



Internet Research Task Force (IRTF)                        S. Mastorakis
Request for Comments: 9507                      University of Notre Dame
Category: Experimental                                           D. Oran
ISSN: 2070-1721                      Network Systems Research and Design
                                                            I. Moiseenko
                                                              Apple Inc.
                                                               J. Gibson
                                                                R. Droms
                                                            Unaffiliated
                                                              March 2024


 Information-Centric Networking (ICN) Traceroute Protocol Specification

Abstract

   This document presents the design of an Information-Centric
   Networking (ICN) Traceroute protocol.  This includes the operation of
   both the client and the forwarder.

   This document is a product of the Information-Centric Networking
   Research Group (ICNRG) of the IRTF.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for examination, experimental implementation, and
   evaluation.

   This document defines an Experimental Protocol for the Internet
   community.  This document is a product of the Internet Research Task
   Force (IRTF).  The IRTF publishes the results of Internet-related
   research and development activities.  These results might not be
   suitable for deployment.  This RFC represents the consensus of the
   Information-Centric Networking Research Group of the Internet
   Research Task Force (IRTF).  Documents approved for publication by
   the IRSG are not candidates for any level of Internet Standard; see
   Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc9507.

Copyright Notice

   Copyright (c) 2024 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
   (https://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.

Table of Contents

   1.  Introduction
     1.1.  Requirements Language
   2.  Background on IP-Based Traceroute Operation
   3.  Traceroute Functionality Challenges and Opportunities in ICN
   4.  ICN Traceroute CCNx Packet Formats
     4.1.  ICN Traceroute Request CCNx Packet Format
     4.2.  ICN Traceroute Reply CCNx Packet Format
   5.  ICN Traceroute NDN Packet Formats
     5.1.  ICN Traceroute Request NDN Packet Format
     5.2.  ICN Traceroute Reply NDN Packet Format
   6.  Forwarder Operation
   7.  Protocol Operation for Locally Scoped Namespaces
   8.  Security Considerations
   9.  IANA Considerations
   10. References
     10.1.  Normative References
     10.2.  Informative References
   Appendix A.  Traceroute Client Application (Consumer) Operation
   Authors' Addresses

1.  Introduction

   In TCP/IP, routing and forwarding are based on IP addresses.  To
   ascertain the route to an IP address and to measure the transit
   delays, the traceroute utility is commonly used.  In Information-
   Centric Networking (ICN), routing and forwarding are based on name
   prefixes.  To this end, the ability to ascertain the characteristics
   of at least one of the available routes to a name prefix is a
   fundamental requirement for instrumentation and network management.
   These characteristics include, among others, route properties such as
   which forwarders were transited and the delay incurred through
   forwarding.

   In order to carry out meaningful experimentation and deployment of
   ICN protocols, new tools analogous to ping and traceroute used for
   TCP/IP are needed to manage and debug the operation of ICN
   architectures and protocols.  This document describes the design of a
   management and debugging protocol analogous to the traceroute
   protocol of TCP/IP; this new management and debugging protocol will
   aid the experimental deployment of ICN protocols.  As the community
   continues its experimentation with ICN architectures and protocols,
   the design of ICN Traceroute might change accordingly.  ICN
   Traceroute is designed as a tool to troubleshoot ICN architectures
   and protocols.  As such, this document is classified as an
   Experimental RFC.

   This specification uses the terminology defined in [RFC8793].

   This RFC represents the consensus of the Information-Centric
   Networking Research Group (ICNRG) of the Internet Research Task Force
   (IRTF).

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
   capitals, as shown here.

2.  Background on IP-Based Traceroute Operation

   In IP-based networks, traceroute is based on the expiration of the
   Time To Live (TTL) IP header field.  Specifically, a traceroute
   client sends consecutive packets (depending on the implementation and
   the user-specified behavior, such packets can be either UDP
   datagrams, ICMP Echo Request packets, or TCP SYN packets) with a TTL
   value increased by 1, essentially performing an expanding ring
   search.  In this way, the first IP packet sent will expire at the
   first router along the path, the second IP packet at the second
   router along the path, etc., until the router (or host) with the
   specified destination IP address is reached.  Each router along the
   path towards the destination responds by sending back an ICMP Time
   Exceeded packet, unless explicitly prevented from doing so by a
   security policy.

   The IP-based traceroute utility operates on IP addresses and in
   particular depends on the IP packets having source IP addresses that
   are used as the destination address for replies.  Given that ICN
   forwards based on names rather than destination IP addresses, that
   the names do not refer to unique endpoints (multi-destination), and
   that the packets do not contain source addresses, a substantially
   different approach is needed.

3.  Traceroute Functionality Challenges and Opportunities in ICN

   In the Named Data Networking (NDN) and Content-Centric Networking
   (CCNx) protocols, the communication paradigm is based exclusively on
   named objects.  An Interest message is forwarded across the network
   based on its name.  Eventually, it retrieves a Content Object from
   either a producer application or some forwarder's Content Store (CS).

   An ICN network differs from an IP network in at least four important
   ways (four of which are as follows):

   *  IP identifies interfaces to an IP network with a fixed-length
      address and delivers IP packets to one or more interfaces.  ICN
      identifies units of data in the network with a variable-length
      name consisting of a hierarchical list of segments.

   *  An IP-based network depends on the IP packets having source IP
      addresses that are used as the destination address for replies.
      On the other hand, ICN Interests do not have source addresses, and
      they are forwarded based on names, which do not refer to a unique
      endpoint.  Data packets follow the reverse path of the Interests
      based on hop-by-hop state created during Interest forwarding.

   *  An IP network supports multi-path, single-destination, stateless
      packet forwarding and delivery via unicast; a limited form of
      multi-destination selected delivery with anycast; and group-based
      multi-destination delivery via multicast.  In contrast, ICN
      supports multi-path and multi-destination stateful Interest
      forwarding and multi-destination data delivery to units of named
      data.  This single forwarding semantic subsumes the functions of
      unicast, anycast, and multicast.  As a result, consecutive (or
      retransmitted) ICN Interest messages may be forwarded through an
      ICN network along different paths and may be forwarded to
      different data sources (e.g., end-node applications, in-network
      storage) holding a copy of the requested unit of data.  The
      ability to discover multiple available (or potentially all) paths
      towards a name prefix is a desirable capability for an ICN
      Traceroute protocol, since it can be beneficial for congestion
      control purposes.  Knowing the number of available paths for a
      name can also be useful in cases where Interest forwarding based
      on application semantics/preferences is desirable.

   *  In the case of multiple Interests with the same name arriving at a
      forwarder, a number of Interests may be aggregated in a common
      Pending Interest Table (PIT) entry.  Depending on the lifetime of
      a PIT entry, the round-trip time of an Interest-Data exchange
      might vary significantly (e.g., it might be shorter than the full
      round-trip time to reach the original content producer).  To this
      end, the round-trip time experienced by consumers might also vary
      even under constant network load.

   These differences introduce new challenges, new opportunities, and
   new requirements regarding the design of ICN Traceroute.  Following
   this communication model, a traceroute client should be able to
   express traceroute requests directed to a name prefix and receive
   responses.

   Our goals are as follows:

   *  Trace one or more paths towards an ICN forwarder (for
      troubleshooting purposes).

   *  Trace one or more paths through which a named data object can be
      reached in the sense that Interest packets can be forwarded
      towards the application hosting the object.

   *  Test whether a specific named object is cached in some on-path CS,
      and, if so, trace the path towards it and return the identity of
      the corresponding forwarder.

   *  Perform transit delay network measurements.

   To this end, a traceroute target name can represent:

   *  An administrative name that has been assigned to a forwarder.
      Assigning a name to a forwarder implies the presence of a
      management application running locally that handles Operations,
      Administration, and Maintenance (OAM) operations.

   *  A name that includes an application's namespace as a prefix.

   *  A named object that might reside in some in-network storage.

   In order to provide stable and reliable diagnostics, it is desirable
   that the packet encoding of a traceroute request enable the
   forwarders to distinguish this request from a normal Interest while
   also diverging as little as possible from the forwarding behavior for
   an Interest packet.  In the same way, the encoding of a traceroute
   reply should minimize any processing differences from those employed
   for a data packet by the forwarders.

   The term "traceroute session" is used for an iterative process during
   which an endpoint client application generates a number of traceroute
   requests to successively traverse more distant hops in the path until
   it receives a final traceroute reply from a forwarder.  It is
   desirable that ICN Traceroute be able to discover a number of paths
   towards the expressed prefix within the same session or subsequent
   sessions.  To discover all the hops in a path, we need a mechanism
   (Interest Steering) to steer requests along different paths.  Such a
   capability was initially published in [PATHSTEERING] and has been
   specified for CCNx and NDN in [RFC9531].

   In the case of traceroute requests for the same prefix from different
   sources, it is also important to have a mechanism to avoid
   aggregating those requests in the PIT.  To this end, we need some
   encoding in the traceroute requests to make each request for a common
   prefix unique, hence avoiding PIT aggregation and further enabling
   the exact matching of a response with a particular traceroute packet.

   The packet types and formats are presented in Section 4.  Procedures
   for determining and indicating that a destination has been reached
   are included in Section 6.

4.  ICN Traceroute CCNx Packet Formats

   In this section, we present the CCNx packet formats [RFC8609] of ICN
   Traceroute where messages exist within outermost containments
   (packets).  Specifically, we propose two types of traceroute packets:
   a traceroute request and a traceroute reply.

4.1.  ICN Traceroute Request CCNx Packet Format

   The format of the traceroute request packet is presented below:

     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
    +---------------+---------------+---------------+---------------+
    |               |               |                               |
    |    Version    | PT_TR_REQUEST |         PacketLength          |
    |               |               |                               |
    +---------------+---------------+---------------+---------------+
    |               |               |               |               |
    |    HopLimit   |    Reserved   |     Flags     |  HeaderLength |
    |               |               |               |               |
    +---------------+---------------+---------------+---------------+
    /                                                               /
    /                        Path Label TLV                         /
    /                                                               /
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |               Traceroute Request Message TLVs                 |
    |                                                               |
    +---------------+---------------+---------------+---------------+

              Figure 1: Traceroute Request CCNx Packet Format

   The existing packet header fields have functionality similar to that
   of the header fields of a CCNx Interest packet.  The value of the
   packet type field is PT_TR_REQUEST.  See Section 9 for the value
   assignment.

   In contrast to the typical format of a CCNx packet header [RFC8609],
   there is a new optional fixed header added to the packet header:

   *  A Path Steering hop-by-hop header TLV, which is constructed hop by
      hop in the traceroute reply and included in the traceroute request
      to steer consecutive requests expressed by a client towards a
      common forwarding path or different forwarding paths.  The Path
      Label TLV is specified in [RFC9531].

   The message of a traceroute request is presented below:

     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
    +---------------+---------------+---------------+---------------+
    |                               |                               |
    |      MessageType = 0x05       |          MessageLength        |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                           Name TLV                            |
    |                                                               |
    +---------------+---------------+---------------+---------------+

                Figure 2: Traceroute Request Message Format

   The traceroute request message is of type T_DISCOVERY.  The Name TLV
   has the structure described in [RFC8609].  The name consists of the
   target (destination) prefix appended with a nonce typed name as its
   last segment.  The nonce can be encoded as a base64-encoded string
   with the URL-safe alphabet as defined in Section 5 of [RFC4648], with
   padding omitted.  The format of this TLV is a 64-bit nonce.  See
   [RFC9508] for the value assignment.  The purpose of the nonce is to
   avoid Interest aggregation and allow client matching of replies with
   requests.  As described below, the nonce is ignored for CS checking.

     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
    +---------------+---------------+---------------+---------------+
    |                               |                               |
    |        Name_Nonce_Type        |      Name_Nonce_Length = 8    |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                                                               |
    |                                                               |
    |                        Name_Nonce_Value                       |
    |                                                               |
    |                                                               |
    +---------------+---------------+---------------+---------------+

                   Figure 3: Name Nonce Typed Segment TLV

4.2.  ICN Traceroute Reply CCNx Packet Format

   The format of a traceroute reply packet is presented below:

     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
    +---------------+---------------+---------------+---------------+
    |               |               |                               |
    |    Version    |  PT_TR_REPLY  |          PacketLength         |
    |               |               |                               |
    +---------------+---------------+---------------+---------------+
    |                               |               |               |
    |            Reserved           |     Flags     | HeaderLength  |
    |                               |               |               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                       Path Label TLV                          |
    |                                                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                 Traceroute Reply Message TLVs                 |
    |                                                               |
    +---------------+---------------+---------------+---------------+

               Figure 4: Traceroute Reply CCNx Packet Format

   The header of a traceroute reply consists of the header fields of a
   CCNx Content Object and a hop-by-hop Path Steering TLV.  The value of
   the packet type field is PT_TR_REPLY.  See Section 9 for the value
   assignment.

   A traceroute reply message is of type T_OBJECT and contains a Name
   TLV (name of the corresponding traceroute request), a PayloadType
   TLV, and an ExpiryTime TLV with a value of 0 to indicate that replies
   must not be returned from network caches.

     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
    +---------------+---------------+---------------+---------------+
    |                               |                               |
    |      MessageType = 0x06       |          MessageLength        |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                           Name TLV                            |
    |                                                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                        PayloadType TLV                        |
    |                                                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                         ExpiryTime TLV                        |
    |                                                               |
    +---------------+---------------+---------------+---------------+

                 Figure 5: Traceroute Reply Message Format

   The PayloadType TLV is presented below.  It is of type
   T_PAYLOADTYPE_DATA, and the data schema consists of three TLVs:

   1)  the name of the sender of this reply (with the same structure as
       a CCNx Name TLV),

   2)  the sender's signature of their own name (with the same structure
       as a CCNx ValidationPayload TLV), and

   3)  a TLV with return codes to indicate whether the request was
       satisfied due to the existence of a local application, a CS hit,
       a match with a forwarder's name, or the HopLimit value of the
       corresponding request reaching 0.

     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
    +---------------+---------------+---------------+---------------+
    |                               |                               |
    |       T_PAYLOADTYPE_DATA      |             Length            |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                      Sender's Name TLV                        |
    |                                                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                    Sender's Signature TLV                     |
    |                                                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                     PT_TR_REPLY Code TLV                      |
    |                                                               |
    +---------------+---------------+---------------+---------------+

             Figure 6: Traceroute Reply PayloadType TLV Format

   The goal of including the name of the sender in the reply is to
   enable the user to reach this entity directly to ask for further
   management/administrative information using generic Interest-Data
   exchanges or by employing a more comprehensive management tool, such
   as CCNinfo [RFC9344], after a successful verification of the sender's
   name.

   The structure of the PT_TR_REPLY Code TLV is presented below (16-bit
   value).  The four assigned values are as follows:

   1:  Indicates that the target name matched the administrative name of
       a forwarder (as served by its internal management application).

   2:  Indicates that the target name matched a prefix served by an
       application (other than the internal management application of a
       forwarder).

   3:  Indicates that the target name matched the name of an object in a
       forwarder's CS.

   4:  Indicates that the HopLimit reached 0.

     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
    +---------------+---------------+---------------+---------------+
    |                               |                               |
    |     PT_TR_REPLY_Code_Type     |  PT_TR_REPLY_Code_Length = 2  |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                    PT_TR_REPLY_Code_Value                     |
    |                                                               |
    +---------------+---------------+---------------+---------------+

                       Figure 7: PT_TR_REPLY Code TLV

5.  ICN Traceroute NDN Packet Formats

   In this section, we present the ICN Traceroute Request and Reply
   packet formats according to the NDN packet format specification
   [NDNTLV].

5.1.  ICN Traceroute Request NDN Packet Format

   A traceroute request is encoded as an NDN Interest packet.  Its
   format is as follows:

           TracerouteRequest = INTEREST-TYPE TLV-LENGTH
                 Name
                 MustBeFresh
                 Nonce
                 HopLimit
                 ApplicationParameters?

               Figure 8: Traceroute Request NDN Packet Format

   The name of a request consists of the target name, a nonce value (it
   can be the value of the Nonce field), and the suffix "traceroute" to
   denote that this Interest is a traceroute request (added as a
   KeywordNameComponent [NDNTLV]).  When the "ApplicationParameters"
   element is present, a ParametersSha256DigestComponent (Section 6) is
   added as the last name segment.

   A traceroute request MAY carry a Path Label TLV in the NDN Link
   Adaptation Protocol [NDNLPv2] as specified in [RFC9531].

   Since the NDN packet format does not provide a mechanism to prevent
   the network from caching specific data packets, we instead use the
   MustBeFresh TLV for requests (in combination with a FreshnessPeriod
   TLV with a value of 1 for replies) to avoid fetching cached
   traceroute replies with a freshness period that has expired
   [REALTIME].

5.2.  ICN Traceroute Reply NDN Packet Format

   A traceroute reply is encoded as an NDN Data packet.  Its format is
   as follows:

           TracerouteReply = DATA-TLV TLV-LENGTH
                           Name
                           MetaInfo
                           Content
                           Signature

                Figure 9: Traceroute Reply NDN Packet Format

   A traceroute reply MAY carry a Path Label TLV in the NDN Link
   Adaptation Protocol [NDNLPv2] as specified in [RFC9531], since it
   might be modified in a hop-by-hop fashion by the forwarders along the
   reverse path.

   The name of a traceroute reply is the name of the corresponding
   traceroute request while the format of the MetaInfo field is as
   follows:

         MetaInfo = META-INFO-TYPE TLV-LENGTH
                  ContentType
                  FreshnessPeriod

                          Figure 10: MetaInfo TLV

   The value of the ContentType TLV is 0.  The value of the
   FreshnessPeriod TLV is 1, so that the replies are treated as stale
   data (almost instantly) as they are received by a forwarder.

   The content of a traceroute reply consists of the following two TLVs:
   Sender's Name (an NDN Name TLV) and Traceroute Reply Code.  There is
   no need to have a separate TLV for the sender's signature in the
   content of the reply, since every NDN Data packet carries the
   signature of the data producer.

   The Traceroute Reply Code TLV format is as follows (with the values
   specified in Section 4.2):

           PT_TR_REPLYCode = TRREPLYCODE-TLV-TYPE TLV-LENGTH 2*OCTET

                    Figure 11: Traceroute Reply Code TLV

6.  Forwarder Operation

   When a forwarder receives a traceroute request, the HopLimit value is
   checked and decremented, and the target name (i.e., the name of the
   traceroute request without the last Nonce name segment as well as the
   suffix "traceroute" and the ParametersSha256DigestComponent in the
   case of a request with the NDN packet format) is extracted.

   If the HopLimit has not expired (i.e., is greater than 0), the
   forwarder will forward the request upstream based on CS lookup, PIT
   creation, Longest Name Prefix Match (LNPM) lookup, and (if present)
   the path steering value.  If no valid next hop is found, an
   InterestReturn indicating "No Route" in the case of CCNx or a network
   NACK in the case of NDN is sent downstream.

   If HopLimit equals 0, the forwarder generates a traceroute reply.
   This reply includes the forwarder's administrative name and
   signature, and a Path Label TLV.  This TLV initially has a null
   value, since the traceroute reply originator does not forward the
   request and thus does not make a path choice.  The reply will also
   include the corresponding PT_TR_REPLY Code TLV.

   A traceroute reply will be the final reply of a traceroute session if
   any of the following conditions are met:

   *  If a forwarder has been given one or more administrative names,
      the target name matches one of them.

   *  The target name exactly matches the name of a Content Object
      residing in the forwarder's CS (unless the traceroute client
      application has chosen not to receive replies due to CS hits as
      specified in Appendix A).

   *  The target name matches (in an LNPM manner) a FIB entry with an
      outgoing face referring to a local application.

   The PT_TR_REPLY Code TLV value of the reply is set to indicate the
   specific condition that was met.  If none of those conditions were
   met, the PT_TR_REPLY Code is set to 4 to indicate that the HopLimit
   reached 0.

   A received traceroute reply will be matched to an existing PIT entry
   as usual.  On the reverse path, the Path Steering TLV of a reply will
   be updated by each forwarder to encode its choice of next hop(s).
   When included in subsequent requests, this Path Steering TLV allows
   the forwarders to steer the requests along the same path.

7.  Protocol Operation for Locally Scoped Namespaces

   In this section, we elaborate on two alternative design approaches in
   cases where the traceroute target prefix corresponds to a locally
   scoped namespace not directly routable from the client's local
   network.

   The first approach leverages the NDN Link Object [SNAMP].
   Specifically, the traceroute client attaches to the expressed request
   a Link Object that contains a number of routable name prefixes, based
   on which the request can be forwarded across the Internet until it
   reaches a network region where the request name itself is routable.
   A Link Object is created and signed by a data producer allowed to
   publish data under a locally scoped namespace.  The way that a client
   retrieves a Link Object depends on various network design factors and
   is out of scope for this document.

   At the time of this writing, and based on the current deployment of
   the Link Object by the NDN team [NDNLPv2], a forwarder at the border
   of the region where an Interest name becomes routable has to remove
   the Link Object from the incoming Interests.  The Interest state
   maintained along the entire forwarding path is based on the Interest
   name regardless of whether it was forwarded based on this name or a
   prefix in the Link Object.

   The second approach is based on prepending a routable prefix to the
   locally scoped name.  The resulting prefix will be the name of the
   traceroute requests expressed by the client.  In this way, a request
   will be forwarded based on the routable part of its name.  When it
   reaches the network region where the original locally scoped name is
   routable, the border forwarder rewrites the request name and deletes
   its routable part.  A forwarder will perform this rewriting operation
   on a request if the following two conditions are met:

   1)  the routable part of the request name matches a routable name of
       the network region adjacent to the forwarder (assuming that a
       forwarder is aware of those names), and

   2)  the remaining part of the request name is routable across the
       network region of this forwarder.

   The state along the path depends on whether the request is traversing
   the portion of the network where the locally scoped name is routable.
   In this case, the forwarding can be based entirely on the locally
   scoped name.  However, where a portion of the path lies outside the
   region where the locally scoped name is routable, the border router
   has to rewrite the name of a reply and prepend the routable prefix of
   the corresponding request to ensure that the generated replies will
   reach the client.

8.  Security Considerations

   A reflection attack could occur in the case of a traceroute reply
   with the CCNx packet format if a compromised forwarder includes in
   the reply the name of a victim forwarder.  This could redirect the
   future administrative traffic towards the victim.  To foil such
   reflection attacks, the forwarder that generates a traceroute reply
   MUST sign the name included in the payload.  In this way, the client
   is able to verify that the included name is legitimate and refers to
   the forwarder that generated the reply.  Alternatively, the forwarder
   could include in the reply payload their routable prefix(es) encoded
   as a signed NDN Link Object [SNAMP].

   This approach does not protect against on-path attacks where a
   compromised forwarder that receives a traceroute reply replaces the
   forwarder's name and the signature in the message with its own name
   and signature to make the client believe that the reply was generated
   by the compromised forwarder.  To foil such attack scenarios, a
   forwarder can sign the reply message itself.  In such cases, the
   forwarder does not have to sign its own name in the reply message,
   since the message signature protects the message as a whole and will
   be invalidated in the case of an on-path attack.  Additionally, a
   forwarder could swap out the name of a traceroute request with a name
   of its choosing.  In this case, however, the response with the
   spoofed name will not be received by a client, since the change of
   name would invalidate the state in the PIT on the path back to the
   client.

   Signing each traceroute reply message can be expensive and can
   potentially lead to computation attacks against forwarders.  To
   mitigate such attack scenarios, the processing of traceroute requests
   and the generation of the replies SHOULD be handled by a separate
   management application running locally on each forwarder.  The
   serving of traceroute replies is thereby separated from load on the
   forwarder itself.  The approaches used by ICN applications to manage
   load may also apply to the forwarder's management application.

   Interest flooding attack amplification is possible in the case of the
   second approach for dealing with locally scoped namespaces as
   described in Section 7.  A border forwarder will have to maintain
   extra state to prepend the correct routable prefix to the name of an
   outgoing reply, since the forwarder might be attached to multiple
   network regions (reachable under different prefixes) or a network
   region attached to this forwarder might be reachable under multiple
   routable prefixes.

   We also note that traceroute requests have the same privacy
   characteristics as regular Interests.

9.  IANA Considerations

   IANA has assigned 0x07 to "PT_TR_REQUEST" and 0x08 to "PT_TR_REPLY"
   in the "CCNx Packet Types" registry established by [RFC8609].

10.  References

10.1.  Normative References

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

   [RFC8174]  Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
              2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
              May 2017, <https://www.rfc-editor.org/info/rfc8174>.

   [RFC8609]  Mosko, M., Solis, I., and C. Wood, "Content-Centric
              Networking (CCNx) Messages in TLV Format", RFC 8609,
              DOI 10.17487/RFC8609, July 2019,
              <https://www.rfc-editor.org/info/rfc8609>.

   [RFC8793]  Wissingh, B., Wood, C., Afanasyev, A., Zhang, L., Oran,
              D., and C. Tschudin, "Information-Centric Networking
              (ICN): Content-Centric Networking (CCNx) and Named Data
              Networking (NDN) Terminology", RFC 8793,
              DOI 10.17487/RFC8793, June 2020,
              <https://www.rfc-editor.org/info/rfc8793>.

10.2.  Informative References

   [NDNLPv2]  NDN team, "NDNLPv2: Named Data Networking Link Adaptation
              Protocol v2", February 2023, <https://redmine.named-
              data.net/projects/nfd/wiki/NDNLPv2>.

   [NDNTLV]   NDN project team, "NDN Packet Format Specification",
              February 2024,
              <https://named-data.net/doc/NDN-packet-spec/current/>.

   [PATHSTEERING]
              Moiseenko, I. and D. Oran, "Path switching in content
              centric and named data networks", ICN '17: Proceedings of
              the 4th ACM Conference on Information-Centric Networking,
              pp. 66-76, DOI 10.1145/3125719.3125721, September 2017,
              <https://dl.acm.org/doi/10.1145/3125719.3125721>.

   [REALTIME] Mastorakis, S., Gusev, P., Afanasyev, A., and L. Zhang,
              "Real-Time Data Retrieval in Named Data Networking", 2018
              1st IEEE International Conference on Hot Information-
              Centric Networking (HotICN), Shenzhen, China, pp. 61-66,
              DOI 10.1109/HOTICN.2018.8605992, August 2018,
              <https://ieeexplore.ieee.org/document/8605992>.

   [RFC4648]  Josefsson, S., "The Base16, Base32, and Base64 Data
              Encodings", RFC 4648, DOI 10.17487/RFC4648, October 2006,
              <https://www.rfc-editor.org/info/rfc4648>.

   [RFC9344]  Asaeda, H., Ooka, A., and X. Shao, "CCNinfo: Discovering
              Content and Network Information in Content-Centric
              Networks", RFC 9344, DOI 10.17487/RFC9344, February 2023,
              <https://www.rfc-editor.org/info/rfc9344>.

   [RFC9508]  Mastorakis, S., Oran, D., Gibson, J., Moiseenko, I., and
              R. Droms, "Information-Centric Networking (ICN) Ping
              Protocol Specification", RFC 9508, DOI 10.17487/RFC9508,
              March 2024, <https://www.rfc-editor.org/info/rfc9508>.

   [RFC9531]  Moiseenko, I. and D. Oran, "Path Steering in Content-
              Centric Networking (CCNx) and Named Data Networking
              (NDN)", RFC 9531, DOI 10.17487/RFC9531, March 2024,
              <https://www.rfc-editor.org/info/rfc9531>.

   [SNAMP]    Afanasyev, A., Yi, C., Wang, L., Zhang, B., and L. Zhang,
              "SNAMP: Secure namespace mapping to scale NDN forwarding",
              2015 IEEE Conference on Computer Communications Workshops
              (INFOCOM WKSHPS), Hong Kong, China, pp. 281-286,
              DOI 10.1109/INFCOMW.2015.7179398, April 2015,
              <https://ieeexplore.ieee.org/abstract/document/7179398>.

Appendix A.  Traceroute Client Application (Consumer) Operation

   This section is an informative appendix regarding the proposed
   traceroute client operation.

   The client application is responsible for generating traceroute
   requests for prefixes provided by users.

   The overall process can be iterative: the first traceroute request of
   each session will have a HopLimit of 1 to reach the first hop
   forwarder, the second request will have a HopLimit of 2 to reach the
   second hop forwarder, and so on.

   When generating a series of requests for a specific name, the first
   request will typically not include a Path Label TLV, since no TLV
   value is known.  After a traceroute reply containing a Path Label TLV
   is received, each subsequent request might include the received path
   steering value in the Path Label header TLV to drive the requests
   towards a common path as part of checking network performance.  To
   discover more paths, a client can omit the Path Label TLV in future
   requests.  Moreover, for each new traceroute request, the client has
   to generate a new nonce and record the time that the request was
   expressed.  The client also sets the lifetime of the traceroute
   request, which carries the same semantics as the Interest Lifetime
   [RFC8609] in an Interest.

   Moreover, the client application might not wish to receive replies
   due to CS hits.  In CCNx, a mechanism to achieve that would be to use
   a Content Object Hash Restriction TLV with a value of 0 in the
   payload of a traceroute request message.  In NDN, the exclude filter
   selector can be used.

   When it receives a traceroute reply, the client would typically match
   the reply to a sent request and compute the round-trip time of the
   request.  It should parse the Path Label value and decode the reply's
   payload to parse the sender's name and signature.  The client should
   verify that both the received message and the forwarder's name have
   been signed by the key of the forwarder, whose name is included in
   the payload of the reply (by fetching this forwarder's public key and
   verifying the contained signature).  In the case that the client
   receives a PT_TR_REPLY Code TLV with a valid value, it can stop
   sending requests with increasing HopLimit values and potentially
   start a new traceroute session.

   In the case that a traceroute reply is not received for a request
   within a certain time interval (lifetime of the request), the client
   should time out and send a new request with a new nonce value up to a
   maximum number of requests to be sent specified by the user.

Authors' Addresses

   Spyridon Mastorakis
   University of Notre Dame
   South Bend, IN
   United States of America
   Email: smastor2@nd.edu


   Dave Oran
   Network Systems Research and Design
   Cambridge, MA
   United States of America
   Email: daveoran@orandom.net


   Ilya Moiseenko
   Apple Inc.
   Cupertino, CA
   United States of America
   Email: iliamo@mailbox.org


   Jim Gibson
   Unaffiliated
   Belmont, MA
   United States of America
   Email: jcgibson61@gmail.com


   Ralph Droms
   Unaffiliated
   Hopkinton, MA
   United States of America
   Email: rdroms.ietf@gmail.com
