Challenges for the Internet Routing Infrastructure Introduced by Changes in Address Semantics
draft-king-irtf-challenges-in-routing-02

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Authors Daniel King  , Joanna Dang  , Adrian Farrel 
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IRTF                                                             D. King
Internet-Draft                                      Lancaster University
Intended status: Informational                                   J. Dang
Expires: November 6, 2021                            Huawei Technologies
                                                               A. Farrel
                                                      Old Dog Consulting
                                                             May 5, 2021

Challenges for the Internet Routing Infrastructure Introduced by Changes
                          in Address Semantics
                draft-king-irtf-challenges-in-routing-02

Abstract

   Historically, the meaning of an IP address has been to identify an
   interface on a network device.  Routing protocols were developed
   based on the assumption that a destination address had this semantic.

   Over time, routing decisions were enhanced to route packets according
   to additional information carried within the packets and dependent on
   policy coded in, configured at, or signaled to the routers.

   Many proposals have been made to add semantics to IP addresses.  The
   intent is usually to facilitate routing decisions based solely on the
   address and without the need to find and process information carried
   in other fields within the packets.

   This document describes the challenges to the existing routing system
   that are introduced by the addition of semantics to IP addresses.  It
   then summarizes the opportunities for research into new or modified
   routing protocols to make use of new address semantics.

   This document is presented as study to support further research into
   clarifying and understanding the issues.  It does not pass comment on
   the advisability or practicality of any of the proposals and does not
   define any technical solutions.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts is at https://datatracker.ietf.org/drafts/current/.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Current Challenges to IP Routing  . . . . . . . . . . . . . .   4
   3.  What is Semantic Routing? . . . . . . . . . . . . . . . . . .   6
     3.1.  Architectural Considerations  . . . . . . . . . . . . . .   8
       3.1.1.  Isolated Domains  . . . . . . . . . . . . . . . . . .   8
       3.1.2.  Bridged Domains . . . . . . . . . . . . . . . . . . .   9
       3.1.3.  Semantic Prefix Domains . . . . . . . . . . . . . . .   9
   4.  Challenges for Internet Routing Research  . . . . . . . . . .  11
     4.1.  Routing Research Questions to be Addressed  . . . . . . .  11
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  14
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  15
   7.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  15
   8.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  15
   9.  Informative References  . . . . . . . . . . . . . . . . . . .  15
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  17

1.  Introduction

   Historically, the meaning of an IP address has been to identify an
   interface on a network device.  Network routing protocols were
   initially designed to determine paths through the network toward
   destination addresses so that IP packets with a common destination
   address converged on that destination.  Anycast and multicast
   addresses were also defined and these new address semantics

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   necessitated variations to the routing protocols and the development
   of new protocols.

   Over time, routing decisions were enhanced to route packets according
   to additional information carried within the packets and dependent on
   policy coded in, configured at, or signaled to the routers.  Perhaps
   the most obvious exmaple is Equal-Cost Multipath (ECMP) where a
   router makes a consistent choice for forwarding packets over a number
   of parallel links or paths based on the values of a set of fields in
   the packet header.

   Many proposals have been made to add semantics to IP addresses.  The
   intent is usually to facilitate routing decisions based solely on the
   address and without the need to find and process information carried
   in other fields within the packets.  We call this approach "Semantic
   Addressing".

   There are many approaches to Semantic Addressing.  These range from
   assigning a prefix to have a special purpose and meaning (such as is
   done for multicast addressing) through allowing the owner of a prefix
   to use the low-order bits of an address for their own purposes.  Some
   Semantic Adressing proposals suggest variable address lengths, others
   offer hierarchical addresses, and some introduce a structure to
   addresses so that they can carry additional information in a common
   way.

   A survey of ways in which routing decisions have been made based on
   additional information carried in packets, and a catalogue of
   proposals for Semantic Addressing can be found in
   [I-D.king-irtf-semantic-routing-survey].

   Some Semantic Addressing proposals are intended to be deployed in
   limited domains [RFC8799] (networks) that are IP-based, while other
   proposals are intended for use across the Internet.  The impact the
   proposals have on routing systems may require clean-slate solutions,
   hybrid solutions, extensions to existing routing protocols, or
   potentially no changes at all.

   This document describes some of the key challenges to routing that
   are present in today's IP networks.  It then defines the concept of
   "Semantic Routing" and presents some of the challenges to the
   existing routing system that Semantic Addressing may present.
   Finally, this document presents a list of releated research questions
   that offer opportunities for future research into new or modified
   routing protocols that make use of Semantic Addressing.

   In this document, the focus is on routing and forwarding at the IP
   layer.  It is possible that a variety of overlay mechanisms exist to

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   perform service or path routing at higher layers, and that those
   approaches may be based on Semantic Addresses, but that is out of
   scope for this document.  Similarly, it is possible that Semantic
   Addresses can be applied in a number of underlay network
   technologies, and that, too, is out of scope for this document.

   This document draws on surveys and analysis performed in "Survey of
   Semantic Internet Routing Techniques"
   [I-D.king-irtf-semantic-routing-survey].

2.  Current Challenges to IP Routing

   Today's IP routing faces several significant challenges which are a
   consequence of the architectural design decisions and exponential
   growth.  These challenges include mobility, multihoming, programmable
   paths, scalability and security, and were not the focus of the
   original design of the Internet.  Nevertheless, IP-based networks
   have, in general, coped well in an incremental manner as each new
   challenge has evolved.  This list is presented to give context to the
   continuing requirements that routing protocols must meet as new
   semantics are applied to IP addresses.

      Mobility - Mobility introduces several challenges, including
      maintaining a relationship between a sender and a receiver in
      cases where sender and/or receiver changes their point of network
      attachment.  The original network must always be informed about
      the mobile node's current location, to allow continuity of
      services.  Mobility users may also consume resources, while
      physical moving.  The mobile user service instances and
      attachments will also change due to varying load or latency, e.g.,
      in Multi-access Edge Computing (MEC) scenarios.

      Multihoming - Multihomed stations or multihomed networks are
      connected to the Internet via more than one access network and
      therefore, may be assigned multiple IP addresses from different
      pools of addresses.  There are challenges concerning how traffic
      is routed back to the source if the source has originated its
      traffic using the wrong address for a particular connection, or if
      one of the connections to the Internet is degraded.

      Multi-path - The Internet was initially designed to find the
      single, "best" path to a destination using a distributed routing
      algorithm.  Current, IP-based networks topologies facilitate
      multiple paths each with different characteristics and with
      different failure likelihoods.  It may be beneficial to send
      traffic over multiple paths to achieve reliability and enhance
      throughput, and it may be desirable to select one path or another
      in order to provide delivery qualities or to avoid transiting

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      specific areas of an IP-based network.  However, the way in which
      packets are routed using the best or shortest path means that
      distinguishing these alternate paths and directing traffic to them
      can be hard.  Further, problems concerning scalability, commercial
      agreements among Service Providers, and the design of BGP make the
      utilization of multi-path techniques difficult for inter-domain
      routing.  (Note that this discussion is distinct from Equal Cost
      Multi-path (ECMP) where packets are directed onto two "parallel"
      paths of identical least cost using a hash algorithm operated on
      some of the packets' header fields.)

      Multicast - Delivering the same packet to multiple destinations
      can place considerable load on a network.  Solutions that
      replicate the packet at the source or at the network edge may
      obviously see multiple copies of the packet flowing along the same
      network links.  A number of solutions have been tried over the
      years to move replication into the network to make more optimal
      use of the network resources, but these approaches are complex to
      set up and manage requiring sophisticated protocols that can
      determine the best multicast delivery topologies, as well as
      hardware that can replicate packets.  In order that packets can be
      addressed to a group of destinations and not be routed using the
      normal unicast approcaches, parts of the addressing space (that
      is, address prefixes) have been reserved to indicate multicast.

      Programmable Paths - The ability to decouple IP-based network
      paths from routing protocols and agreements between Service
      Providers, would allow users and applications to configure and
      select network paths themselves, based on required path (that is,
      traffic-delivery) characteristics.  Currently, user and
      application packets follow the path selected by routing protocols
      and the way traffic is routed through a network is under the
      exclusive control of the Service Provider that owns the network.

      End-Point Selection - As compute resources and content storage
      moves closer to the edge of the network, there are often multiple
      points in the network that can satisfy user requests.  In order to
      make best use of these distributed services and so to not overload
      parts of the network, user traffic needs to be steered to
      appropriate servers or data centres.  In many cases, this function
      may be achieved in the application layer (such as through DNS) or
      in the transport layer (such as using ALTO).  The challenge is to
      balance higher-layer decisions about which application layer
      resources to use with information from the lower layers about the
      availability and load of network resources.

      Scalability - There are many scaling concerns that pose critical
      challenges to the Internet.  Not least among these challenges is

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      the size of the routing tables that routers in an IP-based network
      must maintain and exchange with their peers.  As the number of
      devices attached to the network grows, so the number of addresses
      in use also grows, and because of the address allocation schemes,
      the mobility of devices, and the various connectivity options
      between networks, the routing table sizes also grow and are not
      amenable to aggregation.  This problem exists even in limited
      domains (such as IoT), where the size of the routing table - as
      more devices are added to the network - may be a gating factor in
      there applicability of certain routing protocols.  It may be noted
      that scaling issues are exacerbated by multihoming practices if a
      host that is multihomed is allocated a different address for each
      point of attachment.

      Security - Issues of security and privacy have been largely
      overlooked within the routing systems.  However, there is
      increasing concern that attacks on routing systems can not only be
      disruptive (for example, causing traffic to be dropped), but may
      cause traffic to be routed via inspection points that can breach
      the security or privacy of the payloads.

   Some of the challenges outlined here were previously considered
   within the IETF by the IABs "Routing and Addressing Workshop" held in
   Amsterdam, The Netherlands on October 18-19, 2006 [RFC4984].  Several
   architectures and protocols have since been developed and worked on
   within and outside the IETF, and these are examined in
   [I-D.king-irtf-semantic-routing-survey].

3.  What is Semantic Routing?

   Typically, in an IP-based network packets are forwarded using the
   least cost path to the destination IP address.  Service Providers may
   also use techniques to modify the default forwarding behavior based
   on other information present in the packet and configured or
   programmed into the routers.  These mechansims, sometimes called
   semantic routing techniques include "Preferential Routing", "Policy-
   based Routing", and "Flow steering".

   Examples of semantic routing usuage for IP-based networks include the
   following:

   o  Using addresses to identify different device types so that their
      traffic may be handled differently [SEMANTICRTG].

   o  Expressing how a packet should be handled, prioritized, or
      allocated network resources as it is forwarded through the network
      [TERASTREAMref].

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   o  Deriving IP addresses from the physical layer identifiers and
      using addresses depending on the underlying connectivity.

   o  Indicating the application or network function on a destination
      device or at a specific location; or enable Service Function
      Chaining (SFC).

   o  Providing semantics specific to mobile networks so that a user or
      device may move through the network without disruption to their
      service [CONTENT-RTG-MOBILEref].

   o  Enabling optimized multicast traffic distribution by encoding
      multicast tree and replication instructions within addresses
      [MULTICAST-SRref].

   o  Content-based routing (CBR), forwarding of the packet based on
      message content rather than the destination addresses
      [OPENSRNref].

   o  Identifying hierarchical connectivity so that routing can be
      simplified [EIBPref].

   o  Providing geographic location information within addresses
      [GEO-IPref].

   o  Using cryptographic algorithms to mask the identity of the source
      or destination, masking routing tables within the domain, while
      still enabling packet forwarding across the network
      [BLIND-FORWARDINGref].

   A detailed description of IP-based semantic routing, and a survey of
   semantic routing proposals research projects can be found in
   [I-D.king-irtf-semantic-routing-survey].

   Several technical challenges exist for semantic routing in IP-based
   network.  These include:

   o  Address consumption caused by lower address utility rate.  The
      wastage mainly comes from aligning finite allocation for semantic
      address blocks.

   o  Encoding too many semantics into prefixes will require evaluation
      of which to prioritize.

   o  Risk of privacy/information leakage.

   o  Burdening the user, application, or prefix assignment node.

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   o  Source address spoofing preventing mechanisms may be required.

   o  Overloading of routing protocols causing stability and scaling
      problems.

   o  Depending on encoding mechansims, there may be challenges for data
      planes to scale the processes of finding, reading, and looking up
      semantic data in order to forward packets at line speed.

   o  Backwards compatibility with existing IP-based networking.

3.1.  Architectural Considerations

   Semantic data may be applied in a number of ways to integrate with
   existing routing architectures.  The most obvious is to build an
   overlay such that IP is used only to route packets between network
   nodes that utilize the semantics at a higher layer.  There are a
   number of existing uses of this approach including Service Function
   Chaining (SFC) [RFC7665] and Information Centric Networking (ICN)
   [RFC8763].  An overlay may be achieved in a higher protocol layer, or
   may be performed using tunneling techniques (such as IP-in-IP) to
   traverse the areas of the IP network that cannot parse additional
   semantics thereby joining together those nodes that use the semantic
   data.

   The application of semantics may also be constrained to within a
   limited domain.  In some cases, such a domain will use IP, but be
   disconnected from Internet (see Section 3.1.1).  In other cases,
   traffic from within the domain is exchanged with other domains that
   are connected together across an IP-based network using tunnels or
   via application gateways (see Section 3.1.2).  And in still another
   case traffic from the domain is routed across the Internet to other
   nodes and this requires backward-compatible routing approaches (see
   Section 3.1.3).

3.1.1.  Isolated Domains

   Some IP network domains are entirely isolated from the Internet and
   other IP-based networks.  In these cases, there is no risk to
   external networks from any semantic addressing or routing schemes
   carried out within the domain.  Thus, the challenges are limited to
   enabling the desired function within the domain.

   All of the challenges could exist even in a limited domain, but the
   impact may be significantly reduced both because of the limited size
   of the domain, and because there is no need to interact with native
   IP routers.

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   Many approaches in isolated domains will utilize environment-specific
   routing protocols.  For example, those suited to constrained
   environments (for IoT) or mobile environments (for smart vehicles).
   Such routing protocols can be optimized for the exchange of
   information specific to semantic routing.

3.1.2.  Bridged Domains

   In some deployments, it will be desireable to connect together a
   number of isolated domains to build a larger network.  These domains
   may be connected (or bridged) over an IP network or even over the
   Internet.

   Ideally, the function of the bridged domains should not be impeded by
   how they are connected, and the operation of the IP network providing
   the connectivity should not be compromised by the act of carrying
   traffic between the domains.  This can generally be achieved by
   tunneling the packets between domains using any tunneling technique,
   and this will not require the IP network to know about the semantic
   routing used by the domains.  The challenges in this scenario are
   very similar to those for Section 3.1.1 except that the network
   created from the set of domains may be larger, and some routing
   mechanism must be applied to know in wich remote domain a destination
   is situated.

   An alternative to tunneling is achieved using gateway functionality
   where packets from a domain are mapped at the domain boundary to
   produce regular IP packets that are sent across the IP network to the
   boundary of the destination domain where they are mapped back into
   packets for use within that domain.  Such an approach presents
   additional challenges especially at the boundary of the destination
   domain where some mechanism must enable the mapping back into
   semantic-enabled packets.

3.1.3.  Semantic Prefix Domains

   A semantic prefix domain [I-D.jiang-semantic-prefix] is a portion of
   the Internet over which a consistent set of semantic-based policies
   are administered in a coordinated fashion.  This is achieved by
   assigning a routable address prefix (or a set of prefixes) for use
   with semantic addressing and routing so that packets may be routed
   through the regular IP network (or the Internet) using the prefix and
   without encountering or having to use any semantic addressing.  Once
   delivered to the semantic prefix domain, a packet can be subjected to
   whatever semantic routing is enabled in the domain.

   Examples of semantic prefix domains include:

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   o  Administrative domains

   o  Applications

   o  Autonomous systems

   o  Hosts

   o  Network types

   o  Routers

   o  Trust regions

   o  User groups

   A semantic prefix domain has a set of pre-established semantic
   definitions which are only meaningful locally.  Without an efficient
   mechanism for notification, exchange, or configuration of semantics,
   the definitions of semantics are only meaningful within the local
   semantic prefix domain, and the addresses on a packet from within a
   domain risk being misinterpreted by hosts and routers outside the
   domain.  While, sharing semantic definitions among semantic prefix
   domains would enable wider semantic-based network function, such
   approaches run the risk of complexity caused by overlapping
   semantics, and require a significant trust model between network
   operators.  More successful approaches to multi-domain semantics
   might be to rely either on backwards-compatible techniques or on
   standardised semantics.

   A semantic prefix domain may also span several physical networks and
   traverse multiple service provider networks.  However, when an
   interim network is traversed (such as when an intermediary network is
   used for interconnectivity) the relevance of the semantics is limited
   to network domains that share a common semantic policy, and tunneling
   may be needed to traverse transit domains.

   Examples of prefix-partitioned semantic addressesing that already
   exist include:

   o  Documentation addresses

   o  Loopback addresses

   o  Multicast address space

   o  Private use addresses

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   o  IPv4-IPv6 encoding

   o  Routers

   o  Trust regions

   o  User groups

4.  Challenges for Internet Routing Research

   It may not be possible to embrace all emerging scenarios outlined in
   this document with a single approach or solution.  Requirements such
   as 5G mobility, near-space-networking, and networking for outer-
   space, may need to be handled using separate network technologies.
   Therefore, developing a new Internet architecture that is both
   economically feasible and which has the support of the networking
   equipment vendors, is a significant challenge in the immediate future
   of the Internet.

   Improving IP-based network capabilities and capacity to scale, and
   address a set of growing requirements presents significant research
   challenges, and will require contributions from the networking
   research community.

4.1.  Routing Research Questions to be Addressed

   As research into the scenarios and possible uses of semantic
   addressing progresses, a number of questions need to be addressed in
   the scope of routing.  These questions go beyond "Why do we need this
   function?" and "What could we achieve by carrying this additional
   semantic in an IP address?"  The questions are also distinct from
   issues of how the additional semantics can be encoded within an IP
   address.  All of those issues are, of course, important
   considerations in the debate about semantic addressing, but they form
   part of the essential groundwork of research into semantic addressing
   itself.

   This section sets out some of the concerns about how the routing
   system might be impacted by the use of semantic addressing.  These
   questions need to be addressed in separate research work or folded
   into the discussion of each semantic addressing proposal.

   1.  What is the scope of the semantic address proposal?  This
       question may be answered as:

       *  Global: It is intended to apply to all uses of IP addresses.

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       *  Backbone: It is intended to apply to IP-based network
          connectivity.

       *  Overlay: It is to be used as an overlay network over previous
          uses of IP or other underlay technologies using tunneling.

       *  Gateway: The semantic addressing will be used within a limited
          domain, and communications with the wider Internet will be
          handled by a protocol or application gateway.

       *  Domain: The use of the semantic addressing is entirely limited
          to within a domain or private network.

       Underlying this issue is a broader question about the boundaries
       of the use of IP, and the limit of "the Internet".  If a limited
       domain is used, is it a semantic prefix domain [RFC8799] where a
       part of the IP address space identifies the domain so that an
       address is routable to the domain but the additional semantics
       are used only within the domain, or is the address used
       exclusively within the domain so that the external impact of the
       routability of the address that carries additional semantics is
       not important?

   2.  What will be the impact on existing routing systems?  What would
       happen if an address with additional semantics was released
       according to normal operations, accidentally, or maliciously?
       How would the existing routing systems react?  For example: how
       are cryptographically generated addresses made routable; how are
       the semantic parts of an address distinguished from the routable
       parts; is there an impact on the size and maintenance of routing
       tables due to the addition of semantics to addresses?

   3.  What path characteristics are needed for the routed paths?  Since
       one of the purposes of adding semantics to IP addresses is to
       cause special processing by routers, it is important to
       understand what behaviors are wanted.  Such path characteristics
       include (but are not limited to):

       *  Quality: expressed in terms of throughput, latency, jitter,
          drop precedence, etc.

       *  Resilience: expressed in terms of survival of network failures
          and delivery guarantees;

       *  Destination: How is a destination address to be interpreted if
          it encodes a choice of actual destinations?

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       In these cases, how do the routing protocols utilize the address
       semantics to determine the desired characteristics?  What
       additional information about the network does the protocol need
       to gather?  What changes to the routing algorithm is needed to
       deliver packets according to the desired characteristics?

   4.  Can we solve these routing challenges with existing routing tools
       and methods?  We can break this question into more detailed
       questions.

       *  Is new hardware needed?  Existing deployed hardware has
          certain assumptions about how forwarding is carried out based
          on IP addresses and routing tables.

       *  Do we need new routing protocols?  We might ask some
          subsidiary questions:

          +  Can we make do with existing protocols, possibly by tuning
             configuration parameters or using them out of the box?

          +  Can we make simple backward-compatible modifications to
             existing protocols such that they work for today's IP
             addresses as well as enhanced-semantic addresses?

          +  Do we need entirely new protocols or radically evolutions
             of existing protocols in order to deliver the functions
             that we need?

          +  Should we focus on the benefits of optimized routing
             solutions, or should we attempt to generalize to enable
             wider applicability?

          Do we need new management tools and techniques?  Management of
          the routing system (especially diagnostic management) is a
          crucial and often neglected part of the problem space.

   5.  What is the scalability impact for routing systems?  Scalability
       can be measured as:

       *  Routing table size.  How many entries need to be maintained in
          the routing table?  Some approaches to semantic addressing may
          be explicitly intended to address this problem.

       *  Routing performance.  Routing performance may be considered in
          terms of the volume of data that has to be exchanged both to
          establish and to maintain the routing tables at the
          participating routers.  It may also be measured in terms of

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          how much processing is required to derive new routes when
          there is a change in the network routing information.

       *  Routing convergence is the time that it takes for a routing
          protocol to discover changes (especially faults) in the
          network, to distribute the information about any changes to
          the network, and to reach a stable state across the network
          such that packets are routed consistently.

       For all questions of routing scalability, research that presents
       real numbers based on credible example networks is highly
       desirable.

   6.  To what extent can multicast be developed:

       *  To support programmable SDN systems such as P4 [BIER-P4]?

       *  To satisfy end-to-end applications?

       *  To apply per-packet multicasting to develop new services?

       *  As a separate network layer distinct from IP or by encoding
          group destinations into IP addresses?

   7.  What aspects need to be standardised?  It is really important to
       understand the necessity of standardization within this research.
       What degree of interoperability is expected between devices and
       networks?  Is the limited domain so constrained (for example, to
       a single equipment vendor) that standardization would be
       meaningless?  Is the application so narrow (for example, in niche
       hardware environments) such that interoperability is best handled
       by agreements among small groups of vendors such as in industry
       consortia?

5.  Security Considerations

   Research into semantic addressing and routing must give full
   consideration to the security and privacy issues that are introduced
   by these mechanisms.  Placing additional information into address
   fields might reveal details of what the packet is for, what function
   the user is performing, who the user is, etc.  Furthermore, in-flight
   modification of the additional information might not directly change
   the destination of the packet, but might change how the packet is
   handled within the network and at the destination.

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6.  IANA Considerations

   This document makes no requests for IANA action.

7.  Acknowledgements

   Thanks to Stewart Bryant for useful conversations.  Luigi Iannone,
   Robert Raszuk, Dirk Trossen, Ron Bonica, Marie-Jose Montpetit, Yizhou
   Li, Toerless Eckert, Tony Li, and Joel Halpern made helpful
   suggestions.

   This work is partially supported by the European Commission under
   Horizon 2020 grant agreement number 101015857 Secured autonomic
   traffic management for a Tera of SDN flows (Teraflow).

8.  Contributors

   TBD

9.  Informative References

   [BIER-P4]  Merling, D., Lindner, S., and M. Menth, "Hardware Based
              Evaluation of Scalable and Resilient Multicast with BIER
              in P4", Presentation IETF-108 BIER Working Group Online
              Meeting, 2020,
              <https://datatracker.ietf.org/meeting/108/materials/
              slides-108-bier-05-bier-in-p4-00>.

   [BLIND-FORWARDINGref]
              Simsek, I., "On-Demand Blind Packet Forwarding",
              Paper 30th International Telecommunication Networks and
              Applications Conference (ITNAC), 2020, 2020,
              <https://www.computer.org/csdl/proceedings-article/
              itnac/2020/09315187/1qmfFPPggrC>.

   [CONTENT-RTG-MOBILEref]
              Liu, H. and W. He, "Rich Semantic Content-oriented Routing
              for mobile Ad Hoc Networks", Paper The International
              Conference on Information Networking (ICOIN2014), 2014,
              2014, <https://ieeexplore.ieee.org/document/6799682>.

   [EIBPref]  Shenoy, N., "Can We Improve Internet Performance? An
              Expedited Internet Bypass Protocol", Presentation 28th
              IEEE International Conference on Network Protocols, 2020,
              <https://icnp20.cs.ucr.edu/Slides/NIPAA/D-3_invited.pptx>.

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   [GEO-IPref]
              Dasu, T., Kanza, Y., and D. Srivastava, "Geotagging IP
              Packets for Location-Aware Software-Defined Networking in
              the Presence of Virtual Network Functions", Paper 25th ACM
              SIGSPATIAL International Conference on Advances in
              Geographic Information Systems (ACM SIGSPATIAL 2017),
              2017, <https://about.att.com/ecms/dam/sites/labs_research/
              content/publications/
              AI_Geotagging_IP_Packets_for_Location.pdf>.

   [I-D.jiang-semantic-prefix]
              Jiang, S., Sun, Q., Farrer, I., Bo, Y., and T. Yang,
              "Analysis of Semantic Embedded IPv6 Address Schemas",
              draft-jiang-semantic-prefix-06 (work in progress), July
              2013.

   [I-D.king-irtf-semantic-routing-survey]
              Farrel, A., King, D., and J. Dang, "A Survey of Semantic
              Internet Routing Techniques", draft-king-irtf-semantic-
              routing-survey-00 (work in progress), March 2021.

   [MULTICAST-SRref]
              Jia, W. and W. He, "A Scalable Multicast Source Routing
              Architecture for Data Center Networks", Paper  IEEE
              Journal on Selected Areas in Communications, vol. 32, no.
              1, pp. 116-123, January 2014, 2014,
              <https://ieeexplore.ieee.org/document/6799682>.

   [OPENSRNref]
              Ren, P., Wang, X., Zhao, B., Wu, C., and H. Sun, "OpenSRN:
              A Software-defined Semantic Routing Network Architecture",
              Paper IEEE Conference on Computer Communications Workshops
              (INFOCOM WKSHPS), Hong Kong, 2015, 2015,
              <https://www.researchgate.net/
              publication/308827498_OpenSRN_A_software-
              defined_semantic_routing_network_architecture>.

   [RFC4984]  Meyer, D., Ed., Zhang, L., Ed., and K. Fall, Ed., "Report
              from the IAB Workshop on Routing and Addressing",
              RFC 4984, DOI 10.17487/RFC4984, September 2007,
              <https://www.rfc-editor.org/info/rfc4984>.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <https://www.rfc-editor.org/info/rfc7665>.

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   [RFC8763]  Rahman, A., Trossen, D., Kutscher, D., and R. Ravindran,
              "Deployment Considerations for Information-Centric
              Networking (ICN)", RFC 8763, DOI 10.17487/RFC8763, April
              2020, <https://www.rfc-editor.org/info/rfc8763>.

   [RFC8799]  Carpenter, B. and B. Liu, "Limited Domains and Internet
              Protocols", RFC 8799, DOI 10.17487/RFC8799, July 2020,
              <https://www.rfc-editor.org/info/rfc8799>.

   [SEMANTICRTG]
              Strassner, J., Sung-Su, K., and J. Won-Ki, "Semantic
              Routing for Improved Network Management in the Future
              Internet", Book Chapter Springer, Recent Trends in
              Wireless and Mobile Networks, 2010, 2010,
              <https://link.springer.com/
              chapter/10.1007/978-3-642-14171-3_14>.

   [TERASTREAMref]
              Zaluski, B., Rajtar, B., Habjani, H., Baranek, M., Slibar,
              N., Petracic, R., and T. Sukser, "Terastream
              implementation of all IP new architecture", Paper 36th
              International Convention on Information and Communication
              Technology, Electronics and Microelectronics (MIPRO),
              2013, 2013,
              <https://ieeexplore.ieee.org/document/6596297>.

Authors' Addresses

   Daniel King
   Lancaster University
   UK

   Email: d.king@lancaster.ac.uk

   Joanna Dang
   Huawei Technologies
   China

   Email: dangjuanna@huawei.com

   Adrian Farrel
   Old Dog Consulting
   UK

   Email: adrian@olddog.co.uk

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