Internet Engineering Task Force Nabil Bitar
Internet Draft Verizon
Intended status: Informational
Expires: December 2012 Marc Lasserre
Florin Balus
Alcatel-Lucent
Thomas Morin
France Telecom Orange
June 26, 2012
NVO3 Data Plane Requirements
draft-bl-nvo3-dataplane-requirements-01.txt
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), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
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."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html
This Internet-Draft will expire on December 26, 2012.
Copyright Notice
Copyright (c) 2012 IETF Trust and the persons identified as the
document authors. All rights reserved.
Lasserre, et al. Expires December 26, 2012 [Page 1]
Internet-Draft NVO3 Data Plane Requirements June 2012
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with
respect to this document.
Abstract
Several IETF drafts relate to the use of overlay networks to support
large scale virtual data centers. This draft provides a list of data
plane requirements for Network Virtualization over L3 (NVO3) that
have to be addressed in solutions documents.
Table of Contents
1. Introduction...................................................3
1.1. Conventions used in this document.........................3
1.2. General terminology.......................................3
2. Data Path Overview.............................................4
3. Data Plane Requirements........................................5
3.1. Virtual Access Points (VAPs)..............................5
3.2. Virtual Network Instance (VNI)............................5
3.2.1. L2 VNI..................................................6
3.2.2. L3 VNI..................................................6
3.3. Overlay Module............................................7
3.3.1. NVO3 overlay header.....................................7
3.3.1.1. Virtual Network Context Identification................7
3.3.1.2. Service QoS identifier................................8
3.3.2. NVE Tunneling function..................................9
3.3.2.1. LAG and ECMP..........................................9
3.3.2.2. DiffServ and ECN marking.............................10
3.3.2.3. Handling of BUM traffic..............................10
3.4. External NVO3 connectivity...............................11
3.4.1. GW Types...............................................11
3.4.1.1. VPN and Internet GWs.................................11
3.4.1.2. Inter-DC GW..........................................11
3.4.1.3. Intra-DC gateways....................................12
3.4.2. Path optimality between NVEs and Gateways..............12
3.4.2.1. Triangular Routing Issues,a.k.a.: Traffic Tromboning.13
3.5. Path MTU.................................................14
3.6. Hierarchical NVE.........................................14
Lasserre, et al. Expires December 26, 2012 [Page 2]
Internet-Draft NVO3 Data Plane Requirements June 2012
3.7. NVE Multi-Homing Requirements............................14
3.8. OAM......................................................15
3.9. Other considerations.....................................15
3.9.1. Data Plane Optimizations...............................15
3.9.2. NVE location trade-offs................................16
4. Security Considerations.......................................16
5. IANA Considerations...........................................17
6. References....................................................17
6.1. Normative References.....................................17
6.2. Informative References...................................17
7. Acknowledgments...............................................18
1. Introduction
1.1. Conventions used in this document
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 RFC-2119 [RFC2119].
In this document, these words will appear with that interpretation
only when in ALL CAPS. Lower case uses of these words are not to be
interpreted as carrying RFC-2119 significance.
1.2. General terminology
The terminology defined in [NVO3-framework] is used throughout this
document. Terminology specific to this memo is defined here and is
introduced as needed in later sections.
DC: Data Center
BUM: Broadcast, Unknown Unicast, Multicast traffic
TES: Tenant End System
VAP: Virtual Access Point
VNI: Virtual Network Instance
VNID: VNI ID
Lasserre, et al. Expires December 26, 2012 [Page 3]
Internet-Draft NVO3 Data Plane Requirements June 2012
2. Data Path Overview
The NVO3 framework [NVO3-framework] defines the generic NVE model
depicted in Figure 1:
+------- L3 Network ------+
| |
| Tunnel Overlay |
+------------+---------+ +---------+------------+
| +----------+-------+ | | +---------+--------+ |
| | Overlay Module | | | | Overlay Module | |
| +---------+--------+ | | +---------+--------+ |
| |VN context| | VN context| |
| | | | | |
| +-------+--------+ | | +--------+-------+ |
| | |VNI| ... |VNI| | | | |VNI| ... |VNI| |
NVE1 | +-+------------+-+ | | +-+-----------+--+ | NVE2
| | VAPs | | | | VAPs | |
+----+------------+----+ +----+------------+----+
| | | |
-------+------------+-----------------+------------+-------
| | Tenant | |
| | Service IF | |
Tenant End Systems Tenant End Systems
Figure 1 : Generic reference model for NV Edge
When a frame is received by an ingress NVE from a Tenant End System
over a local VAP, it needs to be parsed in order to identify which
virtual network instance it belongs to. The parsing function can
examine various fields in the data frame (e.g., VLANID) and/or
associated interface/port the frame came from.
Once a corresponding VNI is identified, a lookup is performed to
determine where the frame needs to be sent. This lookup can be based
on any combinations of various fields in the data frame (e.g.,
destination MAC addresses and/or destination IP addresses). Note
that additional criteria such as 802.1p and/or DSCP markings might
be used to select an appropriate tunnel or local VAP destination.
Lasserre, et al. Expires December 26, 2012 [Page 4]
Internet-Draft NVO3 Data Plane Requirements June 2012
Lookup tables can be populated using different techniques: data
plane learning, management plane configuration, or a distributed
control plane. Management and control planes are not in the scope of
this document. The data plane based solution is described in this
document as it has implications on the data plane processing
function.
The result of this lookup yields the corresponding tunnel
information needed to build the overlay encapsulation header. This
information includes the destination L3 address of the egress NVE.
Note that this lookup might yield a list of tunnels such as when
ingress replication is used for BUM traffic.
The overlay tunnel encapsulation header MUST include a context
identifier which the egress NVE will use to identify which VNI this
frame belongs to.
The egress NVE checks the context identifier and removes the
encapsulation header and then forwards the original frame towards
the appropriate recipient, usually a local VAP.
3. Data Plane Requirements
3.1. Virtual Access Points (VAPs)
The NVE forwarding plane MUST support VAP identification through the
following mechanisms:
- Using the local interface on which the frames are received, where
the local interface may be an internal, virtual port in a VSwitch
or a physical port on the ToR
- Using the local interface and some fields in the frame header,
e.g. one or multiple VLANs or the source MAC
3.2. Virtual Network Instance (VNI)
VAPs are associated with a specific VNI at service instantiation
time.
A VNI identifies a per-tenant private context, i.e. per-tenant
policies and a FIB table to allow overlapping address space between
tenants.
There are different VNI types differentiated by the virtual network
service they provide to Tenant End Systems. Network virtualization
can be provided by L2 and/or L3 VNIs.
Lasserre, et al. Expires December 26, 2012 [Page 5]
Internet-Draft NVO3 Data Plane Requirements June 2012
3.2.1. L2 VNI
An L2 VNI MUST provide an emulated Ethernet multipoint service as if
Tenant End Systems are interconnected by an 802.1Q LAN over a set of
NVO3 tunnels. An L2 VNI provides per tenant virtual switching
instance with MAC addressing isolation and L3 tunneling. Loop
avoidance capability MUST be provided.
In the absence of a management or control plane, data plane learning
MUST be used to populate forwarding tables. Forwarding table entries
provide mapping information between MAC addresses and L3 tunnel
destination addresses. As frames arrive from VAPs or from overlay
tunnels, the MAC learning procedures described in IEEE 802.1Q are
used: The source MAC address is learned against the VAP or the NVO3
tunnel on which the frame arrived.
Broadcast, Unknown Unicast and Multicast (BUM) traffic handling MUST
be supported. To achieve this, the NVE MUST support ingress
replication and MAY support multicast over an overlay multicast
tree. In this latter case, the NVE must be able to build at least a
default flooding tree per VNI. The flooding tree is equivalent with
a multicast (*,G) construct where all the NVEs for which the
corresponding VNI is instantiated are members. The multicast tree
MAY be established automatically via routing and signaling or pre-
provisioned
When multicast is supported, it SHOULD also be possible to select
whether the NVE provides optimized multicast trees inside the VNI
for individual tenant multicast groups or whether the default VNI
flooding tree is used. If the former option is selected the VNI
SHOULD be able to snoop IGMP/MLD messages in order to efficiently
join/prune Tenant End System from multicast trees.
3.2.2. L3 VNI
L3 VNIs MUST provide virtualized IP routing and forwarding. L3 VNIs
MUST support per-tenant forwarding instance with IP addressing
isolation and L3 tunneling for interconnecting instances of the same
VNI on NVEs.
In the case of L3 VNI, the inner TTL field MUST be decremented by
(at least) 1 as if the NVO3 egress NVE was one (or more) hop(s)
away. The TTL field in the outer IP header must be set to a value
appropriate for delivery of the encapsulated frame to the tunnel
exit point. Thus, the default behavior must be the TTL pipe model
where the overlay network looks like one hop to the sending NVE.
Lasserre, et al. Expires December 26, 2012 [Page 6]
Internet-Draft NVO3 Data Plane Requirements June 2012
Configuration of a "uniform" TTL model where the outer tunnel TTL is
set equal to the inner TTL on ingress NVE and the inner TTL is set
to the outer TTL value on egress MAY be supported.
L2 and L3 VNIs can be deployed in isolation or in combination to
optimize traffic flows per tenant across the overlay network. For
example, an L2 VNI may be configured across a number of NVEs to
offer L2 multi-point service connectivity while a L3 VNI can be co-
located to offer local routing capabilities and gateway
functionality. In addition, integrated routing and bridging per
tenant MAY be supported on an NVE. An instantiation of such service
may be realized by interconnecting an L2 VNI as access to an L3 VNI
on the NVE.
The L3 VNI does not require support for Broadcast and Unknown
Unicast traffic. The L3 VNI MAY provide support for customer
multicast groups. This paragraph will be expanded in a future
version of the draft.
3.3. Overlay Module
The overlay module performs a number of functions related to NVO3
header and tunnel processing. Specifically for a L2 VNI it provides
the capability to encapsulate and send Ethernet traffic over NVO3
tunnels. For a L3 VNI it provides the capability to encapsulate and
carry IP traffic (both IPv4 and IPv6) over NVO3 tunnels.
3.3.1. NVO3 overlay header
An NVO3 overlay header MUST be included after the tunnel
encapsulation header when forwarding tenant traffic. This section
describes the fields that need to be included as part of the NOV3
overlay header. In this version the focus is on the VN instance and
service QoS fields. Future versions may include additional fields.
3.3.1.1. Virtual Network Context Identification
The overlay encapsulation header MUST contain a field which allows
the encapsulated frame to be delivered to the appropriate virtual
network endpoint by the egress NVE. The egress NVE uses this field
to determine the appropriate virtual network context in which to
process the packet. This field MAY be an explicit, unique (to the
administrative domain) virtual network identifier (VNID) or MAY
express the necessary context information in other ways (e.g. a
locally significant identifier).
Lasserre, et al. Expires December 26, 2012 [Page 7]
Internet-Draft NVO3 Data Plane Requirements June 2012
It SHOULD be aligned on a 32-bit boundary so as to make it
efficiently processable by the data path. It MUST be distributable
by a control-plane or configured via a management plane.
In the case of a global identifier, this field MUST be large enough
to scale to 100's of thousands of virtual networks. Note that there
is no such constraint when using a local identifier.
3.3.1.2. Service QoS identifier
Traffic flows originating from different applications could rely on
differentiated forwarding treatment to meet end-to-end availability
and performance objectives. Such applications may span across one or
more overlay networks. To enable such treatment, support for
multiple Classes of Service across or between overlay networks is
required.
To effectively enforce CoS across or between overlay networks, NVEs
should be able to map CoS markings between networking layers, e.g.,
Tenant End Systems, Overlays, and/or Underlay, enabling each
networking layer to independently enforce its own CoS policies. For
example:
- TES (e.g. VM) CoS
o Tenant CoS policies MAY be defined by Tenant administrators
o QoS fields (e.g. IP DSCP and/or Ethernet 802.1p) in the
tenant frame are used to indicate application level CoS
requirements
- NVE CoS
o NVE MAY classify packets based on Tenant CoS markings or
other mechanisms (eg. DPI) to identify the proper service CoS
to be applied across the overlay network
o NVE service CoS levels are normalized to a common set (for
example 8 levels) across multiple tenants; NVE uses per
tenant policies to map Tenant CoS to the normalized service
CoS fields in the NVO3 header
- Underlay CoS
Lasserre, et al. Expires December 26, 2012 [Page 8]
Internet-Draft NVO3 Data Plane Requirements June 2012
o The underlay/core network may use a different CoS set (for
example 4 levels) than the NVE CoS as the core devices may
have different QoS capabilities compared with NVEs.
o The Underlay CoS may also change as the NVO3 tunnels pass
between different domains.
Support for NVE Service CoS SHOULD be provided through a QoS field,
inside the NVO3 overlay header. Examples of service CoS provided
part of the service tag are 802.1p and DE bits in the VLAN and PBB
ISID tags and MPLS TC bits in the VPN labels.
3.3.2. NVE Tunneling function
This section describes NVE tunneling requirements. From an
encapsulation perspective the IPv4 and IPv6 encapsulations MUST be
supported, MPLS tunneling MAY be supported.
3.3.2.1. LAG and ECMP
For performance reasons, multipath over LAG and ECMP paths SHOULD be
supported.
LAG (Link Aggregation Group) [IEEE 802.1AX-2008] and ECMP (Equal
Cost Multi Path) are commonly used techniques to perform load-
balancing of microflows over a set of a parallel links either at
Layer-2 (LAG) or Layer-3 (ECMP). Existing deployed hardware
implementations of LAG and ECMP uses a hash of various fields in the
encapsulation (outermost) header(s) (e.g. source and destination MAC
addresses for non-IP traffic, source and destination IP addresses,
L4 protocol, L4 source and destination port numbers, etc).
Furthermore, hardware deployed for the underlay network(s) will be
most often unaware of the carried, innermost L2 frames or L3 packets
transmitted by the TES. Thus, in order to perform fine-grained load-
balancing over LAG and ECMP paths in the underlying network the NVO3
encapsulation headers and/or tunneling methods MUST contain a
"entropy field" or "entropy label" so the underlying network can
perform fine-grained load-balancing of the NVO3 encapsulated
traffic, (e.g.: [RFC6391], [RFC6438], [draft-kompella-mpls-entropy-
label-02], etc.) It is recommended this entropy label/field be
applied at the ingress VNI, likely using information gleaned from
the ingress VAP. If necessary, the entropy label/field will be
discarded at the egress VNI.
All packets that belong to a specific flow MUST follow the same path
in order to prevent packet re-ordering. This is typically achieved
Lasserre, et al. Expires December 26, 2012 [Page 9]
Internet-Draft NVO3 Data Plane Requirements June 2012
by ensuring that the fields used for hashing are identical for a
given flow.
All paths available to the overlay network SHOULD be used
efficiently. Different flows SHOULD be distributed as evenly as
possible across multiple underlay network paths. For instance, this
can be achieved by ensuring that some fields used for hashing are
randomly generated.
3.3.2.2. DiffServ and ECN marking
When traffic is encapsulated in a tunnel header, there are numerous
options as to how the Diffserv Code-Point (DSCP) and Explicit
Congestion Notification (ECN) markings are set in the outer header
and propagated to the inner header on decapsulation.
[RFC2983] defines two modes for mapping the DSCP markings from inner
to outer headers and vice versa. The Uniform model copies the inner
DSCP marking to the outer header on tunnel ingress, and copies that
outer header value back to the inner header at tunnel egress. The
Pipe model sets the DSCP value to some value based on local policy
at ingress and does not modify the inner header on egress. Both
models SHOULD be supported.
ECN marking MUST be performed according to [RFC6040] which describes
the correct ECN behavior for IP tunnels.
3.3.2.3. Handling of BUM traffic
NVO3 data plane support for either ingress replication or point-to-
multipoint tunnels is required to send traffic destined to multiple
locations on a per-VNI basis (e.g. L2/L3 multicast traffic, L2
broadcast and unknown unicast traffic). It is possible that both
methods be used simultaneously.
L2 NVEs MUST support ingress replication and SHOULD support point-
to-multipoint tunnels. L3 VNIs MAY support either one of the two
methods.
There is a bandwidth vs state trade-off between the two approaches.
User-definable knobs MUST be provided to select which method(s) gets
used based upon the amount of replication required (i.e. the number
of hosts per group), the amount of multicast state to maintain, the
duration of multicast flows and the scalability of multicast
protocols.
Lasserre, et al. Expires December 26, 2012 [Page 10]
Internet-Draft NVO3 Data Plane Requirements June 2012
When ingress replication is used, NVEs must track for each VNI the
related tunnel endpoints to which it needs to replicate the frame.
For point-to-multipoint tunnels, the bandwidth efficiency is
increased at the cost of more state in the Core nodes. The ability
to auto-discover or pre-provision the mapping between VNI multicast
trees to related tunnel endpoints at the NVE and/or throughout the
core SHOULD be supported.
3.4. External NVO3 connectivity
NVO3 services MUST interoperate with current VPN and Internet
services. This may happen inside one DC during a migration phase or
as NVO3 services are delivered to the outside world via Internet or
VPN gateways.
Moreover the compute and storage services delivered by a NVO3 domain
may span multiple DCs requiring Inter-DC connectivity. From a DC
perspective a set of gateway devices are required in all of these
cases albeit with different functionalities influenced by the
overlay type across the WAN, the service type and the DC network
technologies used at each DC site.
A GW handling the connectivity between NVO3 and external domains
represents a single point of failure that may affect multiple tenant
services. Redundancy between NVO3 and external domains MUST be
supported.
3.4.1. GW Types
3.4.1.1. VPN and Internet GWs
Tenant sites may be already interconnected using one of the existing
VPN services and technologies (VPLS or IP VPN). If a new NVO3
encapsulation is used, a VPN GW is required to forward traffic
between NVO3 and VPN domains. Translation of encapsulations MAY be
required. Internet connected Tenants require translation from NVO3
encapsulation to IP in the NVO3 gateway. The translation function
SHOULD NOT require provisioning touches and SHOULD NOT use
intermediate hand-offs, for example VLANs.
3.4.1.2. Inter-DC GW
Inter-DC connectivity may be required to provide support for
features like disaster prevention or compute load re-distribution.
This may be provided through a set of gateways interconnected
Lasserre, et al. Expires December 26, 2012 [Page 11]
Internet-Draft NVO3 Data Plane Requirements June 2012
through a WAN. This type of connectivity may be provided either
through extension of the NVO3 tunneling domain or via VPN GWs.
3.4.1.3. Intra-DC gateways
Even within one DC there may be End Devices that do not support NVO3
encapsulation, for example bare metal servers, hardware appliances
and storage. A gateway device, e.g. a ToR, is required to translate
the NVO3 to Ethernet VLAN encapsulation.
3.4.2. Path optimality between NVEs and Gateways
Within the NVO3 overlay, a default assumption is that NVO3 traffic
will be equally load-balanced across the underlying network
consisting of LAG and/or ECMP paths. This assumption is valid only
as long as: a) all traffic is load-balanced equally among each of
the component-links and paths; and, b) each of the component-
links/paths is of identical capacity. During the course of normal
operation of the underlying network, it is possible that one, or
more, of the component-links/paths of a LAG may be taken out-of-
service in order to be repaired, e.g.: due to hardware failure of
cabling, optics, etc. In such cases, the administrator should
configure the underlying network such that an entire LAG bundle in
the underlying network will be reported as operationally down if
there is a failure of any single component-link member of the LAG
bundle, (e.g.: N = M configuration of the LAG bundle), and, thus,
they know that traffic will be carried sufficiently by alternate,
available (potentially ECMP) paths in the underlying network. This
is a likely an adequate assumption for Intra-DC traffic where
presumably the costs for additional, protection capacity along
alternate paths is not cost-prohibitive. Thus, there are likely no
additional requirements on NVO3 solutions to accommodate this type
of underlying network configuration and administration.
There is a similar case with ECMP, used Intra-DC, where failure of a
single component-path of an ECMP group would result in traffic
shifting onto the surviving members of the ECMP group.
Unfortunately, there are no automatic recovery methods in IP routing
protocols to detect a simultaneous failure of more than one
component-path in a ECMP group, operationally disable the entire
ECMP group and allow traffic to shift onto alternative paths. This
is problem is attributable to the underlying network and, thus, out-
of-scope of any NVO3 solutions.
On the other hand, for Inter-DC and DC to External Network cases
that use a WAN, the costs of the underlying network and/or service
Lasserre, et al. Expires December 26, 2012 [Page 12]
Internet-Draft NVO3 Data Plane Requirements June 2012
(e.g.: IPVPN service) are more expensive; therefore, there is a
requirement on administrators to both: a) ensure high availability
(active-backup failover or active-active load-balancing); and, b)
maintaining substantial utilization of the WAN transport capacity at
nearly all times, particularly in the case of active-active load-
balancing. With respect to the dataplane requirements of NVO3
solutions, in the case of active-backup fail-over, all of the
ingress NVE's MUST dynamically adapt to the failure of an active NVE
GW when the backup NVE GW announces itself into the NVO3 overlay
immediately following a failure of the previously active NVE GW and
update their forwarding tables accordingly, (e.g.: perhaps through
dataplane learning and/or translation of a gratuitous ARP, IPv6
Router Advertisement, etc.) Note that active-backup fail-over could
be used to accomplish a crude form of load-balancing by, for
example, manually configuring each tenant to use a different NVE GW,
in a round-robin fashion. On the other hand, with respect to active-
active load-balancing across physically separate NVE GW's (e.g.:
two, separate chassis) an NVO3 solution SHOULD support forwarding
tables that can simultaneously map a single egress NVE to more than
one NVO3 tunnels. The granularity of such mappings, in both active-
backup and active-active, MUST be unique to each tenant.
3.4.2.1. Triangular Routing Issues,a.k.a.: Traffic Tromboning
L2/ELAN over NVO3 service may span multiple racks distributed across
different DC regions. Multiple ELANs belonging to one tenant may be
interconnected or connected to the outside world through multiple
Router/VRF gateways distributed throughout the DC regions. In this
scenario, without aid from an NVO3 or other type of solution,
traffic from an ingress NVE destined to External gateways will take
a non-optimal path that will result in higher latency and costs,
(since it is using more expensive resources of a WAN). In the case
of traffic from an IP/MPLS network destined toward the entrance to
an NVO3 overlay, well-known IP routing techniques may be used to
optimize traffic into the NVO3 overlay, (at the expense of
additional routes in the IP/MPLS network). In summary, these issues
are well known as triangular routing.
Procedures for gateway selection to avoid triangular routing issues
SHOULD be provided. The details of such procedures are, most likely,
part of the NVO3 Management and/or Control Plane requirements and,
thus, out of scope of this document. However, a key requirement on
the dataplane of any NVO3 solution to avoid triangular routing is
stated above, in Section 3.4.2, with respect to active-active load-
balancing. More specifically, an NVO3 solution SHOULD support
forwarding tables that can simultaneously map a single egress NVE to
Lasserre, et al. Expires December 26, 2012 [Page 13]
Internet-Draft NVO3 Data Plane Requirements June 2012
more than one NVO3 tunnels. The expectation is that, through the
Control and/or Management Planes, this mapping information may be
dynamically manipulated to, for example, provide the closest
geographic and/or topological exit point (egress NVE) for each
ingress NVE.
3.5. Path MTU
The tunnel overlay header can cause the MTU of the path to the
egress tunnel endpoint to be exceeded.
IP fragmentation should be avoided for performance reasons.
The interface MTU as seen by a Tenant End System SHOULD be adjusted
such that no fragmentation is needed. This can be achieved by
configuration or be discovered dynamically.
Either of the following options MUST be supported:
o Classical ICMP-based MTU Path Discovery [RFC1191] [RFC1981] or
Extended MTU Path Discovery techniques such as defined in
[RFC4821]
o Segmentation and reassembly support from the overlay layer
operations without relying on the Tenant End Systems to know
about the end-to-end MTU
o The underlay network may be designed in such a way that the MTU
can accommodate the extra tunnel overhead.
3.6. Hierarchical NVE
It might be desirable to support the concept of hierarchical NVEs,
such as spoke NVEs and hub NVEs, in order to address possible NVE
performance limitations and service connectivity optimizations.
For instance, spoke NVE functionality MAY be used when processing
capabilities are limited. A hub NVE would provide additional data
processing capabilities such as packet replication.
NVEs can be either connected in an any-to-any or hub and spoke
topology on a per VNI basis.
3.7. NVE Multi-Homing Requirements
Multi-homing to a set of NVEs may be required in certain scenarios:
Lasserre, et al. Expires December 26, 2012 [Page 14]
Internet-Draft NVO3 Data Plane Requirements June 2012
. End Device dual-homed to two ToR switches acting as NVEs
. Multi-homing into NVE-GWs providing connectivity between
domains using different technologies
. Hierarchical NVEs: Spoke NVE multi-homed to Hub NVEs
This section will be extended in the next revision.
3.8. OAM
NVE may be able to originate/terminate OAM messages for connectivity
verification, performance monitoring, statistic gathering and fault
isolation. Depending on configuration, NVEs SHOULD be able to
process or transparently tunnel OAM messages, as well as supporting
alarm propagation capabilities.
Given the critical requirement to load-balance NVO3 encapsulated
packets over LAG and ECMP paths, it will be equally critical to
ensure existing and/or new OAM tools allow NVE administrators to
proactively and/or reactively monitor the health of various
component-links that comprise both LAG and ECMP paths carrying NVO3
encapsulated packets. For example, it will be important that such
OAM tools allow NVE administrators to reveal the set of underlying
network hops (topology) in order that the underlying network
administrators can use this information to quickly perform fault
isolation and restore the underlying network.
The NVE MUST provide the ability to reveal the set of ECMP and/or
LAG paths used by NVO3 encapsulated packets in the underlying
network from an ingress NVE to egress NVE. The NVE MUST provide the
ability to provide a "ping"-like functionality that may be used to
determine the health (liveness) of remote NVE's or their VNI's. The
NVE SHOULD provide a "ping"-like functionality to more expeditiously
aid in troubleshooting performance problems, i.e.: blackholing or
other types of congestion occurring in the underlying network, for
NVO3 encapsulated packets carried over LAG and/or ECMP paths.
3.9. Other considerations
3.9.1. Data Plane Optimizations
Data plane forwarding and encapsulation choices SHOULD consider the
limitation of possible NVE implementations, specifically in software
based implementations (e.g. servers running VSwitches)
NVE should provide efficient processing of traffic. For instance,
packet alignment, the use of offsets to minimize header parsing,
Lasserre, et al. Expires December 26, 2012 [Page 15]
Internet-Draft NVO3 Data Plane Requirements June 2012
padding techniques SHOULD be considered when designing NVO3
encapsulation types.
The NV03 encapsulation/decapsulation processing in software-based
NVEs SHOULD make use of hardware assist provided by NICs in order to
speed up packet processing.
3.9.2. NVE location trade-offs
In the case of DC traffic, traffic originated from a VM is native
Ethernet traffic. This traffic can be switched by a local VM switch
or ToR switch and then by a DC gateway. The NVE function can be
embedded within any of these elements.
The NVE function can be supported in various DC network elements
such as a VM, VM switch, ToR switch or DC GW.
The following criteria SHOULD be considered when deciding where the
NVE processing boundary happens:
o Processing and memory requirements
o Datapath (e.g. lookups, filtering,
encapsulation/decapsulation)
o Control plane processing (e.g. routing, signaling, OAM)
o FIB/RIB size
o Multicast support
o Routing protocols
o Packet replication capability
o Fragmentation support
o QoS transparency
o Resiliency
4. Security Considerations
This requirements document does not raise in itself any specific
security issues.
Lasserre, et al. Expires December 26, 2012 [Page 16]
Internet-Draft NVO3 Data Plane Requirements June 2012
5. IANA Considerations
IANA does not need to take any action for this draft.
6. References
6.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
6.2. Informative References
[NVOPS] Narten, T. et al, "Problem Statement: Overlays for Network
Virtualization", draft-narten-nvo3-overlay-problem-
statement (work in progress)
[NVO3-framework] Lasserre, M. et al, "Framework for DC Network
Virtualization", draft-lasserre-nvo3-framework (work in
progress)
[OVCPREQ] Kreeger, L. et al, "Network Virtualization Overlay Control
Protocol Requirements", draft-kreeger-nvo3-overlay-cp
(work in progress)
[FLOYD] Sally Floyd, Allyn Romanow, "Dynamics of TCP Traffic over
ATM Networks", IEEE JSAC, V. 13 N. 4, May 1995
[RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
Networks (VPNs)", RFC 4364, February 2006.
[RFC1191] Mogul, J. "Path MTU Discovery", RFC1191, November 1990
[RFC1981] McCann, J. et al, "Path MTU Discovery for IPv6", RFC1981,
August 1996
[RFC4821] Mathis, M. et al, "Packetization Layer Path MTU
Discovery", RFC4821, March 2007
[RFC2983] Black, D. "Diffserv and tunnels", RFC2983, Cotober 2000
[RFC6040] Briscoe, B. "Tunnelling of Explicit Congestion
Notification", RFC6040, November 2010
Lasserre, et al. Expires December 26, 2012 [Page 17]
Internet-Draft NVO3 Data Plane Requirements June 2012
[RFC6438] Carpenter, B. et al, "Using the IPv6 Flow Label for Equal
Cost Multipath Routing and Link Aggregation in Tunnels",
RFC6438, November 2011
[RFC6391] Bryant, S. et al, "Flow-Aware Transport of Pseudowires
over an MPLS Packet Switched Network", RFC6391, November
2011
7. Acknowledgments
In addition to the authors the following people have contributed to
this document:
Shane Amante, Level3
Dimitrios Stiliadis, Rotem Salomonovitch, Alcatel-Lucent
This document was prepared using 2-Word-v2.0.template.dot.
Authors' Addresses
Nabil Bitar
Verizon
40 Sylvan Road
Waltham, MA 02145
Email: nabil.bitar@verizon.com
Marc Lasserre
Alcatel-Lucent
Email: marc.lasserre@alcatel-lucent.com
Florin Balus
Alcatel-Lucent
777 E. Middlefield Road
Mountain View, CA, USA 94043
Email: florin.balus@alcatel-lucent.com
Thomas Morin
France Telecom Orange
Email: thomas.morin@orange.com
Lasserre, et al. Expires December 26, 2012 [Page 18]