Internet DRAFT - draft-irtf-icnrg-pathsteering
draft-irtf-icnrg-pathsteering
ICNRG I. Moiseenko
Internet-Draft Apple, Inc.
Intended status: Experimental D. Oran
Expires: 1 April 2024 Network Systems Research and Design
29 September 2023
Path Steering in CCNx and NDN
draft-irtf-icnrg-pathsteering-07
Abstract
Path Steering is a mechanism to discover paths to the producers of
ICN content objects and steer subsequent Interest messages along a
previously discovered path. It has various uses, including the
operation of state-of-the-art multipath congestion control algorithms
and for network measurement and management. This specification
derives directly from the design published in _Path Switching in
Content Centric and Named Data Networks_ (4th ACM Conference on
Information-Centric Networking - ICN'17) and therefore does not
recapitulate the design motivations, implementation details, or
evaluation of the scheme. Some technical details are different
however, and where there are differences, the design documented here
is to be considered definitive.
This document is a product of the IRTF Information-Centric Networking
Research Group (ICNRG). It is not an IETF product and is not an
Internet Standard.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on 1 April 2024.
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Copyright Notice
Copyright (c) 2023 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
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Path Steering as an experimental extension to ICN protocol
architectures . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Requirements Language . . . . . . . . . . . . . . . . . . 4
1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Essential elements of ICN path discovery and path steering . 5
2.1. Path Discovery . . . . . . . . . . . . . . . . . . . . . 5
2.2. Path Steering . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Handling Path Steering errors . . . . . . . . . . . . . . 8
2.4. Interactions with Interest Aggregation . . . . . . . . . 9
2.5. How to represent the Path Label . . . . . . . . . . . . . 10
3. Mapping to CCNx and NDN packet encodings . . . . . . . . . . 11
3.1. Path label TLV . . . . . . . . . . . . . . . . . . . . . 11
3.2. Path label encoding for CCNx . . . . . . . . . . . . . . 12
3.3. Path label encoding for NDN . . . . . . . . . . . . . . . 13
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 14
5.1. Cryptographic protection of a path label . . . . . . . . 16
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
6.1. Normative References . . . . . . . . . . . . . . . . . . 17
6.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
Path Steering is a mechanism to discover paths to the producers of
ICN content objects and steer subsequent Interest messages along a
previously discovered path. It has various uses, including the
operation of state-of-the-art multipath congestion control algorithms
and for network measurement and management. This specification
derives directly from the design published in [Moiseenko2017] and
therefore does not recapitulate the design motivations,
implementation details, or evaluation of the scheme. That
publication should be considered a normative reference as it is not
likely a reader will be able to understand all elements of this
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design without first having read the reference. Some technical
details are different however, and where there are differences, the
design documented here is to be considered definitive.
Path discovery and subsequent path steering in ICN networks is
facilitated by the symmetry of forward and reverse paths in the CCNx
and NDN architectures. Path discovery is achieved by a consumer
endpoint transmitting an ordinary Interest message and receiving a
Content (Data) message containing an end-to-end path label
constructed on the reverse path by the forwarding plane. Path
steering is achieved by a consumer endpoint including a path label in
the Interest message, which is forwarded to each nexthop through the
corresponding egress interfaces in conjunction with longest name
prefix match (LNPM) lookup in the Forwarding Information Base (FIB).
This document is a product of the IRTF Information-Centric Networking
Research Group (ICNRG). It was supported by the ICNRG participants
during its development and through Research Group last call. It has
received detailed review by experts in both the CCNx and NDN
communities.
1.1. Path Steering as an experimental extension to ICN protocol
architectures
There are a number of important use cases to justify extending ICN
architectures such as CCNx [RFC8569] or NDN [NDN] to provide these
capabilities. These are summarized as follows:
* Support the discovery, monitoring and troubleshooting of multi-
path network connectivity based on names and name prefixes.
Analogous functions have been shown to be a crucial operational
capability in multicast and multi-path topologies for IP. The
canonical tools are the well-known _traceroute_ and _ping_. For
point-to-multipoint MPLS the more recent tree trace [RFC8029]
protocol is used. Equivalent diagnostic functions have been
defined for CCNx through the ICN Ping [I-D.irtf-icnrg-icnping] and
ICN Traceroute [I-D.irtf-icnrg-icntraceroute] specifications, both
of which are capable of exploiting path steering if available.
* Perform accurate online measurement of network performance, which
generally requires multiple consecutive packets follow the same
path under control of an application.
* Improve the performance and flexibility of multi-path congestion
control algorithms. Congestion control schemes such as
[Mahdian2016] and [Song2018] depend on the ability of a consumer
to explicitly steer packets onto individual paths in a multi-path
and/or multi-destination topology.
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* A consumer endpoint can mitigate content poisoning attacks by
directing its Interests onto the network paths that bypass
poisoned caches.
The path discovery machinery described here may (and likely will)
discover paths with varying properties. [RFC9217] discusses a number
of open questions in path aware networking, among which is how to
assess and exploit paths having different properties. Experimenting
with ICN path steering may be helpful in further elucidating these
questions and perhaps shedding light on which path properties are
most useful for the use cases cited above.
One nuance compared to other path aware networking approaches is that
ICN path steering piggybacks path discovery on the base ICN data
exchange, rather than having a separate path advertisement or
discovery mechanism. That means when the recorded path comes back in
an ICN Data message response, the properties of the path are known
only implicitly to the consumer as opposed to being explicitly
labeled. That makes the question of what properties a consumer uses
to choose a path one of observation or measurement rather than
advance selection based on an explicit advertised property (e.g SCION
[I-D.dekater-panrg-scion-overview]).
The utility and overall technical quality of this path steering
capability can be assessed by how well it enables the above use cases
and what performance and robustness effects it has on the underlying
ICN protocols and their use in various applications. A few of the
open questions that should be addressed through experimentation with
path steering include:
* how much more accurate and useful are measurements of RTT, packet
loss, etc. through ping and traceroute when utilizing path
steering?
* how much is the performance and robustness of multi-path
forwarding enhanced by the use of this explicit path steering
capability?
1.2. Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14 [RFC2119]
[RFC8174] when, and only when, they appear in all capitals, as shown
here.
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1.3. Terminology
This document uses the general ICN terms that are defined in
[RFC8793]. In addition we define the following terms specific to
path steering:
Path Discovery: The process of sending an Interest requesting
discovery of a path and if successful, receiving a Data containing
a Path Label for the path the corresponding Interest traversed
Path Steering: The process of sending an Interest message containing
the Path Label of a previously discovered path in order that the
forwarders use that path when forwarding that particular Interest
message.
Path Label: An optional field in the packet indicating a particular
path from a consumer to either a producer, or a forwarder cache
that can respond with the requested item. In an Interest message,
the Path Label gets built up hop by hop as the interest traverses
a path. In a Data message, the Path Label carries the full path
information back to the consumer for use in one or more subsequent
Interest messages.
Nexthop Label: One entry in a Path Label representing the next hop
for the corresponding forwarder to use when a path-steered
Interest message arrives at that forwarder. A sequence of Nexthop
Labels constitutes a full Path Label.
2. Essential elements of ICN path discovery and path steering
We elucidate the design using CCNx semantics [RFC8569] and extend its
Packet Encoding [RFC8609] as defined in Section 3.2. While the
terminology is slightly different, this design can be applied also to
NDN, by extending its bespoke packet encodings [NDNTLV] (See
Section 3.3).
2.1. Path Discovery
_End-to-end Path Discovery_ for CCNx is achieved by creating a _path
label_ and placing it as a hop-by-hop TLV in a CCNx Content (Data)
message. The path label is constructed hop-by-hop as the message
traverses the reverse path of transit CCNx forwarders as shown in the
first example in Figure 1. The path label is updated by adding to
the existing path label the nexthop label of the interface at which
the Content (Data) message has arrived. Eventually, when the
Content(Data) message arrives at the consumer, the path label
identifies the complete path the Content (Data) message took to reach
the consumer. As shown in the second example in the figure, when
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multiple paths are available, subsequent Interests may be able to
discover additional paths by omitting a path steering TLV and
obtaining a new path label on the returning interest.
Discover and use first path:
Consumer Interest 1 ___ Interest 2
| | ^ |
| | | |
| | | |
Forwarder 1 v | V
| (nexthop 1) (nexthop 1) ^ (nexthop 1)
| | | |
| | | |
Forwarder 2 v | v
(nexthop 3) / \ (nexthop 2) (nexthop 2) ^ (nexthop 2)
/ \ | | |
/ \ | | |
/ \ | | |
/ \ | | |
/ \ | | |
Forwarder 4 Forwarder 3 v | v
(nexthop 5)\ / (nexthop 4) (nexthop 4) ^ (nexthop 4)
\ / | | |
\ / | | |
\ / | | |
\ / | | |
\ / | | |
\ / v | v
Producer ___ Data 1 ___
or
Content Store
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Discover and use second path:
Consumer Interest 3 ___ Interest 4
| | ^ |
| | | |
| | | |
Forwarder 1 v | V
| (nexthop 1) (nexthop 1) ^ (nexthop 1)
| | | |
| | | |
Forwarder 2 v | v
(nexthop 3) / \ (nexthop 2) (nexthop 3) ^ (nexthop 3)
/ \ | | |
/ \ | | |
/ \ | | |
/ \ | | |
/ \ | | |
Forwarder 4 Forwarder 3 v | v
(nexthop 5)\ / (nexthop 4) (nexthop 5) ^ (nexthop 5)
\ / | | |
\ / | | |
\ / | | |
\ / | | |
\ / | | |
\ / v | v
Producer ___ Data 2 ___
or
Content Store
Figure 1: Basic example of path discovery and steering
2.2. Path Steering
Due to the symmetry of forward and reverse paths in CCNx, a consumer
application can reuse a discovered path label to fetch the same or
similar (e.g. next chunk, or next Application Data Unit, or next
pointer in a Manifest [I-D.irtf-icnrg-flic]) Content (Data) message
over the discovered network path. This _Path Steering_ is achieved
by processing the Interest message's path label at each transit ICN
forwarder and forwarding the Interest through the specified nexthop
among those identified as feasible by LNPM FIB lookup (Figure 2).
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----------------------------------------------------------------------
FORWARD PATH
----------------------------------------------------------------------
Interest +---------+ +-----+ (path label) +--------+ (match) Interest
-------->| Content |->| PIT | ------------>| Label |---------------->
| Store | +-----+ | Lookup |
+---------+ | \ (no path label) +--------+
| | \ |\(path label mismatch)
Data | | \ | \
<---------+ v \ | \
aggregate \ | \
\ | \
\ | +-----+ Interest
+--------------|---->| FIB | -------->
| +-----+
Interest-Return (NACK) v | (no route)
<----------------------------------------------+<-------+
----------------------------------------------------------------------
REVERSE PATH
----------------------------------------------------------------------
Interest-return(NACK) +-----+(update path label) Interest-Return(NACK)
<---------------------| |<----------------------------------------
| |
Data +---------+ | PIT | (update path label) Data
<------| Content |<---| |<----------------------------------------
| Store | | |
+---------+ +-----+
|
| (no match)
v
Figure 2: Path Steering CCNx / NDN data plane
2.3. Handling Path Steering errors
Over time, the state of interfaces and the FIB on forwarders may
change such that, at any particular forwarder, a given nexthop is no
longer valid for a given prefix. In this case, the path label will
point to a now-invalid nexthop. This is detected by failure to find
a match between the decoded nexthop ID and the nexthops of the FIB
entry after LNPM FIB lookup.
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On detecting an invalid path label, the forwarder SHOULD respond to
the Interest with an Interest-Return. We therefore define a new
_Invalid path label_ response code for the Interest Return message
and include the current path label as a hop-by-hop header. Each
transit forwarder processing the Interest-Return message updates the
path label in the same manner as Content (Data) messages, so that the
consumer receiving the Interest-Return (NACK) can easily identify
which path label is no longer valid.
A consumer may alternatively request that a forwarder detecting the
inconsistency forward the Interest by means of normal LNPM FIB lookup
rather than returning an error. The consumer endpoint, if it cares,
can keep enough information about outstanding Interests to determine
if the path label sent with the Interest fails to match the path
label in the corresponding returned Content (Data), and use that
information to replace stale path labels. It does so by setting the
FALLBACK MODE flag of the path label TLV in its Interest message.
2.4. Interactions with Interest Aggregation
If two or more Interests matching the same PIT entry arrive at a
forwarder, under current behavior they will be aggregated whether or
not they carry identical Path Labels TLVs. This may or may not be
appropriate. For example, multiple Interests with different MODES
(e.g. one with DISCOVERY MODE and one without) will get aggregated,
and the behavior of the forwarder might therefore be dependent on the
arrival order of those Interests. In particular,
* If the DISCOVERY MODE Interest arrives first, it will be forwarded
and potentially discover a new path, while the other Interest
would be aggregated. If that Interest carried no Path Label, its
behavior is essentially unchanged, but if it carried a non
DISCOVERY MODE Path Label, the consumer's intent for the Interest
to traverse the specified path will be ignored and it is
indeterminate if the chosen path will actually be used.
* If the two Interests arrive in the reverse order, the DISCOVERY
MODE Interest will be aggregated and the consumer issuing it does
not achieve its desire to discover a new path.
Multiple Interests intended to discover paths (i.e. by carrying the
DISCOVERY MODE flag defined in Section 2.5) might also be aggregated
by a forwarder. This limits the ability to discover multiple paths
in parallel and instead must be discovered incrementally in
subsequent exchanges. In other words, aggregated Interests will all
discover only one single path carried by one single Data packet.
This has implications for management applications like Traceroute
[I-D.irtf-icnrg-icntraceroute] which would likely perform much better
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if they discover paths in parallel. Hence, it is RECOMMENDED when
employing Path Steering that such applications craft their Interests
with unique name suffixes in order to avoid being aggregated.
| While path steering still operates correctly if DISCOVERY MODE
| Interests are aggregated, after further experimentation it may
| be appropriate to advise that:
|
| * a forwarder SHOULD NOT aggregate Interests carrying
| different Path Labels, and
|
| * SHOULD apply a rate limit to DISCOVERY MODE Interests in
| order to limit redundant traffic.
2.5. How to represent the Path Label
[Moiseenko2017] presents various options for how to represent a path
label, with different tradeoffs in flexibility, performance and space
efficiency. For this specification, we choose the _Polynomial
encoding_ which achieves reasonable space efficiency at the cost of
establishing a hard limit on the length of paths that can be
represented.
The polynomial encoding utilizes a fixed-size bit array. Each
transit ICN forwarder is allocated a fixed sized portion of the bit
array. This design allocates 12 bits (i.e. 4095 as a _generator
polynomial_) to each intermediate ICN forwarder. This matches the
scalability of today's commercial routers that support up to 4096
physical and logical interfaces and usually do not have more than a
few hundred active ones.
+------------------------------------------------------------------+
| Path Label bitmap |
+----------+-----------------+-----------------+-------------------+
| index | nexthop label | nexthop label | |
+----------+-----------------+-----------------+-------------------+
|<- 8bit ->|<---- 12bit ---->|<---- 12bit ---->|<----------------->|
Figure 3: Fixed size path label
A forwarder that receives a Content (Data) message encodes the
nexthop label in the next available slot and increments label index.
Conversely, a forwarder that receives an Interest message reads the
current nexthop label and decrements label index. Therefore, the
extra computation required at each hop to forward either an interest
or Content Object message with a path label is minimized and
constitutes a fairly trivial additional overhead compared to FIB
lookup and other required operations.
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This approach results in individual path label TLV instances being of
fixed pre-computed size. While this places a hard upper bound on the
maximum number of network hops that can be represented, this is not a
significant a practical problem in NDN and CCNx, since the size can
be pre-set during Content(Data) message encoding based on the exact
number of network hops traversed by the Interest message. Even long
paths of 24 hops will fit in a path label bitmap of 36 bytes if
nexthop label is encoded in 12 bits.
3. Mapping to CCNx and NDN packet encodings
3.1. Path label TLV
A Path label TLV is the tuple: {[Flags], [Path Label Hop Count],
[Nexthop Label], [Path label bitmap]}.
+================+=============+
| Flag | Value (hex) |
+================+=============+
| DISCOVERY_MODE | 0x00 |
+----------------+-------------+
| FALLBACK_MODE | 0x01 |
+----------------+-------------+
| STRICT_MODE | 0x02 |
+----------------+-------------+
| Unassigned | 0x03-0xFF |
+----------------+-------------+
Table 1: Path label flags
The Path Label Hop Count (PLHC) MUST be incremented by NDN and CCNx
forwarders if the Interest packet carries a path label and DISCOVERY
mode flag is set. A producer node or a forwarder with cached data
packet MUST use PLHC in calculation of a path label bitmap size
suitable for encoding the entire path to the consumer. The Path
Label Hop Count (PLHC) MUST be set to zero in newly created Data or
Interest-Return (NACK) packets. A consumer node MUST reuse Path
Label Hop Count (PLHC) together with the Path label bitmap (PLB) in
order to correctly forward the Interest(s) along the corresponding
network path.
If an NDN or CCNx forwarder supports path labeling, the Nexthop label
MUST be used to determine the correct egress interface for an
Interest packet carrying either the FALLBACK MODE or STRICT MODE
flag. If any particular NDN or CCNx forwarder is configured to
decrypt path labels of Interest packets (Section Security
Considerations (Section 5)), then the forwarder MUST
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1. decrypt the path label with its own symmetric key,
2. update the nexthop label with outermost label in the path label,
3. decrement Path Label Hop Count (PLHC), and
4. remove the outermost label from the path label.
If any particular NDN or CCNx forwarder is NOT configured to decrypt
path labels of Interest packets, then path label decryption SHOULD
NOT be performed.
The Nexthop label MUST be ignored by NDN and CCNx forwarders if
present in Data or Interest-Return (NACK) packets. If any particular
NDN or CCNx forwarder is configured to encrypt path labels of Data
and Interest-Return (NACK) packets (Section Security Considerations
(Section 5)), then the forwarder MUST encrypt existing path label
with its own symmetric key, append the nexthop label of the ingress
interface to the path label, and increment Path Label Hop Count
(PLHC). If any particular NDN or CCNx forwarder is NOT configured to
encrypt path labels of Interest packets, then path label encryption
SHOULD NOT be performed.
NDN and CCNx forwarders MUST fallback to longest name prefix match
(LNPM) FIB lookup if an Interest packet carries an invalid nexthop
label and the FALLBACK MODE flag is set.
CCNx forwarders MUST respond with an Interest Return packet
specifying a T_RETURN_INVALID_PATH_LABEL code if Interest packet
carries an invalid path label and the STRICT MODE flag is set. This
is a new Interrest return code defined herein (see Section 4 for the
value allocation).
CCNx forwarders MUST respond with an Interest Return packet
specifying the existing T_RETURN_MALFORMED_INTEREST code if the
Interest packet carries a path label TLV with both FALLBACK MODE and
STRICT MODE flags set.
3.2. Path label encoding for CCNx
Path Label is an optional Hop-by-Hop header TLV that can be present
in CCNx Interest, InterestReturn and Content Object packets.
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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_PATH_LABEL | Length + 4 |
+---------------+---------------+---------------+---------------+
| Flags | Path Label | Nexthop Label |
| | Hop Count | |
+---------------+---------------+---------------+---------------+
/ /
/ Path label bitmap (Length octets) /
/ /
+---------------+---------------+---------------+---------------+
Figure 4: Path label Hop-by-Hop header TLV for CCNx
3.3. Path label encoding for NDN
Path Label is an optional TLV for NDN Interest and Data packets which
is carried in the NDN Link Adaptation Protocol [NDNLPv2] used to wrap
NDN packets for carriage over various link layer protocols. NDNLPv2
was chosen over the NDN packet itself since it can carry hop-by-hop
information that potentially mutates at each hop and therefore cannot
be included in the secured hash computation or the signature of NDN
packets. Further, it can be used instead of the existing
NextHopFaceId TLV since it not only can specify the single outgoing
face for a consumer, but manages the selection and forwarding over an
entire path. The Path Label TLV in NDNLPv2 is defined below:
PathLabel = PATH-LABEL-TYPE TLV-LENGTH
PathLabelFlags
PathLabelBitmap
PathLabelFlags = PATH-LABEL-FLAGS-TYPE
TLV-LENGTH ; == 1
OCTET
NexthopLabel = PATH-LABEL-NEXTHOP-LABEL-TYPE
TLV-LENGTH ; == 2
2 OCTET
PathLabelHopCount = PATH-LABEL-HOP-COUNT-TYPE
TLV-LENGTH ; == 1
OCTET
PathLabelBitmap = PATH-LABEL-BITMAP-TYPE
TLV-LENGTH ; == 64
64 OCTET
Figure 5: Path label TLV for NDN
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+============================+=========================+
| Flag | (Suggested) Value (hex) |
+============================+=========================+
| T_PATH_LABEL | 0x0A |
+----------------------------+-------------------------+
| T_PATH_LABEL_FLAGS | 0x0B |
+----------------------------+-------------------------+
| T_PATH_LABEL_BITMAP | 0x0D |
+----------------------------+-------------------------+
| T_PATH_LABEL_NEXTHOP_LABEL | 0x0E |
+----------------------------+-------------------------+
| T_PATH_LABEL_HOP_COUNT | 0x0F |
+----------------------------+-------------------------+
Table 2: TLV-TYPE number assignments for NDN
4. IANA Considerations
IANA is requested to make the following assignments:
1. Please assign the value 0x000A (if still available) for
T_PATH_LABEL in the *CCNx Hop-by-Hop Types* registry established
by [RFC8609].
2. Please assign the value 0x0A (if still available) for the
T_RETURN_INVALID_PATH_LABEL in the *CCNx Interest Return Code
Types"* registry established by [RFC8609].
5. Security Considerations
A path is invalidated by renumbering nexthop label(s). A malicious
consumer can attempt to mount an attack by transmitting Interests
with path labels which differ only in a single now-invalid nexthop
label in order to _brute force_ a valid nexthop label. If such an
attack succeeds, a malicious consumer would be capable of steering
Interests over a network path that may not match the paths computed
by the routing algorithm or learned adaptively by the forwarders.
When a label lookup fails, by default an _Invalid path label_
Interest-Return (NACK) message is returned to the consumer. This
contains a path label identical to the one included in the
corresponding Interest message. A malicious consumer can therefore
analyze the message's Hop Count field to infer which specific nexthop
label had failed and direct an attack to influence path steering at
that hop. This threat can be mitigated by the following
countermeasures:
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* A nexthop label of larger size is harder to crack. If nexthop
labels are not allocated in a predictable fashion by the routers,
brute forcing a 32-bit nexthop label requires on average O(2^31)
Interests. However, this specification uses nexthop labels with
much less entropy (12 bits), so depending on computational
hardness is not workable.
* An ICN forwarder can periodically update nexthop labels to limit
the maximum lifetime of paths. It is RECOMMENDED that forwarders
update path labels at least every few minutes.
* A void Hop Count field in an _Invalid path label_ Interest-Return
(NACK) message would not give out the information on which
specific nexthop label had failed. An attacker might need to
brute force all nexthop labels in all combinations. However, some
useful diagnostic capability is lost by obscuring the hop count.
For example the locus of routing churn is harder to pin down
through analysis of path-steered pings or traceroutes. A
forwarder MAY choose to invalidate the hop count in addition to
changing nexthop labels periodically as above.
Because ICN forwarders maintain per-face state and forwarding state
for Interest messages, state inflation attacks are a general concern.
The addition of path steering capabilities in Interest and Data
messages does not, however, constitute a meaningful increase in
susceptibility to such attacks. This is because:
* The labels that identify each forwarding face is state O(number of
faces) and constitutes a small increase to the existing state
needed to represent a face.
* Interest message data is placed in the PIT. The path steering
header does in fact inflate the size of the Interest message and
hence the PIT state, but not by an amount that is a concern. The
forwarder needs to protect against state inflation attacks on the
PIT in general, and an attacker can mount one as or more easily
just by issuing interests with long names and/or by including
Interest payload data.
ICN protocols can be susceptible to a variety of cache poisoning
attacks, where a colluding consumer and producer arrange for bogus
content (with either invalid or inappropriate signatures) to populate
forwarder caches. These are generally confined to on-path attacks.
It is also theoretically possible to launch a similar attack without
a cooperating producer such that the caches of on-path routers become
poisoned with the content from off-path routers (i.e. physical
connectivity, but no route in a FIB for a given prefix). We estimate
that without any prior knowledge of the network topology, the
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complexity of this type of attack is in the ballpark of Breadth-
First-Search and Depth-First-Search algorithms with the additional
burden of transmitting 2^31 Interests in order to crack a nexthop
label on each hop. Relatively short periodic update of nexthop
labels and anti- _label scan_ heuristics implemented in the ICN
forwarder may successfully mitigate this type of attack.
5.1. Cryptographic protection of a path label
If the countermeasures listed above do not provide sufficient
protection against malicious mis-steering of Interests, the path
label can be made opaque to the consumer endpoint via hop-by-hop
symmetric cryptography applied to the path labels (Figure 6). This
method is viable due to the symmetry of forward and reverse paths in
CCNx and NDN architectures combined with ICN path steering requiring
only reads/writes of the topmost nexthop label (i.e. active nexthop
label) in the path label. This way a path steering capable ICN
forwarder receiving a Data (Content) message encrypts the current
path label with its own non-shared symmetric key prior to adding a
new nexthop label to the path label. The Data (Content) message is
forwarded downstream with unencrypted topmost (i.e active) nexthop
label and encrypted remaining content of the path label. As a
result, a consumer endpoint receives a Data (Content) message with a
unique path label exposing only the topmost nexthop label as
cleartext. A path steering forwarder receiving an Interest message
performs label lookup using the topmost nexthop label, decrypts the
path label with its own non-shared symmetric key, and forwards the
message upstream.
Cryptographic protection of a path label does not require any key
negotiation among ICN forwarders, and is no more expensive than
MACsec or IPsec. It is also quite possible that strict hop-by-hop
path label encryption is not necessary and path label encryption only
on the border routers of the trusted administrative or routing
domains may suffice.
Producer
| ^
| |
Path Label TLV | | Path Label TLV
+-----------------------+ | | +-----------------------+
|nexthop label=456 | v | |nexthop label=456 |
|encrypted path label={}| Forwarder 3 |encrypted path label={}|
+-----------------------+ | ^ +-----------------------+
| |
path label is encrypted | | path label is decrypted
with Forwarder 3 | | with Forwarder 3
symmetric key | | symmetric key
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| |
| |
| |
| |
| |
Path Label TLV | | Path Label TLV
+-----------------------+ | | +-----------------------+
|nexthop label=634 | v | |nexthop label=634 |
|encrypted path label= | Forwarder 2 |encrypted path label= |
| {456} | | ^ | {456} |
+-----------------------+ | | +-----------------------+
| |
path label is encrypted | | path label is decrypted
with Forwarder 2 | | with Forwarder 2
symmetric key | | symmetric key
| |
| |
| |
| |
| |
Path Label TLV | | Path Label TLV
+-----------------------+ | | +-----------------------+
|nexthop label=912 | v | |nexthop label=912 |
|encrypted path label= | Forwarder 1 |encrypted path label= |
| {634, encrypted path | | ^ | {634, encrypted path |
| label {456}} | | | | label {456}} |
+-----------------------+ | | +-----------------------+
| |
path label is encrypted | | path label is decrypted
with Forwarder 1 | | with Forwarder 1
symmetric key | | symmetric key
| |
| |
| |
| |
v |
Consumer
Figure 6: Path label protection with hop-by-hop symmetric
cryptography
6. References
6.1. Normative References
[Moiseenko2017]
Moiseenko, I. and D. Oran, "Path Switching in Content
Centric and Named Data Networks, in 4th ACM Conference on
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Information-Centric Networking (ICN 2017)",
DOI 10.1145/3125719.3125721, September 2017,
<https://conferences.sigcomm.org/acm-icn/2017/proceedings/
icn17-2.pdf>.
[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>.
[RFC8569] Mosko, M., Solis, I., and C. Wood, "Content-Centric
Networking (CCNx) Semantics", RFC 8569,
DOI 10.17487/RFC8569, July 2019,
<https://www.rfc-editor.org/info/rfc8569>.
[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>.
6.2. Informative References
[I-D.dekater-panrg-scion-overview]
de Kater, C., Rustignoli, N., and A. Perrig, "SCION
Overview", Work in Progress, Internet-Draft, draft-
dekater-panrg-scion-overview-04, 7 September 2023,
<https://datatracker.ietf.org/doc/html/draft-dekater-
panrg-scion-overview-04>.
[I-D.irtf-icnrg-flic]
Tschudin, C., Wood, C. A., Mosko, M., and D. R. Oran,
"File-Like ICN Collections (FLIC)", Work in Progress,
Internet-Draft, draft-irtf-icnrg-flic-04, 24 October 2022,
<https://datatracker.ietf.org/doc/html/draft-irtf-icnrg-
flic-04>.
[I-D.irtf-icnrg-icnping]
Mastorakis, S., Oran, D. R., Gibson, J., Moiseenko, I.,
and R. Droms, "ICN Ping Protocol Specification", Work in
Progress, Internet-Draft, draft-irtf-icnrg-icnping-12, 28
August 2023, <https://datatracker.ietf.org/doc/html/draft-
irtf-icnrg-icnping-12>.
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[I-D.irtf-icnrg-icntraceroute]
Mastorakis, S., Oran, D. R., Moiseenko, I., Gibson, J.,
and R. Droms, "ICN Traceroute Protocol Specification",
Work in Progress, Internet-Draft, draft-irtf-icnrg-
icntraceroute-11, 17 August 2023,
<https://datatracker.ietf.org/doc/html/draft-irtf-icnrg-
icntraceroute-11>.
[Mahdian2016]
Mahdian, M., Arianfar, S., Gibson, J., and D. Oran,
"MIRCC: Multipath-aware ICN Rate-based Congestion Control,
in Proceedings of the 3rd ACM Conference on Information-
Centric Networking", DOI 10.1145/2984356.2984365, 2022,
<http://conferences2.sigcomm.org/acm-icn/2016/proceedings/
p1-mahdian.pdf>.
[NDN] "Named Data Networking", various,
<https://named-data.net/project/execsummary/>.
[NDNLPv2] "Named Data Networking Link Adaptation Protocol v2",
various, <https://redmine.named-
data.net/projects/nfd/wiki/NDNLPv2>.
[NDNTLV] "NDN Packet Format Specification 0.3.", 2022,
<https://named-data.net/doc/NDN-packet-spec/current/>.
[RFC8029] Kompella, K., Swallow, G., Pignataro, C., Ed., Kumar, N.,
Aldrin, S., and M. Chen, "Detecting Multiprotocol Label
Switched (MPLS) Data-Plane Failures", RFC 8029,
DOI 10.17487/RFC8029, March 2017,
<https://www.rfc-editor.org/info/rfc8029>.
[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>.
[RFC9217] Trammell, B., "Current Open Questions in Path-Aware
Networking", RFC 9217, DOI 10.17487/RFC9217, March 2022,
<https://www.rfc-editor.org/info/rfc9217>.
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[Song2018] Song, J., Lee, M., and T. Kwon, "SMIC: Subflow-level
Multi-path Interest Control for Information Centric
Networking, in 5th ACM Conference on Information-Centric
Networking", DOI 10.1145/3267955.3267971, 2018,
<https://conferences.sigcomm.org/acm-icn/2018/proceedings/
icn18-final62.pdf>.
Authors' Addresses
Ilya Moiseenko
Apple, Inc.
Cupertino, CA
United States of America
Email: iliamo@mailbox.org
Dave Oran
Network Systems Research and Design
4 Shady Hill Square
Cambridge, MA 02138
United States of America
Email: daveoran@orandom.net
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