o  Set the DiffServ codepoint to CS0 [RFC4594]

   o  Set the ICMP Type to Extended Echo Reply

   o  Copy the Identifier from the Extended Echo Request message to the
      Extended Echo Reply



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   o  Copy the Sequence Number from the Extended Echo Request message to
      the Extended Echo Reply

   o  Set the Code field as described Section 4.1

   o  If the Code Field is equal to No Error (0) and the L-bit is clear,
      set the A-Bit.

   o  If the Code Field is equal to No Error (0) and the L-bit is set
      and the probed interface is active, set the A-bit.

   o  If the A-bit is set, set the F-bit, S-bit and E-bit as
      appropriate.  Otherwise, clear the F, S and E bits.

   o  Set the checksum appropriately

   o  Forward the ICMP Extended Echo Reply to its destination

4.1.  Code Field Processing

   The Code field MUST be set to Malformed Query (1) if any of the
   following conditions apply:

   o  The ICMP Extended Echo Request does not include an ICMP Extension
      Structure

   o  The ICMP Extension Structure does not include an Interface
      Identification Object

   o  The ICMP Extension Structure contains more than two Interface
      Identification Objects

   o  The L-bit is clear and the Interface Identification Object
      identifies the probed interface by ifName or ifIndex

   o  The query is otherwise malformed

   The Code field MUST be set to No Such Interface (2) if any of the
   following conditions apply:

   o  The L-bit is set and the ICMP Extension Structure does not
      identify any local interfaces

   o  The L-bit is clear and the address or addresses found in the
      Interface Identification object appear in neither the IPv4 Address
      Resolution Protocol (ARP) Table nor the IPv6 Neighbor Cache





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   The Code field MUST be set to Multiple Interfaces Satisfy Query (3)
   if any of the following conditions apply:

   o  The L-bit is set and the ICMP Extension Structure identifies more
      than one local interfaces

   o  The L-bit is clear and the address or addresses found in the
      Interface Identification object map to multiple IPv4 ARP or IPv6
      Neighbor Cache entries

   Otherwise, the Code field MUST be set to No Error (0)

5.  Use-Cases

   In the scenarios listed below, network operators can use PROBE to
   determine the status of a probed interface, but cannot use PING for
   the same purpose.  In all scenarios, assume bidirectional
   connectivity between the probing and proxy interfaces.  However,
   bidirectional connectivity between the probing and probed interfaces
   is lacking.

   o  The probed interface is unnumbered

   o  The probing and probed interfaces are not directly connected to
      one another.  The probed interface has an IPv6 link-local address,
      but does not have a more globally scoped address

   o  The probing interface runs IPv4 only while the probed interface
      runs IPv6 only

   o  The probing interface runs IPv6 only while the probed interface
      runs IPv4 only

   o  For lack of a route, the probing node cannot reach the probed
      interface.

6.  Updates to RFC 4884

   Section 4.6 of RFC 4884 provides a list of extensible ICMP messages
   (i.e., messages that can carry the ICMP Extension Structure).  This
   document adds the ICMP Extended Echo message and the ICMP Extended
   Echo Reply message to that list.

7.  IANA Considerations

   This document requests the following actions from IANA:





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   o  Add an entry to the "ICMP Type Number" registry, representing the
      Extended Echo Request.  This entry has one code (0).

   o  Add an entry to the "Internet Control Message Protocol version 6
      (ICMPv6) Parameters" registry, representing the Extended Echo
      Request.  This entry has one code (0).

   o  Add an entry to the "ICMP Type Number" registry, representing the
      Extended Echo Reply.  This entry has the following codes: (0) No
      Error, (1) Malformed Query, (2) No Such Interface, (3) Multiple
      Interfaces Satisfy Query.  Protocol Flag Bit mappings are as
      follows: Bit 0 (IPv4), Bit 1 (IPv6), Bit 2 (Ethernet), Bits 3-15
      (Reserved).

   o  Add an entry to the "Internet Control Message Protocol version 6
      (ICMPv6) Parameters" registry, representing the Extended Echo
      Reply.  This entry has the following codes: (0) No Error, (1)
      Malformed Query, (2) No Such Interface, (3) Multiple Interfaces
      Satisfy Query.  Protocol Flag Bit mappings are as follows: Bit 0
      (IPv4), Bit 1 (IPv6), Bit 2 (Ethernet), Bits 3-15 (Reserved).

   o  Add an entry to the "ICMP Extension Object Classes and Class Sub-
      types" registry, representing the Interface Identification Object.
      It has C-types Reserved (0), Identifies Interface By Name (1),
      Identifies Interface By Index (2), Identifies Interface By Address
      (3)

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

8.  Security Considerations

   The following are legitimate uses of PROBE:

   o  to determine the operational status of an interface

   o  to determine which protocols (e.g., IPv4, IPv6) are active on an
      interface

   However, malicious parties can use PROBE to obtain additional
   information.  For example, a malicious party can use PROBE to
   discover interface names.  Having discovered an interface name, the
   malicious party may be able to infer additional information.
   Additional information may include:

   o  interface bandwidth





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   o  the type of device that supports the interface (e.g., vendor
      identity)

   o  the operating system version that the above-mentioned device
      executes

   Understanding this risk, network operators establish policies that
   restrict access to ICMP Extended Echo functionality.  In order to
   enforce these polices, nodes that support ICMP Extended Echo
   functionality MUST support the following configuration options:

   o  Enable/disable ICMP Extended Echo functionality.  By default, ICMP
      Extend Echo functionality is disabled.

   o  Define enabled L-bit settings.  By default, L-bit set is enabled
      and L-bit clear is disabled.

   o  Define enabled query types (i.e., by ifName, by ifIndex, by
      Address).  By default, all query types are disabled.

   o  For each enabled query type, define the prefixes from which ICMP
      Extended Echo Request messages are permitted

   o  For each interface, determine whether ICMP Echo Request messages
      are accepted

   When a node receives an ICMP Extended Echo Request message that it is
   not configured to support, it MUST silently discard the message.  See
   Section 4 for details.

   PROBE MUST NOT leak information about one Virtual Private Network
   (VPN) into another.  Therefore, when a node receives an ICMP Extended
   Echo Request and the proxy interface is in a different VPN than the
   probed interface, the node MUST return an ICMP Extended Echo Reply
   with error code equal to (2) No Such Interface.

   In order to protect local resources, implementations SHOULD rate-
   limit incoming ICMP Extended Echo Request messages.

9.  References

9.1.  Normative References

   [RFC0792]  Postel, J., "Internet Control Message Protocol", STD 5,
              RFC 792, DOI 10.17487/RFC0792, September 1981,
              <http://www.rfc-editor.org/info/rfc792>.





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   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC2277]  Alvestrand, H., "IETF Policy on Character Sets and
              Languages", BCP 18, RFC 2277, DOI 10.17487/RFC2277,
              January 1998, <http://www.rfc-editor.org/info/rfc2277>.

   [RFC2863]  McCloghrie, K. and F. Kastenholz, "The Interfaces Group
              MIB", RFC 2863, DOI 10.17487/RFC2863, June 2000,
              <http://www.rfc-editor.org/info/rfc2863>.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", STD 63, RFC 3629, DOI 10.17487/RFC3629, November
              2003, <http://www.rfc-editor.org/info/rfc3629>.

   [RFC4443]  Conta, A., Deering, S., and M. Gupta, Ed., "Internet
              Control Message Protocol (ICMPv6) for the Internet
              Protocol Version 6 (IPv6) Specification", STD 89,
              RFC 4443, DOI 10.17487/RFC4443, March 2006,
              <http://www.rfc-editor.org/info/rfc4443>.

   [RFC4884]  Bonica, R., Gan, D., Tappan, D., and C. Pignataro,
              "Extended ICMP to Support Multi-Part Messages", RFC 4884,
              DOI 10.17487/RFC4884, April 2007,
              <http://www.rfc-editor.org/info/rfc4884>.

9.2.  Informative References

   [RFC2151]  Kessler, G. and S. Shepard, "A Primer On Internet and TCP/
              IP Tools and Utilities", FYI 30, RFC 2151,
              DOI 10.17487/RFC2151, June 1997,
              <http://www.rfc-editor.org/info/rfc2151>.

   [RFC4594]  Babiarz, J., Chan, K., and F. Baker, "Configuration
              Guidelines for DiffServ Service Classes", RFC 4594,
              DOI 10.17487/RFC4594, August 2006,
              <http://www.rfc-editor.org/info/rfc4594>.

Appendix A.  The PROBE Application

   The PROBE application accepts input parameters, sets a counter and
   enters a loop to be exited when the counter is equal to zero.  On
   each iteration of the loop, PROBE emits an ICMP Extended Echo
   Request, decrements the counter, sets a timer, waits for the timer to
   expire.  If an expected ICMP Extended Echo Reply arrives while PROBE
   is waiting for the timer to expire, PROBE relays information returned



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   by that message to its user.  However, on each iteration of the loop,
   PROBE waits for the timer to expire, regardless of whether an
   Extended Echo Reply message arrives.

   PROBE accepts the following parameters:

   o  Count

   o  Wait

   o  Probing Interface Address

   o  Hop Count

   o  Proxy Interface Address

   o  Local

   o  Probed Interface Identifier

   Count is a positive integer whose default value is 3.  Count
   determines the number of times that PROBE iterates through the above-
   mentioned loop.

   Wait is a positive integer whose minimum and default values are 1.
   Wait determines the duration of the above-mentioned timer, measured
   in seconds.

   Probing Interface Address specifies the source address of ICMP
   Extended Echo Request.  The Probing Interface Address MUST be a
   unicast address and MUST identify an interface that is local to the
   probing node.

   The Proxy Interface Address identifies the interface to which the
   ICMP Extended Echo Request message is sent.  It can be an IPv4 or
   IPv6 address.  If it is an IPv4 address, PROBE emits an ICMPv4
   message.  If it is an IPv6 address, PROBE emits an ICMPv6 message.

   Local is a boolean value.  It is TRUE if the proxy and probed
   interfaces both reside on the probed node.  It is FALSE if the proxy
   interface resides on the probed node and the probed interface is
   directly connected to the probed node.

   The probed interface is the interface whose status is being queried.
   It is identified by one of the following:

   o  an interface name




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   o  an address from any address family (e.g., IPv4, IPv6, IEEE 802,
      48-bit MAC, 64-bit MAC)

   o  an ifIndex

   If the probed interface identifier is an address, it does not need to
   be of the same address family as the proxy interface address.  For
   example, PROBE accepts an IPv4 destination interface address and an
   IPv6 probed interface identifier

Acknowledgments

   Thanks to Sowmini Varadhan, Jeff Haas, Carlos Pignataro, Jonathan
   Looney and Joe Touch for their thoughtful review of this document.

Authors' Addresses

   Ron Bonica
   Juniper Networks
   2251 Corporate Park Drive
   Herndon, Virginia  20171
   USA

   Email: rbonica@juniper.net


   Reji Thomas
   Juniper Networks
   Elnath-Exora Business Park Survey
   Bangalore, Karnataka  560103
   India

   Email: rejithomas@juniper.net


   Jen Linkova
   Google
   1600 Amphitheatre Parkway
   Mountain View, California  94043
   USA

   Email: furry@google.com









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   Chris Lenart
   Verizon
   22001 Loudoun County Parkway
   Ashburn, Virginia  20147
   USA

   Email: chris.lenart@verizon.com


   Mohamed Boucadair
   Orange
   Rennes 35000
   France

   Email: mohamed.boucadair@orange.com




































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