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ICNRG                                                       I. Moiseenko
Internet-Draft                                             Cisco Systems
Intended status: Informational                                   D. Oran
Expires: July 19, 2019               Network Systems Research and Design
                                                        January 15, 2019


         Flow Classification in Information Centric Networking
                   draft-moiseenko-icnrg-flowclass-03

Abstract

   For the ubiquitous and highly important Internet protocols (TCP, UDP,
   IP), flows are conventionally identified by the "5-tuple" of source
   and destination IP addresses, source and destination port, and
   protocol type in an IP packet.  Information Centric Networking (ICN)
   is a new paradigm where network communications are accomplished by
   requesting named content, instead of sending packets to destination
   addresses.  This document describes mechanisms allowing ICN
   forwarders, consumers, producers and other ICN nodes to encode,
   decode, and process equivalence class identifiers (flows) at any
   desired granularity of a routable name prefix and beyond the routable
   name prefix.  This document is a product of the IRTF Information-
   Centric Networking Research Group (ICNRG).

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
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   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on July 19, 2019.

Copyright Notice

   Copyright (c) 2019 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   This document is subject to BCP 78 and the IETF Trust's Legal
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   (https://trustee.ietf.org/license-info) in effect on the date of
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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Flow Identification Challenges and Opportunities in ICN . . .   3
   3.  Flow Encoding Schemes . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Equivalence class component count (EC3) . . . . . . . . .   5
     3.2.  Equivalence class name component type (ECNCT) . . . . . .   6
   4.  Producer operation  . . . . . . . . . . . . . . . . . . . . .   7
   5.  Consumer operation  . . . . . . . . . . . . . . . . . . . . .   8
   6.  Forwarder operation . . . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   The problem of identifying groups of packets that get consistent
   treatment in a network and allowing that treatment to be independent
   and isolated from the treatment of other groups of packets, is
   ubiquitous and long-standing.  The purposes to which this
   identification can be put is highly varied, including such functions
   are providing differentiated quality of service, traffic engineering,
   traffic filtering for security functions like intrusion detection and
   firewalling, etc.

   Providing the capability to apply different functions to groupings
   (formally equivalence classes) of packets is generally known as the
   "flow identification problem" where the definition of what
   constitutes a "flow" is highly dependent on the particular protocol
   or protocols carrying the packets.  Some of the above uses of flows
   also bring a mechanism requirement that the flow identification
   technique be useful to have not just equivalence classes, but the
   ability to apply some useful notion of fairness among the instances
   of each equivalence class.  There are many possible flow
   identification techniques that are either too granular (spatially or




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   temporally) to establish fairness, or conversely too coarse and
   cannot separate traffic a fine enough level to have useful fairness.

   For the ubiquitous and highly important Internet protocols (TCP, UDP,
   IP), flows are conventionally identified by the "5-tuple" of source
   and destination IP addresses, source and destination port, and
   protocol type in an IP packet.  Some systems augment this by further
   distinguishing equivalence classes by the TOS/DSCP field, but this is
   secondary to the 5-tuple methods. 2-party flows are present where the
   source and destination addresses are unicast IP addresses.  Multi-
   party flows can exist when the destination IP address is a multicast
   address.  One key common characteristic is that the identification of
   flows depends in a very deep way on the presence of source addresses
   in the packets, and the limited richness of IP addresses is
   correspondingly constraining as a means to classify traffic in a
   semantically meaningful way.

   The purpose of this document is to devise a mechanism allowing ICN
   forwarders, consumers, producers and other ICN nodes to encode,
   decode, and process equivalence class identifiers (flows) at any
   desired granularity of a routable name prefix and beyond the routable
   name prefix.

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 RFC 2119 [RFC2119].

2.  Flow Identification Challenges and Opportunities in ICN

   ICN systems differ from IP-based designs in a number of ways, three
   of which are quite fundamental.

   1.  The packets are addressed to a rich namespace of packets, which
       is hierarchical and carry semantic information that can be useful
       for classification of flows.

   2.  Conversely, the packets do not contain source addresses of any
       kind, which means that identifying flows as groups of packets
       between a single pair of endpoints (in the unicast case) is not
       possible for intermediate forwarders (other than possibly the
       first-hop forwarder if it serves a single consumer per
       interface).

   3.  Instead of group-based multicast, ICN systems use multi-
       destination delivery semantics.  This allows a different way to
       map packets to flows, and in fact in the IP world multicast has



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       been difficult to use partly because there is no good way to make
       use of flow identification for multicast flows (for a variety of
       reasons).

   These differences lead to a need to find a different method to
   identify flows than used in the IP protocol suite.  Ideally, the
   method would provide semantics that map well with the expected uses
   of ICN to build applications.  It would also use native capabilities
   in the ICN protocols rather than having to change the protocol
   architecture in ways that affect the semantics or utility of an ICN
   approach to networking.

   In NDN and CCN protocols, Interest and Data names are the only
   identifiers in the network; neither source addresses nor destination
   addresses are employed.  Each Interest packet is responded by exactly
   one Data packet, producing a useful property known as "flow balance".
   This means that flow identification can be tied directly to the
   Interest/Data exchanges.  The key to having useful flow
   identification is for the equivalence classes to be associated with
   the names in the corresponding Interest and Data packets, and to be
   stable over multiple exchanges using different names that share some
   common "handle" that can be used to separate the names into
   equivalence classes.  As mentioned above, simply using the routing
   state that maps name prefixes to routes does not provide a useful set
   of equivalence classes, because:

   o  in general, routing prefixes are too coarse; many equivalence
      classes of packets are generally covered by a single routing
      prefix because they are present at the same set of destinations
      from a routing perspective;

   o  practical, scalable routing needs to do route aggregation, which
      further blurs the discrimination of the equivalence classes.

   Therefore, NDN and CCN protocols need to have something that both
   relates to the name structure but provides finer granularity for flow
   classification purposes.  This document describes two alternative
   mechanisms addressing these issues.

3.  Flow Encoding Schemes

   Flow encoding schemes described in this document allow ICN systems to
   perform flow identification at any desired granularity of a routable
   name prefix and beyond the routable name prefix.  Techniques
   described herein permit both consumer nodes and forwarders to use
   equivalence classes to perform per-flow functions.  The encoding to
   achieve the flow classification is lightweight and does not require
   changes to the protocol architecture in ways that affect the



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   semantics or utility of an ICN approach to networking.  Furthermore,
   equivalence classes can be specified by the data producer, in
   contrast to IP protocols in which the data producer can only control
   the destination port as an equivalence-class discriminator.

   No matter what method is used to identify equivalence classes that
   can be treated as flows, there is the independent but critically
   important issue of how to scale any state that is kept on a per-flow
   basis when the flow count is very high.  For consumers and producers,
   this state scales naturally with the number of applications and
   application interactions are going on simultaneously.  Therefore the
   scaling limit is not likely to be in the producers or consumers.  For
   ICN forwarders this state could scale quadratically or worse if the
   forwarders need classic prior resource reservation to
   deterministically partition resources on a producer/consumer pair
   basis.  This need not be the case however.  Practical resource
   control algorithms exist that keep state only for "active" flows
   (those with packets either currently or recently moving through the
   network).  Further state reduction is also possible with some loss of
   accuracy using approximate techniques, like stochastic fair queuing
   (SFQ).  If the ICN forwarder cannot keep all the state due to memory
   or processing limitations, it faces the common problem of which flows
   to remember and which to forget.  This problem is fundamental, and is
   mostly independent of the choice of flow identification method in the
   protocol.  Flow encoding schemes described in this document provide a
   method for identifying equivalence classes using protocol machinery
   that already has to scale (e.g. name parsing and lookup) and hence
   does not introduce a new class of problems not inherently present.

3.1.  Equivalence class component count (EC3)

   For this encoding scheme a new field called equivalence class
   component count (EC3) is introduced into the Data packets.  It is set
   by a producer and counts the number of name components in the
   corresponding name that are to be considered, when grouped together
   under the same prefix part of the name, to be one equivalence class
   instance.  This allows either finer (or coarser) granularity than
   provided by routing prefixes.  Because the EC3 is a separate field of
   the packet (Figure 1), producers can "regroup" equivalence classes
   dynamically by including more or fewer levels of the name hierarchy
   when they respond to Interests for the corresponding Data packets.
   This brings a set of clear advantages and disadvantages.  The primary
   advantage is flexibility in re-grouping equivalence classes,
   especially in aggregating flows at different granularities.  The main
   disadvantage is that the binding of the equivalence class into the
   namespace is not explicit, and hence it is harder to enforce
   consistent interpretation among producers, consumers and forwarders.




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   An additional consideration with the EC3 encoding scheme is whether
   or not the field is inside or outside the security envelope that
   provides cryptographic packet integrity to the name and data in the
   data packet.  Either approach is possible; however having the field
   outside the security envelope would allow ICN forwarders to modify
   it, allowing the aggregation/disaggregation of flows to be performed
   by the forwarders as well as the consumers.  Conversely, leaving the
   field outside the security envelope may enhance certain attack
   scenarios against flow classification when employed for quality of
   service differentiation or firewall filtering.

   +-------------------------------------------------------------------+
   |  /youtube |  /<mediaID>  |  /video  OR |  <frameID>  | <segment#> |
   |           |              |  /audio     |             |            |
   +-----------+--------------+-------------+-------------+------------+
   | Name      | Name         | Name        | Name        | Segment    |
   | component | component    | component   | component   | component  |
   | type      | type         | type        | type        | type       |
   +-----------+--------------+-------------+-------------+------------+
   |                                                                   |
   | Equivalence Class Component Count = 2 (up to MediaID stream)      |
   |                          OR                                       |
   | Equivalence Class Component Count = 3 (video or audio substream)  |
   +-------------------------------------------------------------------+

              An example of EC3 encoding of flow information.

                                 Figure 1

3.2.  Equivalence class name component type (ECNCT)

   For this scheme the equivalence class information is encoded directly
   in the name, by adding a name component to the name of the Interest
   and Data packets.  This new typed named component is called
   equivalence class name component type (ECNCT).  It is set by the
   producer as part of constructing all Data packets in the desired
   equivalence class and is therefore immutable for the lifetime of the
   associated named data.  A consequence of this is that the ECNCT is
   present in Interest packets as well, and hence may affect both PIT
   matching and FIB matching.  The Equivalence Class name component both
   names the equivalence class explicitly, and implicitly makes all Data
   packets named below it in the hierarchy part of that equivalence
   class.  In other words, the name can have multiple equivalence class
   (e.g. flow and subflows) markings using this scheme (Figure 2).  As
   in EC3 encoding scheme, depending where in the name component
   hierarchy the ECNCT is placed, one can have either finer or coarser
   granularity than provided by routing prefixes.




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   The exact details of how to encode the ECNCT name component may
   differ among ICN architectures.  The CCN design has explicitly typed
   name components, so for that protocol an explicit name component type
   can be assigned straightforwardly.  The NDN design eschews typed name
   components and instead uses textual naming conventions for name
   components.  In that case an architectural constant string would be
   chosen to distinguish ECNCT from other name component semantics.

   +------------------------------------------------------------+
   | /youtube | /<mediaID> | /video OR | <frameID> | <segment#> |
   |          |            | /audio    |           |            |
   +----------+------------+-----------+-----------+------------+
   | Name     | Flow       | Flow      | Name      | Segment    |
   | component| component  | component | component | component  |
   | type     | type       | type      | type      | type       |
   +----------+------------+-----------+-----------+------------+

             An example of ECNCT encoding of flow information.

                                 Figure 2

   When an ICN forwarder receives a packet with a name carrying
   ECNCT(s), it can be processed on a component-by-component basis, and
   substreams can be identified according to name prefixes indicated by
   the equivalence class identifiers.  The identification of substreams
   enables special treatment of selected substreams.  For example, video
   substreams can be discriminated from other substreams, such as audio
   substreams.  In the example in Figure 2, two name components include
   equivalence class identifiers to define a hierarchy of flows (or
   substreams).  Specifically, two flow components are encoded to define
   the following hierarchy of flows:

   First level name prefix: /youtube/<mediaID>

   Second level name prefix: /youtube/<mediaID>/video

   Second level name prefix: /youtube/<mediaID>/audio

4.  Producer operation

   In ECNCT encoding scheme, an ICN producer receives an Interest packet
   carrying equivalence class identifiers in the name.  A producer might
   use the equivalence class identifiers for demultiplexing, load
   sharding and other purposes, and reply with a Data packet matching
   the Interest name.

   In EC3 encoding scheme, an ICN producer receives an Interest packet
   that might not carry an equivalence class identifier.  In such case,



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   the producer may refer to the name schemas used in a particular
   application to dynamically determine the equivalence class identifier
   for Interest demultiplexing, load sharding and other purposes, and
   for replying with a Data packet carring the equivalence class
   identifer in EC3 field.

5.  Consumer operation

   An ICN consumer may also use the knowledge of equivalence classes of
   packets to take certain actions.  For example, when a Data packet
   with a name specifying a particular equivalence class arrives at a
   consumer in response to a previously sent Interest packet, the
   consumer can associate the data packet with the correct equivalence
   class.  Consequently, the consumer can manage subsequent Interest/
   Data exchanges with the same name prefix and equivalence class
   identifier (e.g., EC3 or ECNCT) as one flow.  Associated measurements
   such as round trip time (RTT) or marginal delay can be leveraged to
   perform flow and congestion management for the equivalence class as a
   whole.

6.  Forwarder operation

   A flow table may be provisioned in ICN node to enable the node to
   make decisions about performing actions on Interest and/or Data
   packets based on one or more equivalence classes.  The flow table can
   include name prefixes mapped to equivalence class identifiers
   obtained from previous Interest-Data exchanges.  In ECNCT encoding
   scheme, Interest packets carry the equivalence class identifier,
   therefore flow table may only include name prefixes.  Typically, name
   prefixes in flow table are more granular than prefixes in the FIB,
   but less granular than names in the PIT.  Flow table could be
   separate from other elements of ICN node or could be integrated with
   FIB or PIT.

   Flow management logic can be configured to treat flows having the
   same equivalence class similarly.  Actions taken that are related to
   flows or objects having a similar equivalence class can include, but
   are not limited to, dropping a packet, using a particular interface
   for a packet, security related actions (e.g., filtering traffic for
   security functions like intrusion detection and firewalling), quality
   of service (QoS) related actions (e.g., types of resources to
   allocate to the packets, moving a packet up in the queue for
   forwarding purposes, etc.), and/or traffic engineering (e.g.,
   selecting one path over another path).  Flow management logic can
   enable such actions to be taken on a particular flow based on the
   equivalence class associated with the flow or object and policies
   related to the equivalence class.




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   Specific examples of how ICN node can use the knowledge of
   equivalence classes of packets include, but are not limited to, the
   following:

   1.  Enforce rate control for the equivalence class as a whole (e.g.,
       dropping packets, queuing packets, etc.);

   2.  Estimate the number of simultaneous flows traversing a bottleneck
       link, which can improve the performance of many congestion
       control schemes; and

   3.  Make more intelligent selections of which packets to cache at the
       ICN forwarder, for example, to prefer to cache many packets of
       the same equivalence class.

7.  IANA Considerations

   This memo includes no request to IANA.

8.  Security Considerations

   Certain attack scenarios against flow classification for quality of
   service or firewall filtering may be prevented if the EC3 field
   located inside the security envelope.  ICN forwarders can read, but
   not change, the EC3 value, because the EC3 field is covered by a
   security signature and not encrypted.

   If the EC3 field is outside of the security envelope, it can be
   placed in the hop-by-hop headers and, therefore, be modified by the
   transit ICN forwarders.  This allows the transit ICN forwarders to
   override the flow definitions set by the producer applications, but
   opens the system to various attack scenarios.

   Modification of equivalence class identifiers in ECNCT encoding
   scheme effectively modifies the packet name, and therefore, ECNCT
   does not introduce any additional security threats.

9.  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>.








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Authors' Addresses

   Ilya Moiseenko
   Cisco Systems
   USA

   Email: ilmoisee@cisco.com


   Dave Oran
   Network Systems Research and Design
   4 Shady Hill Square
   Cambridge, MA  02138
   USA

   Email: daveoran@orandom.net



































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