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Versions: (draft-zjns-mpls-lsp-ping-relay-reply) 00 01 02 03 04 05 06 07 08 09 10 11 RFC 7743

Network Working Group                                        J. Luo, Ed.
Internet-Draft                                                       ZTE
Updates: 4379 (if approved)                                  L. Jin, Ed.
Intended status: Standards Track
Expires: October 4, 2014                                  T. Nadeau, Ed.
                                                             Lucidvision
                                                         G. Swallow, Ed.
                                                                   Cisco
                                                           April 2, 2014


               Relayed Echo Reply mechanism for LSP Ping
                draft-ietf-mpls-lsp-ping-relay-reply-03

Abstract

   In some inter autonomous system (AS) and inter-area deployment
   scenarios for RFC 4379 "Label Switched Path (LSP) Ping and
   Traceroute", a replying LSR may not have the available route to the
   initiator, and the Echo Reply message sent to the initiator would be
   discarded resulting in false negatives or complete failure of
   operation of LSP Ping and Traceroute.  This document describes
   extensions to LSP Ping mechanism to enable the replying Label
   Switching Router (LSR) to have the capability to relay the Echo
   Response by a set of routable intermediate nodes to the initiator.
   This document updates RFC 4379.

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 October 4, 2014.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.



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   This document is subject to BCP 78 and the IETF Trust's Legal
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   it for publication as an RFC or to translate it into languages other
   than English.






























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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
     1.1.  Conventions Used in This Document  . . . . . . . . . . . .  4
   2.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  4
   3.  Extensions . . . . . . . . . . . . . . . . . . . . . . . . . .  6
     3.1.  Relayed Echo Reply message . . . . . . . . . . . . . . . .  6
     3.2.  Relay Node Address Stack . . . . . . . . . . . . . . . . .  6
     3.3.  New Return Code  . . . . . . . . . . . . . . . . . . . . .  8
   4.  Procedures . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     4.1.  Sending an Echo Request  . . . . . . . . . . . . . . . . .  8
     4.2.  Receiving an Echo Request  . . . . . . . . . . . . . . . .  8
     4.3.  Originating an Relayed Echo Reply  . . . . . . . . . . . .  9
     4.4.  Relaying an Relayed Echo Reply . . . . . . . . . . . . . .  9
     4.5.  Sending an Echo Reply  . . . . . . . . . . . . . . . . . . 10
     4.6.  Receiving an Echo Reply  . . . . . . . . . . . . . . . . . 10
   5.  LSP Ping Relayed Echo Reply Example  . . . . . . . . . . . . . 10
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   7.  Backward Compatibility . . . . . . . . . . . . . . . . . . . . 12
   8.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 13
     8.1.  New Message Type . . . . . . . . . . . . . . . . . . . . . 13
     8.2.  New TLV  . . . . . . . . . . . . . . . . . . . . . . . . . 13
     8.3.  New Return Code  . . . . . . . . . . . . . . . . . . . . . 13
   9.  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 14
   10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 14
   11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     11.1. Normative References . . . . . . . . . . . . . . . . . . . 14
     11.2. Informative References . . . . . . . . . . . . . . . . . . 14
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15






















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1.  Introduction

   This document describes the extensions to the Label Switched Path
   (LSP) Ping as specified in [RFC4379], by adding a relayed echo reply
   mechanism which could be used to detect data plane failures for the
   inter autonomous system (AS) and inter-area LSPs.  The extensions are
   to update the [RFC4379].  Without these extensions, the ping
   functionality provided by [RFC4379] would fail in many deployed
   inter-AS scenarios, since the replying LSR in one AS may not have the
   available route to the initiator in the other AS.  The mechanism in
   this document defines a new message type referred as "Relayed Echo
   Reply message", and a new TLV referred as "Relay Node Address Stack
   TLV".

1.1.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].


2.  Motivation

   LSP Ping [RFC4379] defines a mechanism to detect the data plane
   failures and localize faults.  The mechanism specifies that the Echo
   Reply should be sent back to the initiator using an UDP packet with
   the IPv4/ IPv6 address of the originating LSR.  This works in
   administrative domains where IP addresses reachability are allowed
   among LSRs, and every LSR is able to route back to the originating
   LSR.  However, in practice, this is often not the case due to intra-
   provider routing policy, route hiding, and network address
   translation at autonomous system border routers (ASBR).  In fact, it
   is almost uniformly the case that in inter-AS scenarios, it is not
   allowed the distribution or direct routing to the IP addresses of any
   of the nodes other than the ASBR in another AS.

   Figure 1 demonstrates a case where one LSP is set up between PE1 and
   PE2.  If private addresses were in use within AS1, a traceroute from
   PE1 directed to PE2 could fail if the fault exists somewhere between
   ASBR2 and PE2.  Because P2 cannot forward packets back to PE1 given
   that it is a private address within AS1.  In this case, PE1 would
   detect a path break, as the Echo Reply messages would not be
   received.  Then localization of the actual fault would not be
   possible.







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   +-------+   +-------+   +------+   +------+   +------+   +------+
   |       |   |       |   |      |   |      |   |      |   |      |
   |  PE1  +---+   P1  +---+ ASBR1+---+ ASBR2+---+  P2  +---+  PE2 |
   |       |   |       |   |      |   |      |   |      |   |      |
   +-------+   +-------+   +------+   +------+   +------+   +------+
   <---------------AS1-------------><---------------AS2------------>
   <---------------------------- LSP ------------------------------>


                Figure 1: Simple Inter-AS LSP Configuration


   A second example that illustrates how [RFC4379] would be insufficient
   would be the inter-area situation in a seamless MPLS architecture
   [I-D.ietf-mpls-seamless-mpls] as shown below in Figure 2.  In this
   example LSRs in the core network would not have IP reachable route to
   any of the ANs.  When tracing an LSP from one AN to the remote AN,
   the LSR1/LSR2 node could not make a response to the Echo Request
   either, like the P2 node in the inter-AS scenario in Figure 1.


              +-------+   +-------+   +------+   +------+
              |       |   |       |   |      |   |      |
           +--+ AGN11 +---+ AGN21 +---+ ABR1 +---+ LSR1 +--> to AGN
          /   |       |  /|       |   |      |   |      |
   +----+/    +-------+\/ +-------+   +------+  /+------+
   | AN |              /\                     \/
   +----+\    +-------+  \+-------+   +------+/\ +------+
          \   |       |   |       |   |      |  \|      |
           +--+ AGN12 +---+ AGN22 +---+ ABR2 +---+ LSR2 +--> to AGN
              |       |   |       |   |      |   |      |
              +-------+   +-------+   +------+   +------+
   static route     ISIS L1 LDP             ISIS L2 LDP
   <-Access-><--Aggregation Domain--><---------Core--------->


                   Figure 2: Seamless MPLS Architecture


   This document describes extensions to the LSP Ping mechanism to
   facilitate a response from the replying LSR, by defining a simple
   mechanism that uses a relay node (e.g, ASBR) to relay the message
   back to the initiator.  Every designated or learned relay node must
   have an IP route to the next relay node or to the initiator.  Using a
   recursive approach, relay node could relay the message to the next
   relay node until the initiator is reached.





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3.  Extensions

   [RFC4379] describes the basic MPLS LSP Ping mechanism, which defines
   two message types, Echo Request and Echo Reply message.  This
   document defines a new message, Relayed Echo Reply message.  This new
   message is used to replace Echo Reply message which is sent from the
   replying LSR to a relay node or from a relay node to another relay
   node.

   A new TLV named Relay Node Address Stack TLV is defined in this
   document, to carry the IP addresses of the possible relay nodes for
   the replying LSR.

   In addition, a new Return Code is defined to notify the initiator
   that the packet length is exceeded unexpected by the Relay Node
   Address Stack TLV.

   It should be noted that this document focuses only on detecting the
   LSP which is set up using a uniform IP address family type.  That is,
   all hops between the source and destination node use the same address
   family type for their LSP ping control planes.  This does not
   preclude nodes that support both IPv6 and IPv4 addresses
   simultaneously, but the entire path must be addressable using only
   one address family type.  Supporting for mixed IPv4-only and IPv6-
   only is beyond the scope of this document.

3.1.  Relayed Echo Reply message

   The Relayed Echo Reply message is a UDP packet, and the UDP payload
   has the same format with Echo Request/Reply message.  A new message
   type is requested from IANA.

   New Message Type:
       Value    Meaning
       -----    -------
       TBD      MPLS Relayed Echo Reply


   The use of TCP and UDP port number 3503 is described in [RFC4379] and
   has been allocated by IANA for LSP Ping messages.  The Relayed Echo
   Reply message will use the same port number.

3.2.  Relay Node Address Stack

   The Relay Node Address Stack TLV is an optional TLV.  It MUST be
   carried in the Echo Request, Echo Reply and Relayed Echo Reply
   messages if the echo reply relayed mechanism described in this
   document is required.  Figure 3 illustrates the TLV format.



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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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                Type           |               Length          |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |   Initiator Source Port       |   Number of Relayed Addresses |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                                                               |
     ~                Stack of Relayed Addresses                     ~
     |                                                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


                  Figure 3: Relay Node Address Stack TLV

   -  Type: to be assigned by IANA.  A value should be assigned from
      32768-49161 as suggested by [RFC4379] Section 3.

   -  Length: the length of the value field in octets.

   -  Initiator Source Port: the source UDP port that the initiator
      sends the Echo Request message, and also the port that is expected
      to receive the Echo Reply message.

   -  Number of Relayed Addresses: an integer indicating the number of
      relayed addresses in the stack.

   -  Stack of Relayed Addresses: a list of relay node addresses.

   The format of each relay node address is as below:

     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
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |        Address  Type          | Address Length|  Reserved   |K|
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     ~           Relayed Address (0, 4, or 16 octects)               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Type#   Address Type   Address Length
   ----    ------------   ------------
   0       Unspecified    0
   1       IPv4           4
   2       IPv6           16

   Reserved: This field is reserved and MUST be set to zero.




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   K bit: if the K bit is set to 1, then this sub-TLV MUST be kept in
   Relay Node Address Stack during TLV compress process described in
   section 4.2.  The K bit may be set by ASBRs whose address would be
   kept in the stack if necessary.

   Relayed Address: this field specifies the node address, either IPv4
   or IPv6.

3.3.  New Return Code

   A new Return Code is used by the replying LSR to notify the initiator
   that the packet length is exceeded unexpected by the Relay Node
   Address Stack TLV.

   New Return Code:
       Value    Meaning
       -----    -------
       TBD      Response Packet length was exceeded by the Relay Node
                Address Stack TLV unexpected



4.  Procedures

4.1.  Sending an Echo Request

   In addition to the procedures described in section 4.3 of [RFC4379],
   a Relay Node Address Stack TLV MUST be carried in the Echo Request
   message to facilitate the relay functionality.

   When the Echo Request is first sent by the initiator, a Relay Node
   Address Stack TLV with the initiator address in the stack and its
   source UDP port MUST be included.  That will ensure that the first
   relay node address in the stack will always be the initiator address.

   For the subsequent Echo Request messages, the initiator would copy
   the Relay Node Address Stack TLV from the received Echo Reply
   message.

4.2.  Receiving an Echo Request

   In addition to the processes in section 4.4 of [RFC4379], the
   procedures of the Relay Node Address Stack TLV are defined here.

   Upon receiving a Relay Node Address Stack TLV of the Echo Request
   message, the receiver MUST check the addresses of the stack in
   sequence from top to bottom (the first address in the stack will be
   the first one to be checked), to find out the first public routable



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   IP address.  Those address entries behind of the first routable IP
   address in the address list with K bit set to 0 MUST be deleted, and
   the address entry of the replying LSR MUST be added at the bottom of
   the stack.  Those address entries with K bit set to 1 MUST be kept in
   the stack.  The updated Relay Node Address Stack TLV MUST be carried
   in the response message.

   If the replying LSR is configured to hide its routable address
   information, the address entry added in the stack SHOULD be a blank
   entry with Address Type set to unspecified.  The blank address entry
   in the receiving Echo Request SHOULD be treated as an unroutable
   address entry.

   If the packet length was exceeded unexpectedly by the Relay Node
   Address Stack TLV, the TLV SHOULD be returned back unchanged in the
   Echo Reply message.  And the new return code in section 3.3 SHOULD be
   used to notify the initiator of the situation.

   If the first routable IP address is the first address in the stack,
   the replying LSR SHOULD respond an Echo Reply message to the
   initiator.

   If the first routable IP address is an intermediate node, other than
   the first address in the stack, the replying LSR SHOULD send a
   Relayed Echo Reply instead of an Echo Reply as a response.

   An LSR not recognize the Relay Node Address Stack TLV, SHOULD ignore
   it according to section 3 of [RFC4379].

4.3.  Originating an Relayed Echo Reply

   When the replying LSR receives an Echo Request with the first IP
   address in the Relay Node Address Stack TLV is IP unroutable, the
   replying LSR SHOULD send a Relayed Echo Reply message to the first
   routable intermediate node.  The processing of Relayed Echo Reply is
   the same with the procedure of the Echo Reply described in Section
   4.5 of [RFC4379], except the destination IP address and the
   destination UDP port.  The destination IP address of the Relayed Echo
   Reply is set to the first routable IP address from the Relay Node
   Address Stack TLV, and both the source and destination UDP port is
   set to 3503.

4.4.  Relaying an Relayed Echo Reply

   Upon receiving an Relayed Echo Reply message with its own address as
   the destination address in the IP header, the relay node SHOULD check
   the address items in Relay Node Address Stack TLV in sequence from
   top to down, and find the first routable node address.



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   If the first routable address is the top one of the address list,
   e.g, the initiator address, the relay node SHOULD send an Echo Reply
   message to the initiator containing the same payload with the Relayed
   Echo Reply message received.  See section 4.5 for detail.

   If the first routable address is not the top one of the address list,
   e.g, another intermediate relay node, the relay node SHOULD send an
   Relayed Echo Reply message to this relay node with the payload
   unchanged.

   Note, the replying LSR SHOULD send a Relayed Echo Reply message to
   the first relay node found in Relay Node Address Stack TLV that is
   routable by the router.  The routable address MUST be located before
   the source IP address of the received Relayed Echo Reply which must
   be also in the stack, otherwise the Relayed Echo Reply should not be
   sent, so as to avoid potential loop.

4.5.  Sending an Echo Reply

   The Echo Reply is sent in two cases:

   1.  When the replying LSR receives an Echo Request with the first IP
   address in the Relay Node Address Stack TLV IP routable, the replying
   LSR would send an Echo Reply to the initiator.  In addition to the
   procedure of the Echo Reply described in Section 4.5 of [RFC4379],
   the Relay Node Address Stack TLV would be carried in the Echo Reply.

   2.  When the intermediate relay node receives a Relayed Echo Reply
   with the first IP address in the Relay Node Address Stack TLV IP
   routable, the intermediate relay node would send the Echo Reply to
   the initiator with the UDP payload unchanged other than the Message
   Type field (change from type of Relayed Echo Reply to Echo Reply).
   The destination IP address of the Echo Reply is set to the first IP
   address in the stack, and the destination UDP port would be copied
   from the Initiator Source Port field of the Relay Node Address Stack
   TLV.  The source UDP port should be 3503.

4.6.  Receiving an Echo Reply

   In addition to the processes in Section 4.6 of [RFC4379], the
   initiator would copy the Relay Node Address Stack TLV received in the
   Echo Reply to the next Echo Request.


5.  LSP Ping Relayed Echo Reply Example

   Considering the inter-AS scenario in Figure 4 below.




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   +-------+   +-------+   +------+   +------+   +------+   +------+
   |       |   |       |   |      |   |      |   |      |   |      |
   |  PE1  +---+   P1  +---+ ASBR1+---+ ASBR2+---+  P2  +---+  PE2 |
   |       |   |       |   |      |   |      |   |      |   |      |
   +-------+   +-------+   +------+   +------+   +------+   +------+
   <---------------AS1-------------><---------------AS2------------>
   <--------------------------- LSP ------------------------------->


                      Figure 4: Example Inter-AS LSP


   In the example, an LSP has been created between PE1 to PE2.  When
   performing LSP traceroute on the LSP, the first Echo Request sent by
   PE1 with outer-most label TTL=1, contains the Relay Node Address
   Stack TLV with PE1's address.

   After processed by P1, P1's address will be added in the Relay Node
   Address Stack TLV address list following PE1's address in the Echo
   Reply.

   PE1 copies the Relay Node Address Stack TLV into the next Echo
   Request when receiving the Echo Reply.

   Upon receiving the Echo Request, ASBR1 checks the address list in the
   Relay Node Address Stack TLV in sequence, and finds out that PE1's
   address is routable.  Then deletes P1's address, and adds its own
   address following PE1 address.  As a result, there would be PE1's
   address followed by ASBR1's address in the Relay Node Address Stack
   TLV of the Echo Reply sent by ASBR1.

   PE1 then sends an Echo Request with outer-most label TTL=3,
   containing the Relay Node Address Stack TLV copied from the received
   Echo Reply message.  Upon receiving the Echo Request message, ASBR2
   checks the address list in the Relay Node Address Stack TLV in
   sequence, and finds out that PE1's address is IP route unreachable,
   and ASBR1's address is the first routable one in the Relay Node
   Address Stack TLV.  ASBR2 adds its address as the last address item
   following ASBR1's address in Relay Node Address Stack TLV, sets
   ASBR1's address as the destination address of the Relayed Echo Reply,
   and sends the Relayed Echo Reply to ASBR1.

   Upon receiving the Relayed Echo Reply from ASBR2, ASBR1 checks the
   address list in the Relay Node Address Stack TLV in sequence, and
   finds out that PE1's address is first routable one in the address
   list.  Then ASBR1 sends an Echo Reply to PE1 with the payload of the
   received Relayed Echo Reply no changes other than the Message Type
   field.



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   For the Echo Request with outer-most label TTL=4, P2 checks the
   address list in the Relay Node Address Stack TLV in sequence, and
   finds out that both PE1's and ASBR1's addresses are not IP routable,
   and ASBR2's address is the first routable address.  Then P2 sends an
   Relayed Echo Reply to ASBR2 with the Relay Node Address Stack TLV
   containing four addresses, PE1's, ASBR1's, ASBR2's and P2's address
   in sequence.

   Then according to the process described in section 4.4, ASBR2 sends
   the Relayed Echo Reply to ASBR1.  Upon receiving the Relayed Echo
   Reply, ASBR1 sends an Echo Reply to PE1 which is routable.  And as
   relayed by ASBR2 and ASBR1, the Echo Reply would finally be sent to
   the initiator PE1.

   For the Echo Request with outer-most label TTL=5, the Echo Reply
   would relayed to PE1 by ASBR2 and ASBR1, similar to the case of
   TTL=4.

   The Echo Reply from the replying node which has no IP reachable route
   to the initiator is finally transmitted to the initiator by multiple
   relay nodes.


6.  Security Considerations

   The Relayed Echo Reply mechanism for LSP Ping creates an increased
   risk of DoS by putting the IP address of a target router in the Relay
   Node Address Stack.  These messages then could be used to attack the
   control plane of an LSR by overwhelming it with these packets.  A
   rate limiter SHOULD be applied to the well-known UDP port on the
   relay node as suggested in [RFC4379].  The node which acts as a relay
   node SHOULD validate the relay reply against a set of valid source
   addresses and discard packets from untrusted border router addresses.
   An implementation SHOULD provide such filtering capabilities.

   If an operator wants to obscure their nodes, it is RECOMMENDED that
   they may replace the replying node address that originated the Echo
   Reply with blank address in Relay Node Address Stack TLV.

   Other security considerations discussed in [RFC4379], are also
   applicable to this document.


7.  Backward Compatibility

   When one of the nodes along the LSP does not support the mechanism
   specified in this document, the node will ignore the Relay Node
   Address Stack TLV as described in section 4.2.  Then the initiator



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   may not receive the Relay Node Address Stack TLV in Echo Reply
   message from that node.  In this case, an indication should be
   reported to the operator, and the Relay Node Address Stack TLV in the
   next Echo Request message should be copied from the previous Echo
   Request, and continue the ping process.  If the node described above
   is located between the initiator and the first relay node, the ping
   process could continue without interruption.


8.  IANA Considerations

   IANA is requested to assign one new Message Type, one new TLV and one
   new Return Code.

8.1.  New Message Type

   This document requires allocation of one new message type from
   "Multi-Protocol Label Switching (MPLS) Label Switched Paths (LSPs)
   Ping Parameters" registry, the "Message Type" registry:

        Value    Meaning
        -----    -------
        TBD      MPLS Relayed Echo Reply

   The value should be assigned from the "Standards Action" range
   (0-191), and using the lowest free value within this range.

8.2.  New TLV

   This document requires allocation of one new TLV from "Multi-Protocol
   Label Switching (MPLS) Label Switched Paths (LSPs) Ping Parameters"
   registry, the "TLVs" registry:

        Type    Meaning
        ----    --------
        TBD     Relay Node Address Stack TLV

   A suggested value should be assigned from "Standards Action" range
   (32768-49161) as suggested by [RFC4379] Section 3, using the first
   free value within this range.

8.3.  New Return Code

   This document requires allocation of one new return code from "Multi-
   Protocol Label Switching (MPLS) Label Switched Paths (LSPs) Ping
   Parameters" registry, the "Return Codes" registry:





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    Value    Meaning
    -----    -------
    TBD      Response Packet length was exceeded unexpected by the Relay
             Node Address Stack TLV unexpected


   The value should be assigned from the "Standards Action" range
   (0-191), and using the lowest free value within this range.


9.  Acknowledgement

   The authors would like to thank Carlos Pignataro, Xinwen Jiao, Manuel
   Paul, Loa Andersson, Wim Henderickx, Mach Chen, Thomas Morin and
   Gregory Mirsky for their valuable comments and suggestions.


10.  Contributors

   Ryan Zheng
   JSPTPD
   371, Zhongshan South Road
   Nanjing, 210006, China
   Email: ryan.zhi.zheng@gmail.com



11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC4379]  Kompella, K. and G. Swallow, "Detecting Multi-Protocol
              Label Switched (MPLS) Data Plane Failures", RFC 4379,
              February 2006.

11.2.  Informative References

   [I-D.ietf-mpls-seamless-mpls]
              Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
              M., and D. Steinberg, "Seamless MPLS Architecture",
              draft-ietf-mpls-seamless-mpls-06 (work in progress),
              February 2014.






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Authors' Addresses

   Jian Luo (editor)
   ZTE
   50, Ruanjian Avenue
   Nanjing, 210012, China

   Email: luo.jian@zte.com.cn


   Lizhong Jin (editor)
   Shanghai, China

   Email: lizho.jin@gmail.com


   Thomas Nadeau (editor)
   Lucidvision

   Email: tnadeau@lucidvision.com


   George Swallow (editor)
   Cisco
   300 Beaver Brook Road
   Boxborough , MASSACHUSETTS 01719, USA

   Email: swallow@cisco.com























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