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ICNRG                                                      S. Mastorakis
Internet-Draft                                                      UCLA
Intended status: Experimental                                  J. Gibson
Expires: August 23, 2019                                    I. Moiseenko
                                                           Cisco Systems
                                                                R. Droms
                                                             Google Inc.
                                                                 D. Oran
                                     Network Systems Research and Design
                                                       February 19, 2019


                    ICN Ping Protocol Specification
                   draft-mastorakis-icnrg-icnping-04

Abstract

   This document presents the design of an ICN Ping protocol.  It
   includes the operations both on the client and the forwarder side.

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 https://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 August 23, 2019.

Copyright Notice

   Copyright (c) 2019 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.  Code Components extracted from this document must



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   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.  Requirements Language . . . . . . . . . . . . . . . . . .   2
   2.  Background on IP-Based Ping Operation . . . . . . . . . . . .   3
   3.  Ping Functionality Challenges and Opportunities in ICN  . . .   3
   4.  ICN Ping Echo CCNx Packet Formats . . . . . . . . . . . . . .   5
     4.1.  ICN Ping Echo Request CCNx Packet Format  . . . . . . . .   5
     4.2.  Ping Echo Reply CCNx Packet Format  . . . . . . . . . . .   8
   5.  ICN Ping Echo NDN Packet Formats  . . . . . . . . . . . . . .  11
     5.1.  ICN Ping Echo Request NDN Packet Format . . . . . . . . .  11
     5.2.  Ping Echo Reply NDN Packet Format . . . . . . . . . . . .  12
   6.  Forwarder Handling  . . . . . . . . . . . . . . . . . . . . .  13
   7.  Protocol Operation For Locally-Scoped Namespaces  . . . . . .  14
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  15
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  15
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  15
     10.2.  Informative References . . . . . . . . . . . . . . . . .  15
   Appendix A.  Ping Client Application (Consumer) Operation . . . .  16
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   Determining data plane reachability to a destination and taking
   coarse performance measurements of round trip time are fundamental
   facilities for network administration and troubleshooting.  In IP,
   where routing and forwarding are based on IP addresses, ICMP echo and
   ICMP echo response are the protocol mechanisms used for this purpose,
   generally exercised through the familiar ping utility.  In ICN, where
   routing and forwarding are based on name prefixes, the ability to
   determine reachability of names is required.

   This document proposes protocol mechanisms for a ping equivalent in
   ICN networks.  A non-normative appendix suggests useful properties
   for an ICN ping client application, analogous to IP ping, that
   originates echo requests and process echo replies.

1.1.  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 [RFC2119].




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2.  Background on IP-Based Ping Operation

   In IP-based ping, an IP address is specified, either directly, or via
   translation of a domain name through DNS.  The ping client
   application sends a number of ICMP Echo Request packets with the
   specified IP address as the IP destination address and an IP address
   from the client's host as the IP source address.

   An ICMP Echo Request is forwarded across the network based on its
   destination IP address.  If it eventually reaches the destination,
   the destination responds by sending back an ICMP Echo Reply packet to
   the IP source address from the ICMP Echo Request.

   If an ICMP Echo Request does not reach the destination or the Echo
   reply is lost, the ping client times out.  Any ICMP error messages,
   such as "no route to destination", generated by the ICMP Echo Request
   message are returned to the client and reported.

3.  Ping Functionality Challenges and Opportunities in ICN

   In ICN protocols (e.g., NDN and CCNx), the communication paradigm is
   based exclusively on named objects.  An Interest is forwarded across
   the network based on its name.  Eventually, it retrieves a content
   object either from a producer application or some forwarder's Content
   Store (CS).

   IP-based ping was built as an add-on on top of an already existing
   network architecture.  In ICN, we have the opportunity to incorporate
   diagnostic mechanisms directly in the network layer protocol, and
   hopefully provide more powerful diagnostic capability than can be
   realized through the layered ICMP Echo approach.

   An ICN network differs from an IP network in at least 4 important
   ways:

   o  IP identifies interfaces to an IP network with a fixed-length
      number, 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 components.

   o  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
      end-point.  Data packets follow the reverse path of the Interests
      based on hop-by-hop state created during Interest forwarding.





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   o  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.  This can
      lead to a significant variance in round-trip times, which might
      not be desirable in the case of a network troubleshooting
      mechanism like ping.

   o  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 an Interest-Data exchange might
      significantly vary (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.

   These differences introduce new challenges, new opportunities and new
   requirements in the design of an ICN ping protocol.  Following this
   communication model, a ping client should be able to express ping
   echo requests with some name prefix and receive responses.

   Our goals are the following:

   o  Test the reachability and the operation of an ICN forwarder.

   o  Test the reachability of an application (in the sense of whether
      Interests for a prefix that it serves can be forwarded to it) and
      discover the forwarder with local connectivity to (an instance of)
      the application.

   o  Test whether a specific named object is cached in some on-path CS,
      and, if so, return the administrative name of the corresponding
      forwarder.

   o  Perform some simple network performance measurements.

   To this end, a ping name can represent:

   o  An administrative name that has been assigned to a forwarder.




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

   o  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 ping echo request enable the forwarders
   to distinguish a ping from a normal Interest, while also allowing for
   forwarding behavior to be as similar as possible to that of an
   Interest packet.  In the same way, the encoding of a ping echo reply
   should allow for forwarder processing as close as possible to that
   used for data packets.

   The ping protocol should also enable relatively robust round-trip
   time measurements.  To this end, it is important to have a mechanism
   to steer consecutive ping echo requests for the same name towards an
   individual path [PATHSTEERING].

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

4.  ICN Ping Echo CCNx Packet Formats

   In this section, we describe the Echo Packet Format according to the
   CCNx packet format [CCNMessages], where messages exist within
   outermost containments (packets).  Specifically, we propose two types
   of ping packets, an echo request and an echo reply packet type.

4.1.  ICN Ping Echo Request CCNx Packet Format

   The format of the ping echo request packet is presented below:

















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    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    |  EchoRequest  |         PacketLength          |
    |               |               |                               |
    +---------------+---------------+---------------+---------------+
    |               |               |               |               |
    |    HopLimit   |    Reserved   |     Flags     |  HeaderLength |
    |               |               |               |               |
    +---------------+---------------+---------------+---------------+
    /                                                               /
    /                       PathSteering TLV                        /
    /                                                               /
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                   Echo Request Message TLVs                   |
    |                                                               |
    +---------------+---------------+---------------+---------------+


                      Echo Request CCNx Packet Format

   The existing packet header fields have the same definition as the
   header fields of a CCNx Interest packet.  The value of the packet
   type field is Echo Request.  The exact numeric value of this field
   type is to be assigned in the Packet Type IANA Registry for CCNx (see
   section 4.1 of [CCNMessages].

   Compared to the typical format of a CCNx packet header [CCNMessages],
   there is a new optional fixed header TLV added to the packet header:

   o  A PathSteering hop-by-hop header TLV, which is constructed hop-by-
      hop in the echo reply and included in the echo request to steer
      consecutive echo requests expressed by a ping client towards a
      common forwarding path.  An example of such a scheme is presented
      in [PATHSTEERING].














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    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

    +---------------+---------------+---------------+---------------+
    |                               |                               |
    |      PathSteering_Type        |      PathSteering_Length      |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                      PathSteering_Value                       |
    |                                                               |
    +---------------+---------------+---------------+---------------+


                             PathSteering TLV

   The message of an echo 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 = 1        |          MessageLength        |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                          Name TLV                             |
    |                                                               |
    +---------------+---------------+---------------+---------------+



                        Echo Request Message Format

   The echo request message is of type Interest in order to leverage the
   Interest forwarding behavior provided by the network.  The Name TLV
   has the structure described in [CCNMessages].  The name consists of
   the prefix that we would like to ping appended with a nonce typed
   name component as its last component.  The exact numeric value of
   this field type is to be assigned in the Name Component Type IANA
   Registry for CCNx (see section 4.5 of [CCNMessages].  The value of
   this TLV is a 64-bit nonce.  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.








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    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

    +---------------+---------------+---------------+---------------+
    |                               |                               |
    |           Nonce_Type          |       Nonce_Length = 8        |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                                                               |
    |                                                               |
    |                          Nonce_Value                          |
    |                                                               |
    |                                                               |
    +---------------+---------------+---------------+---------------+




                      Nonce Typed Name Component TLV

4.2.  Ping Echo Reply CCNx Packet Format

   The format of a ping echo 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    |   EchoReply   |          PacketLength         |
    |               |               |                               |
    +---------------+---------------+---------------+---------------+
    |                               |               |               |
    |            Reserved           |     Flags     | HeaderLength  |
    |                               |               |               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                        PathSteering TLV                       |
    |                                                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                    Echo Reply Message TLVs                    |
    |                                                               |
    +---------------+---------------+---------------+---------------+



                       Echo Reply CCNx Packet Format




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   The header of an echo reply consists of the header fields of a CCNx
   Content Object and a hop-by-hop PathSteering TLV.  The value of the
   packet type field is Echo Reply.  The exact numeric value of this
   field type is to be assigned in the Packet Type IANA Registry for
   CCNx (see section 4.1 of [CCNMessages].  The PathSteering header TLV
   is as defined for the echo request packet.

   A ping echo reply message is of type Content Object, contains a Name
   TLV (name of the corresponding echo request), a PayloadType TLV and
   an ExpiryTime TLV with a value of 0 to indicate that echo 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 = 2        |          MessageLength        |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                            Name TLV                           |
    |                                                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                         PayloadType TLV                       |
    |                                                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                         ExpiryTime TLV                        |
    |                                                               |
    +---------------+---------------+---------------+---------------+



                         Echo Reply Message Format

   The PayloadType TLV is presented below.  It is of type
   T_PAYLOADTYPE_DATA, and the data schema consists of 3 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), 3) a TLV with a return
   code to indicate what led to the generation of this reply (i.e.,
   existence of a local application, a CS hit or a match with a
   forwarder's administrative name as specified in Section 6).







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    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                     /
    /                                                               /
    +---------------+---------------+---------------+---------------+
    /                                                               /
    /                     Echo Reply Code TLV                       /
    /                                                               /
    +---------------+---------------+---------------+---------------+



                         Echo Reply Message Format

   The goal of including the name of the sender in the echo 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 [CCNInfo] after a successful verification of the sender's
   name.

   The structure of the Echo Reply Code TLV is presented below (16-bit
   value).  The defined values are the following:

   o  1: Indicates that the target name matched the administrative name
      of a forwarder.

   o  2: Indicates that the target name matched a prefix served by an
      application.

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









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    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

    +---------------+---------------+---------------+---------------+
    |                               |                               |
    |     Echo_Reply_Code_Type      |  Echo_Reply_Code_Length = 2   |
    |                               |                               |
    +---------------+---------------+---------------+---------------+
    |                                                               |
    |                      Echo_Reply_Code_Value                    |
    +---------------+---------------+---------------+---------------+




                            Echo Reply Code TLV

5.  ICN Ping Echo NDN Packet Formats

   In this section, we present the ICN Ping Echo Request and Reply
   Format according to the NDN packet specification [NDNTLV].

5.1.  ICN Ping Echo Request NDN Packet Format

   An echo request is encoded as an NDN Interest packet.  Its format is
   the following:

           EchoRequest ::= INTEREST-TYPE TLV-LENGTH
                             Name
                             MustBeFresh
                             Nonce
                             Parameters?

                      Echo Request NDN Packet Format

   The name of an echo request consists of the prefix to be pinged, a
   nonce value (it can be the value of the Nonce field) and the suffix
   "ping" to denote that this Interest is a ping request.

   The "Paremeters" field of the Request contains the following
   PathSteering TLV:

           PathSteering TLV ::= PATHSTEERING-TLV-TYPE TLV-LENGTH BYTE{8}

                             PathSteering TLV

   Since the NDN packet format does not provide a mechanism to prevent
   the network from caching specific data packets, we use the
   MustBeFresh selector for echo requests (in combination with a



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   Freshness Period TLV of value 0 for echo replies) to avoid fetching
   cached echo replies with an expired freshness period [REALTIME].

5.2.  Ping Echo Reply NDN Packet Format

   An echo reply is encoded as an NDN Data packet.  Its format is the
   following:

           EchoReply ::= DATA-TLV TLV-LENGTH
                           PathSteering TLV
                           Name
                           MetaInfo
                           Content
                           Signature

                       Echo Reply NDN Packet Format

   Compared to the format of a regular NDN Data packet, an echo reply
   contains a PathSteering TLV field, which is not included in the
   security envelope, since it might be modified in a hop-by-hop fashion
   by the forwarders along the reverse path.

   The name of an echo reply is the name of the corresponding echo
   request, while the format of the MetaInfo field is the following:

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

                               MetaInfo TLV

   The value of the ContentType TLV is 0.  The same applies to the value
   of the FreshnessPeriod TLV, so that the replies are treated as stale
   data as soon as they are received by a forwarder.

   The content of an echo reply consists of the following 2 TLVs:
   Sender's name (with a structure similar as an NDN Name TLV) and Echo
   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 Echo Reply Code TLV format is the following (with the values
   specified in Section 4.2):

           EchoReplyCode ::= ECHOREPLYCODE-TLV-TYPE TLV-LENGTH BYTE{2}

                            Echo Reply Code TLV




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6.  Forwarder Handling

   When a forwarder receives an echo request, it first extracts the
   message's base name (i.e., the request name with the Nonce name
   component excluded and the suffix "ping" in the case of an echo
   request with the NDN packet format).

   In some cases, the forwarder originates an echo reply, sending the
   reply downstream through the face on which the echo request was
   received.  This echo reply includes the forwarder's own name and
   signature and the appropriate echo reply code based on the condition
   that triggered the reply generation.  It also includes a pathSteering
   TLV, initially containing a null value (since the echo reply
   originator did not forward the request and, thus, does not make a
   path choice).

   The forwarder generates and returns an echo reply in the following
   cases:

   o  Assuming that a forwarder has been given one or more
      administrative names, the echo request base name exactly matches
      any of the forwarder's administrative name(s).

   o  The echo request's base name exactly matches the name of a
      content-object residing in the forwarder's CS (unless the ping
      client application has chosen not to receive replies due to CS
      hits as specified in Appendix A).

   o  The echo request base name matches (in a Longest Prefix Match
      manner) a FIB entry with an outgoing face referring to a local
      application.

   If none of the conditions to reply to the echo request are met, the
   forwarder will attempt to forward the echo request upstream based on
   the path steering value (if present), the results of the FIB LPM
   lookup and PIT creation (based on the name including the nonce typed
   name component and the suffix "ping" in the case of an echo request
   with the NDN packet format).  If no valid next-hop is found, an
   InterestReturn is sent downstream indicating "no route" (as with a
   failed attempt to forward an ordinary Interest).

   A received echo reply will be matched to an existing PIT entry as
   usual.  On the reverse path, the path steering TLV of an echo reply
   will be updated by each forwarder to encode its next-hop choice.
   When included in subsequent echo requests, this pathSteering TLV
   allows the forwarders to steer the echo requests along the same path.





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7.  Protocol Operation For Locally-Scoped Namespaces

   In this section, we elaborate on 2 alternative design approaches in
   cases that the pinged 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 ping 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 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 the
   scope of the current draft.

   Based on the current usage of the LINK Object by the NDN team, a
   forwarder at the border of the region where an Interest name becomes
   routable must remove the LINK Object from 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
   its name or a routable 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
   echo 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.  There are two conditions for a forwarder to
   perform this rewriting operation on a request: 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 maintained along the path, where the locally-scoped name is
   not routable, is based on the routable prefix along with the locally-
   scoped prefix.  Within the network region that the locally-scoped
   prefix is routable, the state is based only on it.  To ensure that
   the generated replies reach the ping client, the border forwarder has
   also to rewrite the name of a reply and prepend the routable prefix
   of the corresponding echo request.








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8.  Security Considerations

   A reflection attack could in the case of an echo 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 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].

   Interest flooding attack amplification is possible in the case of the
   second approach to deal with locally-scoped namespaces described in
   Section 7.  To eliminate such amplification, a border forwarder will
   have to maintain extra state in order 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.

9.  Acknowledgements

   The authors would like to thank Mark Stapp for the fruitful
   discussion on the objectives of the ICN ping protocol.

10.  References

10.1.  Normative References

   [CCNMessages]
              Mosko, M., Solis, I., and C. Wood, "CCNx Messages in TLV
              Format.", 2018, <https://tools.ietf.org/html/
              draft-irtf-icnrg-ccnxmessages-08>.

   [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>.

10.2.  Informative References

   [CCNInfo]  Asaeda, H. and X. Shao, "CCNinfo: Discovering Content and
              Network Information in Content-Centric Networks.", 2018,
              <https://tools.ietf.org/html/
              draft-asaeda-icnrg-ccninfo-01/>.




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   [NDNTLV]   NDN Project Team, "NDN Packet Format Specification.",
              2016, <http://named-data.net/doc/ndn-tlv/>.

   [PATHSTEERING]
              Moiseenko, I. and D. Oran, "Path switching in content
              centric and named data networks, in Proceedings of the 4th
              ACM Conference on Information-Centric Networking", 2017.

   [REALTIME]
              Mastorakis, S., Gusev, P., Afanasyev, A., and L. Zhang,
              "Real-Time Data Retrieval in Named Data Networking, in
              Proceedings of the 1st IEEE International Conference on
              Hot Topics in Information-Centric Networking", 2017.

   [SNAMP]    Afanasyev, A. and et al, "SNAMP: Secure namespace mapping
              to scale NDN forwarding, in Proceedings of the IEEE
              Conference on Computer Communications Workshops (INFOCOM
              WKSHPS)", 2015.

Appendix A.  Ping Client Application (Consumer) Operation

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

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

   When generating a series of echo requests for a specific name, the
   first echo request will typically not include a PathSteering TLV,
   since no TLV value is known.  After an echo reply containing a
   PathSteering TLV is received, each subsequent echo request can
   include the received path steering value in the PathSteering 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 steering TLV in future requests.  Moreover, for each new ping
   echo request, the client has to generate a new nonce and record the
   time that the request was expressed.  It will also set the lifetime
   of an echo request, which will have identical semantics to the
   lifetime of an Interest.

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

   When it receives an echo reply, the client would typically match the
   reply to a sent request and compute the round-trip time of the



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   request.  It should parse the PathSteering value and decode the
   reply's payload to parse the 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).  The
   client can also decode the Echo Reply Code TLV to understand the
   condition that triggered the generation of the reply.

   In the case that an echo 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 some
   maximum number of requests to be sent specified by the user.

Authors' Addresses

   Spyridon Mastorakis
   UCLA
   Los Angeles, CA
   US

   Email: mastorakis@cs.ucla.edu


   Jim Gibson
   Cisco Systems
   Cambridge, MA
   US

   Email: gibson@cisco.com


   Ilya Moiseenko
   Cisco Systems
   San Jose, CA
   US

   Email: iliamo@mailbox.org


   Ralph Droms
   Google Inc.
   Cambridge, MA
   US

   Email: rdroms.ietf@gmail.com





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   Dave Oran
   Network Systems Research and Design
   Cambridge, MA
   US

   Email: daveoran@orandom.net













































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