Internet DRAFT - draft-baker-openstack-ipv6-model
draft-baker-openstack-ipv6-model
Network Working Group F. Baker, Ed.
Internet-Draft C. Marino
Intended status: Informational I. Wells
Expires: August 12, 2015 R. Agarwalla
S. Jeuk
G. Salgueiro
Cisco Systems
February 8, 2015
A Model for IPv6 Operation in OpenStack
draft-baker-openstack-ipv6-model-02
Abstract
This is an overview of a network model for OpenStack, designed to
dramatically simplify scalable network deployment and operations.
Requirements Language
The key words 'MUST', 'MUST NOT', 'REQUIRED', 'SHALL', 'SHALL NOT',
'SHOULD', 'SHOULD NOT', 'RECOMMENDED', 'MAY', and 'OPTIONAL' in this
document are to be interpreted as described in [RFC2119].
Design Principle
Perfection is achieved, not when there is nothing more to add, but
when there is nothing left to take away.
Antoine de Saint-Exupery
Status of This Memo
This Internet-Draft is submitted in full conformance with the
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This Internet-Draft will expire on August 12, 2015.
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Copyright Notice
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document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. What is OpenStack? . . . . . . . . . . . . . . . . . . . 3
1.2. OpenStack Scaling Issues . . . . . . . . . . . . . . . . 4
2. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 5
2.1. Design approach . . . . . . . . . . . . . . . . . . . . . 5
2.2. Multiple Data Centers . . . . . . . . . . . . . . . . . . 6
2.3. Large Data Centers . . . . . . . . . . . . . . . . . . . 6
2.4. Multi-tenancy . . . . . . . . . . . . . . . . . . . . . . 6
2.5. Isolation . . . . . . . . . . . . . . . . . . . . . . . . 6
2.5.1. Inter-tenant isolation . . . . . . . . . . . . . . . 6
2.5.2. Intra-tenant isolation . . . . . . . . . . . . . . . 7
2.6. Operational Simplicity . . . . . . . . . . . . . . . . . 7
2.7. Address space . . . . . . . . . . . . . . . . . . . . . . 7
2.8. Data Center Federation . . . . . . . . . . . . . . . . . 7
2.9. Path MTU Issues . . . . . . . . . . . . . . . . . . . . . 7
3. Models . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
3.1. Configuration Model . . . . . . . . . . . . . . . . . . . 8
3.2. Data Center Model . . . . . . . . . . . . . . . . . . . . 8
3.2.1. Tenant Address Model . . . . . . . . . . . . . . . . 9
3.2.2. Use of Global Addresses by the Data Center . . . . . 13
3.3. Inter-tenant security services . . . . . . . . . . . . . 13
3.4. IPv6 Tenant Isolation using the Label . . . . . . . . . . 14
3.5. Isolation in Routing . . . . . . . . . . . . . . . . . . 14
4. BCP 38 Ingress Filtering . . . . . . . . . . . . . . . . . . 15
5. Moving virtual machines . . . . . . . . . . . . . . . . . . . 15
5.1. Recreation of the VM . . . . . . . . . . . . . . . . . . 16
5.2. Live Migration of a Running Virtual Machine . . . . . . . 16
6. OpenStack implications . . . . . . . . . . . . . . . . . . . 18
6.1. Configuration implications . . . . . . . . . . . . . . . 18
6.2. vSwitch implications . . . . . . . . . . . . . . . . . . 18
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 19
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8. Security Considerations . . . . . . . . . . . . . . . . . . . 19
9. Privacy Considerations . . . . . . . . . . . . . . . . . . . 19
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 20
11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 20
12. References . . . . . . . . . . . . . . . . . . . . . . . . . 20
12.1. Normative References . . . . . . . . . . . . . . . . . . 20
12.2. Informative References . . . . . . . . . . . . . . . . . 20
Appendix A. Change Log . . . . . . . . . . . . . . . . . . . . . 24
Appendix B. Alternative Labels considered . . . . . . . . . . . 24
B.1. IPv6 Flow Label . . . . . . . . . . . . . . . . . . . . . 24
B.1.1. Metaconsiderations . . . . . . . . . . . . . . . . . 25
B.2. Federated Identity . . . . . . . . . . . . . . . . . . . 25
B.2.1. Introduction . . . . . . . . . . . . . . . . . . . . 25
B.2.2. Federated identity Option . . . . . . . . . . . . . . 26
B.2.3. Metaconsiderations . . . . . . . . . . . . . . . . . 28
B.3. Universal Cloud Classification . . . . . . . . . . . . . 29
B.3.1. Introduction . . . . . . . . . . . . . . . . . . . . 29
B.3.2. Universal Cloud Classification Options . . . . . . . 30
B.3.3. UCC Extension Header . . . . . . . . . . . . . . . . 30
B.4. Policy List in Segment Routing Header . . . . . . . . . . 31
B.4.1. Metaconsiderations . . . . . . . . . . . . . . . . . 31
B.5. RFC 4291 Interface Identifier (IID) . . . . . . . . . . . 32
B.5.1. Address Format . . . . . . . . . . . . . . . . . . . 32
B.5.2. Metaconsiderations . . . . . . . . . . . . . . . . . 34
B.6. Modified IID using modified Privacy Extension . . . . . . 36
B.6.1. Metaconsiderations . . . . . . . . . . . . . . . . . 36
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 37
1. Introduction
OpenStack, and its issues.
1.1. What is OpenStack?
OpenStack is a cloud computing orchestration solution developed using
an open source community process. It consists of a collection of
'projects', each implementing the creation, control, and
administration of tenant resources. There are separate OpenStack
projects for managing compute, storage and network resources.
Neutron is the project that manages OpenStack networking. It exposes
a northbound API to the other OpenStack projects for programmatic
control over tenant network connectivity. The southbound interface
is implemented as one or more device driver plugins that are built to
interact with specific devices in the network. This approach
provides the flexibility to deploy OpenStack networking using a range
of alternative techniques.
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An OpenStack tenant, in the Kilo and earlier releases, is required to
create what OpenStack identifies as a 'Neutron Network' connecting
their virtual machines. This Network is instantiated via the plugins
as either a layer 2 network, a layer 3 network, or as an overlay
network. The actual implementation is unknown to the tenant. The
technology used to provide these networks is selected by the
OpenStack operator based upon the requirements of the cloud
deployment.
The tenant also is required, in the Kilo and earlier releases, to
specify an 'IP Subnet' for each Network. This specification is made
by providing a CIDR prefix for IPv4 address allocation via DHCP or
for IPv6 address allocation via DHCP or SLAAC. This address range
may be from within the address range of the datacenter (non-
overlapping), or overlapping [RFC1918] addresses. Tenants may create
multiple Networks, each with its own Subnet.
An OpenStack Subnet is a logical layer 2 network and requires layer 3
routing for packets to exit the Subnet. This is achieved by
attaching the Subnet to a Neutron Router. The Neutron router
implements Network Address Translation for external traffic from
tenant networks as well for providing connectivity to tenant networks
from the outside. Using Linux utilities, OpenStack can support
overlapping RFC 1918 addresses between tenants.
OpenStack Subnets are typically implemented as VLANs in a datacenter.
When tenant scalability requirement grow large, an overlay approach
is typically used. Because of the difficulties in scaling and
administering large layer 2 and/or overlay networks, some OpenStack
integrations chose not to provide isolated Subnets and simply offer
tenants a layer 3 based network alternative.
OpenStack uses Layer 3 and Layer 2 Linux utilities on hosts to
provide protection against IP/MAC spoofing and ARP poisoning.
1.2. OpenStack Scaling Issues
One of the fundamental requirements of OpenStack Networking (Neutron)
is to provide scalable, isolated tenant networks. Today this is
achieved via L2 segmentation using either a) standard 802.1Q VLANs or
b) an overlay approach based on one of several L2 over L3
encapsulation techniques available today such as 802.1ad, VXLAN, STT
or NVGRE.
However, these approaches still struggle to provide scalable,
transparent, manageable, high performance, isolated tenant networks.
VLAN's don't scale beyond 4096 (2^12) networks and have complex
trunking requirements when tenants span host and racks. IEEE 802.1ad
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(QinQ) partially solves that, but adds another limit - at most 2^12
tenants, each of which may have 2^12 VLANs. IP Encapsulation
introduces additional complexity on host computers running
hypervisors as well as impact performance of tenant applications
running on virtual machines. Overlay based isolation techniques may
also impair traditional network monitoring and performance management
tools. Moreover, when these isolated (L2) networks require external
access to other networks or the public Internet, they require even
more complex solutions to accommodate overlapping IP prefixes and
network address translation (NAT).
As more capabilities are built on to these layer 2 based 'virtual'
networks, complexity continues to grow.
This draft presents a new Layer 3 based approach to OpenStack
networking using IPv6 that can be deployed natively on IPv6 networks.
It will be shown that this approach can provide tenant isolation
without the limitations of existing alternatives, as well as deliver
high performance networks transparently using a simplified tenant
network connectivity model, without the overhead of encapsulation or
managing overlapping IP addresses and address translations. We note
that some large content providers, notably Google and Facebook
[FaceBook-IPv6], are going in exactly this direction.
2. Requirements
In this section, we attempt to list critical requirements.
2.1. Design approach
As a design approach, we presume an IPv6-only data center in a world
that might have IPv4 or IPv6 clients outside of it. This design
explicitly does not depend on VLANs, QinQ, VXLAN, MPLS, Segment
Routing, LISP, IP/IP or GRE tunnels, or any other supporting
encapsulation. Data center operators remain free to use any of those
tools, but they are not required. If we can do everything required
for OpenStack networking with IPv6 alone, these other networking
technologies may be used as optimizations. If we are unable to
satisfy the OpenStack requirements that also is something we wish to
know and understand.
OpenStack is designed to be used by many cloud users or 'tenants'.
Scalable, secure and isolated tenant networks are a requirement for
building a multi-tenant cloud datacenter. The OpenStack
administrator/operator can design and configure a cloud environment
to provide network isolation using the approach described in this
document, alone, or in combination with any of the above network
technologies . However, all the details of the underlying technology
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and implementation details are completely transparent to the tenant
itself.
2.2. Multiple Data Centers
A common requirement in network and data center operations is
reliability, serviceability, and maintainability of their operations
in the presence of an outage. At minimum, this implies multihoming
in the sense of having multiple upstream ISPs; in many cases, it also
implies multiple and at times duplicate data centers, and tenants
stretched or able to be readily moved or recreated across multiple
data centers.
2.3. Large Data Centers
Microsoft Azure [Microsoft-Azure] has purchased a 100 acre piece of
land for the construction of a single data center. In terms of
physical space, that is enough for a data center with about half a
million 19' RETMA racks.
With even modest virtual machine density, infrastructure at this
scale easily exhausts the 16M available RFC 1918 private addresses
(i.e. 10.0.0.0/8) and explains the recent efforts by webscale cloud
providers to deploy IPv6 throughout their new datacenters.
2.4. Multi-tenancy
While it is possible that a single tenant would require a 100 acre
data center, it would be unusual. In most such data centers, one
would expect a large number of tenants.
2.5. Isolation
Isolation is required between tenants, and at times between tenants
hierarchically related to larger tenants.
2.5.1. Inter-tenant isolation
A 'tenant' is defined as a set of resources under common
administrative control. It may be appropriate for tenants to
communicate with each other within the context of an application or
relationships among their owners or operators. However, unless
specified otherwise, tenants are intended to operate as if they were
on their own company's premises and be isolated from one another.
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2.5.2. Intra-tenant isolation
There are often security compartments within a corporate network,
just as there are security barriers between companies. As a result,
there is a recursive isolation requirement: it must be possible to
isolate an identified part of a tenant (which we also think of as a
tenant) from another part of the same tenant.
2.6. Operational Simplicity
To the extent possible (and, for operators, the concept will bring a
smile), operation of a multi-location multi-tenant data center, and
the design of an application that runs in one, should be simple and
uncoupled.
As discussed in [RFC3439], this requires that the operational model
required to support a tenant with only two physical machines, or
virtual machines in the same physical chassis, should be the same as
that required to support a tenant running a million machines in a
federated multiple data center application. Additionally, this same
operational model should scale from running a single tenant up to
many thousands of tenants.
2.7. Address space
As described in Section 1.1, currently, an OpenStack tenant is
required to specify a Subnet's CIDR prefix for IP address allocation.
With this proposal, this is no longer required.
2.8. Data Center Federation
It must be possible to extend the architecture across multiple data
centers. These data centers may be operated by distinct entities,
with security policies that apply to their interconnection.
2.9. Path MTU Issues
An issue in virtualized data center architectures is Path MTU
Discovery [RFC1981] implementation. Implementing Path MTU requires
the ICMPv6 [RFC4443] Packet Too Big message to get from the
originating router or middleware to the indicated host, which is in
this case virtual and potentially hidden within a tunnel. This is a
special case of the issues raised in [RFC2923].
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3. Models
3.1. Configuration Model
In the OpenStack model, the cloud computing user, or tenant, is
building something Edward Yourdon might call a 'structured design'
for the application they are building. In the 1960's, when Yourdon
started specifying process and data flow diagrams, these were job
steps in a deck of Job Control Language cards; in OpenStack, they are
multiple, individual machines, virtual or physical, running parts of
a structured application.
In these, one might find a load balancer that receives and
distributes requests to request processors, a set of stored data
processing applications, and the storage they depend on. What is
important to the OpenStack tenant is that 'this' and 'that'
communicate, potentially using or not using multicast communications,
and don't communicate with 'the other'. Typically unnecessary is any
and all information regarding how this communication actually needs
to occur (i.e. placement of routers, switches, and IP subnets,
prefixes, etc.).
An IPv6 based networking model simplifies the configuration of tenant
connectivity requirements. Global reachability eliminates the need
for network address translation devices as well as tenant-specified
Subnet prefixes (Section 2.7), although tenant-specified ULA prefixes
or prefixes from the owner of the tenant's address space are usable
with it. With the exception of network security functions, no
network devices need to be specified or configured to provide
connectivity.
3.2. Data Center Model
The premises of the routing and addressing models are that
o The address tells the routing system what topological location to
deliver a packet to, and within that, what interface to deliver it
to, and
o The routing system should deliver traffic to a resource if and
only if the sender is authorized to communicate with that
resource.
o Contrary to the OpenStack Neutron Networking Model, tunnels are
not necessary to provide tenant network isolation; we include
resources in a tenant network by a Role-based Access Control
model, but address the tenant resources within the data center in
a manner that scales for the data center.
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We expect to find the data center to be composed of some minimal unit
of connectivity and maintenance, such as a rack or row, and equipped
with one or more Top-of-Rack or End-of-Row switch(es); each
configured with at least one subnet prefix, perhaps one per such
switch. For the purposes of this note, these will be called Racks
and Top-of-Rack switches, and when applied to other architectures the
appropriate translation needs to be imposed.
Figure 1 describes a relatively typical rack design. It is a simple
fat-tree architecture, with every device in a pair, so that any
failure has an immediate hot backup. There are other common designs,
such as those that consider each rack to be in a 'row' and in a
'column', with one or more distribution switches in each.
Distribution Switches connecting
/ Layer / racks in a pod, and
/ / connecting pods
/ /
+-+-+ +-+-+ Mutual backup TOR
+-+TOR+---+TOR+-+ switches
| +---+ +---+ |
| +-----------+ |
+-+ host +-+ Each host has two
| +-----------+ | Ethernet interfaces
+-+ host +-+ with separate subnets
| +-----------+ |
| . . |
| . . |
| . . | Design premise: complete
| +-----------+ | redundancy, with every
+-+ host +-+ switch and every cable
| +-----------+ | backed up by a doppelganger
+-+ host +-+
+-----------+
Figure 1: Typical Rack Design
3.2.1. Tenant Address Model
Tenant resources need to be told, by configuration or naming, the
addresses of resources they communicate with. This is true
regardless of their location or relationship to a given tenant. In
environments with well-known addresses, this becomes complex and
unscalable. This was learned very early with Internet hostnames; a
single 'hostfile' was maintained by a central entity and updated
daily, which quickly became unwieldy. The result was the development
of the Domain Name System; the level of indirection between names and
addresses improved scalability. It also facilitated ongoing
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maintenance. If a service needed multiple servers, or a server
needed to change its address, that was trivially solved by changing
the DNS Resource Record; every resource that needed the new address
would obtain it the next time it queried the DNS. It has also
facilitated the IPv4/IPv6 transition; a resource that has an IPv6
address is given a AAAA record in addition to, or to replace, its
IPv4 A record.
Similarly, today's reliance on NAPT technology frequently limits the
capabilities of an application. It works reasonably well for a
client accessing a client/server application when the protocol does
not carry addressing information. If there is an expectation that
one resource's private address will be meaningful to a peer, such as
when an SIP client presents its address in SDP or an HTTP server
presents an address in a redirection, either the resource needs to
understand the difference between an 'inside' and an 'outside'
address and know which is which, or it needs a traversal algorithm
that changes the addresses. For peer-to-peer applications, this
ultimately means providing a network design in which those issues
don't apply.
IPv6 provides global addresses, enough of them that there is no real
expectation of running out any time soon, making these issues go
away. In addition, with the IPv4 address space running out, both
globally and within today's large datacenters, there aren't
necessarily addresses available for an IPv4 application to use, even
as a floating IP address.
Hence, the model we propose is that a resource in a tenant is told
the addresses of the other resources with which it communicates.
They are IPv6 addresses, and the data center takes care to ensure
that inappropriate communications do not take place.
3.2.1.1. Use of Global Unicast Addresses by Tenants
A unicast address in an IP network identifies a topological location,
by association with an IP prefix (which might be for a subnet or any
aggregate of subnets). It also identifies a single interface located
within that subnet, which may or may not be instantiated at the time.
We assume that there is a subnet associated with a top-of-rack switch
or whatever its counterpart would be in a given network design, and
that the physical and virtual machines located in that rack have
addresses in that subnet. This is the same prefix that is used by
the datacenter administrator.
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3.2.1.2. Unique Local Addresses
A common requirement is that tenants have the use of some form of
private address space. In an IPv6 network, a Unique Local IPv6
Unicast Address [RFC4193] may be used to accomplish this. In this
case, however, the addresses will need to be explicitly assigned to
physical or virtual machines used by the tenant, perhaps using DHCP
or YANG, where a standard IPv6 address could be allocated using
SLAAC, DHCPv6, or other technologies.
The value of this is that the distinction between a Global Address
and a Unique Local Address is a corner case in the data center; a ULA
will not generally be useful when communicating outside the data
center, but within the data center it is rational. Tenants have no
routing information or other awareness of the prefix. This is not
intended for use behind a NAPT; resources that need accessibility to
or from resources outside the tenant, and especially outside the data
center, need global addresses.
3.2.1.3. Multicast Domains
Multicast capability is a capability enjoyed by some groups of
resources, that enables them to send a single message and have it
delivered to multiple destinations roughly simultaneously. At the
link layer, this means sending a message once that is received by a
specified set of recipient resources using hardware capabilities. IP
multicast can be implemented on a LAN as specified in [RFC4291], and
can also cross multiple subnets directly, using routing protocols
such as Protocol Independent Multicast [RFC4601] [RFC4602] [RFC4604]
[RFC4605] [RFC4607]. In IPv6, the model would be that when a group
of resources is created with a multicast capability, it is allocated
one or more source-specific transient group addresses as defined in
section 2.7 of that RFC.
3.2.1.4. IPv4 Interaction Model
OpenStack IPv4 Neutron uses "floating IPv4 addresses" - global or
public IPv4 addresses and Network Address Translation - to enable
remote resources to connect to tenant private network endpoints.
Tenant end points can connect out to remote resources through an
"External Default Gateway". Both of these depend on NAPT (DNAT/SNAT)
[RFC2391] to ensure that IPv4 end points are able communicate and at
the same time ensure tenant isolation.
If IPv6 is deployed in a data center, there are fundamentally two
ways a tenant can interact with IPv4 peers:
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o it can run existing IPv4 OpenStack technology in parallel with the
IPv6 deployment, or
o It can have a translator at the data center edge (such as
described in [I-D.ietf-v6ops-siit-dc]) that associates an IPv4
address or address plus port with an IPv6 address or address plus
port. The IPv4 address, in this model, becomes a floating IPv4
address attached to an internal IPv6 address. The 'data center
edge' is, by definition, a system that has IPv4 reachability to at
least the data center's upstream ISP and all IPv4 systems in the
data center, IPv6 connectivity to all of the IPv6 systems in the
data center, and (if the upstream offers IPv6 service) IPv6
connectivity to the upstream as well.
The first model is complex, if for no other reason than that there
are two fundamental models in use, one with various encapsulations
hiding overlapping address space and one with non-overlapping address
space.
To simplify the network, as noted in Section 2.1, we suggest that the
data center be internally IPv6-only, and IPv4 be translated to IPv6
at the data center edge. The advantage is that it enables IPv4
access while that remains in use, and as IPv6 takes over, it reduces
the impact of vestigial support for IPv4.
The SIIT Translation model in [I-D.ietf-v6ops-siit-dc] has IPv4
traffic come to an translator [RFC6145][RFC6146] having a pre-
configured translation, resulting in an IPv6 packet indistinguishable
from the packet the remote resource might have sent had it been
IPv6-capable, with one exception. The IPv6 destination address is
that of the endpoint (the same address advertised in a AAAA record),
but the source address is an IPv4-Embedded IPv6 Address [RFC6052]
with the IPv4 address of the sender embedded in a prefix used by the
translator.
Access to external IPv4 resources is provided in the same way: an
DNS64 [RFC6147] server is implemented that contains AAAA records with
an IPv4-Embedded IPv6 Address [RFC6052] with the IPv4 address of the
remote resource embedded in a prefix used by the translator.
This follows the Framework for IPv4/IPv6 Translation [RFC6144],
making the internal IPv4 address a floating IP address attached to an
internal IPv6 address, and the external 'dial-out' address
indistinguishable from a native IPv6 address.
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3.2.1.5. Legacy IPv4 OpenStack
The other possible model, applicable to IPv4-only devices, is to run
a legacy OpenStack environment inside IPv6 tunnels. This preserves
the data center IPv6-only, and enables IPv4-only applications,
notably those whose licenses tie them to IPv4 addresses, to run.
However, it adds significant overhead in terms of encapsulation size
and network management complexity.
3.2.2. Use of Global Addresses by the Data Center
Every rack and physical host requires an IP prefix that is reachable
by the OpenStack operator. This will normally be a global IPv6
unicast address. For scalability purposes, as isolation is handled
separately, this is normally the same prefix as is used by tenants in
the rack.
3.3. Inter-tenant security services
In this model, the a label is used to identify a set of virtual or
physical systems under common ownership and administration that are
authorized to communicate freely among themselves - a tenant.
Tenants are not generally authorized to communicate with each other,
but interactions between specified tenants may be authorized, and
specific systems may be authorized to communicate generally.
The fundamental premise is that the vSwitch can determine whether a
VM is authorized to send or receive a given message. It does so by
finding the label in a message being sent or received and comparing
it to a locally-held authorization policy. This policy would
indicate that the VM is permitted to send or receive messages
containing one of a small list of labels. In the case of a label
contained in the IID of an IPv6 address, it would also need to verify
the prefix used in the address, as this type of policy would be
specific to an IPv6 prefix.
A set of possible choices that were considered is to be found in
Appendix B. The key questions are a list of considerations, presented
in no particular order:
o In what way does the approach the IPv6 Path MTU?
o How does the address come into being?
o What security implications apply? For example, how hard would it
be for a VM to spoof the source address or attack a random
destination?
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o What is the service offered? Can, for example, policy be applied
at
* The sender of a datagram?
* The receiver of a datagram?
* An arbitrary point between the sender and receiver?
* At the data center edge, on arriving or departing traffic other
data centers?
* At the data center edge, on arriving or departing traffic
random locations?
o In what way does the approach the IPv6 Path MTU?
3.4. IPv6 Tenant Isolation using the Label
Neutron today already implements a form of Network Ingress Filtering
[RFC2827]. It prevents the VM from emitting traffic with an
unauthorized MAC, IPv4, or IPv6 source address.
In addition to this, in this model Neutron prevents the VM from
transmitting a network packet with an unauthorized label value. The
VM MAY be configured with and authorized to use one of a short list
of authorized label values, as opposed to simply having its choice
overridden; in that case, Neutron verifies the value and overwrites
one not in the list.
When a hypervisor is about to deliver an IPv6 packet to a VM, it
checks the label value against a list of values that the VM is
permitted to receive. If it contains an unauthorized value, the
hypervisor discards the packet rather than deliver it. If the Flow
Label is in use, Neutron zeros the label prior to delivery.
The intention is to hide the label value from malware potentially
found in the VM, and enable the label to be used as a form of first
and last hop security. This provides basic tenant isolation, if the
label is assigned as a tenant identifier, and may be used more
creatively such as to identify a network management application as
separate from a managed resource.
3.5. Isolation in Routing
This concept has the weakness that if a packet is not dropped at its
source, it is dropped at its destination. It would be preferable for
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the packet to be dropped in flight, such as at the top-of-rack switch
or an aggregation router.
Concepts discussed in IS-IS LSP Extendibility
[I-D.baker-ipv6-isis-dst-flowlabel-routing][RFC5120][RFC5308] and
OSPFv3 LSA Extendibility [I-D.baker-ipv6-ospf-dst-flowlabel-routing]
[I-D.ietf-ospf-ospfv3-lsa-extend][RFC5340] may be used to isolate
tenants in the routing of the data center backbone. This is not
strictly necessary, if Section 3.4 is uniformly and correctly
implemented. It does, however, present a second defense against
misconfiguration, as the filter becomes ubiquitous in the data center
and as scalable as routing.
4. BCP 38 Ingress Filtering
As noted in Section 3.4, Neutron today implements a form of Network
Ingress Filtering [RFC2827]. It prevents the VM from emitting
traffic with an unauthorized MAC, IPv4, or IPv6 source address.
In IPv6, this is readily handled when the address or addresses used
by a VM are selected by the OpenStack operator. It may then
configure a per-VM filter with the addresses it has chosen, following
logic similar to the Source Address Validation Solution for DHCP
[I-D.ietf-savi-dhcp] or SEND [RFC7219]. This is also true of IPv6
Stateless Address Autoconfiguration (SLAAC) [RFC4862] when the MAC
address is known and not shared.
However, when SLAAC is in use and either the MAC address is unknown
or SLAAC's Privacy Extensions [RFC4941][RFC7217], are in use, Neutron
will need to implement the provisions of FCFS SAVI: First-Come,
First-Served Source Address Validation [RFC6620] in order to learn
the addresses that a VM is using and include them in the per-VM
filter.
5. Moving virtual machines
This design supports these kinds of required layer 2 networks with
the additional use of a layer 2 over layer 3 encapsulation and
tunneling protocol, such as VXLAN [RFC7348]. The important point
here being that these overlays are used to address specific tenant
network requirements and NOT deployed to remove the scalability
limitations of OpenStack networking.
There are at least three ways VM movement can be accomplished:
o Recreation of the VM
o VLAN Modification
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o Live Migration of a Running Virtual Machine
5.1. Recreation of the VM
The simplest and most reliable is to
1. Create a new VM in the new location,
2. Add its address to the DNS Resource Record for the name, allowing
new references to the name to send transactions there,
3. Remove the old address from the DNS Resource Record (including
the SIIT translation, if one exists), ending the use of the old
VM for new transactions,
4. Wait for the period of the DNS Resource Record's lifetime
(including the SIIT translation, if one exists), as it will get
new requests throughout that interval,
5. Wait for the for the old VM to finish any outstanding
transactions, and then
6. Kill the old VM.
This is obviously not movement of an existing VM, but preservation of
the same number and function of VMs by creation of a new VM and
killing the old.
5.2. Live Migration of a Running Virtual Machine
At http://blogs.vmware.com/vsphere/2011/02/vmotion-whats-going-on-
under-the-covers.html, VMWare describes its capability, called
vMotion, in the following terms:
1. Shadow VM created on the destination host.
2. Copy each memory page from the source to the destination via the
vMotion network. This is known as preCopy.
3. Perform another pass over the VM's memory, copying any pages that
changed during the last preCopy iteration.
4. Continue this iterative memory copying until no changed pages
(outstanding to be-copied pages) remain or 100 seconds elapse.
5. Stun the VM on the source and resume it on the destination.
In a native-address environment, we add three steps:
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1. Shadow VM created on the destination host.
2. Copy each memory page from the source to the destination via the
vMotion network. This is known as preCopy.
3. Perform another pass over the VM's memory, copying any pages that
changed during the last preCopy iteration.
4. Continue this iterative memory copying until no changed pages
(outstanding to be-copied pages) remain or 100 seconds elapse.
5. Stitch routing for the old address.
6. Stun the VM on the source and resume it on the destination.
7. Renumber the VM as instructed in [RFC4192].
8. Unstitch routing for the old address.
If the VM is moved within the same subnet (which usually implies the
same rack), there is no stitching or renumbering apart from ensuring
that the MAC address moves with the VM. When the VM moves to a
different subnet, however, we need to restitch routing, at least
temporarily. This obviously calls for some definitions.
Stitching Routing: The VM is potentially in communication with two
sets of peers: VMs in the same subnet, and VMs in different
subnets.
* The router in the new subnet is instructed to advertise a host
route (/128) to the moved VM, and to install a static route to
the old address with the VM's address in the new subnet as its
next hop address. Traffic from VMs from other subnets will now
follow the host route to the VM in its new location.
* The router in the old subnet is instructed to direct LAN
traffic to the VM's MAC Address to its IPv6 forwarding logic.
Traffic from other VMs in the old subnet will now follow the
host route to the moved VM.
Renumbering: This step is optional, but is good hygiene if the VM
will be there a while. If the VM will reside in its new location
only temporarily, it can be skipped.
Note that every IPv6 address, unlike an IPv4 address, has a
lifetime. At least in theory, when the lifetime expires, neighbor
relationships with the address must be extended or the address
removed from the system. The Neighbor Discovery [RFC4861] process
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in the subnet router will periodically emit a Router
Advertisement; the VM will gain an IPv6 address in the new subnet
at that time if not earlier. As described in [RFC4192], DNS
should be changed to report the new address instead of the old.
The DNS lifetime and any ambient sessions using the old address
are now allowed to expire. That this point, any new sessions will
be using the new address, and the old is vestigial.
Waiting for sessions using the address to expire can take an
arbitrarily long interval, because the session generally has no
knowledge of the lifetime of the IPv6 address.
Unstitching Routing: This is the reverse process of stitching. If
the VM is renumbered, when the old address becomes vestigial, the
address will be discarded by the VM; if the VM is subsequently
taken out of service, it has the same effect. At that point, the
host route is withdrawn, and the MAC address in the old subnet
router's tables is removed.
6. OpenStack implications
6.1. Configuration implications
1. Neutron MUST be configured with a pre-determined default label
value for each tenant virtual network Section 3.4.
2. Neutron MAY be configured with a set of authorized label values
for each tenant virtual network Section 3.4.
3. A virtual tenant network MAY be configured with a set of
authorized label values Section 3.4.
4. Neutron MUST be configured with one or more label values per
virtual tenant network that the network is permitted to receive
Section 3.4.
6.2. vSwitch implications
On messages transmitted by a virtual machine
Label Correctness: As described in Section 3.3, ensure that the
label in the packet is one that the VM is authorized to use.
Exactly what label is in view is a deferred, and potentially
configurable, option. Again Depending on configuration, the
vSwitch may overwrite whatever value is there, or may ratify that
the value there is as specified in a VM-specific list.
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Source Address Validation: As described in Section 4, force the
source address to be among those the VM is authorized to use. The
VM may simultaneously be authorized to use several addresses.
Destination Address Validation: OpenStack for IPv4 permits a NAT
translation, called a 'floating IP address', to enable a VM to
communicate outside the domain; without that, it cannot. For
IPv6, the destination address should be permitted by some access
list, which may permit all addresses, or addresses matching one or
more CIDR prefixes such as permitted multicast addresses, and the
prefix of the data center.
On messages received for delivery to a virtual machine
Label Authorization: As described in Section 3.4, the vSwitch only
delivers a packet to a VM if the VM is authorized to receive it.
The VM may have been authorized to receive several such labels.
Each approach in the appendix discusses filtering.
7. IANA Considerations
This document does not ask IANA to do anything.
8. Security Considerations
In Section 2.5 and Section 3.3, this specification considers inter-
tenant and intra-tenant network isolation. It is intended to
contribute to the security of a network, much like encapsulation in a
maze of tunnels or VLANs might, but without the complexities and
overhead of the management of such resources. This does not replace
the use of IPSec, SSH, or TLS encryption or the use authentication
technologies; if these would be appropriate in an on-premises
corporate data center, they remain appropriate in a multi-tenant data
center regardless of the isolation technology. However, one can
think of this as a simple inter-tenant firewall based on the concepts
of role-based access control; if it can be readily determined that a
sender is not authorized to communicate with a receiver, such a
transmission is prevented.
9. Privacy Considerations
This specification places no personally identifying information in an
unencrypted part of a packet.
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10. Acknowledgements
This document grew out of a discussion among the authors and
contributors.
11. Contributors
Puneet Konghot
Cisco Systems
San Jose, California 95134
USA
Email: pkonghot@cisco.com
Shannon McFarland
Cisco Systems
Boulder, Colorado 80301
USA
Email: shmcfarl@cisco.com
Figure 2
12. References
12.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", RFC 2460, December 1998.
12.2. Informative References
[FaceBook-IPv6]
Pepelnjak, I., "Facebook Is Close to Having an IPv6-only
Data Center http://blog.ipspace.net/2014/03/
facebook-is-close-to-having-ipv6-only.html", March 2014.
[I-D.baker-ipv6-isis-dst-flowlabel-routing]
Baker, F., "Using IS-IS with Role-Based Access Control",
draft-baker-ipv6-isis-dst-flowlabel-routing-00 (work in
progress), February 2013.
[I-D.baker-ipv6-ospf-dst-flowlabel-routing]
Baker, F., "Using OSPFv3 with Role-Based Access Control",
draft-baker-ipv6-ospf-dst-flowlabel-routing-02 (work in
progress), May 2013.
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[I-D.ietf-6man-default-iids]
Gont, F., Cooper, A., Thaler, D., and W. Will,
"Recommendation on Stable IPv6 Interface Identifiers",
draft-ietf-6man-default-iids-01 (work in progress),
October 2014.
[I-D.ietf-ospf-ospfv3-lsa-extend]
Lindem, A., Mirtorabi, S., Roy, A., and F. Baker, "OSPFv3
LSA Extendibility", draft-ietf-ospf-ospfv3-lsa-extend-03
(work in progress), May 2014.
[I-D.ietf-savi-dhcp]
Bi, J., Wu, J., Yao, G., and F. Baker, "SAVI Solution for
DHCP", draft-ietf-savi-dhcp-26 (work in progress), May
2014.
[I-D.ietf-v6ops-siit-dc]
tore, t., "SIIT-DC: Stateless IP/ICMP Translation for IPv6
Data Centre Environments", draft-ietf-v6ops-siit-dc-00
(work in progress), December 2014.
[I-D.previdi-6man-segment-routing-header]
Previdi, S., Filsfils, C., Field, B., and I. Leung, "IPv6
Segment Routing Header (SRH)", draft-previdi-6man-segment-
routing-header-04 (work in progress), November 2014.
[Microsoft-Azure]
Sverdlik, Y., "Report: Microsoft Buys 100 Acres of Iowa
land for Data Center http://www.datacenterknowledge.com/
archives/2014/08/01/
report-microsoft-buys-100-acres-iowa-land-data-center/",
August 2014.
[RFC1918] Rekhter, Y., Moskowitz, R., Karrenberg, D., Groot, G., and
E. Lear, "Address Allocation for Private Internets", BCP
5, RFC 1918, February 1996.
[RFC1981] McCann, J., Deering, S., and J. Mogul, "Path MTU Discovery
for IP version 6", RFC 1981, August 1996.
[RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S.
Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1
Functional Specification", RFC 2205, September 1997.
[RFC2391] Srisuresh, P. and D. Gan, "Load Sharing using IP Network
Address Translation (LSNAT)", RFC 2391, August 1998.
Baker, et al. Expires August 12, 2015 [Page 21]
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[RFC2710] Deering, S., Fenner, W., and B. Haberman, "Multicast
Listener Discovery (MLD) for IPv6", RFC 2710, October
1999.
[RFC2827] Ferguson, P. and D. Senie, "Network Ingress Filtering:
Defeating Denial of Service Attacks which employ IP Source
Address Spoofing", BCP 38, RFC 2827, May 2000.
[RFC2923] Lahey, K., "TCP Problems with Path MTU Discovery", RFC
2923, September 2000.
[RFC3439] Bush, R. and D. Meyer, "Some Internet Architectural
Guidelines and Philosophy", RFC 3439, December 2002.
[RFC3697] Rajahalme, J., Conta, A., Carpenter, B., and S. Deering,
"IPv6 Flow Label Specification", RFC 3697, March 2004.
[RFC4192] Baker, F., Lear, E., and R. Droms, "Procedures for
Renumbering an IPv6 Network without a Flag Day", RFC 4192,
September 2005.
[RFC4193] Hinden, R. and B. Haberman, "Unique Local IPv6 Unicast
Addresses", RFC 4193, October 2005.
[RFC4291] Hinden, R. and S. Deering, "IP Version 6 Addressing
Architecture", RFC 4291, February 2006.
[RFC4443] Conta, A., Deering, S., and M. Gupta, "Internet Control
Message Protocol (ICMPv6) for the Internet Protocol
Version 6 (IPv6) Specification", RFC 4443, March 2006.
[RFC4601] Fenner, B., Handley, M., Holbrook, H., and I. Kouvelas,
"Protocol Independent Multicast - Sparse Mode (PIM-SM):
Protocol Specification (Revised)", RFC 4601, August 2006.
[RFC4602] Pusateri, T., "Protocol Independent Multicast - Sparse
Mode (PIM-SM) IETF Proposed Standard Requirements
Analysis", RFC 4602, August 2006.
[RFC4604] Holbrook, H., Cain, B., and B. Haberman, "Using Internet
Group Management Protocol Version 3 (IGMPv3) and Multicast
Listener Discovery Protocol Version 2 (MLDv2) for Source-
Specific Multicast", RFC 4604, August 2006.
[RFC4605] Fenner, B., He, H., Haberman, B., and H. Sandick,
"Internet Group Management Protocol (IGMP) / Multicast
Listener Discovery (MLD)-Based Multicast Forwarding ("IGMP
/MLD Proxying")", RFC 4605, August 2006.
Baker, et al. Expires August 12, 2015 [Page 22]
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[RFC4607] Holbrook, H. and B. Cain, "Source-Specific Multicast for
IP", RFC 4607, August 2006.
[RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman,
"Neighbor Discovery for IP version 6 (IPv6)", RFC 4861,
September 2007.
[RFC4862] Thomson, S., Narten, T., and T. Jinmei, "IPv6 Stateless
Address Autoconfiguration", RFC 4862, September 2007.
[RFC4941] Narten, T., Draves, R., and S. Krishnan, "Privacy
Extensions for Stateless Address Autoconfiguration in
IPv6", RFC 4941, September 2007.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120, February 2008.
[RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, October
2008.
[RFC5340] Coltun, R., Ferguson, D., Moy, J., and A. Lindem, "OSPF
for IPv6", RFC 5340, July 2008.
[RFC5548] Dohler, M., Watteyne, T., Winter, T., and D. Barthel,
"Routing Requirements for Urban Low-Power and Lossy
Networks", RFC 5548, May 2009.
[RFC5673] Pister, K., Thubert, P., Dwars, S., and T. Phinney,
"Industrial Routing Requirements in Low-Power and Lossy
Networks", RFC 5673, October 2009.
[RFC6052] Bao, C., Huitema, C., Bagnulo, M., Boucadair, M., and X.
Li, "IPv6 Addressing of IPv4/IPv6 Translators", RFC 6052,
October 2010.
[RFC6144] Baker, F., Li, X., Bao, C., and K. Yin, "Framework for
IPv4/IPv6 Translation", RFC 6144, April 2011.
[RFC6145] Li, X., Bao, C., and F. Baker, "IP/ICMP Translation
Algorithm", RFC 6145, April 2011.
[RFC6146] Bagnulo, M., Matthews, P., and I. van Beijnum, "Stateful
NAT64: Network Address and Protocol Translation from IPv6
Clients to IPv4 Servers", RFC 6146, April 2011.
Baker, et al. Expires August 12, 2015 [Page 23]
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[RFC6147] Bagnulo, M., Sullivan, A., Matthews, P., and I. van
Beijnum, "DNS64: DNS Extensions for Network Address
Translation from IPv6 Clients to IPv4 Servers", RFC 6147,
April 2011.
[RFC6437] Amante, S., Carpenter, B., Jiang, S., and J. Rajahalme,
"IPv6 Flow Label Specification", RFC 6437, November 2011.
[RFC6620] Nordmark, E., Bagnulo, M., and E. Levy-Abegnoli, "FCFS
SAVI: First-Come, First-Served Source Address Validation
Improvement for Locally Assigned IPv6 Addresses", RFC
6620, May 2012.
[RFC7217] Gont, F., "A Method for Generating Semantically Opaque
Interface Identifiers with IPv6 Stateless Address
Autoconfiguration (SLAAC)", RFC 7217, April 2014.
[RFC7219] Bagnulo, M. and A. Garcia-Martinez, "SEcure Neighbor
Discovery (SEND) Source Address Validation Improvement
(SAVI)", RFC 7219, May 2014.
[RFC7348] Mahalingam, M., Dutt, D., Duda, K., Agarwal, P., Kreeger,
L., Sridhar, T., Bursell, M., and C. Wright, "Virtual
eXtensible Local Area Network (VXLAN): A Framework for
Overlaying Virtualized Layer 2 Networks over Layer 3
Networks", RFC 7348, August 2014.
[UCC] Jeuk, S., Szefer, J., and S. Zhou, "Towards Cloud, Service
and Tenant Classification for Cloud Computing", IEEE
Xplore Digital Library: Cluster, Cloud and Grid Computing
(CCGrid), 2014 14th IEEE/ACM International Symposium, May
2014.
Appendix A. Change Log
Initial Version: October 2014
First update: January 2015
Appendix B. Alternative Labels considered
B.1. IPv6 Flow Label
The IPv6 flow label may be used to identify a tenant or part of a
tenant, and to facilitate access control based on the flow label
value. The flow label is a flat 20 bits, facilitating the
designation of 2^20 (1,048,576) tenants without regard to their
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location. 1,048,576 is less than infinity, but compared to current
data centers is large, and much simpler to manage.
Note that this usage differs from the current IPv6 Flow Label
Specification [RFC6437]. It also differs from the use of a flow
label recommended by the IPv6 Specification [RFC2460], and the
respective usages of the flow label in the Resource ReSerVation
Protocol [RFC2205] and the previous IPv6 Flow Label Specification
[RFC3697], and the projected usage in Low-Power and Lossy Networks
[RFC5548][RFC5673]. Within a target domain, the usage may be
specified by the domain. That is the viewpoint taken in this
specification.
B.1.1. Metaconsiderations
B.1.1.1. Service offered
To Be Supplied
B.1.1.2. Pros and Cons
B.1.1.2.1. The case in favor of this approach
To Be Supplied
B.1.1.2.2. The case against
To Be Supplied
B.1.1.3. Filtering considerations
To Be Supplied
B.2. Federated Identity
B.2.1. Introduction
In the course of developing draft-baker-ipv6-openstack-model, it was
determined that a way was needed to encode a federated identity for
use in Role-Based Access Control. This appendix describes an IPv6
[RFC2460] option that could be carried in the Hop-by-Hop or
Destination Options Header. The format of an option is defined in
section 4.2 of that document, and the Hop-by-Hop and Destination
Options are defined in sections 4.3 and 4.6 of that document
respectively.
A 'Federated Identity', in the words of the Wikipedia, 'is the means
of linking an electronic identity and attributes, stored across
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multiple distinct identity management systems.' In this context, it
is a fairly weak form of that; it is intended for quick
interpretation in an access list at the Internet layer as opposed to
deep analysis for login or other security purposes at the application
layer, and rather than identifying an individual or a system, it
identifies a set of systems whose members are authorized to
communicate freely among themselves and may also be authorized to
communicate with other identified sets of systems. Either two
systems are authorized to communicate or they are not, and
unauthorized traffic can be summarily discarded. The identifier is
defined in a hierarchical fashion, for flexibility and scalability.
'Role-Based Access Control', in this context, applies to groups of
virtual or physical hosts, not individuals. In the simplest case,
the several tenants of a multi-tenant data center might be
identified, and authorized to communicate only with other systems
within the same 'tenant' or with identified systems in other tenants
that manage external access. One could imagine a company purchasing
cloud services from multiple data center operators, and as a result
wanting to identify the systems in its tenant in one cloud service as
being authorized to communicate with the systems its tenant of the
other. One could further imagine a given department within that
company being authorized to speak only with itself and an identified
set of other departments within the same company. To that end, when
a datagram is sent, it is tagged with the federated identify of the
sender (e.g., {datacenter, client, department}), and the receiving
system filters traffic it receives to limit itself to a specific set
of authorized communicants.
B.2.2. Federated identity Option
The option is defined as a sequence of numbers that identify relevant
parties hierarchically. The specific semantics (as in, what number
identifies what party) are beyond the scope of this specification,
but they may be interpreted as being successively more specific; as
shown in Figure 3, the first might identify a cloud operator, the
second, if present, might identify a client of that operator, and the
third, if present, might identify a subset of that client's systems.
In an application entirely used by Company A, there might be only one
number, and it would identify sets of systems important to Company A
such as business units. If Company A uses the services of a multi-
tenant data center #1, it might require that there be two numbers,
identifying Company A and its internal structure. If Company A uses
the services of both multi-tenant data centers #1 and #2, and they
are federated, the identifier might need to identify the data center,
the client, and the structure of the client.
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_.----------------------.
_.----'' `------.
,--'' `---.
,-' DataCenter .---------------------. `-.
,' Company #2,---'' Unauthorized `----. `.
; ,' ,-----+-----. ,--+--------.`. :
| ( ( Department 1)--//--( Department 2) ) |
; `. `-----+----+' `-----------',' |
`. `----. | X Company A _.---' ,'
'-. A|------X------------'' ,-'
`---. u| X _.--'
`------. t| X _.----''
`---h|---------X-------''
o| X
_.--r+-----------X------.
_.----'' i| X `------.
,--'' z| X `---.
,-' DataCenter e|--------------X-----. `-.
,' Company #2,---''d| X `----. `.
; ,' ,-----+-----. ,-+---------.`. :
| ( ( Department 1) ( Department 2) ) |
; `. `-----------' `-----------',' |
`. `----. Company A _.---' ,'
'-. `--------------------'' ,-'
`---. _.--'
`------. _.----''
`----------------------''
Figure 3: Use case: Identifying authorized communicatants in an RBAC
environment
B.2.2.1. Option Format
A number (Figure 4) is represented as a base 128 number whose
coefficients are stored in the lower 7 bits of a string of bytes.
The upper bit of each byte is zero, except in the final byte, in
which case it is 1. The most significant coefficient of a non-zero
number is never zero.
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8 = 8*128^0
+-+------+
|1| 8 |
+-+------+
987 = 7*128^1 + 91*128^0
+-+------+-+------+
|0| 7 |1| 91 |
+-+------+-+------+
121393 = 7*128^2 + 52*128^1 + 49*128^0
+-+------+-+------+-+------+
|0| 7 |0| 52 |1| 49 |
+-+------+-+------+-+------+
Figure 4: Sample numbers
The identifier {8, 987, 121393} looks like
+-------+-------+-+-----+-+-----+-+-----+-+-----+-+-----+-+-----+
| type | len=6 |1| 8 |0| 7 |1| 91 |0| 7 |0| 52 |1| 49 |
+-------+-------+-+-----+-+-----+-+-----+-+-----+-+-----+-+-----+
Figure 5
B.2.2.1.1. Use in the Destination Options Header
In an environment in which the validation of the option only occurs
in the receiving system or its hypervisor, this option is best placed
in the Destination Options Header.
B.2.2.1.2. Use in the Hop-by-Hop Header
In an environment in which the validation of the option occurs in
transit, such as in a firewall or other router, this option is best
placed in the Hop-by-Hop Header.
B.2.3. Metaconsiderations
B.2.3.1. Service offered
To Be Supplied
B.2.3.2. Pros and Cons
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B.2.3.2.1. The case in favor of this approach
To Be Supplied
B.2.3.2.2. The case against
To Be Supplied
B.2.3.3. Filtering considerations
To Be Supplied
B.3. Universal Cloud Classification
B.3.1. Introduction
Cloud environments suffer from ambiguity in identifying their
services and tenants. Traffic from different cloud providers cannot
be distinguished easily on the Internet. Filters are simply not able
to obtain the provider, service and tenant identities from network
packets without leveraging other more latency intense inspection
methods. This appendix describes the Universal Cloud Classification
(UCC) [UCC] approach as a way to identify cloud providers, their
services and tenants on the network layer. It introduces a Cloud-ID,
Service-ID and Tenant-ID. The IDs are incorporated into an IPv6
extension header and can be used for different use-cases both within
and outside a Cloud Environment. The format of the IDs and their
characteristics are defined in Appendix B.3.2 of the document and the
extension header is defined in Appendix B.3.3.
Applications and users are defined in many different ways in cloud
environments, therefore ambiguity is multifold:
1. The first ambiguity is described by how a service is defined in
cloud environments. Here, an application within a Cloud Provider
is called a service. However, the cloud providers network can
not distinguish services from services run on top of other
services. Distinguishing sub-services hosted by a service
becomes critical when applying network services to specific sub-
services.
2. Secondly, a tenant in a cloud provider can have different
meanings. Here, tenant is used to define a consumer of a cloud
service. At the same time a service run on top of another
service can be considered a tenant of that particular service.
These ambiguities make it extremely difficult to uniquely
identify services and their tenants in cloud environments. This
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multi-layered service and tenant relationship is one of the most
complex tasks to handle using existing technologies.
A service can be defined as a group of entities offering a specific
function to a tenant within a Cloud Provider.
B.3.2. Universal Cloud Classification Options
Three IDs are defined that classify a Tenant specific to the service
used within a certain Cloud Provider. The Cloud-ID, Service-ID and
Tenant-ID are defined hierarchically and support service-stacking.
The IDs are based on the 'Digital Object Identifier' scheme and
support incorporating metadata per ID. The ID can be of variable
length but Cloud-ID, Service-ID and Tenant-ID are proposed within a 4
byte, 6 byte and 6 byte tuple respectively.
B.3.2.1. Cloud ID
The Cloud ID is a globally unique ID that is managed by a registrar
similar to DNS. It is 4 bytes in sizes and defined with a 10 bit
location part and a 22 bit provider ID.
B.3.2.2. Service ID
The Service ID is used to identify a service both within and outside
a cloud environment. It is a 6 byte long ID that is separated into
several sub-IDs defining the data center, service and an option
field. The Data Center location is defined by 8 bits, the Service is
32 bits long and the Option field provides another 8 bits. The
option bits can be used to incorporate information used for en-route
or destination tasks.
B.3.2.3. Tenant ID
The Tenant-ID is classifying consumers (tenants) of Cloud Services.
It is a 6 byte long ID that is defined and managed by the Cloud
Provider. Similar to the Service-ID the Tenant-ID incorporates
metadata specific to that tenant. The MetaData field is of variable
length and can be defined by the Cloud Provider as needed.
B.3.3. UCC Extension Header
The UCC proposal [UCC] defines an IPv6 hop-by-hop extension header to
incorporate the Cloud-ID, Service-ID and Tenant-ID. Each ID area
also includes bits to define enroute behavior for devices
understanding/not-understanding the newly defined hop-by-hop
extension header. This is useful for legacy devices on the Internet
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to avoid drops the packet but forward it without processing the added
IPv6 extension header.
0 8 16 24 32 40 48 56 64
+-------+-------+-------+-------+-------+-------+-------+-------+
| FLAG | SIZE | CLOUD-ID | FLAG | SIZE |
+-------+-------+-------+-------+-------+-------+-------+-------+
| SERVICE-ID | FLAG | SIZE |
+-------+-------+-------+-------+-------+-------+-------+-------+
| TENANT-ID |
+-------+-------+-------+-------+-------+-------+
Figure 6: UCC IPv6 hop-by-hop extension header
The overall extension header size is 22 bytes.
B.4. Policy List in Segment Routing Header
The model here suggests using the Policy List described in the IPv6
Segment Routing Header [I-D.previdi-6man-segment-routing-header].
Technically, it would violate that specification, as the Policy List
is described as containing a set of optional addresses representing
specific nodes in the SR path, where in this case it would be a 128
bit number identifying the tenant or other set of communicating
nodes.
B.4.1. Metaconsiderations
B.4.1.1. Service offered
To Be Supplied
B.4.1.2. Pros and Cons
B.4.1.2.1. The case in favor of this approach
To Be Supplied
B.4.1.2.2. The case against
To Be Supplied
B.4.1.3. Filtering considerations
To Be Supplied
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B.5. RFC 4291 Interface Identifier (IID)
The approach starts from the observation that Openstack assigns the
MAC address used by a VM, and can assign it according to any
algorithm it chooses. A desire has been expressed to put the tenant
identifier into the IPv6 address. This would put it into the IID in
that address without modifying the VM OS or the virtual switch.
B.5.1. Address Format
The proposed address format is identical to the IPv6 EUI-48 based
Address [RFC4291], and is derived from the MAC address space
specified in SLAAC [RFC4862]. However, the MAC address provided by
the OpenStack Controller differs from an IEEE 802.3 MAC Address.
Walking through the details, an IEEE 802.3 MAC Address (Figure 7)
consists of two single bit fields, a 22 bit Organizationally Unique
Identifier (OUI), and a serial number or other NIC-specific
identifier. The intention is to create a globally unique address, so
that the NIC may be used on any LAN in the world without colliding
with other addresses.
0 8 16 24 32 40
+-------+-------+-------+-------+-------+-------+
|Organizationally Unique| NIC Specific Number |
| Identifier (OUI) | |
+-------+-------+-------+-------+-------+-------+
AA
|+--- 0=Unicast/1=Multicast
+---- 1=Local/0=Global
Figure 7: Ethernet MAC Address as specified by IEEE 802.3
[RFC4291] describes a transformation from that address (which it
refers to as an EUI-48 address) to the IID of an IPv6 Address
(Figure 8).
0 8 16 24 32 40 48 56
+-------+-------+-------+-------+-------+-------+-------+-------+
|Organizationally Unique| Fixed Value | NIC Specific Number |
| Identifier (OUI) | | |
+-------+-------+-------+-------+-------+-------+-------+-------+
AA
|+--- Reserved
+---- 0=Local/1=Global
Figure 8: RFC 4291 IPv6 Address
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OpenStack today specifies a local IEEE 802.3 address (bit 6 is one).
IPv6 addresses are either installed using DHCP or derived from the
MAC address via SLAAC.
One could imagine the MAC address used in an OpenStack environment
including both a tenant identifier and a system number on a LAN. If
the tenant identifier is 24 bits (it could be longer or shorter, but
for this document it is treated as 24 bits), as in common in VxLAN
and QinQ implementations, that would allow for a 22 bit system
number, plus two magic bits specifying a locally defined unicast
address, as shown in Figure 9. Alternatively, the first byte could
be some specified values such as 0xFA (as is common with current
OpenStack implementations), followed by a 16 bit system number within
the subnet.
0 8 16 24 32 40 47
+-------+-------+-------+-------+-------+-------+
|System Number within | Openstack Tenant |
| LAN | Identifier |
+-------+-------+-------+-------+-------+-------+
AA
|+--- 0=Unicast/1=Multicast
+---- 1=Local/0=Global
Figure 9: Ethernet MAC Address as installed by OpenStack
After being passed through SLAAC, that results in an IID that
contains the Tenant ID in bits 48..63, has bit 6 zero as a locally-
specified unicast address, and a 22 bit system number, as in
Figure 10.
0 8 16 24 32 40 48 56 63
+-------+-------+-------+-------+-------+-------+-------+-------+
|system number within | Fixed Value | 24 bit OpenStack |
| LAN | | Tenant Identifier |
+-------+-------+-------+-------+-------+-------+-------+-------+
AA
|+--- Reserved
+---- 0=Local/1=Global
Figure 10: RFC 4291 IPv6 IID Derived from OpenStack MAC Address
More generally, if SLAAC is not in use and addresses are conveyed
using DHCPv6 or another technology, the IID would be as described in
Figure 11.
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0 8 16 24 32 40 48 56 63
+-------+-------+-------+-------+-------+-------+-------+-------+
| system number within LAN | 24 bit OpenStack |
| | Tenant Identifier |
+-------+-------+-------+-------+-------+-------+-------+-------+
AA
|+--- Reserved
+---- 0=Local/1=Global
Figure 11: Generalized Tenant IID
As noted, the Tenant Identifier might be longer or shorter in a given
implementation. Specifically in Figure 11, a 32 bit Tenant ID would
occupy bit positions 32..63, and a 16 bit Tenant ID would occupy
positions 48..63.
Following the same model, IPv6 Multicast Addresses can be associated
with a tenant identifier by placing the tenant identifier in the same
set of bits and using the remaining bits of the Multicast Group ID as
the ID within the tenant as show in Figure 12. Flags and scope are
as specified in [RFC4291] section 2.7. To avoid clashes with
multicast addresses specified in ibid 2.7.1 and future allocations,
The Tenant Group ID MUST NOT be zero.
| 8 | 4 | 4 | 88 bits 24 bits |
+------ -+----+----+-----------------------------+---------------+
|11111111|flgs|scop| Tenant Group ID | Tenant ID |
+--------+----+----+-----------------------------+---------------+
Figure 12: RFC 4291 Multicast Address with Tenant ID
B.5.2. Metaconsiderations
B.5.2.1. Service offered
The fundamental seervice offered in this model is that the key policy
parameter, the Tenant ID, is encoded in every datagram for both
sender and receiver, and can therefore be tested by sender, receiver,
or any other party. It is secure in the sense that it cannot be
directly spoofed; in the sender vSwitch, the vSwitch prevents the
sender from sending another address as discussed in Section 4, and if
the recipient address is a randomly chosen address, even if it meets
inter-tenant communication policy, there is unlikely to be a matching
destination to deliver it to. Where this breaks down is if a valid
and acceptable destination is discovered and used; that is the
argument for further protection via TLS.
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B.5.2.2. Pros and Cons
B.5.2.2.1. The case in favor of this approach
The case in favor of this approach consists of several observations:
o Many Cisco customers are using and prefer SLAAC for IPv6 clients
in OpenStack environments.
o It is easy to configure this IID from the Neutron Controller
without modifying the VM, or it even knowing it happened.
o From a security perspective, the tenant ID cannot be spoofed per
se; the sender of a message is not permitted to send a message
from the wrong address or to an unauthorized address.
o Since it requires no extension headers or other encapsulations, it
has no impact on Path MTU.
o Filters can be applied anywhere, and notably at the sender and the
receiver of a message.
B.5.2.2.2. The case against
In [I-D.ietf-6man-default-iids], the IETF is moving toward
deprecating [RFC4291]'s Modified EUI-64 IID.
B.5.2.3. Filtering considerations
In this model, the vSwitch needs, for each VM it manages, two access
control lists:
o Zero or more {IPv6 prefix, tenant ID} pairs; these may be read as
'if the IPv6 prefix matches {prefix}, the IID contains a tenant
ID, and it may be {tenant ID}.'
o Zero or more IPv6 prefixes that the VM is authorized to
communicate without regard to tenant ID.
Generally speaking, one would expect at least one of those three
lists to contain an entry - at minimum, the VM would be authorized to
communicate with ::/0, which is to say 'anyone'.
Among the generic IPv6 prefixes that may be communicated with, there
may be zero or more IPv4-embedded IPv6 prefix [RFC6052] prefixes that
the VM is permitted to communicate with. For example, if the
[I-D.ietf-v6ops-siit-dc] translation prefix is 2001:db8:0:1::/96, and
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the enterprise is using 192.0.2.0/24 as its IPv4 address, the filter
would contain the prefix 2001:db8:0:1:0:0:c000:0200/120.
Note that the lists may also include multicast prefixes as specified
in Appendix B.5.1, such as locally-scoped multicast ff01::/104 or
locally-scoped multicast within the tenant {ff01::/16, tenant id} .
While these access lists are applied in both directions (as a sender,
what prefixes may the destination address contain, and as a receiver,
what prefixes may the source address contain), only the destination
address may contain multicast addresses. For multicast, therefore,
the vSwitch should filter Multicast Listener Discovery [RFC2710]
using the multicast subset, permitting the VM to only join relevant
multicast groups.
B.6. Modified IID using modified Privacy Extension
This variant reflects and builds on the IPv6 Addressing Architecture
[RFC4291] Stateless Address Autoconfiguration [RFC4862], and the
associated Privacy Extensions [RFC4941]. The address format is
identical to that of Appendix B.5, with the exception that The
'System Number within the LAN' is a random number determined by the
host rather than being specified by the controller.
It does have implications, however. It will require
o a modification to [RFC4941] to have the host include the Tenant ID
in the IID,
o a means to inform the host of the Tenant ID,
o a means to inform the vSwitch of the Tenant ID,
o a the vSwitch to follow FCFS SAVI [RFC6620] to learn the addresses
being used by the host, and
o a filter to prevent FCFS SAVI from learning addresses that have
the wrong Tenant ID.
B.6.1. Metaconsiderations
B.6.1.1. Service offered
To Be Supplied
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B.6.1.2. Pros and Cons
B.6.1.2.1. The case in favor of this approach
To Be Supplied
B.6.1.2.2. The case against
To Be Supplied
B.6.1.3. Filtering considerations
To Be Supplied
Authors' Addresses
Fred Baker (editor)
Cisco Systems
Santa Barbara, California 93117
USA
Email: fred@cisco.com
Chris Marino
Cisco Systems
San Jose, California 95134
USA
Email: chrmarin@cisco.com
Ian Wells
Cisco Systems
San Jose, California 95134
USA
Email: iawells@cisco.com
Rohit Agarwalla
Cisco Systems
San Jose, California 95134
USA
Email: roagarwa@cisco.com
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Sebastian Jeuk
Cisco Systems
San Jose, California 95134
USA
Email: sjeuk@cisco.com
Gonzalo Salgueiro
Cisco Systems
Research Triangle Park, NC 27709
US
Email: gsalguei@cisco.com
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