ICNRG S. Mastorakis
Internet-Draft UCLA
Intended status: Experimental J. Gibson
Expires: March 25, 2018 I. Moiseenko
Cisco Systems
R. Droms
D. Oran
September 21, 2017
ICN Traceroute Protocol Specification
draft-mastorakis-icnrg-icntraceroute-02
Abstract
This document presents the design of an ICN Traceroute protocol.
This includes the operations both on the client and the forwarder
side. The design expresses the views of the authors and does not
represent the views of the Named Data Networking Project Team.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on March 25, 2018.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Background on IP-Based Traceroute Operation . . . . . . . . . 3
3. Traceroute Functionality Challenges and Opportunities in ICN 3
4. ICN Traceroute CCNx Packet Format . . . . . . . . . . . . . . 5
4.1. ICN Traceroute Request CCNx Packet Format . . . . . . . . 6
4.2. Traceroute Reply CCNx Packet Format . . . . . . . . . . . 8
5. ICN Traceroute NDN Packet Format . . . . . . . . . . . . . . 11
5.1. ICN Traceroute Request NDN Packet Format . . . . . . . . 11
5.2. Traceroute Reply NDN Packet Format . . . . . . . . . . . 12
6. Forwarder Handling . . . . . . . . . . . . . . . . . . . . . 13
7. Protocol Operation For Locally-Scoped Namespaces . . . . . . 14
8. Security Considerations . . . . . . . . . . . . . . . . . . . 15
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 16
9.1. Normative References . . . . . . . . . . . . . . . . . . 16
9.2. Informative References . . . . . . . . . . . . . . . . . 16
Appendix A. Traceroute Client Application (Consumer) Operation . 16
Appendix B. Open Design Questions . . . . . . . . . . . . . . . 17
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
In TCP/IP, routing and forwarding are based on IP addresses. To
determine the route to an IP address and to measure the transit
delays, the traceroute utility is used. In ICN, routing and
forwarding are based on name prefixes. To this end, the problem of
determining the characteristics (i.e., transit forwarders and delays)
of, at least, one of the available routes to a name prefix is
fundamendal.
This document proposes protocol mechanisms for a traceroute
equivalent in ICN networks. This document contains two appendix
sections: 1) A non-normative appendix section suggesting useful
properties for an ICN traceroute client application that originates
traceroute requests and processes traceroute replies and 2) An
appendix section summarizing the open questions of the current
protocol design.
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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].
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 or TCP SYN packets) with a TTL value increased by
1, essentially, performing a 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 with the specified destination IP address is reached.
Each router along the path towards the destination will respond by
sending back an ICMP Time Exceeded packet.
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 different
approach is clearly needed.
3. Traceroute Functionality Challenges and Opportunities in ICN
In NDN and CCN protocols, 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).
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 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
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end-point. Data packets follow the reverse path of the Interests
based on hop-by-hop state created during Interest forwarding.
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. The
property of discovering multiple available (or potentially all)
paths towards a name prefix may be desirable 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 that Interest forwarding based on
application semantics/preferences is desirable.
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 ICN traceroute. Following this
communication model, a traceroute client should be able to express
traceroute requests with some name prefix and receive responses.
Our goals are the following:
o Trace one or more paths towards an ICN forwarder (for
troubleshooting purposes).
o Trace one or more paths along which an application can be reached
in the sense that Interest packets can be forwarded towards it.
o Test whether a specific named object is cached in some on-path CS,
and, if so, trace the path towards it and return the corresponding
forwarder.
o Perform transit delay network measurements.
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To this end, a traceroute target name can represent:
o An administrative name that has been assigned to a forwarder.
Assigning a name to a forwarder requires a management application
running locally, which handles Operations, Administration and
Management (OAM) operations.
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 traceroute request enables the
forwarders to distinguish this request 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
traceroute reply should allow for processing similar to that of 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 may be
desirable that ICN traceroute is 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.
It is also important, in the case of traceroute requests for the same
prefix from different sources, 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, and hence avoid PIT aggregation and further enabling
the exact matching of a response with a particular traceroute packet.
The packet types and format are presented in Section 4. The
procedures, e.g. the procedures for determining and indicating that a
destination has been reached, are specified in Section 6.
4. ICN Traceroute CCNx Packet Format
In this section, we present the CCNx packet format [CCNMessages] of
ICN traceroute, where messages exist within outermost containments
(packets). Specifically, we propose two types of traceroute packets,
a traceroute request and a reply packet type.
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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 | TrRequest | PacketLength |
| | | |
+---------------+---------------+---------------+---------------+
| | | | |
| HopLimit | Reserved | Flags | HeaderLength |
| | | | |
+---------------+---------------+---------------+---------------+
/ /
/ PathSteering TLV /
/ /
+---------------+---------------+---------------+---------------+
| |
| Traceroute Request Message TLVs |
| |
+---------------+---------------+---------------+---------------+
Traceroute Request CCNx Packet Format
The existing packet header fields have similar functionality to the
header fields of a CCNx Interest packet. The value of the packet
type field is TrRequest. The exact numeric value of this field type
is to be determined.
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 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 or different forwarding paths. An example of
such a scheme is presented in [LIPSIN].
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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 |
| |
+---------------+---------------+---------------+---------------+
Path Steering TLV
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 = 1 | MessageLength |
| | |
+---------------+---------------+---------------+---------------+
| |
| Name TLV |
| |
+---------------+---------------+---------------+---------------+
Traceroute Request Message Format
The traceroute 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 target (destination) prefix appended with a nonce
typed name component as its last component (to avoid Interest
aggregation and allow exact matching of requests with responses) The
value of this TLV will be a 64-bit nonce.
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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
+---------------+---------------+---------------+---------------+
| | |
| Name_Nonce_Type | Name_Nonce_Length = 8 |
| | |
+---------------+---------------+---------------+---------------+
| |
| |
| |
| Name_Nonce_Value |
| |
| |
+---------------+---------------+---------------+---------------+
Name Nonce Typed Component TLV
4.2. 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 | TrReply | PacketLength |
| | | |
+---------------+---------------+---------------+---------------+
| | | |
| Reserved | Flags | HeaderLength |
| | | |
+---------------+---------------+---------------+---------------+
| |
| PathSteering TLV |
| |
+---------------+---------------+---------------+---------------+
| |
| Traceroute Reply Message TLVs |
| |
+---------------+---------------+---------------+---------------+
Traceroute Reply CCNx Packet Format
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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 TrReply. The exact numeric value of this
field type is to be determined.
A traceroute reply message is of type Content Object, 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 cached by the network.
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 |
| |
+---------------+---------------+---------------+---------------+
Traceroute Reply Message Format
The PayloadType TLV is presented below. It is of type
T_PAYLOADTYPE_DATA, and the data schema consists of 2 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 return
codes to indicate whether the request was satisfied due to the
existence of a local application, a CS hit or a match with a
forwarder's name, or the HopLimit value of the corresponding request
reached 0.
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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 |
| |
+---------------+---------------+---------------+---------------+
| |
| TrReply Code TLV |
| |
+---------------+---------------+---------------+---------------+
Traceroute Reply Message 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 after a successful verification of the sender's name.
The structure of the TrReply Code TLV is presented below (16-bit
value). The potential values are the following:
o 1: Indicates that the target name matched the administrative name
of a forwarder (as served by its internal management application).
o 2: Indicates that the target name matched a prefix served by an
application (other than the internal management application of a
forwarder).
o 3: Indicates that the target name matched the name of an object in
a forwarder's CS.
o 4: Indicates that the the Hop limit reached the 0 value.
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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
+---------------+---------------+---------------+---------------+
| | |
| TrReply_Code_Type | TrReply_Code_Length = 2 |
| | |
+---------------+---------------+---------------+---------------+
| |
| TrReply_Code_Value |
+---------------+---------------+---------------+---------------+
TrReply Code TLV
5. ICN Traceroute NDN Packet Format
In this section, we present the ICN traceroute Request and Reply
Format according to the NDN packet specification [NDNTLV].
5.1. ICN Traceroute Request NDN Packet Format
A traceroute request is encoded as an NDN Interest packet. Its
format is the following:
TracerouteRequest ::= INTEREST-TYPE TLV-LENGTH
Name
MustBeFresh
Nonce
HopLimit TLV
PathSteering TLV?
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.
A traceroute request contains 2 new fields. The first one is an
optional field for the hop-by-hop PathSteering TLV. The format of
this field is the following:
PathSteering TLV ::= PATHSTEERING-TLV-TYPE TLV-LENGTH BYTE{8}
PathSteering TLV
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The second new field represents the HopLimit. The value of this
field is decremented when the request is received by each next-hop
forwarder. When its value reaches 0, the forwarder has to discard
the request. The format of this request is the following:
HopLimit TLV ::= HOPLIMIT-TLV-TYPE TLV-LENGTH BYTE{1}
HopLimit TLV
Since the NDN packet format does provide a mechanism to prevent the
network from caching specific data packets, we will use the
MustBeFresh selector for requests (in combination with a Freshness
Period TLV of value 0 for replies) to avoid fetching cached
traceroute replies.
5.2. Traceroute Reply NDN Packet Format
A traceroute reply is encoded as an NDN Data packet. Its format is
the following:
TracerouteReply ::= DATA-TLV TLV-LENGTH
PathSteering TLV
Name
MetaInfo
Content
Signature
Traceroute Reply NDN Packet Format
Compared to the format of a regular NDN Data packet, a traceroute
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 a traceroute reply is the name of the corresponding
traceroute 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.
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The content of a traceroute reply consists of the following 2 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 the following (with the
values specified in Section 4.2):
TrReplyCode ::= TRREPLYCODE-TLV-TYPE TLV-LENGTH BYTE{2}
Traceroute Reply Code TLV
6. Forwarder Handling
When a forwarder receives a traceroute request, the hop limit value
will be checked and decremented and the target name (i.e, the name of
the traceroute request without the last nonce name component and the
suffix "traceroute" in the case of a request with the NDN packet
format) will be extracted.
If the HopLimit value is not expired (has not reached 0), the
forwarder will forward the request upstream based on CS lookup, PIT
creation, LPM lookup and the path steering value, if present. If no
valid next-hop is found, an InterestReturn in the case of CCNx and a
network NACK in the case of NDN is sent downstream.
If the HopLimit value is equal to zero, the forwarder will generate a
traceroute reply. This reply will include the forwarder's own name
and signature, and a PathSteering 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 appropriate TrReply Code TLV.
A traceroute reply will be the final reply of a traceroute session if
one of the following conditions are met:
o Assuming that a forwarder has been given one or more
administrative names, the target name matches one of them.
o 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).
o The target name matches (in a Longest Prefix Match manner) a FIB
entry with an outgoing face referring to a local application.
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The TrReply Code TLV value of the reply will indicate the specific
condition that was met. If none of those conditions was met, the
TrReply Code will be 4 to indicate that the hop limit value 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 will
allow the forwarders to steer the requests along the same path.
7. Protocol Operation For Locally-Scoped Namespaces
In this section, we elaborate on 2 alternative design approaches in
cases that 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 has to do with the overall network
architecture design and is out of the scope of the current draft.
Based on the current deployment of the LINK Object by the NDN team, a
forwarder at the boarder 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
requests expressed by the client. In this way, a request will be
forwarded across the Internet based on the routable part of its name.
When it reaches the network region, where the original locally-scoped
name is routable, the boarder forwarder will have to rewrite the
request name and delete 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.
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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, while within the network region that the locally-
scoped prefix is routable is based only on it. To ensure that the
generated replies will reach the client, the boarder forwarder has
also to rewrite the name of a reply and prepend the routable prefix
of the corresponding request.
8. Security Considerations
Reflection attack concerns can arise when a compromised forwarder
generates a traceroute reply. In such cases, the compromised
forwarder can attach the name of a victim forwarder to the reply
payload to redirect future administrative traffic towards the victim.
To mitigate these attack scenarios, the forwarder that generates a
reply has to sign the name TLV contained in the reply message. When
the client receives a traceroute reply, it will be able to verify
that the key that signed the name in the reply message can be trusted
for both the traceroute prefix and the name of the forwarder that
generated the reply. Instead of including a raw name TLV and a
signature in the reply message, the forwarder can include its
routable prefix(es) encoded as a signed NDN Link Object [SNAMP].
Each forwarder can generate the signature of its own name or its LINK
Object in the beginning of its operation instead of doing so during
the generation of each individual reply.
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 mitigate 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 reply message, since
the message signature protects the message as a whole and will be
invalidated in the case of an on-path attack.
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 can be handled by a separate
management application running locally on each forwarder. Serving
traceroute replies is a load on the forwarder. 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 to deal with locally-scoped namespaces described in
Section 7. A boarder forwarder will have to maintain extra state to
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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 should also note that traceroute requests have the same privacy
characteristics as regular Interests.
9. References
9.1. 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>.
9.2. Informative References
[CCNMessages]
Mosko, M., Solis, I., and C. Wood, "CCNx Messages in TLV
Format.", 2016, <https://tools.ietf.org/html/
draft-irtf-icnrg-ccnxmessages-03>.
[LIPSIN] Jokela, P. and et al, "LIPSIN: line speed publish/
subscribe inter-networking, ACM SIGCOMM Computer
Communication Review 39.4: 195-206", 2009.
[NDNTLV] NDN Project Team, "NDN Packet Format Specification.",
2016, <http://named-data.net/doc/ndn-tlv/>.
[SNAMP] Afanasyev, A. and et al, "SNAMP: Secure namespace mapping
to scale NDN forwarding, IEEE Conference on Computer
Communications Workshops (INFOCOM WKSHPS)", 2015.
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 value 1 to reach the first hop
forwarder, the second of value 2 to reach the second hop forwarder
and so on and so forth.
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When generating a series of requests for a specific name, the first
one will typically not include a PathSteering TLV, since no TLV value
is known. After a traceroute reply containing a PathSteering TLV is
received, each subsequent request might include the received path
steering value in the PathSteering header TLV to drive the requests
towards a common path as part of checking the network performance.
To discover more paths, a client can omit the PathSteering 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. It will also set the lifetime of a request,
which will have semantics similar to the lifetime of an Interest.
Moreover, the client application might like not 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 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). In
the case that the client receives an TrReply 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.
Appendix B. Open Design Questions
In this section, we describe the open questions of our ICN traceroute
protocol design.
The current design can steer subsequent traceroute requests along the
same forwarding path (single-path traceroute). It can also
opportunistically forward subsequent requests along different paths
if the client does not attach a PathSteering TLV to the requests
letting the network decide how to forward them. However, one of the
objectives of ICN traceroute, as stated in Section 3, is to discover
a specific number of available paths and steer requests along them in
a deterministic manner (multi-path traceroute). The open question is
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how the ICN multi-path traceroute client could keep track of the
multiple available paths and iteratively traverse them by using
distinct PathSteering TLVs.
In the previous appendix section, we mentioned the mechanism in CCNx
and NDN that a traceroute client can use in order to avoid receiving
replies due to CS hits (bypass the caches along the path). If, in
the future, a specific Interest cache control mechanism to bypass
caches is added to the CCNx and NDN protocol specification, this
mechanism can be used by the ICN traceroute clients as well.
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
Cambridge, MA
US
Email: rdroms.ietf@gmail.com
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Dave Oran
Cambridge, MA
US
Email: daveoran@orandom.net
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