Challenges for the Internet Routing Infrastructure Introduced by Semantic Routing
draft-king-irtf-challenges-in-routing-06
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draft-king-irtf-challenges-in-routing-06
IRTF D. King
Internet-Draft Lancaster University
Intended status: Informational A. Farrel
Expires: 26 July 2022 Old Dog Consulting
C. Jacquenet
Orange
22 January 2022
Challenges for the Internet Routing Infrastructure Introduced by
Semantic Routing
draft-king-irtf-challenges-in-routing-06
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 packets by
placing additional information into existing fields, by adding
semantics to IP addresses, or by adding fields to the packets. The
intent is to facilitate routing decisions based on these additional
semantics in order to provide differentiated paths for different
packet flows distinct from shortest path first or path vector
routing. We call this approach "Semantic Routing".
This document describes the challenges to the existing routing system
that are introduced by Semantic Routing. It then summarizes the
opportunities for research into new or modified routing protocols to
make use of additional semantics.
This document is presented as a 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
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Current Challenges to IP Routing . . . . . . . . . . . . . . 4
3. What is Semantic Routing? . . . . . . . . . . . . . . . . . . 7
3.1. Architectural Considerations . . . . . . . . . . . . . . 9
4. Challenges for Internet Routing Research . . . . . . . . . . 10
4.1. Research Principles . . . . . . . . . . . . . . . . . . . 10
4.2. Routing Research Questions to be Addressed . . . . . . . 10
5. Security and Privacy Considerations . . . . . . . . . . . . . 15
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 15
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 15
9. Informative References . . . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
Historically, the meaning of an IP address has been to identify an
interface on a network device. Routing protocols were developed to
compute, establish, and maintain paths through networks toward
destination prefixes until IP packets eventually reach their
destination. Anycast and multicast addresses were also defined, and
those address semantics sometimes required variations to the routing
protocols or even encouraged the development of new protocols.
Over time, the mechanisms that enabled routing decisions were
enhanced to forward packets according to additional information
carried within the packets or within 'shim' headers, and dependent on
policy coded in, configured at, or signaled to the routers. Perhaps
one of the most iconic examples is Equal-Cost Multipath (ECMP) where
a router makes a 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 packets by
placing additional information into existing fields, by adding
semantics to IP addresses, or by adding fields to the packets. The
intent is to improve route computation and forwarding choices based
on these additional semantics which may lead to the establishment of
distinct paths for different packet flows: for example, shortest path
first or path vector routing. We call this approach "Semantic
Routing" [I-D.farrel-irtf-introduction-to-semantic-routing].
There are many approaches to adding semantics to packet headers.
These range from assigning an address 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 specific purposes (e.g., to provide an indication of
the nature of the service that is associated with these packets).
Some proposals suggest variable address lengths, others offer new
hierarchical address formats, and some introduce a structure to
addresses so that they can carry additional information in a common
way. Other approaches perform routing decisions on fields in the
packet header (such as the IPv6 Flow Label, or the Traffic Class
field), overload packet fields, or add new information to packet
headers.
A survey of ways in which routing decisions have been made based on
additional information carried in packets can be found in
[I-D.king-irtf-semantic-routing-survey].
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Some Semantic Routing proposals are intended to be deployed in
administratively scoped IP domains whose network components (routers,
switches, etc.) are operated by a single administrative entity
(sometimes referred to as 'limited domains' [RFC8799]), 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 Routing may present. Finally,
this document presents a list of related research questions that
offer opportunities for future research into new or modified routing
protocols that make use of Semantic Routing.
In this document, the focus is on routing and forwarding at the IP
layer. A variety of overlay mechanisms exist to perform service or
path routing at higher layers, and those approaches may be based on
similar extensions to packet semantics, but that is out of scope for
this document. Similarly, it is possible that Semantic Routing can
be applied in a number of underlay network technologies, and that,
too, is out of scope for this document.
This document is presented as a 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.
2. Current Challenges to IP Routing
Today's IP routing faces several significant challenges which are a
consequence of architectural design decisions and the continued
exponential traffic 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 networks have, in general, coped well in an incremental manner
whenever a new challenge has arisen. The following list is presented
to give context to the continuing requirements that routing protocols
must meet as new semantics are applied to the routing process.
* Mobility - Mobility introduces several challenges, including
maintaining a relationship between a sender and a receiver in
cases where the sender or receiver changes their point of network
attachment. The network must always be informed about the mobile
node's current location, to allow continuity of services. Mobile
users may also consume network resources, while in motion. The
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mobile user's service instances and attachments will also change
due to varying load or latency, e.g., in Multi-access Edge
Computing (MEC) environments.
* Multihoming - Multihomed stations or multihomed networks are
connected to the Internet via more than one access circuit or
access network and, therefore, may be assigned multiple IP
addresses or prefixes from different pools. There are challenges
concerning how traffic is forwarded back to the source if the
source has originated its traffic using the wrong source 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 network topologies can provide multiple
paths to reach a destination, 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 because of QoS or security considerations for example, or
to avoid transiting specific areas of an IP network, based (for
example) on the reputation of transit provider for example.
However, how packets are forwarded by using the 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 several "parallel" paths of identical least cost
using a hash algorithm operated on some of the packets' header
fields.)
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* 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 cause multiple copies of the packet to flow along the
same network links. Solutions that move deterministic replication
into the network to make more optimal use of the network resources
can be complex to set up and manage since multicast network
designs often assume dynamic tree computation where the multicast
distribution tree can be rooted at the source or in the multicast
network, thereby leading to specific routing tables whose entries
denote the tree structure. More complicated hardware that can
replicate packets may also be required within the network. In
order that packets can be addressed to a group of destinations and
not be forwarded by means of unicast transmission, parts of the
addressing space (that is, address prefixes) have been reserved
for multicast addressing.
* Programmable Paths - The ability to decouple IP paths from routing
protocols and agreements between Service Providers could allow
users and applications to select network paths themselves, based
on the required path characteristics. Another option is to let
the route computation logic select, establish, and maintain paths
on behalf of the user or the application and as a function of
their requirements so that Service Providers can participate in
the route computation "service". Currently, user and application
packets follow the path selected by routing protocols and the way
traffic is forwarded through a network is under the control of the
Service Provider that operates the said network. The
corresponding traffic forwarding policies enforced by the service
provider usually comply with the requirements expressed by the
user or the application. These requirements may have triggered a
dynamic service parameter negotiation cycle that eventually leads
to proper (network, CPU, storage) resource allocation.
* Endpoint Selection - As compute resources and content storage move
closer to the edge of the network, there are often multiple points
in the network that can satisfy user requests. In order to make
the best use of these distributed resources and so as 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
[RFC3467]) or in the transport layer (such as using ALTO
[RFC5693]). 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.
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* Scalability - There are many scaling concerns that pose critical
challenges to the Internet. Not least among these challenges is
the size of the routing tables that routers in an IP network must
maintain. As the number of devices attached to the network grows,
so the number of addresses in use also grows, and because of the
schemes used to assign address prefixes, the mobility of devices,
and the various connectivity options between networks, the routing
table sizes also grow, even more so when prefixes are not always
amenable to aggregation. This problem is exacerbated by some
services (such as those supported by the IoT where several
thousands of objects/sensors may be networked), where, as more
devices are added to the network, the size of the routing table
may affect the operation of certain routing protocols. It may be
noted that scaling issues are also 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 by 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 redirected to 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 IAB's "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?
Semantic Routing is the term applied to routing in an IP network that
relies upon additional information to feed the route computation
process and route selection decisions. Such information may be
present in the packet and configured or programmed into the routers
in addition to the routable part of the destination IP address (the
prefix). Semantic Routing includes mechanisms such as "Preferential
Routing", "Policy-based Routing", and "Flow steering".
In semantic routing, a packet forwarding engine may examine a variety
of fields in a packet and match them against forwarding instructions.
Those forwarding instructions may be installed by routing protocols,
configured through management protocols or a software defined
networking (SDN) controller, or derived by a software component on
the router that considers network conditions and traffic loads. The
packet fields concerned may be the fields of an IP header, those same
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fields but with additional semantics, elements of the packet payload,
or new fields defined for inclusion in the packet header. In the
case of additional semantics included in existing packet header
fields, the approach implies some "overloading" of those fields to
include meaning beyond the original definition. In all cases, a
well-known definition of the encoding of the additional information
is required to enable consistent interpretation within the network.
A more detailed description of semantic routing can be found in
[I-D.farrel-irtf-introduction-to-semantic-routing] and a survey of
semantic routing proposals and research projects can be found in
[I-D.king-irtf-semantic-routing-survey].
Many technical challenges exist for semantic routing in IP networks
depending on which approach is taken. These include (but are not
limited to):
* The continual growth of routing tables.
* Convergence times for large networks.
* Granularity of routing decisions.
* Address consumption caused by lower address utility rate. The
wastage mainly comes from aligning finite allocation for semantic
address blocks.
* Encoding too many semantics into prefixes will require evaluation
of which to prioritize.
* Risk of privacy/information leakage.
* Lack of visibility of the semantic routing information when end-
to-end or edge-to-edge encryption is used.
* Burdening the user, application, or prefix assignment node.
* Source address spoofing prevention mechanisms are required.
* Overloading of routing protocols causing stability and scaling
problems.
* Depending on encoding mechanisms, 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.
* Backwards compatibility with existing IP networking and routing
protocols.
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3.1. Architectural Considerations
Semantic data may be taken into account to integrate with existing
routing architectures. An overlay can be built such that semantic
routing is used to forward traffic between nodes in the overlay, but
regular IP is used in the underlay. 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 the Internet. In
other cases, traffic from within the domain is exchanged with other
domains that are connected together across an IP network using
tunnels or via application gateways. And in still another case
traffic from the domain is forwarded across the Internet to other
nodes and this requires backward-compatible routing approaches.
Isolated Domains: Some IP network domains are entirely isolated from
the Internet and other IP networks. In these cases, packets
cannot "escape" from the isolated domain into external networks
and so the semantic routing schemes applied within the domain can
have no detrimental effects on external domains. Thus, the
challenges are limited to enabling the desired function within the
domain.
Bridged Domains: In some deployments, it will be desirable to
connect together multiple isolated domains to build a larger
network. These domains may be connected (or bridged) over an IP
network or even over the Internet, possibly using tunnels. 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.
Semantic Prefix Domains: A semantic prefix domain 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 routing so that packets may be
forwarded through the regular IP network (or the Internet). Once
delivered to the semantic prefix domain, a packet can be subjected
to whatever semantic routing is enabled in the domain.
Further discussion of architectures for semantic routing can be found
in [I-D.farrel-irtf-introduction-to-semantic-routing].
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4. Challenges for Internet Routing Research
It may not be possible to embrace all emerging scenarios with a
single approach or solution. Requirements such as 5G mobility, near-
space-networking, and networking for outer-space (inter-planetary
networking), may need to be handled using different network
technologies. Improving IP 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. Solutions need to be both
economically feasible and have the support of the networking
equipment vendors as well as the network operators.
4.1. Research Principles
Research into semantic routing should be founded on regular
scientific research principles [royalsoc]. Given the importance of
the Internet today, it is critical that research is targeted,
rigorous, and reproducible.
The most valuable research will go beyond an initial hypothesis, a
report of the work done, and the results observed. Although that is
a required foundation, networking research needs to be independently
reproducible so that claims can be verified or falsified. Further,
the networks on which the research is carried out need to both
reflect the characteristics that are being explicitly tested, and
reproduce the variety of real networks that constitute the Internet.
Thus, when conducting experiments and research to address the
questions in Section 4.2, attention should be given to how the work
is documented and how meaningful the test environment is, with a
strong emphasis on making it possible for others to reproduce and
validate the work.
4.2. Routing Research Questions to be Addressed
As research into the scenarios and possible uses of semantic routing
progresses, a number of questions need to be answered. These
questions go beyond "Why do we need this function?" and "What could
we achieve by carrying 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
routing, but they form only part of the essential groundwork of
research into semantic routing itself.
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This section sets out some of the concerns about how the wider the
use of semantic routing might impact a routing system. These
questions need to be answered in separate research work or folded
into the discussion of each semantic routing proposal.
1. What is the scope of the semantic routing proposal? This
question may lead to various answers:
Global: It is intended to apply to all uses of IP.
Backbone: It is intended to apply to IP network connectivity.
Overlay: It is to be used as an overlay network using tunneling
over IP or other underlay technologies.
Gateway: The semantic routing will be used within a specific
domain, and communications with the wider Internet will be
handled by IP and probably application gateways.
Domain: The use of the semantic routing is strictly limited to
within a domain or private network.
Underlying this question 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 and the additional
semantics is not important?
2. What will be the impact on existing routing systems? What would
happen if a packet carrying additional semantics was subjected to
normal routing operations? How would the existing routing
systems react if such a packet escaped (accidentally or
maliciously) from the planned scope of the proposal? For
example: how are the semantic parts of an address distinguished
from the routable parts (if, indeed, they are separable)?; is
there an impact on the size and maintenance of routing tables due
to the addition of semantics?; how are cryptographically
generated addresses (such as [RFC3972]) made routable and kept
simple enough for management?.
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3. What path characteristics are needed to describe the desired
paths and as input to route computation? Since one of the
implications of adding semantics to IP packets 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? Can traffic be
forwarded over multiple distinct paths if multiple destination
addresses are encoded?
Security: What choices of path reduce the vulnerability of the
traffic to security or privacy attacks?
In these cases, how do the routers utilize the additional
semantics to determine the desired characteristics? Or are such
characteristics used to feed the route computation logic, for
example, by means of metrics? What additional information about
the network do the routing protocols need to gather? What
changes to the routing algorithm are needed to deliver packets
according to the desired characteristics? How can routes be
computed with characteristics that accommodate traffic patterns,
requirements, and constraints?
4. Can we solve these routing challenges with existing routing tools
and methods? We can break this question into a set of 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. But hardware is
increasingly programmable so that it may be possible to
instruct the forwarding components to act on a variety of
elements of the packets.
* 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?
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- Can we make backwards-compatible modifications to existing
protocols such that they work equally for today's IP
addresses or addresses with extra semantics?
- Do we need entirely new protocols or radical evolutions of
existing protocols in order to enforce advanced semantic
routing policies?
- Should we focus on the benefits of routing solutions that
are optimized for specific environments (network
topologies, technologies, use cases), or should we attempt
to generalize to enable wider applicability?
5. Do we need new management tools and techniques? How practical is
it to debug and operate the routing system? Management of the
routing system (especially diagnostic management) is a crucial
and often neglected part of the problem space. A critical part
of this issue is how packets within the network can be inspected
by diagnostic tools (or human operators) and mapped to the
routing and forwarding decisions that were made within the
network in order to understand the actions made at and by
upstream routers.
6. What is the impact of semantic routing on the security of the
routing system?
* Does the introduction of semantic routing provide a greater
attack surface?
* Can semantic routing provide greater opportunities for
security by fine-grain forwarding of flows to be inspected by
different security functions?
* Can semantic routing improve security and privacy by obscuring
information in the packets, or does the inclusion of
additional information risk compromising security and privacy?
* To what extent does deployment within a limited domain
strengthen security or make it less of a concern?
* Does the use of semantic routing make it easier or harder to
impose censorship, prohibit access to the Internet by specific
parties, or block access to certain resources or types of
service?
7. What is the scalability impact of semantic routing on routing
systems? Scalability can be measured as:
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* Routing table size. How many entries need to be maintained in
the routing tables by different routers serving different
roles in the network? Some approaches to semantic routing may
be explicitly intended to address this problem.
* Forwarding table size. The size of the forwarding table may
be less of an issue considering modern hardware, however the
more granular the routing/forwarding decisions made in a
router, the greater the size of this table. The size of the
forwarding table has implications for memory in the forwarding
engine, but also for the lookup time for forwarding each
packet.
* Routing performance. Routing performance may be considered in
terms of the volume of data that has to be exchanged both to
construct and maintain the routing tables at the participating
routers. It may also be measured in terms of how much
processing is required to compute new routes when there is a
change in the network.
* Routing convergence. This 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 its peers, and to reach a stable state across the network
such that packets are forwarded consistently.
For all questions about routing scalability, research that
presents figures based on credible example networks is highly
desirable. Similar questions may be asked about the amount of
forwarding state that has to be maintained in the routers.
8. To what extent can semantic routing be applied to multicast
transmission schemes:
* Can semantic routing facilitate the computation and the
establishment of (service-inferred) multicast distribution
trees?
* Can specific semantics be carried in multicast addresses?
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9. What aspects need to be standardized? It is important to
understand the necessity of standardization within this research.
What degree of interoperability is expected between devices and
networks? Is a given 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 and Privacy Considerations
Research into semantic routing must give full consideration to the
security and privacy issues that are introduced by these mechanisms.
Placing additional information into packet header 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.
It should also be considered how packet encryption techniques that
are increasingly popular for end-to-end or edge-to-edge security may
obscure the semantic information carried in some fields of the packet
header or found deeper in the packet. This may render some semantic
routing techniques impractical and may dictate other methods of
carrying the necessary information to enable semantic routing.
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, Joel Halpern, Stephen Farrell, Carsten
Bormann, David Hutchison, Jeffery He, Dino Farinacci, and Greg Mirsky
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
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Joanna Dang
Email: dangjuanna@huawei.com
9. Informative References
[I-D.farrel-irtf-introduction-to-semantic-routing]
Farrel, A. and D. King, "An Introduction to Semantic
Routing", Work in Progress, Internet-Draft, draft-farrel-
irtf-introduction-to-semantic-routing-02, 14 January 2022,
<https://www.ietf.org/archive/id/draft-farrel-irtf-
introduction-to-semantic-routing-02.txt>.
[I-D.king-irtf-semantic-routing-survey]
King, D. and A. Farrel, "A Survey of Semantic Internet
Routing Techniques", Work in Progress, Internet-Draft,
draft-king-irtf-semantic-routing-survey-03, 26 November
2021, <https://www.ietf.org/archive/id/draft-king-irtf-
semantic-routing-survey-03.txt>.
[RFC3467] Klensin, J., "Role of the Domain Name System (DNS)",
RFC 3467, DOI 10.17487/RFC3467, February 2003,
<https://www.rfc-editor.org/info/rfc3467>.
[RFC3972] Aura, T., "Cryptographically Generated Addresses (CGA)",
RFC 3972, DOI 10.17487/RFC3972, March 2005,
<https://www.rfc-editor.org/info/rfc3972>.
[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>.
[RFC5693] Seedorf, J. and E. Burger, "Application-Layer Traffic
Optimization (ALTO) Problem Statement", RFC 5693,
DOI 10.17487/RFC5693, October 2009,
<https://www.rfc-editor.org/info/rfc5693>.
[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>.
[royalsoc] The Royal Society, "Evidence synthesis : Principles", Web
page, Principles for good evidence synthesis, 19 September
2018, <https://royalsociety.org/topics-policy/projects/
evidence-synthesis/principles/>.
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Authors' Addresses
Daniel King
Lancaster University
United Kingdom
Email: d.king@lancaster.ac.uk
Adrian Farrel
Old Dog Consulting
United Kingdom
Email: adrian@olddog.co.uk
Christian Jacquenet
Orange
Rennes
France
Email: mohamed.boucadair@orange.com
King, et al. Expires 26 July 2022 [Page 17]