LISP L2/L3 EID Mobility Using a Unified Control Plane
draft-ietf-lisp-eid-mobility-11
| Document | Type | Active Internet-Draft (lisp WG) | |
|---|---|---|---|
| Authors | Marc Portoles-Comeras , Vrushali Ashtaputre , Fabio Maino , Victor Moreno , Dino Farinacci | ||
| Last updated | 2023-01-10 | ||
| Replaces | draft-portoles-lisp-eid-mobility | ||
| RFC stream | Internet Engineering Task Force (IETF) | ||
| Intended RFC status | (None) | ||
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| Additional resources | Mailing list discussion | ||
| Stream | WG state | WG Document | |
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draft-ietf-lisp-eid-mobility-11
Network Working Group M. Portoles
Internet-Draft V. Ashtaputre
Intended status: Experimental F. Maino
Expires: 14 July 2023 Cisco Systems
V. Moreno
Google LLC
D. Farinacci
lispers.net
10 January 2023
LISP L2/L3 EID Mobility Using a Unified Control Plane
draft-ietf-lisp-eid-mobility-11
Abstract
The LISP control plane offers the flexibility to support multiple
overlay flavors simultaneously. This document specifies how LISP can
be used to provide control-plane support to deploy a unified L2 and
L3 overlay solution for End-point Identifier (EID) mobility, as well
as analyzing possible deployment options and models.
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].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
This Internet-Draft will expire on 14 July 2023.
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Copyright Notice
Copyright (c) 2023 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 (https://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. Code Components
extracted from this document must include Revised BSD License text as
described in Section 4.e of the Trust Legal Provisions and are
provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 4
3. Reference System . . . . . . . . . . . . . . . . . . . . . . 4
4. L3 Overlays and Mobility Support . . . . . . . . . . . . . . 6
4.1. Reference Architecture and packet flows . . . . . . . . . 6
4.1.1. Routed Traffic Flow: L3 Overlay use . . . . . . . . . 6
4.1.2. L3 Mobility Flow . . . . . . . . . . . . . . . . . . 7
4.1.2.1. L3 Mobility Flow using Data Driven SMRs . . . . . 7
4.1.2.2. L3 Mobility Flow using Publish/Subscribe
Mechanisms . . . . . . . . . . . . . . . . . . . . 8
4.2. Implementation Considerations . . . . . . . . . . . . . . 9
4.2.1. L3 Segmentation . . . . . . . . . . . . . . . . . . . 9
4.2.2. L3 Database-Mappings . . . . . . . . . . . . . . . . 10
4.2.3. LISP Mapping System support . . . . . . . . . . . . . 10
4.2.4. Using SMRs to Track Moved-Away Hosts . . . . . . . . 11
4.2.5. L3 multicast support . . . . . . . . . . . . . . . . 11
4.2.6. Time-to-Live Handling in Data-Plane . . . . . . . . . 11
5. L2 Overlays and Mobility Support . . . . . . . . . . . . . . 11
5.1. Reference Architecture and packet flows . . . . . . . . . 12
5.1.1. Bridged Traffic Flow: L2 Overlay use . . . . . . . . 12
5.1.2. L2 Mobility Flow . . . . . . . . . . . . . . . . . . 13
5.1.2.1. L2 Mobility Flow using Data Driven SMRs . . . . . 13
5.1.2.2. L2 Mobility Flow using Publish/Subscribe
mechanisms . . . . . . . . . . . . . . . . . . . . 14
5.2. Implementation Considerations . . . . . . . . . . . . . . 15
5.2.1. L2 Segmentation . . . . . . . . . . . . . . . . . . . 15
5.2.2. L2 Database-Mappings . . . . . . . . . . . . . . . . 15
5.2.3. Interface to the LISP Mapping System . . . . . . . . 16
5.2.4. SMR support to track L2 hosts that moved away . . . . 16
5.2.5. L2 Broadcast and Multicast traffic . . . . . . . . . 17
5.2.6. L2 Unknown Unicast Support . . . . . . . . . . . . . 17
5.2.7. Time-to-Live Handling in Data-Plane . . . . . . . . . 18
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5.3. Support to ARP resolution through Mapping System . . . . 18
5.3.1. Map-Server support to ARP resolution: Packet Flow . . 18
5.3.2. ARP registrations: MAC as a locator record . . . . . 19
5.3.3. Implementation Considerations . . . . . . . . . . . . 21
5.4. Multihoming Support . . . . . . . . . . . . . . . . . . . 22
5.4.1. Identification of L2 multihomed segments . . . . . . 22
5.4.2. Synchronizatioin of database-mappping tables . . . . 22
5.4.3. All active vs Active-Standby modes . . . . . . . . . 22
5.4.4. Split Horizon support . . . . . . . . . . . . . . . . 22
5.4.5. Designated Forwarder Selection . . . . . . . . . . . 22
6. Optional Deployment Models . . . . . . . . . . . . . . . . . 22
6.1. IP Forwarding of Intra-subnet Traffic . . . . . . . . . . 22
6.2. Data-plane Encapsulation Options . . . . . . . . . . . . 23
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 24
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 24
9.1. Normative References . . . . . . . . . . . . . . . . . . 24
9.2. Informative References . . . . . . . . . . . . . . . . . 25
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 26
1. Introduction
This document describes the architecture and design options required
to offer a unified L2 and L3 overlay solution for End-point
Identifier (EID) mobility using the LISP control-plane.
The architecture takes advantage of the flexibility that LISP
provides to simultaneously support different overlay types. While
the LISP specification defines both the data-plane and the control-
plane, this document focuses on the use of the control-plane to
provide L2 and L3 overlay services with EID mobility. The control
plane may be combined with a data-plane of choice e.g., [LISP],
[VXLAN-GPE], or [VXLAN].
The recommendation on whether a flow is sent over the L2 or the L3
overlay is based on whether the traffic is bridged (intra-subnet or
non-IP) or routed (inter-subnet), respectively. This allows treating
both overlays as separate segments, and enables L2-only and L3-only
deployments (and combinations of them) without modifying the
architecture.
The unified solution for L2 and L3 overlays offers the possibility to
extend subnets and routing domains (as required in state-of-art
Datacenter and Enterprise architectures) with mobility support and
traffic optimization.
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An important use-case of the unified architecture is that, while most
data centers are complete layer-3 routing domains, legacy
applications either have not converted to IP or still use auto-
discovery at layer-2 and assume all nodes in an application cluster
belong to the same subnet. For these applications, the L2-overlay
limits the functionality to where the legacy app lives versus having
to extend layer-2 into the underlay network.
Broadcast, Unknown and Multicast traffic on the overlay are supported
by either replicated unicast, or underlay (RLOC) multicast as
specified in [RFC6831] and [RFC8378].
2. Definition of Terms
LISP related terms are defined as part of the LISP specification
[RFC9300] and [RFC9301], notably EID, RLOC, Map-Request, Map- Reply,
Map-Notify, Ingress Tunnel Router (ITR), Egress Tunnel Router (ETR),
Map- Server (MS) and Map-Resolver (MR).
3. Reference System
The following figure illustrates the reference system used to support
the packet flow description throughout this document. The system
presents 4 sites. Site A and Site D provide access to different
subnets (non-extended), while Site B and Site C extend a common
subnet. The xTR in each one of the sites registers EIDs from the
sites with the LISP Mapping System and provides support to
encapsulate overlay (EID) traffic through the underlay (RLOC space).
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,-------------.
(Mapping System )
-+------------+
+--+--+ +-+---+
|MS/MR| |MS/MR|
+-+---+ +-----+
.-._..-._.--._..|._.,.-._.,|-._.-_._.-.._.-.
.-.' '.-.
( L3 Underlay )
( (RLOC Space) )
'.-._.'.-._.'--'._.'.-._.'.-._.'.-._.'.-._.'.-._.-.'
/ | | \
RLOC=IP_A RLOC=IP_B RLOC=IP_C RLOC=IP_D
+-+--+--+ +-+--+--+ +-+--+--+ +-+--+--+
.| xTR A |.-. .| xTR B |.-. .| xTR C |.-. .| xTR D |.-.
( +-+--+--+ ) ( +-+--+--+ ) ( +-+--+--+ ) ( +-+--+--+ )
.' Site A ) .' Site B ) .' Site C ) .' Site D )
( 1.0.0.0/24 . ( 3.0.0.0/24 . ( 3.0.0.0/24 . ( 2.0.0.0/24 .
'--'._.'. ) '--'._.'. ) '--'._.'. ) '--'._.'. )
/ '--' | '--' | '--' \ '--'
'--------' '--------' '--------' '--------'
: End : : End : : End : : End :
:Device 1: :Device 2: :Device 3: :Device 4:
'--------' '--------' '--------' '--------'
IP: 1.0.0.1 IP: 3.0.0.2 IP: 3.0.0.3 IP: 2.0.0.4
MAC: 0:0:3:0:0:2 MAC: 0:0:3:0:0:3
Figure 1: Reference System Architecture with unified L2 and L3
overlays
The recommended selection between the use of L2 and L3 overlays is to
map them to bridged (intra-subnet or non-IP) and routed (inter-
subnet) traffic. The rest of the document follows this
recommendation to describe the packet flows.
However, note that in a different selection approach, intra-subnet
traffic MAY also be sent over the L3 overlay. Section 6.1 specifies
the changes needed to send all IP traffic using the L3 overlay and
restricting the use of the L2 overlay to non-IP traffic.
When required, the control plane makes use of two basic types of EID-
to-RLOC mappings associated to end-hosts and in order to support the
unified architecture:
* EID = <IID, MAC> to RLOC=<IP>. This is used to support the L2
overlay.
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* EID = <IID, IP> to RLOC=<IP>. This is the traditional mapping as
defined in the original LISP specification and supports the L3
overlay.
4. L3 Overlays and Mobility Support
4.1. Reference Architecture and packet flows
In order to support the packet flow descriptions in this section we
use Figure 1 as reference. This section uses Sites A and D to
describe the flows.
/ | | \
RLOC=IP_A RLOC=IP_B RLOC=IP_C RLOC=IP_D
+-+--+--+ +-+--+--+ +-+--+--+ +-+--+--+
.| xTR A |.-. .| xTR B |.-. .| xTR C |.-. .| xTR D |.-.
( +-+--+--+ ) ( +-+--+--+ ) ( +-+--+--+ ) ( +-+--+--+ )
.' Site A ) .' Site B ) .' Site C ) .' Site D )
( 1.0.0.0/24 . ( 3.0.0.0/24 . ( 3.0.0.0/24 . ( 2.0.0.0/24 .
'--'._.'. ) '--'._.'. ) '--'._.'. ) '--'._.'. )
/ '--' | '--' | '--' \ '--'
'--------' '--------' '--------' '--------'
: End : : End : : End : : End :
:Device 1: :Device 2: :Device 3: :Device 4:
'--------' '--------' '--------' '--------'
(IID1,1.0.0.1) (IID1,3.0.0.2) (IID1,3.0.0.3) (IID1,2.0.0.4)
(IID2,0:0:3:0:0:2) (IID2,0:0:3:0:0:3)
Figure 2: Reference Mobility Architecture
4.1.1. Routed Traffic Flow: L3 Overlay use
Inter-subnet traffic is encapsulated using the L3 overlay. The
process to encapsulate this traffic is the same as described in
[RFC9300] and [RFC9301]. We describe the packet flow here for
completeness
The following is a sequence example of the unicast packet flow and
the control plane operations when in the topology shown in Figure 1
End-Device 1, in LISP site A, wants to communicate with End-Device 4
in LISP site D. Note that both end systems reside in different
subnets. We'll assume that End-Device 1 knows the EID IP address of
End-Device 4 (e.g. it is learned using a DNS service).
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* End-Device 1 sends an IP packet frame with destination 2.0.0.4 and
source 1.0.0.1. As the destination address lies on a different
subnet End-Device 1 sends the packet following its routing table
to ITR A (e.g., it is its default gateway).
* ITR A does a L3 lookup in its local map-cache for the destination
IP 2.0.0.4. When the lookup of 2.0.0.4 is a miss, the ITR sends a
Map-request to the mapping database system looking up for
EID=<IID1,2.0.0.4>.
* The mapping systems forwards the Map-Request to ETR D, that has
registered the EID-to-RLOC mapping of EID=<IID1,2.0.0.4>.
* ETR D sends a Map-Reply to ITR A that includes the EID-to-RLOC
mapping: EID=<IID1,2.0.0.4> -> RLOC=IP_D, where IP_D is the
locator of ETR D.
* ITR A populates the local map-cache with the EID to RLOC mapping,
and encapsulates all subsequent packets with a destination IP
2.0.0.4 using destination RLOC=IP_D.
4.1.2. L3 Mobility Flow
The support to L3 mobility covers the requirements to allow an end-
host to move from a given site to another and maintain correspondence
with the rest of end-hosts that are connected to the same L3 routing
domain. This support MUST ensure convergence of L3 forwarding (IPv4/
IPv6 based) from the old location to the new one when the host
completes its move.
The update of the ITR map-caches when EIDs move MAY be achieved using
Data Driven SMRs or the Publish/Subscribe mechanisms defined in
[I-D.ietf-lisp-pubsub]. The following two sections are sequence
descriptions of the packet flow when End-Device 1 in the reference
figure roams to site D.
4.1.2.1. L3 Mobility Flow using Data Driven SMRs
The following is a sequence description of the packet flow when End-
Device 1 in the reference figure roams to site D. This sequence uses
Data Driven SMRs to trigger the updates of the ITR map-caches.
* When End-Device 1 is attached or detected in site D, ETR D sets up
the database mapping corresponding to EID=<IID1, 1.0.0.1>. ETR D
sends a Map-Register to the mapping system registering RLOC=IP_D
as locator for EID=<IID1, 1.0.0.1>. Now the mapping system is
updated with the new EID-to-RLOC mapping (location) for End-Device
1.
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* The Mapping System, after receiving the new registration for
EID=<IID1, 1.0.0.1> sends a Map-Notify to the departure ETR(s)
(ETR A) to inform it of the move. Then, ETR A removes its local
database mapping information and stops registering EID=<IID1,
1.0.0.1>.
* Any ITR or PiTR participating in the L3 overlay (corresponding to
IID1) that were sending traffic to 1.0.0.1 before the migration
keep sending traffic to ETR A.
* Once ETR A is notified by the Mapping system, when it receives
traffic from an ITR with destination 1.0.0.1, it generates a
Solicit-Map-Request (SMR) back to the ITR (or PiTR) for EID=<IID1,
1.0.0.1>.
* Upon receiving the SMR the ITR invalidates its local map- cache
entry for EID=<IID1, 1.0.0.1> and sends a new Map-Request for that
EID. The Map-Reply includes the new EID-to-RLOC mapping for End-
Device 1 with RLOC=IP_D.
* Similarly, once the local database mapping is removed from ITR A,
non-encapsulated packets arriving at ITR A from a local End-Device
and destined to End-Device 1 result in a cache miss, which
triggers sending a Map-Request for EID=<IID1, 1.0.0.1> to populate
the map-cache of ITR A.
4.1.2.2. L3 Mobility Flow using Publish/Subscribe Mechanisms
When Publish/Subscribe ([I-D.ietf-lisp-pubsub]) mechanisms are used,
the flow of signaling to achieve EID mobility is modified. In this
case, when an local end-device connected via an ITR establishes
communication with a remote mobile end-device (connected to a remote
ETR), the ITR will issue a Map-Request for the mobile end-device.
Following the Mapping Request Subscribe Procedures defined in
[I-D.ietf-lisp-pubsub], the Map-request will be issued with the N-bit
set on the EID-Record so that the ITR is notified of any RLOC-set
changes for the mobile EID-prefix.
The following is a sequence description of the packet flow when End-
Device 1 in the reference figure roams to site D. This sequence
leverages Publish/Subscribe mechanisms to update the ITR map-caches.
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* When an end-Device connected via an ITR establishes communication
with a mobile end-device (e.g. end-device 1), the ITR will issue a
Map-Request for the mobile end-device. Following the Mapping
Request Subscribe Procedures defined in [I-D.ietf-lisp-pubsub],
the Map-request will be issued with the N-bit set on the EID-
Record so that the ITR is notified of any RLOC-set changes for the
mobile EID-prefix.
* When the mobile end-device (End-Device 1) is attached or detected
in a new site (e.g. site D), The ETR at the new site (e.g. ETR D)
sets up the database mapping corresponding to the EID of the
mobile end-device (e.g. EID=<IID1, 1.0.0.1>). The ETR at the new
site (e.g. ETR D) sends a Map-Register to the mapping system
registering its RLOCs (e.g. RLOC=IP_D) as locator for the EID of
the mobile end-device (e.g. EID=<IID1, 1.0.0.1>). Now the
mapping system is updated with the new EID-to-RLOC mapping
(location) for the mobile end-device (e.g. End-Device 1).
* The Mapping System, after receiving the new registration for the
EID of the mobile end-device (EID=<IID1, 1.0.0.1>) sends a Map-
Notify to the departure site (ETR A) to inform it of the move.
Then, the ETR at the departure site (ETR A) removes its local
database mapping information and stops registering the EID for the
mobile end-device (EID=<IID1, 1.0.0.1>).
* Any ITR or PiTR participating in the L3 overlay (corresponding to
IID1) that were sending traffic to the mobile end-device (1.0.0.1)
would have Subscribed to receive notifications of any changes in
the RLOC-set for the EID of the mobile end-device (1.0.0.1). The
Mapping System publishes the updated RLOC-set to the Subscribed
ITRs by sending a Map-Notify to the ITRs or PiTRs per the Mapping
Notification Publish Procedures defined in [I-D.ietf-lisp-pubsub].
* Upon receiving the Map-Notify message, the ITR updates the RLOC-
set in its local map-cache entry for the EID of the mobile end-
device (EID=<IID1, 1.0.0.1>). Once the map-cache is updated,
traffic is tunneled by the ITR to the new location.
4.2. Implementation Considerations
4.2.1. L3 Segmentation
LISP support of segmentation and multi-tenancy is structured around
the propagation and use of Instance-IDs, and handled as part of the
EID in control plane operations. The encoding is described in
[RFC8060] and its use in [RFC8111].
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Instance-IDs can be used to support L3 overlay segmentation, such as
in extended VRFs or multi-VPN overlays ([I-D.ietf-lisp-vpn]).
4.2.2. L3 Database-Mappings
When an end-host is attached or detected in an ETR that provides
L3-overlay services and mobility, a database Mapping is registered to
the mapping system with the following structure:
* The EID 2-tuple (IID, IP) with its binding to a corresponding ETR
locator set (IP RLOC)
The registration of these EIDs MUST follow the LCAF format as defined
in [RFC8060] and the specific EID record to be used is illustrated in
the following figure:
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Record TTL |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E | Locator Count | EID mask-len | ACT |A| Reserved |
I +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
D | Rsvd | Map-Version Number | AFI = 16387 |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | Rsvd1 | Flags | Type = 2 | IID mask-len |
e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
c | 4 + n | Instance-ID... |
o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | ...Instance-ID | EID-AFI = 1 or 2 |
d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | EID-Prefix (IPv4 or IPv6) |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /| Priority | Weight | M Priority | M Weight |
| L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o | Unused Flags |L|p|R| Loc-AFI |
| c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| \| Locator |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The L3 EID record follows the structure as described in [RFC9301].
4.2.3. LISP Mapping System support
The interface between the xTRs and the Mapping System is described in
[RFC9301] and this document follows the specification as described
there. When available, the registrations MAY be implemented over a
reliable transport as described in
[I-D.ietf-lisp-map-server-reliable-transport].
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In order to support system convergence after mobility, when the Map-
Server receives a new registration for a specific EID, it MUST send a
Map-Notify to the entire RLOC set in the site that last registered
this same EID. This Map-Notify is used to track moved-away state of
L3 EIDs as described in Section 4.2.4.
4.2.4. Using SMRs to Track Moved-Away Hosts
One of the key elements to support end-host mobility using the LISP
architecture is the Solicit-Map-Request (SMR). This is a special
message by means of which an ETR can request an ITR to send a new
Map-Request for a particular EID record. In essence the SMR message
is used as a signal to indicate a change in mapping information and
it is described in [RFC9301].
In order to support mobility, an ETR SHALL maintain a list of EID
records for which it has to generate a SMR message whenever it
receives traffic with that EID as destination.
The particular strategy to maintain an Away Table is implementation
specific and it will be typically based on the strategy to detect the
presence of hosts and the use of Map-Notify messages received from
the Map-Server. In essence the table SHOULD provide support to the
following:
* Keep track of end-hosts that were once connected to an ETR and
have moved away.
* Support for L3 EID records, the 2-tuple (IID, IP), for which a SMR
message SHOULD be generated.
4.2.5. L3 multicast support
L3 Multicast traffic on the overlay MAY be supported by either
replicated unicast, or underlay (RLOC) multicast. Specific solutions
to support L3 multicast over LISP controlled overlays are specified
in in [RFC6831], and [RFC8378].
4.2.6. Time-to-Live Handling in Data-Plane
The LISP specification ([RFC9300]) describes how to handle Time-to-
Live values of the inner and outer headers during encapsulation and
decapsulation of packets when using the L3 overlay.
5. L2 Overlays and Mobility Support
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5.1. Reference Architecture and packet flows
In order to support L2 packet flow descriptions in this section we
use Figure 1 as reference. This section uses Sites B and C to
describe the flows.
/ | | \
RLOC=IP_A RLOC=IP_B RLOC=IP_C RLOC=IP_D
+-+--+--+ +-+--+--+ +-+--+--+ +-+--+--+
.| xTR A |.-. .| xTR B |.-. .| xTR C |.-. .| xTR D |.-.
( +-+--+--+ ) ( +-+--+--+ ) ( +-+--+--+ ) ( +-+--+--+ )
.' Site A ) .' Site B ) .' Site C ) .' Site D )
( 1.0.0.0/24 . ( 3.0.0.0/24 . ( 3.0.0.0/24 . ( 2.0.0.0/24 .
'--'._.'. ) '--'._.'. ) '--'._.'. ) '--'._.'. )
/ '--' | '--' | '--' \ '--'
'--------' '--------' '--------' '--------'
: End : : End : : End : : End :
:Device 1: :Device 2: :Device 3: :Device 4:
'--------' '--------' '--------' '--------'
(IID1,1.0.0.1) (IID1,3.0.0.2) (IID1,3.0.0.3) (IID1,2.0.0.4)
(IID2,0:0:3:0:0:2) (IID2,0:0:3:0:0:3)
Figure 3: Reference Mobility Architecture
5.1.1. Bridged Traffic Flow: L2 Overlay use
Bridged traffic is encapsulated using the L2 overlay. This section
provides an example of the unicast packet flow and the control plane
operations when in the topology shown in Figure 1, the End-Device 2
in site B communicates with the End-Device 3 in site C. In this case
we assume that End Device 2, knows the MAC address of End-Device 3
(e.g., learned through ARP).
* End-Device 2 sends an Ethernet/IEEE 802 MAC frame with destination
0:0:3:0:0:3 and source 0:0:3:0:0:2.
* ITR B does a L2 lookup in its local map-cache for the destination
MAC 0:0:3:0:0:3. When the lookup of 0:0:3:0:0:3 is a miss, the
ITR sends a Map-Request to the mapping database system looking up
for EID=<IID2,0:0:3:0:0:3>.
* The mapping systems forwards the Map-Request to ETR C, that has
registered the EID-to-RLOC mapping for EID=<IID2,0:0:3:0:0:3>.
Alternatively, depending on the mapping system configuration, a
Map-Server which is part of the mapping database system MAY send a
Map-Reply directly to ITR B.
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* ETR C sends a Map-Reply to ITR B that includes the EID-to-RLOC
mapping: EID=<IID2, 0:0:3:0:0:3> -> RLOC=IP_C, where IP_C is the
locator of ETR C.
* ITR B populates the local map-cache with the EID to RLOC mapping,
and encapsulates all subsequent packets with a destination MAC
0:0:3:0:0:3 using destination RLOC=IP_C.
5.1.2. L2 Mobility Flow
The support to L2 mobility covers the requirements to allow an end-
host to move from a given site to another and maintain correspondence
with the rest of end-hosts that are connected to the same L2 domain
(e.g. extended VLAN). This support MUST ensure convergence of L2
forwarding (MAC based) from the old location to the new one, when the
host completes its move.
The update of the ITR map-caches when EIDs move MAY be achieved using
Data Driven SMRs or the Publish/Subscribe mechanisms defined in
[I-D.ietf-lisp-pubsub]. The following two sections are sequence
descriptions of the packet flow when End-Device 2 in the reference
figure roams to site C, which is extending its own subnet network.
5.1.2.1. L2 Mobility Flow using Data Driven SMRs
The following is a sequence description of the packet flow when End-
Device 2 in the reference figure roams to site C. This sequence uses
Data Driven SMRs to trigger the updates of the ITR map-caches.
* When End-Device 2 is attached or detected in site C, ETR C sets up
the database mapping corresponding to EID=<IID2, 0:0:3:0:0:2>.
ETR C sends a Map-Register to the mapping system registering
RLOC=IP_B as locator for EID=<IID2, 0:0:3:0:0:2>.
* The Mapping System, after receiving the new registration for
EID=<IID1, 0:0:3:0:0:2> sends a Map-Notify to ETR B with the new
locator set (IP_B). ETR B removes then its local database mapping
and stops registering <IID2, 0:0:3:0:0:2>.
* Any PiTR or ITR participating in the same L2-overlay
(corresponding to IID2) that was encapsulating traffic to
0:0:3:0:0:2 before the migration continues encapsulating this
traffic to ETR B.
* Once ETR B is notified by the Mapping system, when it receives
traffic from an ITR which is destined to 0:0:3:0:0:2, it will
generate a Solicit-Map-Request (SMR) message that is sent to the
ITR for (IID2,0:0:3:0:0:2).
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* Upon receiving the SMR the ITR sends a new Map-Request for the
EID=<IID2,0:0:3:0:0:2>. As a response ETR B sends a Map-Reply
that includes the new EID-to-RLOC mapping for <IID2,0:0:3:0:0:2>
with RLOC=IP_B. This entry is cached in the L2 table of the ITR,
replacing the previous one, and traffic is then forwarded to the
new location.
5.1.2.2. L2 Mobility Flow using Publish/Subscribe mechanisms
When Publish/Subscribe ([I-D.ietf-lisp-pubsub]) mechanisms are used,
the flow of signaling to achieve EID mobility is modified. In this
case, when an End-Device connected via an ITR establishes
communication with a mobile EID-prefix, the ITR will issue a Map-
Request for the mobile End-device. Following the Mapping Request
Subscribe Procedures defined in [I-D.ietf-lisp-pubsub], the Map-
request will be issued with the N-bit set on the EID-Record so that
the ITR is notified of any RLOC-set changes for the mobile EID-
prefix.
The following is a sequence description of the packet flow when End-
Device 2 in the reference figure roams to site C. This sequence
leverages Publish/Subscribe mechanisms to update the ITR map-caches.
* When End-Device 2 is attached or detected in site C, ETR C sets up
the database mapping corresponding to EID=<IID2, 0:0:3:0:0:2>.
ETR C sends a Map-Register to the mapping system registering
RLOC=IP_B as locator for EID=<IID2, 0:0:3:0:0:2>.
* The Mapping System, after receiving the new registration for
EID=<IID1, 0:0:3:0:0:2> sends a Map-Notify to the departure site
(ETR B) with the new locator set (IP_B). ETR B removes then its
local database mapping and stops registering <IID2, 0:0:3:0:0:2>.
* Any ITR or PiTR participating in the same L2-overlay
(corresponding to IID2) that was encapsulating traffic to
0:0:3:0:0:2 before the migration would have Subscribed to receive
notifications of any changes in the RLOC-set for 0:0:3:0:0:2. The
Mapping System publishes the updated RLOC-set to the Subscribed
ITRs by sending a Map-Notify to the ITRs or PiTRs per the Mapping
Notification Publish Procedures defined in [I-D.ietf-lisp-pubsub].
* Upon receiving the Map-Notify message, the ITR updates the RLOC-
set in its local map-cache entry for EID=<IID2, 0:0:3:0:0:2>.
Once the map-cache is updated, traffic is tunneled by the ITR to
the new location.
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5.2. Implementation Considerations
5.2.1. L2 Segmentation
As with L3 overlays, LISP support of L2 segmentation is structured
around the propagation and use of Instance-IDs, and handled as part
of the EID in control plane operations. The encoding is described in
[RFC8060] and its use in [RFC8111]. Instance-IDs are unique to a
Mapping System and MAY be used to identify the overlay type (e.g., L2
or L3 overlay).
An Instance-ID can be used for L2 overlay segmentation. An important
aspect of L2 segmentation is the mapping of VLANs to IIDs. In this
case a Bridge Domain (which is the L2 equivalent to a VRF as a
forwarding context) maps to an IID, a VLAN-ID may map 1:1 to a bridge
domain or different VLAN-IDs on different ports may map to a common
Bridge Domain, which in turn maps to an IID in the L2 overlay. When
ethernet traffic is double tagged, usually the outer 802.1Q tag will
be mapped to a bridge domain on a per port basis, and the inner
802.1Q tag will remain part of the payload to be handled by the
overlay. The IID should therefore be able to carry ethernet traffic
with or without an 802.1Q header. A port may also be configured as a
trunk and we may chose to take the encapsulated traffic and map it to
a single IID in order to multiplex traffic from multiple VLANs on a
single IID. These are all examples of local operations that could be
effected on VLANs in order to map them to IIDs, they are provided as
examples and are not exhaustive.
5.2.2. L2 Database-Mappings
When an end-host is attached or detected in an ETR that provides
L2-overlay services, a database Mapping is registered to the mapping
system with the following structure:
* The EID 2-tuple (IID, MAC) with its binding to a locator set (IP
RLOC)
The registration of these EIDs MUST follow the LCAF format as defined
in [RFC8060] and as illustrated in the following figure:
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+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Record TTL |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E | Locator Count | EID mask-len | ACT |A| Reserved |
I +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
D | Rsvd | Map-Version Number | AFI = 16387 |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | Rsvd1 | Flags | Type = 2 | IID mask-len |
e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
c | 4 + n | Instance-ID... |
o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | ...Instance-ID | EID-AFI = 6 |
d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Layer-2 MAC Address ... |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /| ... Layer-2 MAC Address | Priority | Weight |
| L +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| o | M Priority | M Weight | Unused Flags |L|p|R|
| c +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | Loc-AFI | Locator.... |
| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| \| ... Locator
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The L2 EID record follows the structure as described in [RFC9301].
5.2.3. Interface to the LISP Mapping System
The interface between the xTRs and the Mapping System is described in
[RFC9301] and this document follows the specification as described
there. When available, the registrations MAY be implemented over a
reliable transport.
In order to support system convergence after mobility, when the Map-
Server receives a new registration for a specific EID, it MUST send a
Map-Notify to the entire RLOC set in the site that last registered
this same EID. This Map-Notify is used to track moved-away state of
L2 EIDs as described in Section 5.2.4.
5.2.4. SMR support to track L2 hosts that moved away
In order to support mobility, an ETR SHALL maintain a list of EID
records for which it has to generate a SMR message whenever it
receives traffic with that EID as destination.
The particular strategy to maintain a SMR table is implementation
specific. In essence the table SHOULD provide support for the
following:
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* Keep track of end-hosts that were once connected to an ETR and
have moved away.
* Support for L2 EID records, the 2-tuple (IID, MAC), for which a
SMR message SHOULD be generated.
5.2.5. L2 Broadcast and Multicast traffic
Broadcast and Multicast traffic on the L2-overlay is supported by
either replicated unicast, or underlay (RLOC) multicast.
xTRs that offer L2 overlay services and are part of the same
Instance-ID join a common Multicast Group. When required, this group
allows ITRs to send traffic that needs to be replicated (flooded) to
all ETRs participating in the L2-overlay (e.g., broadcast traffic
within a subnet). When the core network (RLOC space) supports native
multicast ETRs participating in the L2-overlay join a (*,G) group
associated to the Instance-ID.
When multicast is not available in the core network, each xTR that is
part of the same instance-ID SHOULD register a (S,G) entry to the
mapping system using the procedures described in [RFC8378], where S
is 0000-0000-0000/0 and G is ffff-ffff-ffff/48. This strategy allows
and ITR to know which ETRs are part of the L2 overlay and it can
head-end replicate traffic to.
Following the same case, when multicast is not available in the core
network, the procedures in [RFC8378] can be used to ensure proper
distribution of link-local multicast traffic across xTRs
participating in the L2 overlay. In such case, the xTRs SHOULD join
a (S,G) entry with S being 0000-0000-0000/0 and where G is
0100-0000-0000/8.
5.2.6. L2 Unknown Unicast Support
An ITR attempts to resolve MAC destination misses through the Mapping
System. When the destination host remains undiscovered the
destination is considered an Unknown Unicast.
A Map-Server SHOULD respond to a Map-Request for an undiscovered host
with a Negative Map-Reply with action "Native Forward".
Alternatively the action "Drop" may be used in order to suppress
Unknown Unicast forwarding.
An ITR that receives a Negative Map-Reply with Action "Native
Forward" will handle traffic for the undiscovered host as L2
Broadcast traffic and will be unicast replicated or flooded using
underlay multicast to the rest of ETRs in the Layer-2 overlay.
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Upon discovery of a previously unknown unicast MAC EID, a data
triggered SMR for the discovered EID should be sent by the discovery
ETR back to the ITRs that are flooding the unknown unicast traffic.
This would allow ITRs to refresh their caches and stop flooding
unknown unicast traffic as necessary.
5.2.7. Time-to-Live Handling in Data-Plane
When using a L2 overlay and the encapsulated traffic is IP traffic,
the Time-to-Live value of the inner IP header MUST remain unmodified
during encapsulation and decapsulation. Network hops traversed as
part of the L2 overlay SHOULD be hidden to tools like traceroute and
applications that require direct L2 connectivity.
5.3. Support to ARP resolution through Mapping System
5.3.1. Map-Server support to ARP resolution: Packet Flow
A large majority of applications are IP based and, as a consequence,
end systems are typically provisioned with IP addresses as well as
MAC addresses.
In this case, to limit the flooding of ARP traffic and reduce the use
of multicast in the RLOC network, the LISP mapping system MAY be used
to support ARP resolution at the ITR.
In order to provide this support, ETRs handle and register an
additional EID-to-RLOC mapping as follows,
* EID-record contents = <IID, IP>, RLOC-record contents <MAC>.
There is a dedicated IID used for the registration of the ARP/ND
related mappings. Thus, a system with L2 and L3 overlays as well as
ARP/ND mappings would have three IIDs at play. In the spirit of
providing clarity, we will refer to those IIDs as L2-IID, L3-IID and
ARP-IID respectively. By using these definitions, we do not intend
to coin new terminology, nor is there anything special about those
IIDs that would make them differ from the generic definition of an
IID. The types of mappings expected in such a system are summarized
below:
* EID = <IID1, IP> to RLOC = <IP-RLOC> (L3-overlay)
* EID = <IID2, MAC> to RLOC = <IP-RLOC> (L2-overlay)
* EID = <IID3, IP> to RLOC = <MAC-RLOC> (ARP/ND mapping)
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The following packet flow sequence describes the use of the LISP
Mapping System to support ARP resolution for hosts residing in a
subnet that is extended to multiple sites. Using Figure 1, End-
Device 2 tries to find the MAC address of End-Device 3. Note that
both have IP addresses within the same subnet:
* End-Device 2 sends a broadcast ARP message to discover the MAC
address of End-Device 3. The ARP request targets IP 3.0.0.3.
* ITR B receives the ARP message, but rather than flooding it on the
overlay network sends a Map-Request to the mapping database system
for EID = <IID2,3.0.0.3>.
* When receiving the Map-Request, the Map-Server sends a Proxy-Map-
Reply back to ITR B with the mapping EID = <IID2,3.0.0.3> -> MAC
0:0:3:0:0:3.
* Using this Map-Reply, ITR B sends an ARP-Reply back to End-Device
2 with the tuple IP 3.0.0.3, MAC 0:0:3:0:0:3.
* End-Device 2 learns MAC 0:0:3:0:0:3 from the ARP message and can
now send a L2 traffic to End-Device 3. When this traffic reaches
ITR B is sent over the L2-overlay as described above in
Section 5.1.1.
This example shows how LISP, by replacing dynamic data plane learning
(such as Flood-and-Learn) can reduce the use of multicast in the
underlay network.
Note that ARP resolution using the Mapping System is a stateful
operation on the ITR. The source IP,MAC tuple coming from the ARP
request have to be stored to generate the ARP-reply when the Map-
Reply is received.
Note that the ITR SHOULD cache the ARP entry. In that case future
ARP-requests can be handled without sending additional Map-Requests.
5.3.2. ARP registrations: MAC as a locator record
When an end-host is attached or detected in an ETR that provides
L2-overlay services and also supports ARP resolution using the LISP
control-plane, an additional mapping entry is registered to the
mapping system:
* The EID 2-tuple (IID, IP) and its binding to a corresponding host
MAC address.
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In this case both the xTRs and the Mapping System MUST support an
EID-to-RLOC mapping where the MAC address is set as a locator record.
In order to guarantee compatibility with current implementations of
xTRs, the MAC locator record SHALL be encoded following the AFI-List
LCAF Type defined in [RFC8060]. This option would also allow adding
additional attributes to the locator record, while maintaining
compatibility with legacy devices.
This mapping is registered with the Mapping System using the
following EID record structure,
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | Record TTL |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
E | Locator Count | EID mask-len | ACT |A| Reserved |
I +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
D | Rsvd | Map-Version Number | AFI = 16387 |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | Rsvd1 | Flags | Type = 2 | IID mask-len |
e +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
c | 4 + n | Instance-ID... |
o +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
r | ...Instance-ID | EID-AFI = 1 or 2 |
d +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | EID-Prefix (IPv4 or IPv6) |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| /| Priority | Weight | M Priority | M Weight |
| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| M | Unused Flags |L|p|R| AFI = 16387 |
| A +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| C | Rsvd1 | Flags | Type = 1 | Rsvd2 |
| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | 2 + 6 | AFI = 6 |
| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| | | Layer-2 MAC Address ... |
| | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| \| ... Layer-2 MAC Address |
+-> +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+.
An EID record with a locator record that carries a MAC address
follows the same structure as described in [RFC9301]. However, some
fields of the EID record and the locator record require special
consideration:
Locator Count: This value SHOULD be set to 1.
Instance-ID: This is the IID used to provide segmentation of the
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L2-overlays, L3 overlays and ARP tables.
Priority and Weight: IP to MAC bindings are one to one bindings. An
ETR SHOULD not register more than one MAC address in the locator
record together with an IP based EID. The Priority of the MAC
address record is set to 255. The Weight value SHOULD be ignored
and the recommendation is to set it to 0.
L bit: This bit of the locator record SHOULD only be set to 1 when
an ETR is registering its own IP to MAC binding.
p bit: This bit of the locator record SHOULD be set to 0.
R bit: This bit of the locator record SHOULD be set to 0.
Note that an IP EID record that carries a MAC address in the locator
record, SHALL be registered with the Proxy Map-Reply bit set.
5.3.3. Implementation Considerations
While ARP support through the LISP Mapping System fits the LISP
Control-Plane there are a series of considerations to take into
account when providing this feature:
* As indicated, when and end-host is attached the ETR maintains and
registers a mapping with the binding EID = <IID, IP> -> RLOC =
<MAC>.
* ARP support through the LISP Mapping System is OPTIONAL and the
xTRs should allow the possibility to enable or disable the
feature.
* When the ARP entry has not been registered, a Map Server SHOULD
send a Negative Map-Reply with action "No Action" as a response to
an ARP based Map Request.
* In case the ITR receives a Negative Map-Reply for an ARP request
it should fallback to flooding the ARP packet as any other L2
Broadcast packet (as described in Section 5.2.5).
* When receiving a positive Map-Reply for an ARP based Map-Request,
the ETR MUST recreate the actual ARP Reply, impersonating the real
host. As a consequence, ARP support is a stateful operation where
the ITR needs to store enough information about the host that
generates an ARP request in order to recreate the ARP Reply.
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* ARP replies learned from the Mapping System SHOULD be cached and
the information used to reply to subsequent ARP requests to the
same hosts.
5.4. Multihoming Support
5.4.1. Identification of L2 multihomed segments
5.4.2. Synchronizatioin of database-mappping tables
5.4.3. All active vs Active-Standby modes
5.4.4. Split Horizon support
5.4.5. Designated Forwarder Selection
6. Optional Deployment Models
The support of an integrated L2 and L3 overlay solution takes
multiple architectural design options, that depend on the specific
requirements of the deployment environment. While some of the
previous describe specific packet flows and solutions based on the
recommended solution, this section documents OPTIONAL design
considerations that differ from the recommended one but that MAY be
required on alternative deployment environments.
6.1. IP Forwarding of Intra-subnet Traffic
As pointed out at the beginning the recommended selection of the L2
and L3 overlays is not the only one possible. In fact, providing L2
extension to some cloud platforms is not always possible and subnets
need to be extended using the L3 overlay.
In order to send all IP traffic (intra- and inter-subnet) through the
L3 overlay the solution MUST change the ARP resolution process
described in Section 5.3.1 to the following one (we follow again
Figure 1 to drive the example. End-Device 2 queries about End-Device
3):
* End-Device 1 sends a broadcast ARP message to discover the MAC
address of 3.0.0.3.
* ITR B receives the ARP message and sends a Map-Request to the
Mapping System for EID = <IID1,3.0.0.3>.
* In this case, the Map-Request is routed by the Mapping system
infrastructure to ETR C, that will send a Map-Reply back to ITR B
containing the mapping EID = <IID1,3.0.0.3> -> RLOC=IP_C.
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* ITR B populates its local cache with the received entry on the L3
forwarding table. Then, using the cache information it sends a
Proxy ARP-reply with its own MAC (MAC_xTR_B) address to end End-
Device 1.
* End-Device 1 learns MAC_ITR_B from the proxy ARP-reply and sends
traffic with destination address 3.0.0.3 and destination MAC,
MAC_xTR_B.
* As the destination MAC address is the one from xTR B, when xTR B
receives this traffic it is forwarded using the L3-overlay.
* Note that when implementing this solution, when a host that is
local to an ETR moves away, the ETR SHOULD locally send a
Gratuitous ARP with its own MAC address and the IP of the moved
host, to refresh the ARP tables of local hosts and guarantee the
use of the L3 overlay when connecting to the remote host.
It is also important to note that using this strategy to extend
subnets through the L3 overlay but still keeping the L2 overlay for
the rest of traffic MAY lead to flow asymmetries. This MAY be the
case in deployments that filter Gratuitous ARPs, or when moved hosts
continue using actual L2 information collected before a migration.
6.2. Data-plane Encapsulation Options
The LISP control-plane offers independence from the data-plane
encapsulation. Any encapsulation format that can carry a 24-bit
instance-ID can be used to provide the unified overlay.
Common encapsulation formats that can be used are [VXLAN-GPE], [LISP]
and [VXLAN]:
* VXLAN-GPE encap: This encapsulation format is defined in
[RFC9305]. It allows encapsulation both L2 and L3 packets and the
VNI field directly maps to the Instance-ID used in the control
plane. Note that when using this encapsulation for a unified
solution the P-bit is set and the Next-Protocol field is used
(typically with values 0x1 (IPv4) or 0x2 (IPv6) in L3-overlays,
and value 0x3 in L2-overlays).
* LISP encap: This is the encapsulation format defined in the LISP
specification [RFC9300]. The encapsulation allows encapsulating
both L2 and L3 packets. The Instance-ID used in the EIDs directly
maps to the Instance-ID that the LISP header carries. At the ETR,
after decapsulation, the IID MAY be used to decide between L2
processing or L3 processing.
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* VXLAN encap: This is a L2 encapsulation format defined in
[RFC7348]. While being a L2 encapsulation it can be used both for
L2 and L3 overlays. The Instance-ID used in LISP signaling maps
to the VNI field of the VXLAN header. Providing L3 overlays using
VXLAN generally requires using the ETR MAC address as destination
MAC address of the inner Ethernet header. The process to learn or
derive this ETR MAC address is not included as part of this
document.
7. IANA Considerations
This memo includes no request to IANA.
8. Acknowledgements
This draft builds on top of two expired drafts that introduced the
concept of LISP L2/L3 overlays (draft-maino-nvo3-lisp-cp and draft-
hertoghs-nvo3-lisp-controlplane-unified). Many thanks to the
combined authors of those drafts, that SHOULD be considered main
contributors of this draft as well: Vina Ermagan, Dino Farinacci,
Yves Hertoghs, Luigi Iannone, Fabio Maino, Victor Moreno, and Michael
Smith.
9. References
9.1. Normative References
[RFC2119] Bradner, S. and RFC Publisher, "Key words for use in RFCs
to Indicate Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The
Locator/ID Separation Protocol (LISP) for Multicast
Environments", RFC 6831, DOI 10.17487/RFC6831, January
2013, <https://www.rfc-editor.org/info/rfc6831>.
[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, DOI 10.17487/RFC7348, August 2014,
<https://www.rfc-editor.org/info/rfc7348>.
[RFC8060] Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
Address Format (LCAF)", RFC 8060, DOI 10.17487/RFC8060,
February 2017, <https://www.rfc-editor.org/info/rfc8060>.
Portoles, et al. Expires 14 July 2023 [Page 24]
Internet-Draft L2/L3 EID Mobility January 2023
[RFC8111] Fuller, V., Lewis, D., Ermagan, V., Jain, A., and A.
Smirnov, "Locator/ID Separation Protocol Delegated
Database Tree (LISP-DDT)", RFC 8111, DOI 10.17487/RFC8111,
May 2017, <https://www.rfc-editor.org/info/rfc8111>.
[RFC8378] Moreno, V. and D. Farinacci, "Signal-Free Locator/ID
Separation Protocol (LISP) Multicast", RFC 8378,
DOI 10.17487/RFC8378, May 2018,
<https://www.rfc-editor.org/info/rfc8378>.
[RFC9300] Farinacci, D., Fuller, V., Meyer, D., Lewis, D., and A.
Cabellos, Ed., "The Locator/ID Separation Protocol
(LISP)", RFC 9300, DOI 10.17487/RFC9300, October 2022,
<https://www.rfc-editor.org/info/rfc9300>.
[RFC9301] Farinacci, D., Maino, F., Fuller, V., and A. Cabellos,
Ed., "Locator/ID Separation Protocol (LISP) Control
Plane", RFC 9301, DOI 10.17487/RFC9301, October 2022,
<https://www.rfc-editor.org/info/rfc9301>.
[RFC9305] Maino, F., Ed., Lemon, J., Agarwal, P., Lewis, D., and M.
Smith, "Locator/ID Separation Protocol (LISP) Generic
Protocol Extension", RFC 9305, DOI 10.17487/RFC9305,
October 2022, <https://www.rfc-editor.org/info/rfc9305>.
9.2. Informative References
[I-D.ietf-lisp-map-server-reliable-transport]
Lewis, D., Pitta, B., Portoles, M., Kouvelas, I., and C.
Cassar, "LISP Map Server Reliable Transport", Work in
Progress, Internet-Draft, draft-ietf-lisp-map-server-
reliable-transport-01, 10 January 2023,
<https://datatracker.ietf.org/api/v1/doc/document/draft-
ietf-lisp-map-server-reliable-transport/>.
[I-D.ietf-lisp-pubsub]
Rodriguez-Natal, A., Ermagan, V., Cabellos-Aparicio, A.,
Barkai, S., and M. Boucadair, "Publish/Subscribe
Functionality for the Locator/ID Separation Protocol
(LISP)", Work in Progress, Internet-Draft, draft-ietf-
lisp-pubsub-10, 6 January 2023,
<https://www.ietf.org/archive/id/draft-ietf-lisp-pubsub-
10.txt>.
Portoles, et al. Expires 14 July 2023 [Page 25]
Internet-Draft L2/L3 EID Mobility January 2023
[I-D.ietf-lisp-vpn]
Moreno, V. and D. Farinacci, "LISP Virtual Private
Networks (VPNs)", Work in Progress, Internet-Draft, draft-
ietf-lisp-vpn-10, 3 October 2022,
<https://www.ietf.org/archive/id/draft-ietf-lisp-vpn-
10.txt>.
Authors' Addresses
Marc Portoles Comeras
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
United States of America
Email: mportole@cisco.com
Vrushali Ashtaputre
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
United States of America
Email: vrushali@cisco.com
Fabio Maino
Cisco Systems
170 Tasman Drive
San Jose, CA 95134
United States of America
Email: fmaino@cisco.com
Victor Moreno
Google LLC
1600 Amphitheatre Pkwy
Mountain View, CA 94043
United States of America
Email: vimoreno@google.com
Dino Farinacci
lispers.net
San Jose, CA
United States of America
Email: farinacci@gmail.com
Portoles, et al. Expires 14 July 2023 [Page 26]