Internet DRAFT - draft-bryant-arch-fwd-layer-ps
draft-bryant-arch-fwd-layer-ps
INTAREA Working Group S. Bryant
Internet-Draft University of Surrey 5/6GIC
Intended status: Informational U. Chunduri
Expires: 6 February 2023 Intel
T. Eckert
A. Clemm
Futurewei Technologies Inc.
5 August 2022
Forwarding Layer Problem Statement
draft-bryant-arch-fwd-layer-ps-05
Abstract
This document considers the problems that need to addressed in IP in
order to address the use cases and new network services described in
draft-bryant-arch-fwd-layer-uc-00.
Status of This Memo
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This Internet-Draft will expire on 6 February 2023.
Copyright Notice
Copyright (c) 2022 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Forwarding Layer . . . . . . . . . . . . . . . . . . . . . . 4
3. Underlying New Requirements . . . . . . . . . . . . . . . . . 4
3.1. Better than Best Effort . . . . . . . . . . . . . . . . . 5
3.2. Efficient Packet Design . . . . . . . . . . . . . . . . . 5
3.3. Forwarding Identifiers . . . . . . . . . . . . . . . . . 6
3.4. Operational visibility . . . . . . . . . . . . . . . . . 6
3.5. Holistic Solution . . . . . . . . . . . . . . . . . . . . 7
4. Existing Protocol, Layering Challenges and Gaps . . . . . . . 8
4.1. Challenges with IPv6 . . . . . . . . . . . . . . . . . . 8
4.1.1. The End-to-End Model . . . . . . . . . . . . . . . . 8
4.1.2. Fixed Address Length . . . . . . . . . . . . . . . . 12
4.2. Better Than Best Effort E2E Network Services . . . . . . 13
4.3. Adaptive Bit-rate Video streaming . . . . . . . . . . . . 14
4.4. Limited Domain Opportunities . . . . . . . . . . . . . . 15
4.5. DetNet and Higher Precision Networking Service . . . . . 16
4.6. Forwarding Plane vs. Control Plane . . . . . . . . . . . 16
4.7. User-Network/Network-User Interface Signaling . . . . . . 18
5. Candidate Solution Directions . . . . . . . . . . . . . . . . 18
5.1. Variable Length Addresses . . . . . . . . . . . . . . . . 19
5.2. Address Semantics . . . . . . . . . . . . . . . . . . . . 19
5.3. Multiple Instructions . . . . . . . . . . . . . . . . . . 20
5.4. Node and Path Specific Processing Instructions . . . . . 20
5.5. Integrated Assurance and Verification . . . . . . . . . . 21
5.6. For Consideration in a Future Version . . . . . . . . . . 21
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 21
7. Security Considerations . . . . . . . . . . . . . . . . . . . 21
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 21
8.1. Normative References . . . . . . . . . . . . . . . . . . 21
8.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
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1. Introduction
There is an emerging set of new requirements that exceed the network
and transport services of the current Internet, which only delivers
"best effort" service. While many controlled or private networks
include further services, such as other DiffServ QoS in addition to
best effort and traffic engineering with bandwidth guarantees, the
solutions used today only support walled gardens and are thus not
available to application service providers and consumers across the
Internet.
The uses cases and service needs that are foreseen as necessary for
deployment in the medium future are described in
[I-D.bryant-arch-fwd-layer-uc].
The purpose of this document is to examine the shortcomings that the
existing network and transport layer protocols a well as their
associated control plane need to overcome to meet these needs.
The IETF is the body responsible for the long term evolution of the
IP protocol suit, but is missing a work track to discuss the long-
term Internet network architecture evolution. In particular it lacks
a programme for the long term evolution of IP itself.
Approximately 30 years ago, the IETF started a process to
revolutionize the IPv4 [RFC0791] Internet Protocol. In this process,
researchers, industry, and service providers got together, and
brought up a number of new proposals, and worked toward a successor
to IPv4, which became IPv6 [RFC2460] and later [RFC8200].
30 years later, there is heavy resistance to anything more than minor
incremental evolutions to IPv6. There are a number of reasons for
this ranging from opinions that all future IP needs can be met
through minor incremental evolutions to fears that major proposals
for innovation at the IP would be an unwelcome disrupter to the
current business of the vendors or the service providers.
The authors take no position on the scale of the problem or the
difficulties of deploying any solutions at scale in the Internet.
What we seek to do is to establish the scope and nature of the
problem. A decision on which aspects of the problem are economically
tractable is out of scope of this text, but technologies to support
monetization are not.
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As a problem statement, this documents goal is to not propose or
promote specific solutions to the problems raised. Instead it uses
references to not Internet adopted, but proposed or existing
solutions only as example evidence that the described problem can
actually be solved.
Because the document does not propose specific solutions, it also
does not attempt to structure the problem description in a way that
would identify sub-set of problems to be resolved by specific
solution components.
The purpose of this text is thus to stimulate discussion on the
emerging needs of the forwarding layer and to start the process of
determining how they are best satisfied within the IETF protocol
suite.
2. Forwarding Layer
The term "forwarding layer" is used in this work because none of the
standard terms encompass the parts of the network stack that need
attention to address the needs of the applications that are foreseen.
It is possible that development work will need to reach down to layer
2.5 in order to ensure that packets are handled correctly down to the
physical layer. The MAC layer is quite sophisticated and includes
its own switching function so we need to be sure that the good work
done in the network layer is not undone lower down the stack.
Equally it is possible that development work will need to reach into
the transport layer to address new approaches to congestion, and to
ensure that the network layer understands the requirements placed on
it by the application. An open mind is needed on the boundaries of
the layers as they exist today when analyzing the consequential
network changes needed to support the evolving application space.
In the network layer itself, this document is only concerned with the
forwarding component, not path selection or the other components of
routing.
Thus, we use the term forwarding layer to describe the scope of the
stack that this document addresses.
3. Underlying New Requirements
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3.1. Better than Best Effort
The current Internet is essentially of best-effort system, but future
applications require high-precision KPIs on throughput, latency and
packet loss for industrial manufacturing, control, automation, and
machine-to-machine communications.
The emerging use cases for networks require deployment of
capabilities that are beyond best effort. Best effort networks can
do remarkably well by simply throwing bandwidth at the problem and
lightly loading the network. For the case where a greater capability
is needed the IETF has invested effort in deterministic networking
(DN) [RFC8655]. Whilst DN is an improvement over best effort it is
still fundamentally a best effort service with enhancement to
improved the probability of a packet not being delayed or lost due to
congestion. It is an after the fact enhancement to the method of
operation of what is a largely unmodified data plane. I the case of
MPLS [RFC8964] there is some assistance from the PREOF function, but
IP runs the standard data plane and relies entirely on special case
packet selection queue management. It is thus an after-the-fact
enhancement to a minimally changed data plane restricted to a single
network domain.
With upcoming Cellular technologies (5G/B5G) there is a need for
Service Providers to expand the type of customers for metropolitan
size networks to address their better than best-effort traffic needs.
DetNet has been proposed to support this, however:
* Only some aspects of DetNet currently only run on top of current
IP/IPv6.
* DetNet service is constrained: It only supports constant bit rate
(CBR), reserved bandwidth. It does not support flexible
bandwidth. The notion of contracts in a future development of the
forwarding layer will support more flexible managed bandwidth and
managed latency contracts for traffic.
3.2. Efficient Packet Design
The ratio of useful data in the payload to overhead has a direct
financial impact on communication links; these links are of finite
capacity and hence have a finite cost-per-unit-data that can be
calculated. The capacity used to transport information as compared
to the overhead which is unavailable for use by a customer, but
required to transmit is often expresses as a good-put efficiency and
can be related to cost to transmit payload data.
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* There is a need to support large number of low power user
equipment (UE) devices (low-power IoTs) connecting through various
radio networks (LTE/5G/B5G) where spectral efficiency is needed.
This needs to be achieved without header compression techniques
like as [RFC6282] since, compression can result in additional
processing and energy consumption overhead.
* The handling network protocol headers, requires that portions of
each packet be held in memory or buffer structures; the more
levels of information which need to be held for processing by
network nodes, the more memory space will be required, and this
directly effects the cost of operation and cost of manufacture/
provision of such equipment.
On the other hand, in various non-constrained environments where
various network layer functionalities are desired, there are
different set of requirements. For example:
* Segment Routing over IPv6 (SRv6) parameter encoding [RFC8986] in
the SRv6 SID [RFC8754] is limited by the prefix portion of the
IPv6 address.
* In Identifier Locator Addressing (ILA), the identifier (ID)
portion of the address length is limited because of 128 bits
limit.
3.3. Forwarding Identifiers
Developments in IPv6 [RFC8986] formalize a trend that has been
happening for a long time: the morphing of network layer addresses
into forwarding identifiers (FI). However, constraining FIs to a
fixed size ill serves the development of the forwarding layer. There
are clear cases as illustrated above where it would be useful to have
shorter network layer addresses. Equally we can see that there will
be future cases where 128 bits may be insufficient to specify a
forwarding operation. The requirement is thus to formally introduce
the concept of forwarding identifiers in place of network layer
addresses, and use a forwarding identifier construct that supports
multiple semantics and multiple, possibly fully variable, lengths.
There is further discussion on this point in Section 4.1.2.
3.4. Operational visibility
Network operators require facilities that let them better understand
and fine tune detailed network behavior. These features are hard to
retrofit with current IP/IPv6.
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The rise of machine learning has led to the expectation of being able
to better optimize networks This in turn leads to the increase of
network telemetry as a source of data to base these systems on. In-
Situ OAM (IOAM) [RFC9197] represents one of the latest developments
in that space, allowing the data plane to piggy-back telemetry data
onto individual packets in order to diagnose and fine-tune service
levels such as latency or jitter. However, there are several issues
with this approach:
* MTU issues limit amount of data that can be obtained. With IOAM
packet size increases with number of data items and number of
hops.
* The data that can be obtained is very limited.
* The OAM data volume can easily exceeds that of production traffic
which is wasteful
* There is no ability to aggregate OAM data, or make context
dependent OAM collection.
* Integration with other solutions such as DetNet is unclear.
While useful, IOAM exposes the limits of what add-on solutions can
provide. Solutions that provide visibility at the level of flows or
that provide automatic verification of Service Level Objectives are
missing entirely.
3.5. Holistic Solution
It needs to be recognized that it will not be sufficient for
solutions to support new services and capabilities one at a time and
independently from one another. For example, better-than-best-
effort, operational visibility, and efficient packet design should go
together, without leading to additional integration problems ore
requiring users to make a choice.
A piecemeal approach, in which solutions for any one particular
problem are developed and emerge one at a time, results in a
fragmented solution which gets progressively more difficult to
integrate with components previously designed. Thus it is better if
solutions are holistic and be able to support new services and
capabilities in integrated fashion and simultaneously with each
other.
We therefore need to identify an elegant approach that is simple and
naturally extensible to address problems that we do not yet conceive
as requiring addressing.
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Any such solution needs to be intrinsically secure and yet be able to
support security without privacy and privacy without security.
4. Existing Protocol, Layering Challenges and Gaps
Despite IPv4 still having a large user base, and having a number of
useful properties the IETF has abandoned future development of IPv4
as a way to force the deployment of IPv6. For example, in terms of
traffic steering the segment routing could have usefully been applied
to IPv4 to support network operators that wished to retain IPv4 as
their preferred internal protocol.
Given the gaps in each of the existing network layer protocols the
IETF may wish to look at the design of a protocol that both fills the
gaps and unifies its three existing network layer protocols: IPv4,
IPv6 and MPLS.
Additionally there is a clear need for a more sophisticated approach
to indicating the required quality of service that a packet, or flow,
needs in an IP network.
4.1. Challenges with IPv6
4.1.1. The End-to-End Model
IPv6 and specifically [RFC8200] was designed to fit within an
Internet architecture centered around the end-to-end model with
"Internet Paths" potentially passing through one or more networks
without any relationship to the endpoints of a communication such as
most so-called transit-AS. As history already from IPv4 had shown,
anything more than the most simple per-hop processing options can
cause interoperability issues. In result, [RFC8200] has drastically
limited such per-hop processing options.
Two core restrictions of RFC8200 are the following:
* Restrictions on extension headers (EH): EHs must never be deleted
or changed in size by any node on the path the packet takes.
Intermediate nodes are only expected to examine these headers (if
they are configured to do so). Implementations cannot expect
intermediate nodes to examine, or act on, except for hop-by-hop
header (section 4.8 of [RFC8200]).
At the time of writing this is an area of considerable active
discussion in the IETF 6MAN and SPRING working groups. The issues
that arise from allowing unrestricted insertion, deletion or
modification of EHs are for example:
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* Breakage of path MTU discovery
* Impact on the Authentication Header protocol
* Inability to return ICMP error messages to the correct node.
See Section 4.1.1.1 for further discussion.
* No new hop-by-hop headers (HBH) in IPV6: No new EHs that require
hop-by-hop behavior should be defined (section 4 of [RFC8200]) -
the only EH that has hop-by-hop behavior is the Hop-by-Hop Options
header. The only alternative available to the designer is instead
to use destination headers (section 6.8 of [RFC8200]).
4.1.1.1. IPv6 For Controlled Networks
While [RFC8200] is a conservative set of requirements to enable
proliferation of the target use case of "Internet Paths", the same
set of requirements limit the flexibility of IPv6 unnecessarily when
it is used in controlled networks where the constraints and
interoperability issues for "Internet Paths" do not equally apply,
for example the deployment scenarios described in Sections "Embedded
Service" and "Embedded Global Service" of
[I-D.bryant-arch-fwd-layer-uc].
One typical type of controlled networks are service providers (SP)
where SRv6 is used as the architecture within the SP network.
* IPv6 extension headers can not be added on a midpoint. Any
addition/change requires an encapsulation where another IPv6
header with optional SRH extension header is prepended to the
carried IPv6 packet. This is expensive in terms of packet MTU,
and in terms of packet buffer requirements at the ends of the
provider path which can be an economic issue in cost sensitive
network segments.
* The requirement to encapsulate instead of being allowed to add an
EH along the path stems from the desire to isolate any header
changes from Path MTU Discovery (PMTUD). This is a necessary
complexity when traversing uncontrolled hops across the Internet,
but it is unnecessary overhead when only passing through
controlled hops. In MPLS and SR-MPLS, the MPLS header size is not
included in the MTU available to the MPLS payload, instead the
network is managed such that the maximum MPLS header size plus the
available payload MTU is always smaller that the encapsulating L2
frame MTU. In IPv6 instead, the encapsulating and decapsulating
would logically have to perform signaling for PMTUD
(unnecessarily).
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* Because of the authorization header (AH) [RFC4302] and OAM
concerns, [RFC8200] likewise prohibits removing extension headers
or fields thereof on hops along the path, requiring for example
more complex packet parsers. In SR-MPLS it is possible to simply
remove the top SID on a node that has processed it, in SRv6 it is
instead necessary to look up an offset field in the SRH and, read
the appropriate SID (which may be deep in the packet), and then
increment the offset field.
* Even though the number of identifiers required within a controlled
network is often less than 16 bit, and almost always 32 bits,
carrying the overhead of 128 bits per SID in SRv6 can be seen as a
significant unnecessary overhead, and workarounds such a proposed
micro programs [I-D.bonica-6man-comp-rtg-hdr],
[I-D.bonica-spring-srv6-plus],
[I-D.filsfils-spring-net-pgm-extension-srv6-usid] require complex
forwarding plane processing and SRv6 programmability in the lower
64 bit is not required in the majority of use-cases for SIDs on
midpoints.
For use-cases like this, it would be a lot easier to innovate IPv6 by
clone & modify: E.g.: defining (say) IPv7 to be similar to IPv6, but
without the constraints that are not useful for the controlled
network use-case. A better alternative would be to create different
profiles of IPv6 with [RFC8200] being one. However, there is, as
yet, no concept of "profiles" in IPv6.
The issue of IP protocol operation in limited domains is discussed in
[RFC8799].
Some possible solutions are described in
[I-D.herbert-6man-eh-attrib]. This will be considered further in a
future version of this text.
4.1.1.2. IPv6 for Edge-Compute
Today, the majority of end-to-end connections already do not pass via
the traditional "Internet-Path" but instead toward a server in data
center co-located with the access service provider Edge-2-Edge-EP
[DOT]. In this case, there is no transit service provider, but there
is a well-established commercial relationship between either end of
the communications and the access service provider.
Today, the majority of traffic consists of video-streaming/TV
services, but in the future, Edge-Compute will enable ever more
applications to operate in such a controlled environment.
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The difference between the aforementioned use-case of IPv6 within an
service provider, and this use-case is that enhanced services in this
would naturally operate end-to-end between a Data Center application
server and the subscriber endpoints.
In the case of SRv6, it is not necessary to incur the overhead of an
IPv6 in IPv6 encapsulation, the SRH can be inserted by the endpoint
and removed by the endpoint on the other side. Nevertheless, the
[RFC8200] limitations of not being able to add/remove or freely
change the content of the SRH payload or any other EH on a midpoint
router still exists. This seriously limits the usage and evolution
of IPv6 to the edge-to-edge model.
4.1.1.3. Hop-by-Hop Extension Header processing
Hop-by-hop IPv6 extension headers caused interoperability and
performance issues and as a result caused resistance to further
leverage and extend them except for SRv6-SRH RPL-SRH [RFC6554]. In
the authors opinions, this regression on hop-by-hop extension headers
is because of a combination of insufficient specifications and
resulting implementation issues. Both could be solved in future work
with new hop-by-hop processing specifications.
For example, router alert (RA) was (and still maybe) implemented in
routers so that all router alert packets are punted from the fast-
path to the slow-path even when the "value" field identifies a
protocol that the router can not process. As a result, protocols
that rely on RA such as RSVP [RFC2205] or even more so Pragmatic
General Multicast (PGM) [RFC3208] where filtered in networks because
they caused high control plane load on routers that did not support
either protocols but still unnecessarily punted their packets with
RA.
There are no normative statements about the need that fast-path
forwarding planes "MUST" be able to ignore unsupported/not-enabled EH
features at a speed such that such a packet can be forward at the
same speed as the same packet without the EH. For example, for RA,
there is only a "SHOULD" requirement to do this in [RFC6398], a BCP
published a decade after IPv6 router alert [RFC2711]. With such a
gap in time between the specification and the BCP, it is impossible
to rely on the existing RA and expect safe deployment across the
Internet without still running into performance issues.
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4.1.1.4. Segment Routing Header Constraints
The same design paradigm could have been used for the Segment Routing
Header (SRH) [RFC8754], but there is no distinction possible for IPv6
instances running in such a controlled network or running as an
Internetwork instance to form the Internet. This is particularly
unfortunate as we are evolving to a model where, as noted earlier in
this document, in most cases the packet will only travel through two
well-known networks: the hosts network and the service provider
network hosting the server to which the client is interacting.
4.1.2. Fixed Address Length
When IPv6 was designed, the key focus was on solving the problem of
growth of the Internet and resulting growth of global Internet
address space. Variable length and a heterogeneous address approach
were proposed [RFC1347] however, these were rejected partially for
political reasons and partially out of a concern over the difficulty
of parsing the packet and doing a fast address lookup.
There was seemingly no focus on better supporting the now millions of
often network-layer isolated TCP/IP networks in industrial, defense,
research, embedded, industrial or other commercial environments.
One key problems with with 128 bit addresses is the overhead on low-
speed radio/IoT-wire networks. This is especially the case when
using source-routing, where multiple of these addresses have to be
included in the header. Current solutions are only able to resolve
these issues with CPU expensive IETF standardized header compression
techniques [RFC2507], [RFC3095], [RFC5795]. Even though these
approaches are feasible in many of todays IoT networks, there is a
strong desire to reduce power consumption in such devices. This is
particularly the case where they are powered by a single-for-life-
battery, or are self-powering through automatic replenished energy
sources. As a result of this CPU performance in future IoT network
should not be expected to increase but whenever feasible is more
likely to decrease.
Another, often overlooked, problem of the 128 bit IPv6 addresses is
that global address prefix allocation is a a big up-front burden on
many IoT networks, but also isolated networks (industrial, defense,
research, industrial). Often, this leads to the use of Unique Local
Addresses (ULA) [RFC4193], which have the risk of conflicts when
those previously isolated networks need to interconnect with other
networks.
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A further insight into the issues of IPv6 address lengths of 128 bits
can be seen in the tussle over how to compress the address lengths in
Segment Routing and network programming (in no particular order):
[I-D.bonica-6man-comp-rtg-hdr], [I-D.bonica-6man-crh-helper-opt],
[I-D.bonica-spring-sr-mapped-six],
[I-D.cheng-spring-shorter-srv6-sid-requirement],
[I-D.decraene-spring-srv6-vlsid],
[I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc],
[I-D.lc-6man-generalized-srh], [I-D.li-spring-compressed-srv6-np],
[I-D.mirsky-spring-unified-id-network-programming],
[I-D.steinberg-6man-crh-vs-sr-mpls], [I-D.templin-6man-crh-variable].
The root cause of this debate is the inflexibility of IPv6 in terms
of its address length and semantics.
While solutions to these problems may look easier enough, it should
be noted that in the time when IPv6 was designed, variable length
addresses in the fastest forwarding planes were not seen as feasible,
and there was also a lack of experience with the impact of
interconnecting heterogeneous address spaces other than as ships-in-
the-night parallel operation of protocols. A lot of that experience
came later through 14++ IPv4/IPv6 transition solutions designed in
the past 20 years and respective work on address discovery in IETF
frameworks such as SIP/STUN/ICE.
Another issue with the fixed length homogeneous address approach is
the constraints this places on the current practice of overloading
addresses with other functionality for example [RFC8986].
Since the original decision to only support fixed length packet
addresses was taken there has been a significant improvement in the
packet lookup capability of hardware. This is has been driven by the
need to perform complex ACL lookup for security reasons and the
interest in flow based techniques such as OpenFlow. It is thus worth
revisiting the decision to only allow a single fixed address length
and format.
4.2. Better Than Best Effort E2E Network Services
Some of the fastest growing network segments where new services are
being introduced in an End-2-End manner belong to deployment models
as described in [I-D.bryant-arch-fwd-layer-uc]. The requirements
here for service delivery involves stringent E2E latency with no
retransmission and no packet loss. Not all scenarios need "lower"
latency but bounded to a particular value/range. Example use cases
involving an user equipment (UE) consuming service from the provider
cloud network or another UE (e.g. Vehicular device, IIoT) in the
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same network. Here the service endpoints could be connected over
wire or wireless (LTE/NR) and the service termination happens in the
provider network either close to the access network or provider core
network. The existing network layer and best-effort model simply
cannot guarantee needed service level objectives in these scenarios.
Some specific needs and requirements from cellular fixed transport
networks are:
* Need for determinism on E2E throughput and latency. The current
TCP/IP is hence not-suitable for Mission-critical and real-time
E2E applications.
* Need for E2E QoS for ultra-reliable-low-latency communications
(uRLLC).
* Efficient use of protocols in the network by minimizing tunnels
over tunnels and duplicate header fields.
* Efficient deployment of network slicing
4.3. Adaptive Bit-rate Video streaming
Even without going to future application requirements as described
elsewhere in this document, even the majority of existing Internet
traffic is lacking competitively usable and standardized service to
support quality of service.
The majority of traffic today is Adaptive Bit-rate (ABR) based audio/
video streaming. The primary benefit of this approach is that it can
adjust itself to much lower bandwidth than the bandwidth to offer the
ideal/target experience quality to the user. It therefore enabled
Over The Top (OTT) services to offer streaming media. Nevertheless,
ABR itself does not provide any actual quality guarantees.
Service providers that use ABR streaming to their subscribers do
therefore combine ABR with IP developments, some non-published, which
are often out-of-band bandwidth reservation schemes. These allow ABR
video streams to have their ideal/target experience bandwidth within
the SP's network and only need to degrade if there was bandwidth
contention in the subscribers (home) network.
If a subscriber, or a content provider which is not the access
service provider wanted to get the same type of bandwidth guarantees
for other content across the access providers network, they could do
so with existing IETF standards via RSVP [RFC2205] which is widely
implemented, or NSIS [RFC4080], which was to the knowledge of the
authors never implemented in widely used router products (because it
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does not offer sufficient benefits over RSVP). In either case, the
per-flow control-plane based signaling architecture including the
aforementioned router-alert issues make these protocols a difficult,
likely not future-proof solution.
Even more fundamentally, ABR has shown that media streaming can
easily support elastic adjustment between a range of bandwidth limits
in which the quality is between acceptable and ideal, but there is as
of today no standardized mechanisms by which to express relative
bandwidth allocations when streams compete against each other that
goes beyond the very loosely defined "internet fairness". For
example, more intelligent congestion management could defend
bandwidth the more the bandwidth approaches the minimum acceptable
bandwidth, or admission control of bandwidth could be elastic. Some
work in these direction exists in [RFC8698] with its ability for
weighted congestion control or
[I-D.ietf-tsvwg-intserv-multiple-tspec] for (limited) elastic
admission control management.
4.4. Limited Domain Opportunities
Strictly of course this refers to the opportunities that the
acceptance of limited domains [RFC8799] provides to the network
operator in terms of the flexibility to enhance packet delivery in
cases of high value traffic.
The removal of the constraint of a globally uniform protocol, such as
unenhanced IPv6 would allow a best in class, domain specific
forwarding layer to be deployed without the constant of the
requirement that the protocol needed to serve all purposed, for all
applications in all parts of the global network.
These opportunities are are further enhanced by noting that the
delivery protocol to the application server, which as noted elsewhere
in this text is moving closer to the edge, does not need to be the
same as the host to application protocol since this is increasingly
being opaquely tunneled over the delivery protocol. Furthermore, any
distributed set of application servers maybe in their own domain, and
this is not constrained to the same protocol that is used between the
client and the server.
Clearly their are costs and complexities associated with moving from
a globally heterogeneous protocol to a domain specific protocol, but
the deciding factors are whether the application is deliverable over
a globally general purpose forwarding layer, and whether there
application and delivery system are economically attractive.
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4.5. DetNet and Higher Precision Networking Service
Time Critical (TC), Ultra-Reliable, Low Latency (URLLC), Internet-of-
Things is another important use case scenario-set that highlights
requirements that are difficult to satisfy with existing Internet
connectivity paths where a part of that path includes a radio access
link. These kind of close-loop control systems borne over
heterogeneous communications networks have very precision and bounded
latency requirements for the E2E network connecting the sensor and
actuator.
Deterministic networking within the IETF is focused on only one
dimension of the URLLC problem.
DetNet is also far from attempting to identify currently if/how the
services it plans to introduce could be made to operate over the
Internet in general, instead, it focuses mostly on the shorter term
goal to enable them in controlled networks within a limited domains.
Currently, the requirements for a DetNet forwarding plane have been
reasonably mapped out for an MPLS based forwarding layer.
Nevertheless, in addressing these needs within an IP network
[RFC8939] the solution has of necessity been limited to the
capabilities of the IP as it exists today. It has not, for example,
been possible to add the packet replication elimination and
reordering function (PREOF)which allows multiple concurrent packet
delivery attempts in an MPLS network [RFC8964]. The DETNET body of
requirements needs to be revisited in the light of any development to
network forwarding capabilities.
4.6. Forwarding Plane vs. Control Plane
High-end hardware with accelerated forwarding plane devices, can
support a significant number of forwarding states including
destination entries (IP destination/mask, MPLS label, SR SID) as well
as 2, 3 or 5 tuple IP/IPv6 "flow" entries. Nevertheless, the control
plane that builds and changes these entries often limits their
usability because the control plane does not even scale to the number
of hardware accelerated forwarding entries possible, or because the
supported rate of changes is slow.
The root of this problem is that with the increase of speed and scale
of hardware accelerated forwarding hardware, control plane had
challenges to keep up in performance. The performance of
appropriately priced control plane CPUs (relative to the cost of the
forwarding plane) has not grown at the same speed as that of hardware
accelerated forwarding plane chips.
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One of the directions to overcome these challenges is invisible
outside these forwarder devices and it is to optimize the control-
plane to forwarding plane interactions, such as programming the
building of forwarding state directly on the accelerated forwarding
infrastructure (e.g. NPU), but using otherwise existing control
plane protocols.
A more fundamental approach is to redesign control plane protocols
such that they are lighter weight in their signaling and state
machinery, and can therefore be completely implemented in the
hardware accelerated forwarding plane. Effectively turning a control
plane protocol into an advanced forwarding plane protocol function.
This approach is logically most easily applicable to on-path per-flow
signaling mechanisms such as RSVP or RSVP-TE, both of which are quite
complex with their signaling messaging and state keeping and
therefore directly infeasible to become hardware accelerated
forwarding implementations. An example approach to provide similar
functionality to RSVP with signaling light-weight enough to allow
hardware accelerated implementation are the in-band signaling
mechanisms (e.g. for TCP or UDP) described in [DIP1]
[I-D.han-tsvwg-ip-transport-qos] [I-D.han-tsvwg-enhanced-diffserv].
Signaling that is feasible to become part of a complete in-
forwarding-plane signaling solution is not limited to in-band on-path
flow signaling, but would likely also be applied to other signaling
options. Of the aforementioned existing signaling protocols, IGPs
are likely the ones whose signaling could most easily be processed in
an NPU compute elements except that the SPF calculation itself
introduces a complexity that would make this very complex. One
example of a solution that solves this problem by signaling the
actual per-hop adjacencies in IGP and therefore eases NPU
implementation can be found in
[I-D.chunduri-isis-preferred-path-routing].
In summary: The scope of what should be considered forwarding plane
today is defined by decade historic architectures, but should for the
future be scoped by the realities of the new, different "layers" of
hardware and their capabilities. Hence also the use of the term
forwarding plane, because it can span not only across classical
bridging (L2), label/tag/SIG switching (L2.5), network/internetwork
(L3) and transport (L4) layers, but also across the classical "data
plane" and "control plane" components of each such layer.
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4.7. User-Network/Network-User Interface Signaling
Some of the deployment models as described in
[I-D.bryant-arch-fwd-layer-uc], needs specific signaling mechanism
from user/applications. These are needed for E2E service offering
for better than best effort Section 4.2 or high-precision networking
Section 4.5. These may involve new transport mechanisms at hosts,
middle-boxes and routers to meet the E2E service requirements in
these limited domain deployments.
Here one of the functional requirements is to signal the service
level objectives (SLOs) dynamically for a particular service from the
network. This signaling includes the service description, the
service negotiation with the network, the service setup or
modification, or the need to execute some functions at network device
and send the results back to the sender. However, the current IP was
not designed for this. For example, the result of SLO negotiation at
any hop needs to be updated in the IP packet at the router and
returned back to the sender (originating host or gateway device for a
Service Provider).
There are some attempts to achieve the above as described in
[I-D.han-tsvwg-ip-transport-qos], which describes general in-band
signaling for QoS control with IPv6 protocol and
[I-D.han-tsvwg-enhanced-diffserv], which proposes a backward
compatible class-based queuing and scheduling schema for hybrid
service to support guaranteed service from the network (e.g. for
latency and bandwidth).
In summary, it is difficult to do better than best effort or High
Precision Services described in Section Section 4.5, in closed
domains with current IP given the best effort congestion control
(TCP/QUIC) and explicit congestion notification (ECN) framework. A
comprehensive mechanism needs to be explored as the limitations in
silicon technologies or deployment models 30 years ago are not
relevant with respect to security, scalability, packet size change,
MSS or FCS recalculation, etc.
5. Candidate Solution Directions
This section is an incomplete list of solution considerations, but is
not prescriptive about any specific approach or technical solution,
and is provided to stimulate thought on the subject.
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5.1. Variable Length Addresses
When private networks are set up, they only need to use an address
length that allows the construction of networks sufficiently large to
meet the expected service requirements. If a future network layer
protocol could support address length of e.g.: 16, 24, 32, 48, 64 and
128 bits (or maybe more), it would be easy for such networks to pick
a right size. This would allow them to have as efficient packets
without compression as possible, and it would also avoid for them to
have to think about allocation procedures for "global" addresses.
Whenever networks with a smaller address size would later on have to
interconnect to other networks, the shorter length address would have
to be interpreted as the suffix of a sufficiently larger address
space through which those connecting networks could achieve unique,
non-overlapping addresses. At the border between these networks,
high speed forwarding planes could easily perform per-packet
stateless prefix addition/deletion transformations of addresses in
the packet header when the interconnection should be free of further
policy. When such an interconnection is desired to employ specific
traffic control policies, mapping of addresses in a stateful manner
is a convenient way to enforce and support such policies through the
forwarding plane.
5.2. Address Semantics
Classically IP unicast addresses identify an interface. There is the
special case of a loop-back address, but this is normally modeled as
an internal interface. Addresses are often silently mapped to
include other semantics and this is most developed in the IP network
programming concept [RFC8986].
MPLS is more general. It defines the concept of a Forwarding
Equivalence Class in which a Label which can be visualized as an
offset into a specific table with up to 2^20 entries, with the table
containing the instruction to be executed. Thus a single identifier
is able to specify: forward towards an egress, forward along a
specific path, decapsulate and sent to an interface, decapsulate and
forward via an IP lookup in a label specific address table etc.
The semantics of the MPLS label and the size of the label are such
that it is not possible to include any instruction parameters in the
label and very inefficient to include those parameters in one or more
further labels. The only example of doing this is the Entropy Label
indicator [RFC6790] which uses two Label Stack Entries (LSEs). Any
future development along these lines will need at least three LSEs.
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Whilst an IPv6 is larger there is still limited space to add
parameters within the address. In the current work on this the size
is limited to 16 bits, and there is a fundamental limit of 64 bits.
It is clear that move is towards a multiplicity of semantic for the
network layer address, and indeed a formal recognition that the
address is in reality an instruction with a specific scope.
5.3. Multiple Instructions
What we have learned from MPLS and then from SRv6 is that it is often
desirable for a node (be that the originating host or a router) to
impose on a packet a set of instructions to be executed in sequence
by one or more entities in the network. An development of IP or any
successor needs to recognize this and provide a simple and efficient
way to incorporate a list (or stack) of instructions within the
packet header.
5.4. Node and Path Specific Processing Instructions
There is an established need to do node specific instructions as is
indicated by the design of MPLS and Segment Routing (SR). Any
development of the forwarding system needs to retain this feature and
ideally develop a method that is simultaneously both general and
efficient.
References to efficiency include efficiency in packet size and
efficiency decoding and and executing the instruction. The
efficiency of encoding is not simply a matter of on the wire
bandwidth, but is also a matter of the size of the forwarder packet
header cache. This cache has to operate at wire speed can be an
expensive silicon element.
There is also a need to do path specific operations as are done in
RSVP-TE. However RSVP has a significant path set-up and path
maintenance cost. Clearly a per path instruction can be specified as
a set of N per node instructions where N is the number of hops along
the path, for example by using SR, but that is not an efficient
encoding where N is large. It is thus a useful optimization to
include the ability to include per path instructions, and this is the
subject of further study.
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5.5. Integrated Assurance and Verification
Being best effort in nature, assurance for services provided using IP
is left to add-on solutions built after the fact. How to perform
tasks such as verifying of service levels is left as an exercise for
network providers, often approached using statistical approaches that
are themselves "best effort" in nature. This will be no longer
sufficient for mission-critical services such as tele-driving or
tele-operations that demand guarantees, where failure to meet those
guarantees may expose providers and users exposed to liability
demands and call the feasibility of applications relying on those
services into question.
Moving forward, network protocols suitable to deliver high-precision
services for mission critical applications need to address assurance
as an intrinsic property, not left to afterthoughts.
5.6. For Consideration in a Future Version
A future version of this document will consider E2E communication
beyond-best-effort, high precision services, high precision
telemetry, E2E Volumetric data transfer and high precision congestion
control beyond that provided by the diffserv QoS bits.
6. IANA Considerations
This document does not request any allocations from IANA.
7. Security Considerations
Security is likely to be more significant with the applications being
considered in this work. With interest in tightly controlled access
and latency, and contractual terms of business it is going to be
necessary to have provable right of access to network resources.
However heavyweight security is a contra-requirement to the light-
weight process needed for power efficiency, fast forwarding and low
latency. Addressing this will require new insights into network
security.
Further information on the issue of providing security in latency
sensitive environments can be found in [RFC9055] which are a sub-set
of the considerations applicable to the new use cases considered in
this text.
8. References
8.1. Normative References
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[RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DOI 10.17487/RFC0791, September 1981,
<https://www.rfc-editor.org/info/rfc791>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>.
8.2. Informative References
[DIP1] ETSI, "Recommendation for New Transport Technologies, GR
NGP 010", 13 September 2018,
<https://www.etsi.org/deliver/etsi_gr/
NGP/001_099/010/01.01.01_60/gr_NGP010v010101p.pdf>.
[DOT] Huston, G., "The Death of Transit and Beyond", n.d.,
<https://hknog.net/wp-content/uploads/2018/03/01_GeoffHust
on_TheDeath_of_Transit_and_Beyond.pdf>.
[I-D.bonica-6man-comp-rtg-hdr]
Bonica, R., Kamite, Y., Alston, A., Henriques, D., and L.
Jalil, "The IPv6 Compact Routing Header (CRH)", Work in
Progress, Internet-Draft, draft-bonica-6man-comp-rtg-hdr-
28, 18 May 2022, <https://www.ietf.org/archive/id/draft-
bonica-6man-comp-rtg-hdr-28.txt>.
[I-D.bonica-6man-crh-helper-opt]
Li, X., Bao, C., Ruan, E., and R. Bonica, "Compressed
Routing Header (CRH) Helper Option", Work in Progress,
Internet-Draft, draft-bonica-6man-crh-helper-opt-04, 11
October 2021, <https://www.ietf.org/archive/id/draft-
bonica-6man-crh-helper-opt-04.txt>.
[I-D.bonica-spring-sr-mapped-six]
Bonica, R., Hegde, S., Kamite, Y., Alston, A., Henriques,
D., Jalil, L., Halpern, J., Linkova, J., and G. Chen,
"Segment Routing Mapped To IPv6 (SRm6)", Work in Progress,
Internet-Draft, draft-bonica-spring-sr-mapped-six-04, 27
September 2021, <https://www.ietf.org/archive/id/draft-
bonica-spring-sr-mapped-six-04.txt>.
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[I-D.bonica-spring-srv6-plus]
Bonica, R., Hegde, S., Kamite, Y., Alston, A., Henriques,
D., Jalil, L., Halpern, J., Linkova, J., and G. Chen,
"Segment Routing Mapped To IPv6 (SRm6)", Work in Progress,
Internet-Draft, draft-bonica-spring-srv6-plus-06, 15
October 2019, <https://www.ietf.org/archive/id/draft-
bonica-spring-srv6-plus-06.txt>.
[I-D.bryant-arch-fwd-layer-uc]
Bryant, S., Chunduri, U., Eckert, T., and A. Clemm,
"Forwarding Layer Use Cases", Work in Progress, Internet-
Draft, draft-bryant-arch-fwd-layer-uc-03, 24 January 2022,
<https://www.ietf.org/archive/id/draft-bryant-arch-fwd-
layer-uc-03.txt>.
[I-D.cheng-spring-shorter-srv6-sid-requirement]
Cheng, W., Chongfeng, Pang, R., Li, Z., Chen, R., Lijun,
Duan, X., Mirsk, G., Dukes, D., and S. Zadok, "Shorter
SRv6 SID Requirements", Work in Progress, Internet-Draft,
draft-cheng-spring-shorter-srv6-sid-requirement-02, 13
July 2020, <https://www.ietf.org/archive/id/draft-cheng-
spring-shorter-srv6-sid-requirement-02.txt>.
[I-D.chunduri-isis-preferred-path-routing]
Chunduri, U., Li, R., White, R., Tantsura, J., Contreras,
L. M., and Y. Qu, "Preferred Path Routing (PPR) in IS-IS",
Work in Progress, Internet-Draft, draft-chunduri-isis-
preferred-path-routing-00, 18 June 2018,
<https://www.ietf.org/archive/id/draft-chunduri-isis-
preferred-path-routing-00.txt>.
[I-D.decraene-spring-srv6-vlsid]
Decraene, B., Raszuk, R., Li, Z., and C. Li, "SRv6 vSID:
Network Programming extension for variable length SIDs",
Work in Progress, Internet-Draft, draft-decraene-spring-
srv6-vlsid-07, 7 March 2022,
<https://www.ietf.org/archive/id/draft-decraene-spring-
srv6-vlsid-07.txt>.
[I-D.filsfils-spring-net-pgm-extension-srv6-usid]
Filsfils, C., Garvia, P. C., Cai, D., Voyer, D., Meilik,
I., Patel, K., Henderickx, W., Jonnalagadda, P., Melman,
D., Liu, Y., and J. Guichard, "Network Programming
extension: SRv6 uSID instruction", Work in Progress,
Internet-Draft, draft-filsfils-spring-net-pgm-extension-
srv6-usid-13, 13 June 2022,
<https://www.ietf.org/archive/id/draft-filsfils-spring-
net-pgm-extension-srv6-usid-13.txt>.
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[I-D.filsfilscheng-spring-srv6-srh-comp-sl-enc]
Cheng, W., Filsfils, C., Li, Z., Cai, D., Voyer, D., Clad,
F., Zadok, S., Guichard, J. N., and L. Aihua, "Compressed
SRv6 Segment List Encoding in SRH", Work in Progress,
Internet-Draft, draft-filsfilscheng-spring-srv6-srh-comp-
sl-enc-03, 20 May 2021, <https://www.ietf.org/archive/id/
draft-filsfilscheng-spring-srv6-srh-comp-sl-enc-03.txt>.
[I-D.han-tsvwg-enhanced-diffserv]
Han, L., Qu, Y., and R. Li, "Enhanced DiffServ by In-band
Signaling", Work in Progress, Internet-Draft, draft-han-
tsvwg-enhanced-diffserv-00, 4 November 2019,
<https://www.ietf.org/archive/id/draft-han-tsvwg-enhanced-
diffserv-00.txt>.
[I-D.han-tsvwg-ip-transport-qos]
Han, L., Qu, Y., Dong, L., Li, R., Nadeau, T., Smith, K.,
and J. Tantsura, "Resource Reservation Protocol for IP
Transport QoS", Work in Progress, Internet-Draft, draft-
han-tsvwg-ip-transport-qos-03, 15 October 2019,
<https://www.ietf.org/archive/id/draft-han-tsvwg-ip-
transport-qos-03.txt>.
[I-D.herbert-6man-eh-attrib]
Herbert, T., "Attribution Option for Extension Header
Insertion", Work in Progress, Internet-Draft, draft-
herbert-6man-eh-attrib-03, 29 October 2020,
<https://www.ietf.org/archive/id/draft-herbert-6man-eh-
attrib-03.txt>.
[I-D.ietf-tsvwg-intserv-multiple-tspec]
Polk, J. and S. Dhesikan, "Integrated Services (IntServ)
Extension to Allow Signaling of Multiple Traffic
Specifications and Multiple Flow Specifications in
RSVPv1", Work in Progress, Internet-Draft, draft-ietf-
tsvwg-intserv-multiple-tspec-02, 25 February 2013,
<https://www.ietf.org/archive/id/draft-ietf-tsvwg-intserv-
multiple-tspec-02.txt>.
[I-D.lc-6man-generalized-srh]
Li, Z., Li, C., Cheng, W., Xie, C., Li, C., Tian, H., and
F. Zhao, "Generalized Segment Routing Header", Work in
Progress, Internet-Draft, draft-lc-6man-generalized-srh-
03, 9 February 2021, <https://www.ietf.org/archive/id/
draft-lc-6man-generalized-srh-03.txt>.
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[I-D.li-spring-compressed-srv6-np]
Li, Z., Li, C., Xie, C., LEE, K., Tian, H., Zhao, F.,
Guichard, J. N., Li, C., and S. Peng, "Compressed SRv6
Network Programming", Work in Progress, Internet-Draft,
draft-li-spring-compressed-srv6-np-02, 25 February 2020,
<https://www.ietf.org/archive/id/draft-li-spring-
compressed-srv6-np-02.txt>.
[I-D.mirsky-spring-unified-id-network-programming]
Weiqiang, C., Mirsky, G., Aihua, L., and P. Shaofu, "SRv6
network programming using Unified Identifier", Work in
Progress, Internet-Draft, draft-mirsky-spring-unified-id-
network-programming-00, 6 March 2020,
<https://www.ietf.org/archive/id/draft-mirsky-spring-
unified-id-network-programming-00.txt>.
[I-D.steinberg-6man-crh-vs-sr-mpls]
Steinberg, D., Henderickx, W., Li, Z., Cheng, W., and D.
Voyer, "SR-MPLS over IPv6 satisfies CRH requirements",
Work in Progress, Internet-Draft, draft-steinberg-6man-
crh-vs-sr-mpls-00, 29 June 2020,
<https://www.ietf.org/archive/id/draft-steinberg-6man-crh-
vs-sr-mpls-00.txt>.
[I-D.templin-6man-crh-variable]
Templin, F. L., "IPv6 Compressed Routing Header with
Variable Length Addresses", Work in Progress, Internet-
Draft, draft-templin-6man-crh-variable-00, 18 May 2020,
<https://www.ietf.org/archive/id/draft-templin-6man-crh-
variable-00.txt>.
[RFC1347] Callon, R., "TCP and UDP with Bigger Addresses (TUBA), A
Simple Proposal for Internet Addressing and Routing",
RFC 1347, DOI 10.17487/RFC1347, June 1992,
<https://www.rfc-editor.org/info/rfc1347>.
[RFC2205] Braden, R., Ed., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, DOI 10.17487/RFC2205,
September 1997, <https://www.rfc-editor.org/info/rfc2205>.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, DOI 10.17487/RFC2460,
December 1998, <https://www.rfc-editor.org/info/rfc2460>.
[RFC2507] Degermark, M., Nordgren, B., and S. Pink, "IP Header
Compression", RFC 2507, DOI 10.17487/RFC2507, February
1999, <https://www.rfc-editor.org/info/rfc2507>.
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[RFC2711] Partridge, C. and A. Jackson, "IPv6 Router Alert Option",
RFC 2711, DOI 10.17487/RFC2711, October 1999,
<https://www.rfc-editor.org/info/rfc2711>.
[RFC3095] Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
Hannu, H., Jonsson, L-E., Hakenberg, R., Koren, T., Le,
K., Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K.,
Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header
Compression (ROHC): Framework and four profiles: RTP, UDP,
ESP, and uncompressed", RFC 3095, DOI 10.17487/RFC3095,
July 2001, <https://www.rfc-editor.org/info/rfc3095>.
[RFC3208] Speakman, T., Crowcroft, J., Gemmell, J., Farinacci, D.,
Lin, S., Leshchiner, D., Luby, M., Montgomery, T., Rizzo,
L., Tweedly, A., Bhaskar, N., Edmonstone, R.,
Sumanasekera, R., and L. Vicisano, "PGM Reliable Transport
Protocol Specification", RFC 3208, DOI 10.17487/RFC3208,
December 2001, <https://www.rfc-editor.org/info/rfc3208>.
[RFC4080] Hancock, R., Karagiannis, G., Loughney, J., and S. Van den
Bosch, "Next Steps in Signaling (NSIS): Framework",
RFC 4080, DOI 10.17487/RFC4080, June 2005,
<https://www.rfc-editor.org/info/rfc4080>.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, DOI 10.17487/RFC4193, October 2005,
<https://www.rfc-editor.org/info/rfc4193>.
[RFC4302] Kent, S., "IP Authentication Header", RFC 4302,
DOI 10.17487/RFC4302, December 2005,
<https://www.rfc-editor.org/info/rfc4302>.
[RFC5795] Sandlund, K., Pelletier, G., and L-E. Jonsson, "The RObust
Header Compression (ROHC) Framework", RFC 5795,
DOI 10.17487/RFC5795, March 2010,
<https://www.rfc-editor.org/info/rfc5795>.
[RFC6282] Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
DOI 10.17487/RFC6282, September 2011,
<https://www.rfc-editor.org/info/rfc6282>.
[RFC6398] Le Faucheur, F., Ed., "IP Router Alert Considerations and
Usage", BCP 168, RFC 6398, DOI 10.17487/RFC6398, October
2011, <https://www.rfc-editor.org/info/rfc6398>.
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Internet-Draft FWD PS August 2022
[RFC6554] Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
Routing Header for Source Routes with the Routing Protocol
for Low-Power and Lossy Networks (RPL)", RFC 6554,
DOI 10.17487/RFC6554, March 2012,
<https://www.rfc-editor.org/info/rfc6554>.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, DOI 10.17487/RFC6790, November 2012,
<https://www.rfc-editor.org/info/rfc6790>.
[RFC8655] Finn, N., Thubert, P., Varga, B., and J. Farkas,
"Deterministic Networking Architecture", RFC 8655,
DOI 10.17487/RFC8655, October 2019,
<https://www.rfc-editor.org/info/rfc8655>.
[RFC8698] Zhu, X., Pan, R., Ramalho, M., and S. Mena, "Network-
Assisted Dynamic Adaptation (NADA): A Unified Congestion
Control Scheme for Real-Time Media", RFC 8698,
DOI 10.17487/RFC8698, February 2020,
<https://www.rfc-editor.org/info/rfc8698>.
[RFC8754] Filsfils, C., Ed., Dukes, D., Ed., Previdi, S., Leddy, J.,
Matsushima, S., and D. Voyer, "IPv6 Segment Routing Header
(SRH)", RFC 8754, DOI 10.17487/RFC8754, March 2020,
<https://www.rfc-editor.org/info/rfc8754>.
[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>.
[RFC8939] Varga, B., Ed., Farkas, J., Berger, L., Fedyk, D., and S.
Bryant, "Deterministic Networking (DetNet) Data Plane:
IP", RFC 8939, DOI 10.17487/RFC8939, November 2020,
<https://www.rfc-editor.org/info/rfc8939>.
[RFC8964] Varga, B., Ed., Farkas, J., Berger, L., Malis, A., Bryant,
S., and J. Korhonen, "Deterministic Networking (DetNet)
Data Plane: MPLS", RFC 8964, DOI 10.17487/RFC8964, January
2021, <https://www.rfc-editor.org/info/rfc8964>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
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Internet-Draft FWD PS August 2022
[RFC9055] Grossman, E., Ed., Mizrahi, T., and A. Hacker,
"Deterministic Networking (DetNet) Security
Considerations", RFC 9055, DOI 10.17487/RFC9055, June
2021, <https://www.rfc-editor.org/info/rfc9055>.
[RFC9197] Brockners, F., Ed., Bhandari, S., Ed., and T. Mizrahi,
Ed., "Data Fields for In Situ Operations, Administration,
and Maintenance (IOAM)", RFC 9197, DOI 10.17487/RFC9197,
May 2022, <https://www.rfc-editor.org/info/rfc9197>.
Authors' Addresses
Stewart Bryant
University of Surrey 5/6GIC
Email: sb@stewartbryant.com
Uma Chunduri
Intel
Email: umac.ietf@gmail.com
Toerless Eckert
Futurewei Technologies Inc.
Email: tte@cs.fau.de
Alexander Clemm
Futurewei Technologies Inc.
Email: ludwig@clemm.org
Bryant, et al. Expires 6 February 2023 [Page 28]
