Network Working Group H. Grover
Internet-Draft D. Rao
Intended status: Standards Track D. Farinacci
Expires: August 27, 2013 V. Moreno
Cisco Systems
February 23, 2013
Overlay Transport Virtualization
draft-hasmit-otv-04
Abstract
In today's networking environment most enterprise networks span
multiple physical sites. Overlay Transport Virtualization (OTV)
provides a scalable solution for L2/L3 connectivity across different
sites using the currently deployed service provider and enterprise
networks. It is a very cost-effective and simple solution requiring
deployment of a one or more OTV functional device at each of the
enterprise sites. This solution is agnostic to the technology used
in the service provider network and connectivity between the
enterprise and the service provider network. This document provides
an overview of this technology.
Status of this Memo
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This Internet-Draft will expire on August 27, 2013.
Copyright Notice
Copyright (c) 2013 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
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Table of Contents
1. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
2. Control Plane . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1. Provider Control Plane . . . . . . . . . . . . . . . . . . 9
2.2. Overlay Control Plane . . . . . . . . . . . . . . . . . . 9
2.2.1. Edge Device Discovery and Adjacency setup . . . . . . 10
2.2.2. Extended VLANs . . . . . . . . . . . . . . . . . . . . 10
2.2.3. Multiple Instances . . . . . . . . . . . . . . . . . . 11
2.2.4. Advertising Unicast MAC Routes . . . . . . . . . . . . 11
2.2.5. Advertising Multicast Routes . . . . . . . . . . . . . 11
2.2.6. Adjacency Server . . . . . . . . . . . . . . . . . . . 13
2.3. Connecting an Edge Device to the Overlay . . . . . . . . . 13
2.3.1. Edge Devices as MAC Routers . . . . . . . . . . . . . 13
2.3.2. Internal Interface Behavior . . . . . . . . . . . . . 13
2.3.3. Overlay Interface Behavior . . . . . . . . . . . . . . 14
3. Data Plane . . . . . . . . . . . . . . . . . . . . . . . . . . 14
3.1. Encapsulation . . . . . . . . . . . . . . . . . . . . . . 14
3.2. Forwarding Process . . . . . . . . . . . . . . . . . . . . 18
3.2.1. Forwarding between Internal Links . . . . . . . . . . 18
3.2.2. Forwarding from an Internal Link to the Overlay . . . 19
3.2.3. Forwarding from the Overlay to an Internal Link . . . 19
3.2.4. Unicast Packet Flows . . . . . . . . . . . . . . . . . 20
3.2.5. Unknown Unicast Packet Handling . . . . . . . . . . . 20
3.2.6. Multicast Packet Flows . . . . . . . . . . . . . . . . 21
3.2.7. Broadcast Packet Flows . . . . . . . . . . . . . . . . 21
3.3. STP BPDU Handling . . . . . . . . . . . . . . . . . . . . 22
4. MAC Address Mobility . . . . . . . . . . . . . . . . . . . . . 22
5. Multi-homing . . . . . . . . . . . . . . . . . . . . . . . . . 23
5.1. Authoritative Edge Device Selection . . . . . . . . . . . 23
5.2. Site Identifier . . . . . . . . . . . . . . . . . . . . . 24
6. IS-IS as an Overlay Control Protocol . . . . . . . . . . . . . 24
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 26
8. Security Considerations . . . . . . . . . . . . . . . . . . . 26
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 26
10. Normative References . . . . . . . . . . . . . . . . . . . . . 27
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 27
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1. Overview
OTV is a new "MAC in IP" technique for supporting L2 VPNs over an
L2/L3 infrastructure. OTV provides an "over-the-top" method of doing
virtualization among a large number of sites where the routing and
forwarding state is maintained at the network edges, but not within
the site or in the core.
OTV can be incrementally deployed and reside in a small number of
devices at the edge between sites and the core. We call these
devices "Edge Devices" which perform typical layer-2 learning and
forwarding functions on their site facing interfaces (internal
interfaces) and perform IP-based virtualization functions on their
core facing interfaces (for which an overlay network is realized).
Traditional L2VPN technologies rely heavily on tunnels. Rather than
creating stateful tunnels, OTV encapsulates layer 2 traffic with an
IP header ("MAC in IP"), but does not create any fixed tunnels.
Based on the IP header, traffic is forwarded natively in the core
over which OTV is being deployed. This is an important feature as
the native IP treatment of the encapsulated packet allows optimal
multi-point connectivity as well as optimal broadcast and multicast
forwarding, plus any other benefits the routed core may provide to
native IP traffic. OTV virtualization is independent of the
technology deployed in the core; the core network may be a layer-2
metro Ethernet core, a layer-3 IP network core, or an MPLS network
core.
Layer-2 traffic which requires traversing the overlay to reach its
destination, is prepended with an IP header which ensures the packet
is delivered to the edge boxes that provide connectivity to the
Layer-2 destination in the original MAC header. As shown in figure
1, if a destination is reachable via Edge Device X2 (with a core
facing IP address of IPB), other Edge Devices forwarding traffic to
such destination will add an IP header with a destination IP address
of IPB and forward the traffic into the core. The core will forward
traffic based on IP address IPB, once the traffic makes it to Edge
Device X2 it will be stripped of the overlay IP header and it will be
forwarded into the site in the same way a regular bridge would
forward a packet at layer-2. Broadcast or multicast traffic is
encapsulated with a multicast header and follows a similar process.
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+----+ +----+
| H1 |------- ------------ -------| H2 |
+----+ \ / \ / +----+
\+----+IPA / L3 Core \ IPB+----+/
---------| X1 |----< >---| X2 |--------
/+----+ \ Network / +----+\
/ \ / \
------------
+------------+
| DA = IPB |
+------------+
| SA = IPA |
+-----------+ +------------+ +-----------+
| DMAC = H2 | | DMAC = H2 | | DMAC = H2 |
+-----------+ +------------+ +-----------+
| SMAC = H1 | | SMAC = H1 | | SMAC = H1 |
+-----------+ +------------+ +-----------+
| VLAN-ID | | VLAN-ID | | VLAN-ID |
+-----------+ +------------+ +-----------+
| Payload | | Payload | | Payload |
+-----------+ +------------+ +-----------+
Figure 1. Traffic flow from H1 to H2 with encapsulation in the core.
The key piece that OTV adds is the state to map a given destination
MAC address in the L2 VPN to an IP address of the OTV Edge Device
behind which that MAC address is located. OTV forwarding is a
function of mapping a destination MAC address in the VPN site to an
Edge Device IP address in the overlay network.
To achieve all this, a control plane is required to exchange the
reachability information among the different OTV Edge Devices. We
will refer to this control plane as the oURP and oMRP (Overlay
Unicast Routing Protocol and Overlay Multicast Routing Protocol).
OTV does not flood unknown unicast traffic among Edge Devices and
therefore precludes data-plane learning on the "overlay interface".
Data-plane learning continues to happen on the "internal interfaces"
to provide compatibility and transparency within the layer-2 sites
connecting to the OTV overlay. The Edge Devices appear to each VPN
site to be providing L2 switched network connectivity amongst those
sites.
This document describes the use of IS-IS as an IGP capable of
carrying both MAC unicast and multicast and IP multicast group
addresses, thereby serving as both the oURP and oMRP. However, any
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other suitable routing protocol can be used as the OTV control
protocol. The information carried in IS-IS LSPs will be MAC unicast
addresses and multicast addresses with their associated VLAN IDs and
IP next hops. The MAC addresses are those of the hosts connecting to
the network and the IP next hops are the addresses of the Edge
Devices through which these are reachable in the core. Figure 2
shows what the resulting tables would look like in a simple two site
example.
+----+ +----+
| H1 |------- ------------ -------| H2 |
+----+ \ / \ / +----+
E1\+----+IPA / L3 Core \ IPB+----+/E1
---------| X1 |----< >---| X2 |--------
/+----+ \ Network / +----+\
/ Overlay1 \ /Overlay1 \
------------
At X1 At X2
+----------------------------+ +----------------------------+
| Destination | Interface/NH | | Destination | Interface/NH |
|----------------------------| |----------------------------|
| H1 | E1 | | H1 | Overlay1:IPA |
| H2 | Overlay1:IPB | | H2 | E1 |
+----------------------------+ +----------------------------+
Figure 2. OTV Forwarding Tables.
Edge Devices will have an IP address reachable through their core
facing interface(s), and these nodes join a configured ASM/Bidir
multicast group in the core transport network. The core or the
provider network relies on a provider Unicast Routing Protocol (pURP)
and a provider Multicast Routing Protocol (pMRP) to connect the Edge
Devices to one another. It is not strictly required that the Edge
Devices participate in the pURP/pMRP. They typically connect as
hosts to the core network. This is compatible and consistent with
today's interconnection policies. However, the solution also
supports the scenario where the Edge Devices do actively participate
at Layer-3 in the pURP/pMRP.
The multicast group that the Edge Devices join is referred to as the
"Provider Multicast Group (pMG)". The pMG will be used for Edge
Devices to become adjacent with each other to exchange their IS-IS
Hellos, LSPs and CSNPs. Thus, by virtue of the pMG, all Edge Devices
will see each other as if they were directly connected to the same
multi-access multicast-capable segment for the purposes of IS-IS
peering. The pMG also defines a VPN; thus, when an Edge Device joins
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a pMG the site becomes part of a VPN. Multiple pMGs can be defined
to define multiple VPNs.
The pMG can also be used to broadcast data traffic to all Edge
Devices when necessary. Broadcast transmission will not incur head-
end replication overhead. OTV allows the pMRP to efficiently
distribute broadcast traffic by the provider ASM/Bidir group.
When forwarding of VPN multicast is required, new multicast state
will be used in order to tailor the distribution trees to the optimal
group of receivers, these multicast groups are to be created in the
provider control plane (pMRP). For instance, each core device will
resort to using SSM multicast in the core by having the Edge Device
IGMPv3/ MLDv2 join a {source, group} pair.
Edge Devices must combine data-plane learning on their bridged
internal interfaces with control-plane learning on their overlay
interfaces. The key to this combination is a series of rules through
which data-plane events can trigger control-plane advertisements
and/or learning events.
OTV supports L2 multi-homing for sites where one or more of the
bridge domains may be connected to multiple Edge Devices. It
supports both active-backup and active-active multi-homing
capabilities to sites. OTV provides loop elimination for multi-homed
"sites" and does not require the extension of STP across sites. This
means each site can run it own STP rather than have to create one
large STP domain across sites.
1.1. Terminology
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.
Site - A Site is a single or multi-homed connected network which
is typically under the control of a single organization. Sites
are connected together via Edge Devices that operate in an overlay
network. The Edge Devices provide layer-2 connectivity among the
sites. A site will not be used by IS-IS as a transit network. A
layer-2 site is one that is mostly made up of hosts and switches.
Routers may exist but the majority of the topology to the Edge
Devices are L2 switched. The MAC addresses advertised on the
overlay network are all the hosts and routers connected to the L2
devices at the site. The site typically has several VLANs or
bridging domains being actively used. A layer-3 site is one that
is mostly made up of routers connecting to hosts via switches.
The majority of the topology to the Edge Devices are L3 routed.
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The number of MAC addresses advertised on the overlay network are
limited to the router devices at the site.
VPN - A VPN is a collection of sites which are controlled by a
single administration. The addressing plan, router and switch
configuration is consistent as it would be if the sites were
physically at the same location. There is one overlay network per
VPN which connects all sites. Each VPN uses a dedicated ASM/Bidir
provider multicast group allocated by the core network, which
provides the separation from other VPNs for the control plane, as
well as in the data plane.
Edge Device - A modified L2 switch that performs OTV functions.
It will run as an L2 device on the site side, but performs L3
functions on the core facing interfaces. When OTV functionality
is described, this functionality only occurs in an Edge Device.
Internal Interface - These are Layer-2 interfaces connected to
site based switches or site based routers. The internal interface
is layer-2 regardless if it connects to a switch or a router.
Overlay Interface - This is a logical multi-access multicast-
capable interface. The overlay interface can replicate broadcast
and multicast packets efficiently. The overlay interface provides
an IP unicast or multicast encapsulation for L2 frames transmitted
from the site. The overlay interface is realized by one or more
physical core facing interfaces. The core facing interfaces are
assigned IP addresses out of the core provider's address space.
MAC Table - This is a forwarding table of 48-bit MAC addresses.
The table can contain unicast or multicast MAC addresses. The
table is populated by two sources. One being traditional data-
plane learning on internal interfaces and the other by the URP/MRP
at the control-plane on the overlay interface. A MAC table is
scoped by VLAN therefore allowing the same MAC address to be used
in different VLANs, and potentially in different VPNs.
Authoritative Edge Device (AED) - This is an Edge Device that
forwards Layer-2 frames in and out of a site from and to the
overlay interface. Depending on the multi-homing granularity in
use, there will be a single AED in the site for a given VLAN or
for a given MAC-level flow.
Site-ID - Each Edge Device which resides in an OTV site will
advertise over the overlay network the same site-id. The site-id
may be determined dynamically or by static configuration.
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(VLAN, uMAC) - This is the designation of layer-2 network
reachability information as encoded in the URP and as stored in
the MAC table. This notation describes a given unicast MAC
address within a particular VLAN.
(VLAN, mMAC, mIP) - This is the designation of layer-2 network
reachability information as encoded in the MRP and as stored in
the MAC/IP table. This notation describes a given multicast
MAC/IP address within a particular VLAN. The 'mIP' part of the
3-tuple is provided so both Layer-2 switching and the SSM based
tree joins can occur based on the IP group address (since 32-to-1
aliasing can happen for IPv4 group address to MAC mappings and
worse for IPv6).
2. Control Plane
This section discusses the control plane hierarchy. At the very base
of the hierarchy we find the provider control plane, which enables
unicast reachability among the edge boxes and also provides the
multicast group that makes edge boxes adjacent from the overlay
control plane perspective. The provider control plane also provides
the multicast trees in the core that will be used for optimal
forwarding of the layer-2 site data traffic.
At the next level, the overlay control plane provides discovery of
the Edge Devices that are part of the overlay and conveys client-MAC-
address reachability and client-multicast group information between
the edge devices.
In general, the control planes are independent of each other.
However, in order to optimize multicasting, multicast control-plane
events (reports, joins, leaves) that occur in one MRP may initiate
events in another MRP so that the optimal tree is always being used
to forward traffic. Also, events in the overlay control plane are
triggered by forwarding events in the client data plane (however both
client and overlay control planes remain independent of each other).
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|<------------------------ cURP/cMRP ------------------------>|
| |
| |
| |<--------- oURP/oMRP --------->| |
| | | |
| | | |
| | |<--- pURP/pMRP -->| | |
| | | (pMG) | | |
| | | | | |
| | | | | |
+----+ +--+ | | | | +--+ +----+
| R1 |----|S1| | | ------------ | | |S2|----| R2 |
+----+ +--+ | | / \ | | +--+ +----+
\+----+IPA | / L3 Core \ | IPB+----+/
------| X1 |-----< >-----| X2 |-----
/+----+ \ Network / +----+\
\ /
------------
Figure 3. OTV Control Plane Hierarchy
2.1. Provider Control Plane
The provider control plane is the set of routing protocols which run
in the core infrastructure to be able to deliver packets sourced from
the site networks. There is no required coordination of routing
protocols between the site and the core. That is, no more than
typically necessary to connect to a core service. In terms of
addressing, the Edge Device is allocated an IP address out of the
core block of addresses.
For each VPN the Edge Device is to support, a multicast group is
required to be allocated from the provider core at a minimum. This
multicast group is typically ASM/BiDir. In addition, the multicast
state created in the client site network will map to some amount of
state in the core network. However, it is not required to provision
a unique group for every client data group. The Edge Device takes a
client multicast packet and encapsulates it in a core-deliverable
multicast packet.
2.2. Overlay Control Plane
The overlay control plane provides auto-discovery of the Edge Devices
that are members of an Overlay VPN. It also conveys Layer-2 unicast
and multicast reachability information from a site to Edge Devices in
other sites and the VLANs or layer-2 bridge domains being extended.
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The MAC addresses that are locally connected to an Edge Device are
advertised in the overlay URP to other Edge Devices in the VPN.
Thus, MAC learning on the overlay is not based on data plane
flooding, but is based on explicit advertisements of MAC addresses
done by the overlay control plane. Similarly, the multicast groups
that a site has receivers or sources for are advertised in the
overlay MRP to other Edge Devices in the VPN.
2.2.1. Edge Device Discovery and Adjacency setup
The overlay URP establishes adjacencies only between Edge Devices
that are in the same VPN. Edge Devices become part of a VPN when
they join a multicast group defined in the core (provider MRP);
devices using the same group are members of the same VPN. Thus, the
adjacency setup provides a very simple mechanism to automatically
discover members of the VPN. The hellos and updates between overlay-
URP peers travel over the multicast group defined in the pMRP. Thus,
Edge Devices peer with each other as if they were directly connected
at layer-2. This peering is possible as all the traffic for the oURP
is encapsulated with the pMRP group address and sent into the core.
Thus, all Edge Devices in a given VPN receive the oURP multicast
traffic as if they were all on the same segment. Similarly, the
overlay MRP packets are encapsulated with the pMRP group address
corresponding to the VPN. The overlay MRP is used to inform all the
Edge Devices that the subscribers to a particular group are reachable
over the overlay network.
An Edge Device can support multiple overlay VPNs. Each overlay has
its own dedicated provider-multicast group address and a distinct set
of adjacencies. There may be multiple overlay adjacencies between
the same set of Edge Devices, or the membership may be disjoint for
each overlay.
2.2.2. Extended VLANs
Each overlay basically extends a set of VLANs or layer-2 bridge
domains among the member sites. On a given Edge Device, a set of
VLANs is uniquely extended on a specific overlay. Other VLANs may be
extended on other overlays. This entails both advertising and
accepting information in the control plane such as VLANs and their
associated MAC and group information, as well as forwarding unicast,
multicast and broadcast traffic for these VLANs.
To allow scalability of connecting large L2 sites together via the
overlay, by default, an Edge Device will not advertise any
information for any VLANs. To avoid inadvertent merging of VLANs
among sites, Edge Devices will be required to configure the VLANs for
which Edge Devices will advertise reachability information for.
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2.2.3. Multiple Instances
An Edge Device may support bridging of multiple distinct layer-2
domains with overlapping VLANs which are to be treated as distinct.
These VLANs may be extended on the overlay by treating them as
separate instances both in advertising control plane information and
while forwarding in the data plane. A single overlay VPN can support
more than one instance among the Edge Devices in that overlay.
2.2.3.1. VLAN to Instance Mapping
The OTV encapsulation header as specified in this document contains a
24-bit Instance ID. This Instance ID can be used in two different
modes:
1. It distinguishes between multiple distinct 12-bit VLAN domains
being extended across the overlay from a site. Each such domain is
assigned an Instance-ID. In this mode, the "inner" VLANs are
preserved within the 802.1Q header in the OTV payload. The
combination of the Instance-ID and the inner VLAN uniquely identify a
single Layer-2 broadcast domain.
2. At the OTV Edge Device, a local mapping function maps a 12-bit
VLAN to a unique 24-bit Instance-ID before sending the encapsulated
packets on the overlay. In this case, the inner 802.1Q header is
stripped before sending the encapsulated packets on the overlay. The
Instance ID uniquely identifies a Layer-2 broadcast domain.
2.2.4. Advertising Unicast MAC Routes
When a MAC address is learned by arrival of a data packet on an
internal interface, the Edge Device advertises the MAC address on the
overlay URP. In addition to conveying the MAC address reachability
to other edge devices, it also provides a mapping to one of the IP
addresses of the advertising Edge Device; i.e., the IP next-hop and
encapsulation for that MAC address. Typically, even if a site is
multi-homed, a unicast MAC address is advertised by a single Edge
device, that is the Authoritative Edge Device. Hence, remote Edge
Devices will see a single path to reach a given MAC address.
However, when active-active multihoming is being used, there will be
equal-cost paths to reach a MAC address in a site and the sender Edge
Device will load-balance flows among the paths.
2.2.5. Advertising Multicast Routes
An Edge Device learns about the multicast groups that hosts in the
site are interested in by snooping IGMP/MLD reports on the internal
interfaces. When a multicast MAC or group address is learned, the
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Edge Device notifies other Edge Devices about it by placing a
(VLAN,mMAC,mIP) entry in a multicast control PDU. Thus, the overlay
MRP informs all the Edge Devices that the subscribers to a particular
group are reachable over the overlay network. This information is
used by Edge Devices to populate their multicast oif-list at the
source site. As long as there is one site that has a receiver for a
multicast group, the Edge Devices at the source site will forward
traffic for that group onto the overlay. Edge Devices at the
receiving sites will also join the corresponding multicast group in
the provider plane (pMRP). Thus, multicast trees are built natively
in the core, not on the overlay, and provide optimal delivery of
multicast data.
2.2.5.1. Delivery Groups
Delivery groups are multicast groups used in the core network to
transport site multicast traffic. Multicast data for various
customer data groups are aggregated into a typically smaller set of
core multicast trees, without requiring extensive coordination
between OTV edge boxes. Delivery group selection is centralized at
each source OTV Edge Device which controls the mapping of a (S,G) to
a (DS, DG). It exports this mapping to other Edge Devices so that
they can join the (DS, DG) in the core. Link-local site multicast
groups may also map to a specific delivery group instead of the
provider multicast group used for control packets. Delivery group
mapping allows for fair amount of flexibility for the customer sites
and the provider to decide control of state versus bandwidth tradeoff
in the core.
When a receiver site Edge Device learns a (S, G) to (DS, DG) mapping,
it joins the (DS, DG) tree in the core. As an optimization, this
join may be done only if there are local receivers for the group. It
also installs a layer-3 multicast route for (DS,DG) to decapsulate
incoming packets with the appropriate core uplink interface as the
RPF interface.
2.2.5.2. Active Source Discovery
An OTV Edge Device will advertise a delivery group mapping for a
(*,G) or (S,G) route only when there is an active source sending data
in its site. For this, the Edge Device will learn the active sources
by snooping multicast data received on the internal interfaces. If a
remote receiver interested in this group, a (VLAN, S,G) entry is
installed with the overlay as an OIF and the (DS,DG) as outer
encapsulation. When IGMP/MLD is being used on the core uplink, the
(DS,DG) encapsulated packet may be emitted directly on the uplink
interface. The first-hop router on the other end of the core uplink
will then forward this packet along the core multicast tree.
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2.2.6. Adjacency Server
In case the provider core does not support ASM/Bidir multicast, there
is an alternate mechanism to discover the remote Edge Devices which
are part of a VPN. In this scenario, an Edge Device is configured as
an Adjacency Server. All other Edge Devices inform the Adjacency
Server regarding their reachability and capability information via
the overlay control plane. Adjacency Server is responsible for
informing all the other existing Edge Devices regarding addition or
loss of an Edge Device. Based on the reachability information, the
Edge Devices can further communicate with one another directly using
unicast or multicast data path.
2.3. Connecting an Edge Device to the Overlay
In order to successfully connect to the overlay, the Edge Device has
several functions on its different interfaces. These are summarized
in this section.
2.3.1. Edge Devices as MAC Routers
The Edge Device need not participate in the provider URP (pURP) as a
router, but can simply behave as a host. This keeps its requirements
and functionality simple. In this mode, the Edge Device has an IP
address which is significant in the core/provider addressing space.
The Edge Device joins the multicast groups in the core by issuing
IGMPv3/MLDv2 reports, just like a host would. Thus the Edge Device
does not have an IGP relationship with the core. This allows for
simpler insertion into any type of core network.
However, the Edge Device does participate in the overlay URP and its
IP address is used as a router ID and a next-hop address for unicast
traffic by the overlay URP. However, the Edge Device does not build
an IP routing table with the information received from the oURP, but
rather builds a hybrid table where MAC address destinations are
reachable via IP next-hop addresses. This may be termed as a MAC
router because it can route packets based on MAC addresses.
Thus, Edge Devices are IP hosts in the provider plane, MAC routers in
the overlay plane and bridges in the client bridging plane. It
should be noted that Edge Devices can also support full IP routing
functionality and participate in the pURP/pMRP as routers.
2.3.2. Internal Interface Behavior
The internal interfaces on an Edge Device are bridged interfaces and
are indifferent to whether the site itself is L2 or L3. These
interfaces behave as regular switch interfaces and learn the source
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MAC addresses of traffic they receive. Spanning tree BPDUs are
received, processed and sourced on internal interfaces as they would
on a regular 802.1d, 802.1s and 802.1w switch. IGMP/MLD and data
snooping is enabled on internal interfaces to discover local
receivers and sources in the site. Additionally, traffic received on
internal interfaces may trigger oURP/oMRP advertisements and/or pMRP
group joins as described earlier.
Traffic received on an internal interface will be forwarded according
to the MAC and multicast tables either onto other internal interfaces
(regular bridging) or onto the overlay (OTV forwarding). This is
explained in detail in the Forwarding section.
2.3.3. Overlay Interface Behavior
An overlay interface is a logical interface which is associated with
an IP address in the provider/core address space. Traffic out of
these interfaces is encapsulated with an IP header, and traffic
received on these interfaces must be de-capsulated to produce a L2
frame. The encapsulated packets exit the Edge Device on one or more
underlying physical or logical L3 interfaces.
STP BPDUs are not sourced from overlay interfaces, therefore there
should not be STP BPDUs in the core, nor do the overlay interfaces
participate in the spanning tree protocol.
The IP addresses assigned to the overlay interfaces are used as next-
hop addresses by the overlay-URP, therefore the MAC table for the
overlay interface will include a remote IP address as the next-hop
information for remote MAC addresses.
3. Data Plane
3.1. Encapsulation
The overlay encapsulation format is a Layer-2 ethernet frame
encapsulated in UDP inside of IPv4 or IPv6.
The format of OTV UDP IPv4 encapsulation is as follows:
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1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| IHL |Type of Service| Total Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identification |Flags| Fragment Offset |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Time to Live | Protocol = 17 | Header Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source-site OTV Edge Device IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination-site OTV Edge Device (or multicast) Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = xxxx | Dest Port = 8472 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP length | UDP Checksum = 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|R|R|R|I|R|R|R| Overlay ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Frame in Ethernet or 802.1Q Format |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The format of OTV UDP IPv6 encapsulation is as follows:
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Version| Traffic Class | Flow Label |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Payload Length | Next Header=17| Hop Limit |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Source-site OTV Edge Device IPv6 Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| |
+ Destination-site OTV Edge Device (or multicast) Address +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source Port = xxxx | Dest Port = 8472 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| UDP Length | UDP Checksum |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R|R|R|R|I|R|R|R| Overlay ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Instance ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Frame in Ethernet or 802.1Q Format |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Outer IPv4 (or IPv6) Header:
Version: Set to value 4 (or 6) in decimal.
IHL: Set to value 5 in decimal meaning there are no IP options
present in an OTV encapsulated packet.
Type of Service/Traffic Class: The 802.1P bits from the Ethernet
Frame are copied to this field.
Total Length: The total length of the IPv4 datagram in bytes. This
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includes the IPv4 header, the UDP header, the OTV header, and the L2
frame without the preamble and CRC fields.
Payload length: The length of the IPv6 payload in bytes. This
includes the UDP header, the OTV header, and the L2 frame without the
preamble and CRC fields.
Identification: Set randomly by the OTV Edge Device.
Flags: The DF bit should be set to 1.
Time to Live/Hop Limit: Set by the OTV Edge Device and is
configurable.
Protocol/Next Header: Since the packet is UDP encapsulated, this
field is set to 17 decimal.
Header Checksum: Must be computed by the OTV Edge Device over the IP
header fields.
Source Address: The IPv4 (or IPv6) address of the OTV Edge Device
doing the encapsulation of the L2 frame.
Destination Address: The IPv4 (or IPv6) unicast or multicast address
set by the OTV Edge Device which is encapsulating the L2 frame. The
Edge Device decides when the address is set to a unicast or multicast
addresss.
UDP Header:
Source Port: Is chosen by the OTV Edge Device which is encapsulating
the L2 frame based on a hash of the L2 frame. This allows packets to
be load-split evenly over LAGs and ECMP links on routers in the core,
responsible for delivering these IP encapsulated packets.
Destination Port: This is an IANA assigned well-known user port
number. Packets encapsulated by an OTV Edge Device put value 8472 in
the destination port field.
UDP Length: Is the length in bytes of the UDP header, the OTV header,
and the L2 frame without the preamble and CRC fields.
UDP Checksum: This is set to 0 by the OTV Edge Device when doing
encapsulation and ignored by the OTV Edge Device which is
decapsulating at the destination site.
OTV Header:
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Flags:
'I' - Instance ID bit. When set to 1, it indicates the Instance ID
should be used in the forwarding lookup.
'R' - Reserved bits.
Overlay ID: Is used only for control plane packets such as the URP/
MRP (IS-IS) to identify packets for a specific overlay.
Instance ID: Set by the OTV Edge Device doing the encapsulation to
specify a logical table that should be used for lookup by the OTV
Edge Device at the destination site.
L2 Ethernet Frame:
The L2 Frame minus the preamble and CRC received on an internal link
by an OTV Edge Device.
The addition of OTV encapsulation headers increases the size of an L2
packet received on an internal interface such that the core uplinks
on the Edge Device as well as the routers in the core need to support
an appropriately larger MTU. OTV encapsulated packets must not get
fragmented as they traverse the core, and hence the IP header is
marked to not fragment by the Edge Device. The Edge Device drops
packets that exceed the core uplink MTU.
The following tables enumerates how MAC level packets are
encapsulated in the OTV header.
MAC-level Frame OTV IP Encapsulation
--------------- --------------------
Unicast Frame IP unicast packet
Broadcast Frame ASM/Bidir IP multicast packet
Link-local Multicast Frame ASM/Bidir IP multicast packet
Data Multicast Frame SSM IP multicast packet
3.2. Forwarding Process
Most of the interesting forwarding cases happen when a packet comes
from the Overlay Link to be forwarded to an Internal Link, or vice
versa. But for completeness, forwarding between internal links is
also described
3.2.1. Forwarding between Internal Links
When an Edge Device has internal links, it operates like a
traditional L2 switch. That is, it will send unicast packets on a
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port where the MAC was learned; it will send multicast packets on the
ports it has IGMP/MLD-snooped; and it will send broadcast packets out
all ports for a given VLAN or layer-2 bridge domain
3.2.2. Forwarding from an Internal Link to the Overlay
An Edge Device will decide to forward a Layer-2 unicast, multicast,
or broadcast packet over the overlay interface when the overlay
control plane has put the logical port of the overlay interface in
the forwarding table, such as for the corresponding unicast or
multicast address. When a packet is sent over the overlay interface,
it is first prepended with an OTV header that includes the IP address
of the overlay next-hop. The packet as received from the internal
interface is not touched other than to remove the preamble and FCS
from the frame. The IP address, outer MAC address and other
encapsulation information are all installed in the forwarding
hardware by the control plane so the OTV header can be prepended and
the packet forwarded at high rate.
The Edge Device has to be eligible to forward this packet as per the
control plane, such as being the Authoritative Edge Device. Multi-
homing of sites imposes additional rules on the forwarding of traffic
as described later in this document.
3.2.3. Forwarding from the Overlay to an Internal Link
When a packet is received on the overlay interface, it will need to
be IP decapsulated to reveal the inner MAC header for forwarding.
The inner MAC header SA and DA addresses and VLAN-ID will used for
forwarding actions. For any type of packet received on the overlay
interface, it will be accepted only if the Edge Device is the
Authoritative Edge Device as determined by an inspection of the
received packet header.
When a unicast packet is received on the overlay interface, the outer
OTV IP header is removed, and the VLAN-ID and the MAC DA from the
inner header is used to do the MAC table lookup. Here onwards, this
is a regular bridging operation, whether the MAC address entry is
present or not.
When a multicast packet is received on the overlay interface, the
outer OTV IP header is removed. The VLAN-ID and inner MAC header SA
and DA or inner IP header SA and DA are used to do a Layer-2
multicast table lookup and forward the packet on the right internal
interfaces. A multicast packet received from the overlay will not be
sent back out on the overlay.
When a broadcast packet is received on the overlay interface, the
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outer OTV IP header is removed and the packet is then flooded on all
internal interfaces.
3.2.4. Unicast Packet Flows
Hosts typically generate ARP requests and learn the MAC addresses of
other hosts from ARP requests and replies. Switches learn the source
MACs from packet headers and store this state to optimally forward
traffic destined to these MACs. The OTV Edge Devices will also learn
the MACs locally on their site facing interfaces, and will install
remote MACs received over the overlay control plane into the local
MAC table with the appropriate remote Edge Devices as next-hops.
Once these actions take place, every switch will forward the L2
packet based on the MAC table entry. The OTV Edge Device at the
source site will also do a MAC table lookup which will yield a next-
hop entry pointing to a remote Edge Device. Once the OTV header with
the IP address is prepended, the packet is then forwarded to the
destination Edge Device at Layer-3 as a regular IP packet.
The Edge Device as well as the core routers may load-balance these
encapsulated packets among equal-cost multiple Layer-3 paths, with
packets belonging to a single Layer-2 flow being hashed to a specific
equal-cost path.
3.2.5. Unknown Unicast Packet Handling
When the switched network at an OTV site has no state for a MAC
address, it will flood the unicast packet on the spanning tree
throughout the site. The Edge Devices are on the spanning tree (like
any other switch at the site) so they will receive these unknown
unicast packets.
It is imperative that the Edge Devices hold previously learned MAC
addresses for an extended period of time so that remote Edge Devices
can get reachability to these local MACs. So the cache timers will
be longer than the traditional MAC aging timers on switches. In
fact, the Edge Device MAC aging timers generally need to be greater
than the ARP request interval from any host. Either an unknown flood
or a broadcast packet could cause an update of the MAC entries in the
Edge Device. And when MACs go inactive, an Authoritative Edge Device
must withdraw the MAC address from the overlay control plane.
Traffic to these unknown destinations will not be forwarded onto the
overlay. Thus, OTV does not flood unknown unicasts. In an OTV
network unknown destinations become known the moment the host emits
at least one packet. The assumption is that no host on the network
is completely silent.
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3.2.6. Multicast Packet Flows
A multicast receiver host sends out IGMP/MLD reports for the
multicast groups it wants to join. The sites may use either IGMPv2
or IGMPv3. A multicast capable switch will forward these reports to
router ports and querier ports. The OTV Edge Device behaves as
either a querier or a router in the network and hence receives these
reports.
A host in a site may be a source for an (S,G) group and sends data.
This data is flooded or forwarded along IGMP/MLD snooped links by the
site switches. When an Edge Device receives this packet, it does a
Layer-2 multicast table lookup which may yield several OIFs. If the
overlay interface is part of the OIF-list, then the Edge Device
encapsulates the packet in an OTV IP header which includes the
delivery group (DS, DG) IP addresses. It then emits the resulting IP
multicast packet into the core which is forwarded along a core
multicast tree to the receiver site edge devices.
The receiver site Edge Device also joins one or more (DS, DG) core
multicast trees as directed by various source site Edge Devices.
This allows it to receive data from other sites. The core multicast
trees may either be SSM or ASM though this document focusses on the
SSM case.
3.2.7. Broadcast Packet Flows
A broadcast packet originated at an OTV site needs to be delivered to
all sites of the same VPN. This is typically done with the ASM/Bidir
group encapsulation which is the same group used for the oURP/oMRP
(pMG). A different data group can also be used to forward broadcast
traffic.
A broadcast packet, sourced in a site, gets to all Edge Devices
because each Edge Device is on the site spanning tree. However,
duplicates must not be allowed to appear on the overlay network when
there are multiple Edge Devices, so the Authoritative Edge Device for
the VLAN is the only Edge Device that forwards the packet on the
overlay network. All edge devices at a remote site will receive the
broadcast packet over the core multicast group. To prevent
duplicates going into the site, only the Authoritative Edge Device in
that site will forward the packet into the site. And once sent into
the site, the packet gets to all switches on the site spanning tree.
Because only the AED can forward broadcast packets in or out of the
site, broadcast loops are avoided.
Other types of packets such as link-local multicast packets and
non-IP Layer-2 packets may also be sent along the pMG or on a
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dedicated data group.
3.3. STP BPDU Handling
Since the Edge Device acts as an L2 switch it does participate in the
Spanning Tree Protocol if the site has been configured to use it.
However, there is no STP activity on the overlay interface. The
following are the rules an OTV Edge Device will follow:
o When STP is configured at a site, an Edge Device will send and
receive BPDUs on internal interfaces. An OTV Edge Device will not
originate or forward BPDUs on the overlay network.
o An OTV Edge Device can become a root of one or more spanning trees.
o An OTV Edge Device will take the typical action when receiving
Topology Change Notification (TCNs) messages.
o When on OTV Edge Device detects another Edge Device in it's site
has come up or gone down, it may send a TCN so it can gather new
state for when its authoritative status changes for a VLAN.
To allow the L2 switch network to scale to larger number of nodes and
MAC addresses, it is considered a feature of OTV to maintain and keep
the spanning trees small and per site.
4. MAC Address Mobility
In a traditional layer-2 switched network, mobility of a host is
easily achievable because each switch in the network tracks the
source MAC address in each packet and the interface the last packet
was received on. So if that MAC is later seen on another interface,
the new interface can be updated at the same time the packet is
forwarded. These fast MAC moves need to be achieved when a MAC moves
from one OTV site to another. The Authoritative Edge Device for a
VLAN determines a MAC move in combination with traditional learning
on the internal interfaces and explicit MAC advertisements on the
overlay.
If an Authoritative Edge Device has a MAC address stored in the MAC
forwarding table which points to the overlay interface, it means that
an Edge Device in another site has explicitly advertised the MAC as
being local to it's site. Therefore, any packets coming from the MAC
will be coming from the overlay. Once that MAC is heard on an
internal interface, it has moved into the site. Since it has moved
into a new site, the Authoritative Edge Device in the new site is
responsible for advertising it.
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When a MAC appears in a new site, the Authoritative Edge Device will
advertise the new MAC address with a metric value of 0. When the
Edge Device in the site the MAC has moved from hears the
advertisement, it will withdraw the MAC address that it had
previously advertised. Once the MAC address is withdrawn, the Edge
Device where the MAC has moved to will change the metric value to 1.
All remote sites sending to this MAC address will start using the new
Edge Device as soon as they hear it's MAC advertisement with metric
0.
5. Multi-homing
A site typically will be multi-homed with multiple Edge Devices
connecting to the overlay. This provides the site with increased
network redundancy and resilience to failures.
When sites are multi-homed, there is a potential for loops to be
created between the OTV overlay and the layer-2 domains at different
sites. One option to address such loops is to transport STP BPDUs on
the overlay and rely on STP to break any loops that may form when
multi-homed sites connect to the overlay. However, this is not
desirable as it leads to very large or complex STP domains. OTV
multi-homing avoids loops through a combination of techniques in the
control plane and data plane.
OTV does not transport STP BPDUs over the core. As a result, each
site will have its own STP domain, which is separate and independent
from the STP domains in other sites, even though all sites will be
part of a common broadcast or Layer-2 domain. It also does not flood
unknown unicast traffic on the overlay.
5.1. Authoritative Edge Device Selection
An Authoritative Edge Device is an Edge Device that forwards Layer-2
frames in and out of a site from and to the overlay network. When a
site is multi-homed to the overlay, a proper Authoritative Edge
Device selection ensures that traffic crossing the site-overlay
boundary does not get duplicated, create loops or cause any churn in
the MAC tables of switches within the local and remote sites.
The Authoritative Edge Device (AED) may be statically assigned or
determined via an election among the devices in the same site. A
unique AED may be selected for each VLAN or it may be on a finer MAC-
level granularity. In either case, for a given MAC-level flow, the
data path will be symmetric.
An Authoritative Edge Device has the primary responsibility to
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advertise locally learned source MAC addresses and IGMP/MLD-snooped
multicast addresses in the oURP and oMRP.
When done per-VLAN, an AED will be authoritative for all unicast and
multicast addresses within a single VLAN. The authoritative
responsibility can be shared with other Edge Devices for other VLANs
so traffic can be load balanced among all Edge Devices across
different VLANs.
For the particular scenario of all-active multi-homing and load
balancing, AEDs may be elected on a finer granularity. Thus there
may be several AEDs in any given VLAN in this case and different
flows can use different Edge Devices.
Protocol adjacencies are set up among the Edge Devices in the same
site. The AED is selected from this list of Edge Devices in the same
site. The AED selection algorithm tries to ensures an even spread of
VLANs across the Edge Devices. A simple mechanism may be via a hash
of the VLAN-ID. Alternatively, a static AED assignment may be to use
a VLAN range division among all Edge Devices in the site. The local
VLAN/AED specific information may be advertised to other Edge
Devices.
Each Edge Device keeps track of the other Edge Devices in the same
site. If an Edge Device has a failure such that it is incapable of
forwarding traffic for its authorized VLANs, other Edge Devices in
the same site will detect or be notified of this event and run the
AED selection procedure to reassign authority for the failed device's
VLANs.
5.2. Site Identifier
All Edge Devices that belong to a single Layer-2 site will advertise
a Site-ID on the overlay control plane. This information is used by
remote Edge Devices to identify the members of the same site. The
Site-ID influences the AED election and path selection from remote
Edge Devices to the local site. The Site-ID may be statically
assigned or dynamically computed by the devices in the same site.
6. IS-IS as an Overlay Control Protocol
This section describes the use of the IS-IS protocol to serve as the
Overlay URP and MRP. The details of the IS-IS PDUs and TLVs defined
for OTV are described in [IS-IS-OTV].
It is highly desired to leverage the native and existing IS-IS
protocol functionality where feasible. There are some protocol
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extensions specific to OTV which are described in this document.
The overlay network serves as a logical multi-access Ethernet LAN
connecting the various Edge Devices. Hence, IS-IS hellos and LSPs
can be exchanged directly over the overlay network similar to IS-IS
operation on a LAN. These IS-IS packets are encapsulated in the OTV
IP multicast header and reach other Edge Devices on the core
multicast tree. In addition, OTV IS-IS packets use a distinct
Layer-2 multicast destination address. Therefore, OTV IS-IS packets
do not conflict with IS-IS packets used for other technologies even
if they may be sent over the same links in the core or arrive at an
Edge Device on the same core uplink interfaces.
IS-IS packets belonging to different overlay VPNs are mutually
isolated and distinguished by the OTV control packet header and the
use of distinct multicast groups in the core. Standard IS-IS
authentication mechanisms may additionally be used to provide further
isolation and authentication of VPN membership.
OTV IS-IS employs IS-IS LAN procedures on the overlay network. It
forms IS-IS adjacencies with all other Edge Devices in the overlay
and elects a Designated Router (DIS). The IS-IS system ID uniquely
identifies an Edge Device in the IS-IS control plane.
IS-IS IIHs are sent and received on the overlay by all Edge Devices.
The IP addresses assigned to the overlay on an Edge Device is
advertised in the IIHs and provides the IP reachability information
to the edge device through the core.
CSNPs are sent on the overlay by the DIS and used to achieve reliable
delivery of the link state database. This link state database holds
LSPs that describe the Edge Device connectivity to the pseudo-node
(or the multi-access overlay network). The LSPs also hold the
unicast MAC information that is advertised by a site Edge Device.
CSNPs are also used to reliably deliver the Group Membership link
state database that holds LSPs describing the multicast MAC group
addresses. OTV IS-IS only maintains the Level-1 link state database.
Unicast MAC address information is carried in LSPs in the MAC-
Reachability (MAC-RI) TLV defined in [RFC6165]. All MAC addresses
are typically advertised with a metric of 1. When using the MAC move
procedures, the metric will be set to 0. Definition of the fields
used by OTV is specified in [IS-IS-OTV].
Multicast related information is carried in LSPs in several different
TLVs specified in [IS-IS-OTV]. The multicast groups that a site has
receivers for are carried in the sub-TLVs of the Group Address TLV.
Multicast sources discovered in a site are advertised in a Group
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Membership Active Source TLV. This TLV includes the list of groups
for which the source is sending data along with the core Delivery
Groups to which the advertising Edge Device will map the site data
groups.
When an Adjacency Server is being used, all Edge Devices inform the
Adjacency Server regarding their reachability and capability
information by including in their hellos the Adjacency Server TLV.
The Adjacency Server includes a list of all the Edge Devices it has
heard from, and their capabilities, in its hello PDUs.
The Site-ID information is contained in the Site Identifier TLV and
sent in IS-IS IIHs.
7. Acknowledgements
The authors would like to thank many for their careful review. They
include Venu Nair, Victor Moreno, Ashok Chippa, Sameer Merchant, Tony
Speakman, Raghava Sivaramu, Nataraj Batchu, Sreenivas Duvvuri, Gaurav
Badoni, Veena Raghavan, Marc Woolward and Tim Stevenson.
Many have received individual presentations of OTV and provided
critical feedback early in the design process. These reviewers
include Vince Fuller, Peter Lothberg, Dorian Kim, Peter Schoenmaker,
Mark Berly, Scott Kirby, Dana Blair, Tom Edsall, Dinesh Dutt,
Parantap Lahiri, and Jeff Jensen.
8. Security Considerations
The specifications in this document do not add any new security
issues to Layer-2 bridging technologies. Existing security
mechanisms may be used both in the control plane and in data
forwarding to achieve any security requirements.
This document specifies the use of IS-IS as a control protocol for
OTV. It adds no additional security risks to IS-IS, nor does it
provide any additional security for IS-IS.
9. IANA Considerations
There are new IS-IS PDUs and TLVs being proposed for OTV, and are
defined in [IS-IS-OTV].
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10. Normative References
[IS-IS] ISO/IEC 10589, "Intermediate System to Intermediate System
Intra-Domain Routing Exchange Protocol for use in
Conjunction with the Protocol for Providing the
Connectionless-mode Network Service (ISO 8473)", 2005.
[IS-IS-OTV]
Rao, D., "IS-IS Extensions to support OTV", 2011.
[RFC6165] Banerjee, A. and D. Ward, "Extensions to IS-IS for Layer-2
Systems", RFC 6165, April 2011.
Authors' Addresses
Hasmit Grover
Cisco Systems
170 W Tasman Drive
San Jose, CA 95138
US
Email: hasmit@cisco.com
Dhananjaya Rao
Cisco Systems
170 W Tasman Drive
San Jose, CA 95138
US
Email: dhrao@cisco.com
Dino Farinacci
Cisco Systems
170 W Tasman Drive
San Jose, CA 95138
US
Email: dino@cisco.com
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Victor Moreno
Cisco Systems
170 W Tasman Drive
San Jose, CA 95138
US
Email: vimoreno@cisco.com
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