Internet DRAFT - draft-v6ops-ipv6rtr-reqs
draft-v6ops-ipv6rtr-reqs
Network Working Group Z. Kahn, Ed.
Internet-Draft LinkedIn
Intended status: Informational J. Brzozowski, Ed.
Expires: November 6, 2017 Comcast
R. White, Ed.
LinkedIn
May 5, 2017
Requirements for IPv6 Routers
draft-v6ops-ipv6rtr-reqs-00
Abstract
The Internet is not one network, but rather a collection of networks.
The interconnected nature of these networks, and the nature of the
interconneted systems that make up these networks, is often more
fragile than it appears. Perhaps "robust but fragile" is an
overstatement, but the actions of each vendor, implementor, and
operator in such an interconneted environment can have a major impact
on the stability of the overall Internet (as a system). The
widespread adoption of IPv6 could, particularly, disrupt network
operations, in a way that impacts the entire system.
This time of transition is an opportune time to take stock of lessons
learned through the operation of large scale networks on IPv4, and
consider how to apply these lessons to IPv6. This document provides
an overview of the design and architectural decisions that attend
IPv6 deployment, and a set of IPv6 requirements for routers,
switches, and middleboxes deployed in IPv6 networks. The hope of the
editors and contributors is to provide the neccessary background to
guide equipment manufacturers, protocol implemenetors, and network
operators in effective IPv6 deployment.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on November 6, 2017.
Copyright Notice
Copyright (c) 2017 IETF Trust and the persons identified as the
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Contributors . . . . . . . . . . . . . . . . . . . . . . 4
1.2. Acknowledgements . . . . . . . . . . . . . . . . . . . . 4
2. Review of the Internet Architecture . . . . . . . . . . . . . 4
2.1. Robustness Principle . . . . . . . . . . . . . . . . . . 4
2.2. Complexity . . . . . . . . . . . . . . . . . . . . . . . 6
2.2.1. Elegance . . . . . . . . . . . . . . . . . . . . . . 6
2.2.2. Tradeoffs . . . . . . . . . . . . . . . . . . . . . . 7
2.3. Layered Structure . . . . . . . . . . . . . . . . . . . . 8
2.4. Routers . . . . . . . . . . . . . . . . . . . . . . . . . 9
3. Requirements Related to Device Management and Security . . . 11
3.1. Programmable Device Access . . . . . . . . . . . . . . . 11
3.2. Human Readable Device Access . . . . . . . . . . . . . . 12
3.3. Supporting Zero Touch Provisioning for Connected Devices 12
3.4. Device Protection against Denial of Service Attacks . . . 13
4. Requirements Related to Telemetry . . . . . . . . . . . . . . 14
4.1. Device State and Traceablity . . . . . . . . . . . . . . 14
4.2. Topology State and Traceability . . . . . . . . . . . . . 15
5. Requirements Related to IPv6 Forwarding and Addressing . . . 15
5.1. The IPv6 Address is not a Host Identifier . . . . . . . . 15
5.2. Router IPv6 Addresseses . . . . . . . . . . . . . . . . . 16
5.3. The Maximum Transmission Unit . . . . . . . . . . . . . . 17
5.4. ICMP Considerations . . . . . . . . . . . . . . . . . . . 18
5.5. Machine Access to the Forwarding Table . . . . . . . . . 19
5.6. Processing IPv6 Extension Headers . . . . . . . . . . . . 20
5.7. IPv6 Only Operation . . . . . . . . . . . . . . . . . . . 20
5.8. Prefix Length Handling in IPv6 PAcket Forwarding . . . . 20
6. Security Considerations . . . . . . . . . . . . . . . . . . . 20
6.1. Robustness and Security . . . . . . . . . . . . . . . . . 21
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6.2. Programmable Device Access and Security . . . . . . . . . 21
6.3. Zero Touch Provisioning and Security . . . . . . . . . . 22
7. Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . 22
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 22
8.1. Normative References . . . . . . . . . . . . . . . . . . 22
8.2. Informative References . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction
This memo defines and discusses requirements for devices that perform
forwarding for Internet Protocol version 6 (IPv6). This can include
(but is not limited to) the devices described below.
o Devices which are primarily designed to forward traffic between
multiple interfaces. These are normally referred to by the
Internet community as routers or, in some cases, intermediate
systems.
o Devices which are designed to modify packets rather than "just"
forwarding them. These are often referred to by the Internet
community as middleboxes. See [RFC7663] for a fuller definition
of middleboxes.
Readers should recognize that while this memo applies to IPv6,
routers and middleboxes IPv6 packets will often also process IPv4
packets, forward based on MPLS labels, and potentially process many
other protocols. This memo will only discuss IPv4, MPLS, and other
protocols as they impact the behavior of an IPv6 forwarding device;
no attempt is made to specify requirements for protocols other than
IPv6. The reader should, therefore, not count on this document as a
"sole source of truth," but rather use this document as a guide.
For IPv4 router requirements, readers are referred to [RFC1812]. For
simplicity, the term "devices" is used interchangeably with the
phrase "routers and middleboxes" and the term "routers" throughout
this document. These three terms represent stylistic differences,
rather than substantive differences.
This document is broken into the following sections: a review of
Internet architecture and principles, requirements relating to device
management, requirements related to telemetry, requirements related
to IPv6 forwarding and addressing, and future considerations.
Following these sections, a short conclusion is provided for review.
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1.1. Contributors
Shawn Zandi, Pete Lumbis, Fred Baker, and Lee Howard contributed
significant text and ideas to this draft.
1.2. Acknowledgements
The editors and contributors would like to thank Ron Bonica, Lorenzo
Coitti, Brian E. Carpenter, Tim Chown, Peter Lothberg, and ... for
their comments, edits, and ideas on the text of this draft.
2. Review of the Internet Architecture
The Internet relies on a number of basic concepts and considerations.
These concepts are not explicitly called out in any specification,
nor do they necessarily impact protocol design or packet forwarding
directly. This section provides an overview of these concepts and
considerations to help the reader understand the larger context of
this document.
2.1. Robustness Principle
Every point where multiple protocols interact, is an interaction
surface that can threaten the robustness of the overall system.
While it may seem the global Internet has achieved a level of
stability that makes it immune to such considerations, the reality is
every network is a complex system, and is therefore subject to
massive non repeatable unanticipated failures. Postel's Robustness
Principle countered this problem with a simple statement, explicated
in [RFC7922]: "Be conservative in what you do, and liberal in what
you accept from others."
However, since this time, it has been noted that following this law
allows errors in protocols to accumulate over time, with overall
negative effects on the system as a whole. [RFC1918] describes
several points in conjunction with this principle that bear updating
based on further experience with large scale protocol and network
deployments within the Internet community, including:
o Applications should deal with error states gracefully; an
application should not degrade in a way that will cause the
failure of adjacent systems when possible. For instance, when a
routing protocol implementation fails, it should not do so in a
way that will cause the spreading of or continued existence of
false reachability information, nor should it fail in a way that
overloads adjacent routers or interacting protocols and causing a
cascading failure.
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o It is best to assume the network is filled with poor
implementations and malevolent actors, both of which will find
every possible failure mode over time.
o It is best to assume every technology will be used to the limits
of its technical capabilities, rather than assuming a particular
protocol's scope of use will align (in any way) with the intent of
the original designer(s). [RFC5218] defines a wildly sucessful
protocol as one that "far exceeds its original goals, in terms of
purpose (being used in scenarios far beyond the initial design),
in terms of scale (being deployed on a scale much greater than
originally envisaged), or both." Successful implementations
attract more functionality, much like a few nodes in a scale free
graph eventually become connectivity hubs.
o Protocols and implementations change over time. A corollary of
the assumption that protocols will be used until they reach their
technical limits is that protocols will change over time as they
gain new functionality. [RFC5218] points out several problems
with "wild success" in a protocol: undesirable side effects,
performance problems, and becoming a high value attack target.
Protocol and implementation design should take into account use
cases that have not yet been thought of by building flexibility
into protocols. Protocols should also remained focused on a
narrow range of use cases; it is often wise to invent a new
protocol than to extend a single protocol into a broad set of use
cases.
o Protocols are sometimes replaced or updated to new versions in
order to add new capabilities or features. Updating a protocol
requires great care in providing for a transition mechanism
between older and newer versions. draft-iab-protocol-transitions
[I-D.iab-protocol-transitions] provides sound advice on protocol
transition planning and mehanisms.
o Obscure, but legal, protocol features are often ignored or left
unimplemented. Protocols must handle receiving unexpected
information gracefully so they do not fail because of incomplete
or partial implementations. Protocols should avoid specifying
contradictory states, or features that will cause interoperability
issues if multiple implementations choose to implement different
feature sets.
o Monocultures are almost always bad. While multiple
implementations can represent an interaction surface which
increases complexity, particularly if a brad set of protocol
capabilities and/or implementation features are used, using the
same implementation at every point in a deployment results in a
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monoculture. In a monoculture, a single event can trigger a
defect in every router, causing a network failure. Monocultures
must be carefully balanced against interaction surfaces; often
this is best accomplished by using multiple implementations and
minimal, widely implemented, and well understood protocol
features.
A summary of the points above might be this: It is important to work
within the bounds of what is actually implemented in any given
protocol, and to leave corner cases for another day. It is often
easy to assume "virtual oceans" are easier to boil than physical
ones, or for an ocean to appear much smaller because it is being
implemented in software. This is often deceptive. It is never
helpful to boil the ocean whether in a design, an implementation, or
a protocol.
2.2. Complexity
Complexity, as articulated by Mike O'Dell (see [RFC3439]), is "the
primary mechanism which impede efficient scaling, and as a result is
the primary driver of increases in both capital expenditures (CAPEX)
and operational expenditures (OPEX)." At the same time, complexity
cannot be "solved," but rather must be "managed." The simplest and
most obvious solution to any problem is often easy to design, deploy,
and manage. It's also often wrong and/or broken. As much as
developers, designers, and operators might like to make things as
simple as possible, hard problems require complex solutions. See
Alderson and Doyle [COMPLEXHARD] for a discussion of the relationship
between hard problems and complex solutions.
The following sections contain observations which apply to the
management of complexity in both protocol and network design.
2.2.1. Elegance
Elegance should be the goal of protocol and network design. Rather
than seeking out simple solutions because they are simple, seek out
solutions that will solve the problem in the simplest way possible
(and no simpler). Often this will require:
o Ensuring the goal is actually the goal. Many times the goal is
taken from the operational realm into the protocol design realm
before enough thought has been applied to ensure the correct
problem is being addressed.
o Seeing the problem from different angles, trying to break the
problem up in multiple ways; and trying, abandoning, and
rebuilding ideas and implementations until a better way is found.
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o Sometimes the complexity of the solution will overwhelm the use
case; sometimes it is better to leave the apparent problem
unsolved, or allow the community time and space to find a simpler
solution.
2.2.2. Tradeoffs
There are always tradeoffs. For any protocol, network, or
operational design decision, there will always be a tradeoff between
at least two competing goals. If some problem appears to have a
single solution without tradeoffs, this doesn't mean the tradeoffs
don't exist. Rather, it means the tradeoffs haven't been discovered
yet. In the area of protocol and network design, these tradeoffs
often take the form of common "choose two or three" situations, such
as "quick, cheap, high quality." In network and protocol design, the
tradeoffs are often:
o The amount of state carried in the system and the speed at which
it changes, or simply the state. The amount of state required to
operate a system as it scales tends to be nonlinear. Some
instances of this are described in [RFC3439] section 2.2.1, the
Amplification Principle.
o The number of interaction surfaces between the components that
make up the complete system, and the depth of those interaction
surfaces. Some examples of surfaces are described in
[RFC3439]section 2.2.2, the Coupling Principle. Layering is
essentially a form of abstraction; all abstractions are subject to
the law of leaky abstractions, [LEAKYABS] which states: "all
nontrivial absractions leak."
o The desired optimization, including efficient use of network
resources, optimal support for business objectives, and optimal
support for a specific set of applications.
These three make up a "triangle problem." For instance, to increase
the optimization of traffic flow through a network generally requires
adding more state to the control plane, leading to problems in
complexity due to amplification. To reduce amplification, the
control plane (or perhaps the various functions the control plane
serves) can be broken up into subsystems, or modules. Breaking the
control plane up into subsystems, however, introduces interaction
surfaces between the components, which is another form of complexity.
[RFC7980] provides a good overview of network complexity; in
particular, section 3 of that document provides some examples of
complexity tradeoffs.
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2.3. Layered Structure
The Internet data plane is organized around broad top and bottom
layers, and much thinner middle layer. This is illustrated in the
figure below.
\ /
\ HTTP, FTP, SNMP, ETC. /
\ /
\ TCP, UDP /
\ /
\ IPv6 /
/ (IPv4) \
/ \
/ (MPLS) \
/ Ethernet, Wireless \
/ Physical Media \
/ \
Figure 1
This layering emulates or mirrors many naturally occurring systems;
it is a common strategy for managing complexity (see Meyer's
presentation on complexity). [COMPLEXLAYER] The single protocol in
the center, IPv6, serves to separate the complexity of the lower
layers from the complexity of the upper layers. This center layer of
the Internet ecosystem has traditionally been called the Network
Layer, in reference to the Department of Defense (DoD) [DoD] and OSI
models. [OSI] The Internet ecosystem includes two different
protocols in this central location.
o IPv4, an older network protocol that, it is anticipated, will be
replaced over time as the Internet ecosystem standardizes on IPv6
o IPv6, a newer network protocol that is being adopted
MPLS is often used as a "middle" subtransport layer, and at other
times as "middle" sub data link layer; hence MPLS is difficult to
classify within the strictly hierarchical model depicted here. These
protocols are often treated as if they exist in strict hierarchical
layers with a well defined and followed Application Programming
Interface (API), data models, Remote Procedure Calls (RPCs), sockets,
etc. The reality, however, is there are often solid reasons for
violating these layers, creating interaction surfaces that are often
deeper than intended or understood without some experience. Beyond
this, such layering mechanisms act as information abstractions. It
is well known that all such abstractions leak (see above on the law
of leaky abstractions). Because of these intentional and
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unintentional leakages of information, the interactions between
protocols is often subtle.
2.4. Routers
A router connects to two or more logical interfaces and at least one
physical interface. A router processes packets by:
o Receiving a packet through an interface
o Stripping the data link, physical header, or tunnel encapsulation
off the packet
o Examining the packet for errors, and determining if this packet
needs to be punted to another process on the router
o Looking up the destination in a local forwarding table
o Rewriting the data link and/or physical layer header
o Transmitting the packet out an interface
When consulting the forwarding table, the router searches for a match
based on:
o The longest prefix containing the destination address (this is the
most common matching element)
o A label, such as a flow label or MPLS label
o The source address or other header fields (not common)
The router then examines the information in the matching entry to
determine the next hop, or rather the next logically connected device
to forward the packet to. The next hop will either be another
router, which will presumably carry the packet closer to the final
destination, or it will be the destination host itself. The
following figure provides a conceptual model of a router; not all
routers actually have this set of tables and interactions, and some
have many more moving parts. This model is simply used as a common
reference to promote understanding.
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+-------------+ +-------------+
| Candidate | | Startup |
| Config |<--+ +-->| Config |
+--+----------+ | | +-------+-----+
| | | |
v | | v
+-----------------+----+-----------------+
| Running Configuration +------>----------+
+---+----------+----------+----------+---+ |
| | | | |
v | | | |
+-------+ | | | |
| IS-IS |<-----------------------------------> Adjacent |
+---+---+ v | | Routers |
| +-------+ | | |
| | BGP |<------------------------> Peers |
| +---+---+ v | |
| | +-------+ | |
| | | OSPF |<-------------> Adjacent |
| | +---+---+ v Routers |
| | | +-------+ |
| | | | Other | |
| | | +---+---+ |
| | | | |
+---+----------+----------+----------+---+ |
| RIB Manager | |
+---+------------------------------------+ |
| |
+---+------------------------------------+ |
| Routing Information Base (RIB) | |
+---+------------------------------------+ |
| |
+---+------------------------------------+ |
| Forwarding Information Base (FIB) | |
+---+----------+---------------------+---+ |
| | | |
+---+---+ +---+---+ +---+---+ |
| Int 1 | | Int 2 | ... | Int X | <---------------+
+-------+ +-------+ +-------+
^ |
| v
Packets In Packets Out
Figure 2
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3. Requirements Related to Device Management and Security
Network engineering began in the era of Command Line Interfaces
(CLIs), and has generally stayed with these CLIs even as the
Graphical User Interface (GUI) has become the standard way of
interacting with almost every other computing device. Direct human
interaction with routers and middleboxes in large scale and complex
environments, however, tends to result in an unacceptably low Mean
Time Between Mistakes (MTBM), directly impacting the overall
availability of the network. In reaction to this, operators have
increased their reliance on automation, specifically targetting
machine to machine intefaces, such as Remote Procesdure Calls (RPCs)
and Application Programming Interface (API) solutions, to manage and
configure routers and middleboxes. This section considers the
various components of device management.
3.1. Programmable Device Access
Configuration primarily relates to the startup, candidate, and
running configurations in the router model shown above. In order to
deploy networks at scale, operators rely on automated management of
router configuration. This effort has traditionally focused on
Simple Network Management Protocol (SNMP) Management Information Base
(MIBs). In the future, operators expect to move towards open source/
open standards YANG models.
Vendors and implementors should implement machine readable interfaces
with overlays to support human interaction, rather than human
readable interfaces with overlays to support machine to machine
interaction. Emphasis should be placed on machine to machine
interaction for day to day operations, rather than on human readable
interfaces, which are largely used in the process of troubleshooting.
Within the realm of machine to machine interfaces, emphasis should be
placed on marshaling information in YANG models.
To support automated router configuration, IPv6 routers and routers
SHOULD support YANG and SNMP configuration, including (but not
limited to):
o Openconfig models [OPENCONF] related to the protocols configured
on the device, interface state, and device state
o [RFC7223]: A YANG Data Model for Interface Management
o [RFC7224]: IANA Interface Type YANG Module
o [RFC7277]: A YANG Data Model for IP Management
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o [RFC7317]: A YANG Data Model for System Management
o Simple Network Management Protocol (SNMP) MIBs as appropriate
3.2. Human Readable Device Access
To operate a network at scale, operators rely on the ability to
access routers and middleboxes to troubleshoot and gather state
manually through a number of different interfaces. These interfaces
should provide current device configuration, current device state
(such as interface state, packets drops, etc.), and current control
plane contents (such as the RIB in the figure above). In other
words, manual interfaces should provide information about the router
(the whole device stack).
To support manual state gathering and troubleshooting, IPv6 routers
and middleboxes SHOULD support:
o TELNET ([RFC0854]): TELNET SHOULD be disabled by default, but
should be available for operational purposes as required or as
configured by the operator
o SSH ([RFC4253]): SSH SHOULD be the default access for IPv6 capable
routers
3.3. Supporting Zero Touch Provisioning for Connected Devices
To operate a network at scale, operators rely on protocols and
mechanisms that reduce provisioning time to a minimum. The preferred
state is zero touch provisioning; plug a new router in and it just
works without any manual configuration. The closer an operator can
come to this ideal, the more MTBM and Operational Expenses (OPEX) can
be reduced -- an important goals in the real world. IPv6 routers
should support several standards, including, but not limited to:
o [I-D.ietf-dhc-rfc3315bis]: Dynamic Configuration Protocol for IPv6
MUST be supported. SLAAC MUST be able to be disabled by operators
who prefer to use some other mechanism for address management and
assignment (specifically for customer facing edge ports).
o [RFC4862]: IPv6 Stateless Address Autoconfiguration (SLAAC) MUST
be supported, and MUST be enabled by default on all router
interfaces.
o [RFC7217]: Semantically Opaque Interface Identifiers SHOULD be
supported.
o [RFC7527]: Enhanced Duplicate Address Detection MUST be supported.
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o [RFC8028]: First-Hop Router Selection by Hosts, specifically
section 2.1, which says a router SHOULD be able to send a PIO with
both the L and A bits cleared.
o [RFC3810]: Routers supporting IPv6 MUST support Multicast Listener
Discovery Version 2
The provisioning of Domain Name Systems (DNS) system information is a
contentious topic, based on provider, operating system, interface,
and other requirements. This document therefore addresses the
mechanisms that must be included in IPv6 router implementations, but
leaves the option of what to configure and deploy to the network
operator. Routers supporting IPv6, and intended for user facing
connections, SHOULD support:
o [RFC3646]: DNS Configuration options for Dynamic Host
Configuration Protocol for IPv6 (DHCPv6).
o [RFC8106]: IPv6 Router Advertisement Options for DNS
Configuration. This includes the ability to send Router
Advertisements (RAs) with DNS information.
Whether these are enabled by default, or require extra configuration,
is left as an exercise for providers and implementation developers to
determine on a case by case basis.
3.4. Device Protection against Denial of Service Attacks
Denial of Service (DoS) and Distributed Denial of Service (DDoS)
attacks are unfortunately common in the Internet globally; these
types of attacks cost network operators a great deal in opportunity
and operational costs in prevention and responses. To provide for
effective counters to DoS and DDoS attacks directly on routers:
o Manufacturers and system integrators should test and clearly
report the packet/traffic load handling capabilities of devices
with and without various encryption methods enabled
o Routers should be able to police traffic destined to the control
plane based on the rate of traffic received, including the ability
ot police individual flows, targeted services, etc., at individual
rates as described in [RFC6192]
o Ideally, devices should be able to statefully filter traffic
destined to the control plane
There are other useful techniques for dealing with DDoS attacks at
the network level, including: transferring sessions to a new address
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and abandoning the address under attack, using BGP communities to
spread the attack over multiple ingress ports and "consume" it, and
requiring mutual authentication before allocating larger resource
pools to a connection. These techniques are not "device level," and
hence are not considered further here.
4. Requirements Related to Telemetry
Telemetry relates to information devices push to systems used to
monitor and track the state of the network. This applies to
individual devices as well as the network as a system. Two major
challenges face operators in the area of telemetry:
o Information that is laid out primarily for human, rather than
machine, consumption. While human consumption of telemetry is
important in some situations, this information should be supplied
in a form that focuses on machine readability with an overlay or
interpretor that allows human consumption.
o Software systems that require information to be queried (or polled
or even pushed) on a per-item basis. This form of organization
can produce a lot of information, and a lot of individual packets,
very quickly, overwhelming monitoring systems and consuming a
large amount of available network resources. Instead, telemetry
should be focused on bulk collection.
There are three broad categories of telemetry: device state and
traceability, topology state and traceability, and flow traceability.
These three roughly correspond to the management plane, the control
plane, and the forwarding plane of the network. Each of the sections
below considers one of these three telemetry types.
4.1. Device State and Traceablity
Ideally, the entire network could be monitored using a single
modeling language to ease implementation of telemetry systems and
increase the pace at which new software can be deployed in production
environments. In real deployments, it is often impossible to reach
this ideal; however, reducing the languages and methods used, while
focusing on machine readibility, can greatly ease the deployment and
management of a large scale network. Specifically, IPv6 routers
SHOULD support:
o [RFC6241]: NETCONF/RESTCONF transporting telemetry formatted
according to YANG (see above)
o [RFC5424]: Syslog
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o gRPC based telemetry interfaces [GRPC]
o SNMP as appropriate
Syslog and SNMP access for telemetry should be considered "legacy,"
and should not be the focus of new telemetry access development
efforts.
4.2. Topology State and Traceability
IPv6 routers are part of a system of devices that, combined, make up
the entire network. Viewing the network as a system is often crucial
for operational purposes. For instance, being able to understand
changes in the topology and utlization of a network can lead to
insights about traffic flow and network growth that lead to a greater
understanding of how the network is operating, where problems are
developing, and how to improve the network's performance. To support
systemic monitoring of the network topology, IPv6 devices SHOULD
support at least:
o [RFC5424]: North-Bound Distribution of Link-State and Traffic
Engineering (TE) Information using BGP
o [I-D.ietf-i2rs-yang-l2-network-topology]: An I2RS model for layer
2 topologies
o [I-D.ietf-i2rs-yang-l3-topology]: An I2RS model for layer 3
topologies
o [I-D.ietf-i2rs-yang-network-topo]: A Data Model for Network
Topologies
5. Requirements Related to IPv6 Forwarding and Addressing
There are a number of capabilities that a device SHOULD have to be
deployed into an IPv6 network, and several forwarding plane
considerations operators and vendors need to bear in mind. The
sections below explain these considerations.
5.1. The IPv6 Address is not a Host Identifier
The IPv6 address is commonly treated as a host identifier; it is not.
Rather, it is an interface identifier that describes the topological
point where a particular host connects to the Internet.
Specifically:
o The IPv6 address will change when a device changes where it
connects to the network.
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o A single host can have multiple addresses. For instance, a host
may have one address per interface, or multiple addresses assigned
through different mechanisms, or through multiple connection
points.
o A single IPv6 address may represent many hosts, as in the case of
a group of hosts reachable through multicast address, or a set of
services reachable through an anycast address.
Because the host address may change at any time, it is generally
harmful to embed IPv6 addresses inside upper layer headers to
identify a particular host.
5.2. Router IPv6 Addresseses
Internet Routing Registries may allocate a network operator a wide
range of prefix lengths (see [RFC6177] for further information).
Within this allocation, network operators will often suballocate
address space along nibble boundaries (/48, /52, /56, /60, and /64)
for ease of configuration and management. Several common practices
are:
o Each multiaccess interface is allocated a /64
o Point-to-point links are allocated a /64, but SHOULD be addressed
with a longer prefix length to prevent certain kinds of denial of
service attacks ([RFC3627] originally mandated 64 bit prefix
lengths on point-to-point links; [RFC6164] explains possible
security issues with assigning a 64 bit prefix length to a point-
to-point, and recommends a /127 instead)
o Although aggregation may only performed to the nibble boundaries
noted above, variances are possible
o Loopback addresses are assigned a /128
Given these common practices, routers designed to run IPv6 SHOULD
support the following addressing conventions:
o The default prefix length on any interface other than a loopback
SHOULD be a /64
o Configuring a prefix length longer than a /64 on any multi-access
interface SHOULD require additional configuration steps to prevent
manual configuration errors
o Routers MUST NOT assume IPv6 prefix lengths only on nibble
boundaries
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o Routers SHOULD support any prefix length shorter or greater than
/64
o Loopback interfaces SHOULD default to a /128 prefix length unless
some additional configuration is undertaken to override this
default setting
o Routers MUST be able to generate link local addresses on all links
and/or interfaces using stateless address autoconfiguration (see
[RFC6434]).
5.3. The Maximum Transmission Unit
The long history of the Maximum Transmission Unit (MTU) in networks
is not a happy one. Specific problems with MTU sizing include:
o Many different default sizes on different media types, from very
small (576 bytes on X.25) to very large (17914 bytes on 16Mbps
Token Ring)
o Many different ways to calcualte the MTU on any given link; for
instance a 9000 byte MTU can be calculated as 8184 bytes on one
operating system, 8972 on another, and 9000 on a third
o The increasing use of tunnel encapsulations in the network; for
instance MPLS over GRE over IP over...
o The wide variety of default MTUs across many different end hosts
and operating systems
o The general ineffectiveness of path MTU discovery to operate
correctly in the face of packet filters and rate limiters (see the
section on ICMP filtering below)
o Lower speed links at the network edge which require a lot of time
to serialize a packet with a large MTU
o Increased jitter caused by the disparity between large and small
packet size across a lower bandwidth links
The final point requires some further elucidation. The time required
to serialize various packets at various speeds are:
o 64 byte packet onto a 10Mb/s link: .5ms
o 1500 byte packet onto a 10Mb/s link: 1.2ms
o 9000 byte packet onto a 10Mb/s link: 7.2ms
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o 64 byte packet onto a 100Mb/s link: .05ms
o 1500 byte packet onto a 100Mb/s link: .12ms
o 9000 byte packet onto a 100Mb/s link: .72ms
A 64 byte packet trapped behind a single 1500 byte packet on a 10Mb/s
link suffers 1.2ms of serialization delay. Each additional 1500 byte
packet added to the queue in front of the 64 byte packet adds and
addtional 1.2ms of delay. In contrast, a 64 byte packet trapped
behind a single 9000 byte packet on a 10Mb/s link suffers 7.7ms of
serialization delay. Each additional 9000 byte packet added to the
queue adds an additional 7.2ms of serialization delay. The practical
result is that larger MTU sizes on lower speed links can add a
significant amount of delay and jitter into a flow. On the other
hand, increasing the MTU on higher speed links appears to add
megligable additional delay and jitter.
The result is that it costs less in terms of overall systemic
performance to use higher MTUs on higher speed links than on lower
speed links. Based on this, increasing the MTU across any particular
link may not increase overall end-to-end performance, but can greatly
enhance the performance of local applications (such as a local BGP
peering session, or a large/long standing elephant flow used to
transfer data across a local fabric), while also providing room for
tunnel encapsulations to be added with less impact on lower MTU end
systems.
The general rule of thumb is to assume the largest size MTU should be
used on higher speed transit only links in order to support a wide
array of available link sizes, default MTUs, and tunnel
encapsulations. Routers designed for a network core, data center
core, or use on the global Internet SHOULD support at least 9000 byte
MTUs on all interfaces. MTU detection mechanisms, such as IS-IS
hello padding, described in [RFC7922], SHOULD be enabled to ensure
correct point-to-point MTU configuration. Devices SHOULD also
support:
o [RFC1981]: Path MTU Discovery for IP version 6
o [RFC4821]: Packetization Layer Path MTU Discovery
5.4. ICMP Considerations
Internet Control Message Protocool (ICMP) is described in [RFC0792]
and [RFC4443]. ICMP is often used to perform a traceroute through a
network (normally by using a TTL expired ICMP message), for Path MTU
discovery, and, in IPv6, for autoconfiguration and neighbor
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discovery. ICMP is often blocked by middleboxes of various kinds
and/or ICMP filters configured on the ingress edge of a provider
network, most often to prevent the discovery of reachable hosts and
network topology. Routers implementing IPv6:
o SHOULD NOT filter ICMP unreachables by default, as this has
negative impacts on many aspects of IPv6 operation, particularly
path MTU
o SHOULD filter ICMP echo and echo response by default, to prevent
the discovery of reachable hosts and topology.
o SHOULD rate limit the generation of ICMP messages relative to the
ability of the device to generate packets and to block the use of
ICMP packets being used as part of a distributed denial of service
attack
o SHOULD implement the filtering suggestions in
[I-D.gont-opsec-icmp-ingress-filtering]
There are implications for path MTU discovery and other useful
mechanisms in filtering and rate limiting ICMP. The tradeoff here is
between allowing unlimited ICMP, which would allow path MTU detection
to work, or limiting ICMP in a way that prevents negative side
effects for individual devices, and hence the operational
capabilities of the network as a whole. Operators rightly limit ICMP
to reduce the attack surface against their network, as well as the
opportinity for "perfect storm" events that inadvertently reduce the
capability of routers and middleboxes. Hence ICMP can be treated as
"quasi-reliable" in many situations; existence of an ICMP message can
prove, for instance, that a particular host is unreachable. The non-
existence of an ICMP message, however, does not prove a particular
host exists or does not.
5.5. Machine Access to the Forwarding Table
In order to support treating the "network as a whole" as a single
programmable system, it is important for each router have the ability
to directly program forwarding information. This programmatic
interface allows controllers, which are programmed to support
specific business logic and applications, to modify and filter
traffic flows without interfering with the distributed control plane.
While there are several programmatic interfaces available, this
document suggests that the I2RS interface to the RIB be supported in
all IPv6 routers. Specifically, these drafts should be supported to
enable network programmability:
o [I-D.ietf-i2rs-fb-rib-data-model]: Filter-Based RIB Data Model
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o [I-D.ietf-i2rs-fb-rib-info-model]: Filter-Based RIB Information
Model
o [I-D.ietf-i2rs-rib-data-model]: A YANG Data Model for Routing
Information Base (RIB)
o [RFC7922]: I2RS Traceability
5.6. Processing IPv6 Extension Headers
(To be added)
5.7. IPv6 Only Operation
While the transition to IPv6 only networks may take years (or perhaps
decades), a number of operators are moving to deploy IPv6 on internal
networks supporting transport and data center fabric applications
more quickly. Routers and middleboxes that support IPv6 SHOULD
support IPv6 only operation, including:
o Link Local addressing MUST be configurable and useable as the
primary address on all interfaces on a device.
o IPv4 and/or MPLS SHOULD NOT be required for proper device
operation. For instance, an IPv4 address should not be required
to determine the router ID for any protocol. See [RFC6540]
section 2.
o Any control plane protocol implementations MUST support the
recommendations in [RFC7404] for operation using link local
addresses only.
5.8. Prefix Length Handling in IPv6 PAcket Forwarding
Routers MUST support IPv6 destination lookups in the forwarding
process on a single bit prefix length increments, in accordance with
[RFC7608].
6. Security Considerations
This document addresses several ways in which devices designed to
support IPv6 forwarding. Some of the recommendations here are
designed to increase device security; for instance, see the section
on device access. Others may intersect with security, but are not
specifically targeted at security, such as running IPv6 link local
only on links. These are not discussed further here, as they improve
the security stance of the network. Other areas discussed in this
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draft are more nuanced. This section gathers the intersection
between operational concerns and security concerns into one place.
ICMP security is already considered in the section on ICMP; it will
not be considered further here. Link local only addressing wil
increase security by removing transit only links within the network
as a reachable destination.
6.1. Robustness and Security
Robustness, particularly in the area of error handling, largely
improves security if designed and implemented correctly. Many
attacks take advantage of mistakes in implementations and variations
in protocols. In particular, any feature that is unevenly
implemented among a number of implementations often offers an attack
surface. Hence, reducing protocol complexity helps reduce the
breadth of attack surfaces.
Another point to consider at the intersection of robustness and
security is the issue of monocultures. Monocultures are in and of
themselves a potential attack surface, in that finding a single
failure mode can be exploited to take an entire network (or operator)
down. On the other hand, reducing the number of implementations for
any particular protocol will decrease the set of "random" features
deployed in the network. These two goals will often be opposed to
one another. Network designers and operators need to consider these
two sides of this tradeoff, and make an intelligent decision about
how much diversity to implement versus how to control the attack
surface represented by deploying a wide array of implementations.
6.2. Programmable Device Access and Security
Programmable interfaces, including programmable configuration,
telemetry, and machine interface to the routing table, introduce a
large attack surface; operators should be careful to ensure this
attack surface is properly secured. Specifically:
o Prevent external access to any administrative access points used
for device programmability
o Use AAA systems to ensure only valid devices and/or users access
devices
o Rate limit the change rate and protect management interfaces from
DoS and DDoS attacks
Such interfaces should be treated no differently than SSH, SFTP, and
other interfaces available to manage routers and middleboxes.
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6.3. Zero Touch Provisioning and Security
Zero touch provisioning opens a new attack surface; insider attackers
can simply install a new device, and assume it will be autoconfigured
into the network. A "simple" solution would be to install door
locks, but this will likely not be enough; defenses need to be
layered to be effective. It is recommended that devices installed in
the network need to contain a hardware or software identification
system that allows the operator to identify devices that are
installed in the network.
7. Conclusion
The deployment of IPv6 throughout the Internet marks a point in time
where it is good to review the overall Internet architecture, and
assess the impact on operations of these changes. This document
provides an overview of a lot of these changes and lessons learned,
as well as providing pointers to many of the relevant documents to
understand each topic more deeply.
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>.
8.2. Informative References
[COMPLEXHARD]
Alderson, D. and J. Doyle, "Contrasting Views of
Complexity and Their Implications For Network-Centric
Infrastructures", 2010,
<http://ieeexplore.ieee.org/abstract/
document/5477188/?reload=true>.
[COMPLEXLAYER]
Meyer, D., "Macro Trends, Architecture, and the Hidden
Nature of Complexity", 2010,
<http://www.slideshare.net/dmm613/
macro-trends-complexityandsdn-32951199>.
[DoD] Wikipedia, "The Internet Protocol Suite", 2016,
<https://en.wikipedia.org/wiki/Internet_protocol_suite>.
[GRPC] gRPC, "gRPC", 2016, <http://www.grpc.io>.
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[I-D.gont-opsec-icmp-ingress-filtering]
Gont, F., Hunter, R., Massar, J., and S. LIU, "Defeating
Attacks which employ Forged ICMP/ICMPv6 Error Messages",
draft-gont-opsec-icmp-ingress-filtering-02 (work in
progress), March 2016.
[I-D.iab-protocol-transitions]
Thaler, D., "Planning for Protocol Adoption and Subsequent
Transitions", draft-iab-protocol-transitions-08 (work in
progress), March 2017.
[I-D.ietf-dhc-rfc3315bis]
Mrugalski, T., Siodelski, M., Volz, B., Yourtchenko, A.,
Richardson, M., Jiang, S., Lemon, T., and T. Winters,
"Dynamic Host Configuration Protocol for IPv6 (DHCPv6)
bis", draft-ietf-dhc-rfc3315bis-07 (work in progress),
March 2017.
[I-D.ietf-i2rs-fb-rib-data-model]
Hares, S., Kini, S., Dunbar, L., Krishnan, R., Bogdanovic,
D., and R. White, "Filter-Based RIB Data Model", draft-
ietf-i2rs-fb-rib-data-model-01 (work in progress), March
2017.
[I-D.ietf-i2rs-fb-rib-info-model]
Kini, S., Hares, S., Dunbar, L., Ghanwani, A., Krishnan,
R., Bogdanovic, D., and R. White, "Filter-Based RIB
Information Model", draft-ietf-i2rs-fb-rib-info-model-00
(work in progress), June 2016.
[I-D.ietf-i2rs-rib-data-model]
Wang, L., Ananthakrishnan, H., Chen, M.,
amit.dass@ericsson.com, a., Kini, S., and N. Bahadur, "A
YANG Data Model for Routing Information Base (RIB)",
draft-ietf-i2rs-rib-data-model-07 (work in progress),
January 2017.
[I-D.ietf-i2rs-yang-l2-network-topology]
Dong, J. and X. Wei, "A YANG Data Model for Layer-2
Network Topologies", draft-ietf-i2rs-yang-l2-network-
topology-03 (work in progress), July 2016.
[I-D.ietf-i2rs-yang-l3-topology]
Clemm, A., Medved, J., Varga, R., Liu, X.,
Ananthakrishnan, H., and N. Bahadur, "A YANG Data Model
for Layer 3 Topologies", draft-ietf-i2rs-yang-
l3-topology-08 (work in progress), January 2017.
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[I-D.ietf-i2rs-yang-network-topo]
Clemm, A., Medved, J., Varga, R., Bahadur, N.,
Ananthakrishnan, H., and X. Liu, "A Data Model for Network
Topologies", draft-ietf-i2rs-yang-network-topo-12 (work in
progress), March 2017.
[I-D.ietf-netconf-restconf]
Bierman, A., Bjorklund, M., and K. Watsen, "RESTCONF
Protocol", draft-ietf-netconf-restconf-18 (work in
progress), October 2016.
[LEAKYABS]
Spolsky, J., "The Law of Leaky Abstractions", 2002,
<https://www.joelonsoftware.com/2002/11/11/the-law-of-
leaky-abstractions/>.
[OPENCONF]
OpenConfig, "Openconfig release YANG models", 2016,
<https://github.com/openconfig/public/tree/master/
release>.
[OSI] Wikipedia, "OSI Model", 2016,
<https://en.wikipedia.org/wiki/OSI_model>.
[RFC0792] Postel, J., "Internet Control Message Protocol", STD 5,
RFC 792, DOI 10.17487/RFC0792, September 1981,
<http://www.rfc-editor.org/info/rfc792>.
[RFC0854] Postel, J. and J. Reynolds, "Telnet Protocol
Specification", STD 8, RFC 854, DOI 10.17487/RFC0854, May
1983, <http://www.rfc-editor.org/info/rfc854>.
[RFC1812] Baker, F., Ed., "Requirements for IP Version 4 Routers",
RFC 1812, DOI 10.17487/RFC1812, June 1995,
<http://www.rfc-editor.org/info/rfc1812>.
[RFC1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., de Groot, G.,
and E. Lear, "Address Allocation for Private Internets",
BCP 5, RFC 1918, DOI 10.17487/RFC1918, February 1996,
<http://www.rfc-editor.org/info/rfc1918>.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, DOI 10.17487/RFC1981, August
1996, <http://www.rfc-editor.org/info/rfc1981>.
[RFC2629] Rose, M., "Writing I-Ds and RFCs using XML", RFC 2629,
DOI 10.17487/RFC2629, June 1999,
<http://www.rfc-editor.org/info/rfc2629>.
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[RFC3439] Bush, R. and D. Meyer, "Some Internet Architectural
Guidelines and Philosophy", RFC 3439,
DOI 10.17487/RFC3439, December 2002,
<http://www.rfc-editor.org/info/rfc3439>.
[RFC3552] Rescorla, E. and B. Korver, "Guidelines for Writing RFC
Text on Security Considerations", BCP 72, RFC 3552,
DOI 10.17487/RFC3552, July 2003,
<http://www.rfc-editor.org/info/rfc3552>.
[RFC3627] Savola, P., "Use of /127 Prefix Length Between Routers
Considered Harmful", RFC 3627, DOI 10.17487/RFC3627,
September 2003, <http://www.rfc-editor.org/info/rfc3627>.
[RFC3646] Droms, R., Ed., "DNS Configuration options for Dynamic
Host Configuration Protocol for IPv6 (DHCPv6)", RFC 3646,
DOI 10.17487/RFC3646, December 2003,
<http://www.rfc-editor.org/info/rfc3646>.
[RFC3810] Vida, R., Ed. and L. Costa, Ed., "Multicast Listener
Discovery Version 2 (MLDv2) for IPv6", RFC 3810,
DOI 10.17487/RFC3810, June 2004,
<http://www.rfc-editor.org/info/rfc3810>.
[RFC4253] Ylonen, T. and C. Lonvick, Ed., "The Secure Shell (SSH)
Transport Layer Protocol", RFC 4253, DOI 10.17487/RFC4253,
January 2006, <http://www.rfc-editor.org/info/rfc4253>.
[RFC4443] Conta, A., Deering, S., and M. Gupta, Ed., "Internet
Control Message Protocol (ICMPv6) for the Internet
Protocol Version 6 (IPv6) Specification", RFC 4443,
DOI 10.17487/RFC4443, March 2006,
<http://www.rfc-editor.org/info/rfc4443>.
[RFC4821] Mathis, M. and J. Heffner, "Packetization Layer Path MTU
Discovery", RFC 4821, DOI 10.17487/RFC4821, March 2007,
<http://www.rfc-editor.org/info/rfc4821>.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862,
DOI 10.17487/RFC4862, September 2007,
<http://www.rfc-editor.org/info/rfc4862>.
[RFC5218] Thaler, D. and B. Aboba, "What Makes For a Successful
Protocol?", RFC 5218, DOI 10.17487/RFC5218, July 2008,
<http://www.rfc-editor.org/info/rfc5218>.
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[RFC5424] Gerhards, R., "The Syslog Protocol", RFC 5424,
DOI 10.17487/RFC5424, March 2009,
<http://www.rfc-editor.org/info/rfc5424>.
[RFC6164] Kohno, M., Nitzan, B., Bush, R., Matsuzaki, Y., Colitti,
L., and T. Narten, "Using 127-Bit IPv6 Prefixes on Inter-
Router Links", RFC 6164, DOI 10.17487/RFC6164, April 2011,
<http://www.rfc-editor.org/info/rfc6164>.
[RFC6177] Narten, T., Huston, G., and L. Roberts, "IPv6 Address
Assignment to End Sites", BCP 157, RFC 6177,
DOI 10.17487/RFC6177, March 2011,
<http://www.rfc-editor.org/info/rfc6177>.
[RFC6192] Dugal, D., Pignataro, C., and R. Dunn, "Protecting the
Router Control Plane", RFC 6192, DOI 10.17487/RFC6192,
March 2011, <http://www.rfc-editor.org/info/rfc6192>.
[RFC6241] Enns, R., Ed., Bjorklund, M., Ed., Schoenwaelder, J., Ed.,
and A. Bierman, Ed., "Network Configuration Protocol
(NETCONF)", RFC 6241, DOI 10.17487/RFC6241, June 2011,
<http://www.rfc-editor.org/info/rfc6241>.
[RFC6434] Jankiewicz, E., Loughney, J., and T. Narten, "IPv6 Node
Requirements", RFC 6434, DOI 10.17487/RFC6434, December
2011, <http://www.rfc-editor.org/info/rfc6434>.
[RFC6540] George, W., Donley, C., Liljenstolpe, C., and L. Howard,
"IPv6 Support Required for All IP-Capable Nodes", BCP 177,
RFC 6540, DOI 10.17487/RFC6540, April 2012,
<http://www.rfc-editor.org/info/rfc6540>.
[RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217,
DOI 10.17487/RFC7217, April 2014,
<http://www.rfc-editor.org/info/rfc7217>.
[RFC7223] Bjorklund, M., "A YANG Data Model for Interface
Management", RFC 7223, DOI 10.17487/RFC7223, May 2014,
<http://www.rfc-editor.org/info/rfc7223>.
[RFC7224] Bjorklund, M., "IANA Interface Type YANG Module",
RFC 7224, DOI 10.17487/RFC7224, May 2014,
<http://www.rfc-editor.org/info/rfc7224>.
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[RFC7277] Bjorklund, M., "A YANG Data Model for IP Management",
RFC 7277, DOI 10.17487/RFC7277, June 2014,
<http://www.rfc-editor.org/info/rfc7277>.
[RFC7317] Bierman, A. and M. Bjorklund, "A YANG Data Model for
System Management", RFC 7317, DOI 10.17487/RFC7317, August
2014, <http://www.rfc-editor.org/info/rfc7317>.
[RFC7404] Behringer, M. and E. Vyncke, "Using Only Link-Local
Addressing inside an IPv6 Network", RFC 7404,
DOI 10.17487/RFC7404, November 2014,
<http://www.rfc-editor.org/info/rfc7404>.
[RFC7527] Asati, R., Singh, H., Beebee, W., Pignataro, C., Dart, E.,
and W. George, "Enhanced Duplicate Address Detection",
RFC 7527, DOI 10.17487/RFC7527, April 2015,
<http://www.rfc-editor.org/info/rfc7527>.
[RFC7608] Boucadair, M., Petrescu, A., and F. Baker, "IPv6 Prefix
Length Recommendation for Forwarding", BCP 198, RFC 7608,
DOI 10.17487/RFC7608, July 2015,
<http://www.rfc-editor.org/info/rfc7608>.
[RFC7663] Trammell, B., Ed. and M. Kuehlewind, Ed., "Report from the
IAB Workshop on Stack Evolution in a Middlebox Internet
(SEMI)", RFC 7663, DOI 10.17487/RFC7663, October 2015,
<http://www.rfc-editor.org/info/rfc7663>.
[RFC7922] Clarke, J., Salgueiro, G., and C. Pignataro, "Interface to
the Routing System (I2RS) Traceability: Framework and
Information Model", RFC 7922, DOI 10.17487/RFC7922, June
2016, <http://www.rfc-editor.org/info/rfc7922>.
[RFC7980] Behringer, M., Retana, A., White, R., and G. Huston, "A
Framework for Defining Network Complexity", RFC 7980,
DOI 10.17487/RFC7980, October 2016,
<http://www.rfc-editor.org/info/rfc7980>.
[RFC8028] Baker, F. and B. Carpenter, "First-Hop Router Selection by
Hosts in a Multi-Prefix Network", RFC 8028,
DOI 10.17487/RFC8028, November 2016,
<http://www.rfc-editor.org/info/rfc8028>.
[RFC8106] Jeong, J., Park, S., Beloeil, L., and S. Madanapalli,
"IPv6 Router Advertisement Options for DNS Configuration",
RFC 8106, DOI 10.17487/RFC8106, March 2017,
<http://www.rfc-editor.org/info/rfc8106>.
Kahn, et al. Expires November 6, 2017 [Page 27]
Internet-Draft Requirements for IPv6 Routers May 2017
Authors' Addresses
Zaid Ali Kahn (editor)
LinkedIn
xxx
xxx, CA xxx
USA
Email: zaid@linkedin.com
John Brzozowski (editor)
Comcast
xxx
xxx, xxx xxx
USA
Email: John_Brzozowski@comcast.com
Russ White (editor)
LinkedIn
Oak Island, NC 28465
USA
Email: russ@riw.us
Kahn, et al. Expires November 6, 2017 [Page 28]
