Internet DRAFT - draft-haindl-lisp-gb-atn
draft-haindl-lisp-gb-atn
LISP Working Group B. Haindl
Internet-Draft M. Lindner
Intended status: Informational Frequentis
Expires: 28 September 2023 V. Moreno
Google
M. Portoles
F. Maino
B. Venkatachalapathy
Cisco Systems
27 March 2023
Ground-Based LISP for the Aeronautical Telecommunications Network
draft-haindl-lisp-gb-atn-09
Abstract
This document describes the use of the LISP architecture and
protocols to address the requirements of the worldwide Aeronautical
Telecommunications Network with Internet Protocol Services, as
articulated by the International Civil Aviation Organization.
The ground-based LISP overlay provides mobility and multi-homing
services to the IPv6 networks hosted on commercial aircrafts, to
support Air Traffic Management communications with Air Traffic
Controllers and Air Operation Controllers. The proposed architecture
doesn't require support for LISP protocol in the airborne routers,
and can be easily deployed over existing ground infrastructures.
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/.
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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 28 September 2023.
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
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provided without warranty as described in the Revised BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Definition of Terms . . . . . . . . . . . . . . . . . . . . . 3
3. Design Overview . . . . . . . . . . . . . . . . . . . . . . . 4
4. Basic Protocol Operation . . . . . . . . . . . . . . . . . . 7
4.1. Endsystem Registration . . . . . . . . . . . . . . . . . 7
4.2. Ground to Airborne Traffic Flow . . . . . . . . . . . . . 8
4.3. Airborne to Ground Traffic Flow . . . . . . . . . . . . . 8
4.4. Default forwarding path . . . . . . . . . . . . . . . . . 9
4.5. Traffic symmetry . . . . . . . . . . . . . . . . . . . . 10
5. Multi-Homing and Mobility . . . . . . . . . . . . . . . . . . 10
6. Convergence . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Use of RLOC-probing . . . . . . . . . . . . . . . . . . . 12
6.2. Use of Solicit-Map-Request . . . . . . . . . . . . . . . 12
6.3. Use of LISP pub-sub . . . . . . . . . . . . . . . . . . . 12
7. Multi-domain structure of the ATN/IPS . . . . . . . . . . . . 13
8. Security Considerations . . . . . . . . . . . . . . . . . . . 13
8.1. LISP Basic Security Mechanisms . . . . . . . . . . . . . 13
8.2. Control Plane overload protection . . . . . . . . . . . . 14
8.3. Protecting the LISP control plane from overclaim
attacks . . . . . . . . . . . . . . . . . . . . . . . . . 14
8.4. LISP Reliable Transport . . . . . . . . . . . . . . . . . 14
8.5. Reachability Control . . . . . . . . . . . . . . . . . . 16
8.6. Data Plane Security . . . . . . . . . . . . . . . . . . . 17
8.6.1. Segmentation . . . . . . . . . . . . . . . . . . . . 17
8.6.2. Automated RLOC Filtering . . . . . . . . . . . . . . 17
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8.6.3. Confidentiality, Integrity and Anti-replay
protection . . . . . . . . . . . . . . . . . . . . . 18
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 18
11.1. Normative References . . . . . . . . . . . . . . . . . . 18
11.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction
This document describes the use of the LISP [RFC9300] architecture
and protocols to address the requirements of the worldwide
Aeronautical Telecommunications Network with Internet Protocol
Services (ATN/IPS), as articulated by the International Civil
Aviation Organization (ICAO).
ICAO is proposing to replace the existing aeronautical communication
services with an IPv6 based infrastructure that supports Air Traffic
Management (ATM) between commercial aircrafts, Air Traffic
Controllers (ATC) and Air Operation Controllers (AOC).
This document describes how a LISP overlay can be used to offer
mobility and multi-homing services to the IPv6 networks hosted on
commercial aircrafts without requiring LISP support in the airborne
routers. Use of the LISP protocol is limited to the ground-based
routers, hence the name "ground-based LISP". The material for this
document is derived from [GBL].
2. Definition of Terms
AOC: Airline Operational Control
ATN/IPS: Aeronautical Telecommunications Network with Internet
Protocol Services
AC-R: Access Ground Router
A/G-R: Air/Ground Router
G/G-R: Ground/Ground Router
A-R: Airborne Router
A-E: Airborne Endsystem
ATS-E: ATS Endsystem
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For definitions of other terms, notably Map-Register, Map-Request,
Map-Reply, Routing Locator (RLOC), Solicit-Map-Request (SMR), Ingress
Tunnel Router (ITR), Egress Tunnel Router (ETR), xTR (ITR or ETR),
Map-Server (MS), and Map-Resolver (MR) please consult the LISP
specification [RFC9300].
3. Design Overview
In the ATN/IPS architecture the airborne endsystems hosted on an
aircraft are part of an IPV6 network connected to the ground network
by one or more Airborne Routers (A-R). A-Rs have multiple radio
interfaces that connects them via various radios infrastructures
(e.g. SATCOM, LDACS, AeroMACS) to a given radio region, also known
as subnetwork, on the ground. Typically an A-R has a corresponding
ground based Access Router (AC-R) that terminates the radio protocol
with the A-R and provides access services to the ground based portion
of the radio network infrastructure. Each radio region is
interconnected with the ATN/IPS ground network via an Air-to-Ground
router (AG-R).
Similarly, the Air Traffic Controllers and Air Operation Controllers
Endsystems (ATS-E and AOC-E) are part of IPv6 networks reachable via
one or more Ground-to-Ground Routers (G/G-Rs).
The ATN/IPS ground network infrastructure is the internetworking
region located between the A/G routers and the G/G routers.
In the ground-based LISP architecture, a LISP overlay is laid over
the ATN/IPS internetworking region (that is in the LISP RLOC space)
and provides connectivity between endsystems (that are in the LISP
EID space) hosted in the aircrafts and in the AOC/ATS regions. The
A/G-Rs and the G/G-Rs assume the role of LISP xTRs supported by a
LISP mapping system infrastructure.
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,------,
,---------. : A-E1 :
,' `./'------'
( AIRCRAFT )
`. +-----+ ,'\ ,------,
`-| A-R |-' \: A-E2 :
+-----+ '------'
// \\
// \\
+---+--+ +-+--+--+
.--.-.| AC-R1|'.-. .| AC-R2 |.-.
( +---+--+ ) ( +-+--+--+ )
( __. ( '.
..'SATCOM Region ) .' LDACS Region )
( .'-' ( .'-'
' +-------+ ) ' +-------+ )
'-| A/G-R |-' '-| A/G-R |-''
| | | |
| xTR1 | | xTR2 |
+-------+ +-------+
\ /
\ .--..--. .--. ../
\ ( ' '.--.
.-.' Internetworking '' '-------'
( region )--: MS/MR :
( (RLOC SPACE) '-'' '-------'
._.'--'._.'.-._.'.-._)
/ \
+---+---+ +-+--+--+
-.-.| G/G-R |'. .| G/G-R |.
( | | ) ( | | )
( | xTR3 | ) ( | xTR4 | )
( +---+---+ ) ( +-+--+--+ )
( _._. ( '.
..' ATS Region ) .' AOC Region )
( .'-' ( .'-'
'--'._.'. )\ '--'._.'. )\
/ '--' \ / '--' \
'--------' '--------' '--------' '--------'
: ATS-E1 : : ATS-E2 : : AOC-E1 : : AOC-E2 :
'--------' '--------' '--------' '--------'
Figure 1: ATN/IPS and ground-based LISP overlay
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Endsystems in the AOC/ATS regions are mapped in the LISP overlay by
the G/G-Rs, that are responsible for the registration of the AOC/ATS
endsystems to the LISP mapping system. Each G/G-R is basically an
xTR which has direct connections only to the terrestrial regions,
i.e. no direct connection to the radio regions.
Aircrafts will attach to a specific radio region, via the radio
interfaces of the A-Rs. How the radio attachment works is specific
to each particular radio infrastructure, and out of the scope of this
document, see [GBL].
Typically at the end of the attachment phase, the access router (AC-
R) corresponding to the A-R, will announce the reachability of the
EID prefixes corresponding to the attached aircraft (the announcement
is specific to each particular radio infrastructure, and is out of
the scope of this document). A/G-Rs in that particular radio region
are responsible to detect those announcements, and, since they act as
xTRs, register to the LISP mapping systems the corresponding IPv6 EID
prefixes on behalf of the A-R, but with the RLOC of the A/G-R.
The EID prefixes registered by the A/G-Rs are then reachable by any
of the AOC/ATS Endsystems that are part of the ground based LISP
overlay.
The LISP infrastructure is used to support seamless aircraft mobility
from one radio network to another, as well as multi-homing attachment
of an aircraft to multiple radio networks with use of LISP weight and
priorities to load balance traffic directed toward the aircraft.
The rest of this document provides further details on how ground-
based LISP is used to address the requirements of the ATN/IPS use
cases. The main design goals are:
* minimize added complexity on the aircraft
- airborne routers can assume that any ground system is reachable
via any A/G router. Static routing policies can be used on
board
- no need for routing/mobility protocols on board. Routing/
mobility is managed on the ground ATN/IPS network
- on-board outgoing link selection can be done with simple static
policy
* seamless support for aircraft mobility and multi-homing with
minimal traffic overhead on the A/G datalink
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* minimize complexity of ground deployment
- ground-based LISP can be easily deployed over existing ATN/IPS
ground infrastructure
- it is based on COTS solutions
- can ease IPv4 to IPv6 transition issues
4. Basic Protocol Operation
Figure 1 provides the reference topology for a description of the
basic operation. A more detailed description of the basic protocol
operation is described in [GBL].
4.1. Endsystem Registration
The following are the steps via which airborne endsystem prefixes are
registered with the LISP mapping system:
1. Each Airborne Endsystem (A-E) is assigned an IPv6 address that is
the endsystem EID. Each EID includes a Network-ID prefix that
comprises (1) an ICAO ID which uniquely identifies the aircraft,
and possibly (2) an aircraft network identifier. Airborne
devices are grouped in one (and possibly several) IPv6 EID
prefixes. As an example an IPv6 EID prefix could be used for all
ATC applications located in a safety critical domain of the
aircraft network, another IPv6 EID prefix could be used for AOC
applications located in a less safety critical domain.
2. After the Airborne Router (A-R) on an aircraft attaches to one
radio region, the corresponding Access Router (AC-R) learns the
IPv6 EID prefixes belonging to the aircraft. The AC-R also
announces reachability of these prefixes in the radio region
(subnetwork) e.g. by using an IGP protocol like OSPF. The
attachment to a radio includes a preference parameter and a
quality parameter, these parameters are used e.g. to calculate
the IGP reachability advertisement metric.
3. The Air/Ground Router (A/G-R) in the subnetwork receives the
radio region announcements which contain reachablity information
for the IPv6 EID prefixes corresponding to the Airborne
Endsystems. Since each A/G-R is also an xTR, the A/G-R registers
the IPv6 EID prefixes with the LISP MS/MR on behalf of the A-R,
but with the RLOC of the A/G-R. The included quality parameter
(e.g. IGP metric) is converted to a LISP priority, so that a
lower quality metric results in a lower LISP priority value.
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Ground based endsystems are part of ground subnetworks where the
Ground/Ground Router (G/G-R) is an xTR. Each G/G-R therefore
registers the prefixes corresponding to the AOC endsystems and ATS
endsystems with the LISP mapping system, as specified in [RFC9300].
4.2. Ground to Airborne Traffic Flow
Here is an example of how traffic flows from the ground to the
airborne endsystems, when ATS endsystem 1 (ATS-E1) has traffic
destined to airborne endsystem 1 (A-E1):
1. The default route in the ATS region takes the traffic to xTR3
which is also a Ground/Ground Router (G/G-R).
2. xTR3 sends a Map-Request message for the address of A-E1 to the
LISP mapping system. xTR2 sends a Map-Reply to xTR3 with RLOC set
to its address which is reachable from xTR3 via the
internetworking region.
3. xTR3 encapsulates the traffic to xTR2 using the RLOC information
in the Map-Reply message.
4. xTR2 decapsulates the traffic coming from xTR3. The destination
address of the inner packet belongs to A-E1 which has been
advertised by the AC-R in the same region. The traffic is
therefore forwarded to AC-R2.
5. AC-R2 sends the traffic to the Airborne Router of the aircraft
and the A-R sends it to the endsystem.
4.3. Airborne to Ground Traffic Flow
Here is an example of how traffic flows from the airborne endsystems
to the ground when airborne endsystem 2 (A-E2) has traffic destined
to ATS endsystem 2 (ATS-E2):
1. The default route in the aircraft points to the Airborne Router
(A-R). The latter forwards the traffic over the radio link to
AC-R2.
2. The default route on AC-R2 points to xTR2 (also an A/G-R), so the
traffic is sent from AC-R2 to xTR2.
3. xTR2 sends a Map-Request message for the address of ATS-E2 to the
LISP mapping system. xTR3 sends a Map-Reply to xTR2 with RLOC set
to its address which is reachable from xTR2 via the
internetworking region.
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4. xTR2 encapsulates the traffic to xTR3 using the RLOC information
in the Map-Reply message.
5. xTR3 decapsulates the traffic coming from xTR2, and forwards it
to ATS-E2.
4.4. Default forwarding path
When an xTR is waiting for a Map-Reply for an EID, the xTR does not
know how to forward the packets destined to that EID. This means
that the first packets for ground-to-air traffic would get dropped
until the Map-Reply is received and a map-cache entry is created.
However if a device acting as RTR, see
[I-D.ermagan-lisp-nat-traversal], has mappings for all EIDs, the xTR
could use the RTR as default path for packets which have to be
encapsulated. How the RTR gets all the mappings is outside the scope
of this document but one example is the use of LISP pub-sub as
specified in [I-D.ietf-lisp-pubsub]. Note that the RTR does not have
to be a new device, the device which has the MS/MR role can also act
as RTR. It is only the RTR which needs to subscribe to all the
aircraft EIDs, the XTRs (i.e. the A/G-Rs and G/G-Rs) do not need to
subscribe.
RTRs stitch two legs of a communication flow by acting as an ETR for
the purposes of the first leg and as an ITR for the purposes of the
second leg. As an ITR (second leg), the RTR will follow all standard
procedures of an ITR (issue requests, cache mappings, subscribe to
EIDs, etc). In the specific case of the first packet drop scenario,
the RTR will subscribe to the entire EID space registered in the
Mapping System and maintain a complete cache of all relevant
destinations. Any changes to the registration state will be
published promptly to the RTR using the pub/sub mechanisms. This ITR
role can be made redundant by simply having each RTR in the
redundancy group subscribe to the Mapping System. From an ETR
perspective, the RTR will also follow all standard procedures for an
ETR, but rather than registering specific prefixes, the RTRs will
(optionally) register themselves as the “First Packet Handlers”. The
ITRs sending traffic requiring first packet handling will be
configured to forward traffic to the First Packet Handlers if there
isn’t a mapping already cached for the destination.
The ITRs will know who the first packet handlers are by one of two
mechanisms:
1. Configuration of the RLOCs of the first packet handlers on the
ITR. This configuration would be done by a network management
system.
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2. Subscription of the ITR to the “First Packet Handler” EID. As
First Packet Handler RLOCs are added or removed the subscribing ITRs
are updated.
In both cases the resiliency mechanisms for the RLOCs are the same as
for any other RLOC: Routing table reachability combined with optional
data plane probes can be leveraged to accelerate failover. In the
case in which subscriptions to the “First Packet Handler” EID are
used, the RTR will also benefit from the updates in the publication
to trigger failover processes.
4.5. Traffic symmetry
The requirements for traffic symmetry are still TBD.
5. Multi-Homing and Mobility
Multi-homing support builds on the procedures described in Section 4:
1. The Airborne Router (A-R) on an aircraft attaches to multiple
radio regions. As an example, and referring to Figure 1, the A-R
attaches to the LDACS and SATCOM regions, via AC-R2 and AC-R1
respectively.
2. Through the preference parameter sent to each region, the A-R has
control over which path (i.e. radio region) ground to air traffic
flows. For example, A-R would indicate preference of the LDACS
region by choosing a better preference value for the LDACS region
compared to the preference value sent to the SATCOM region.
3. Both xTR1 and xTR2 register the IPv6 EID prefixes with the LISP
mapping system using merge semantic, as specified in section 4.6
of [RFC9301]. Since the priority used in the LISP registrations
is derived from the preference and quality parameters, xTR2 would
use a lower priority value than xTR1. In this way the LISP
mapping system will favour xTR2 (A/G-R for the LDACS region) over
xTR1 (A/G-R for the SATCOM region), as specified by the
preference and quality parameters.
4. Upon registration the LISP MS/MR will send Map-Notify messages to
both xTR1 and xTR2, to inform that they have reachability to the
aircraft's IPv6 EID prefixes. Both xTRs are notified because
they have both set the merge-request and want-map-notify bits in
their respective Map-Register message.
5. Upstream and downstream traffic flows on the same path, i.e. both
use the LDACS region.
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With mobility, the aircraft could want to switch traffic from one
radio link to another. For example while transiting from an area
covered by LDACS to an area covered by SATCOM, the aircraft could
desire to switch all traffic from LDACS to SATCOM. For air-to-ground
traffic, the A-R has complete control over which radio link to use,
and will simply select the SATCOM outgoing interface. For ground-to-
air traffic:
1. The A-R sends a radio advertisement to AC-R1 indicating a better
preference for the SATCOM link.
2. This leads to AC-R1 lowering its quality parameter (e.g. IGP
metric) for the IPv6 EID prefixes.
3. Upon receiving the better preference value, xTR1 registers the
IPv6 EID prefixes with the MS/MR, using a lower priority value
than what xTR2 had used. Both xTR1 and xTR2 receives Map-Notify
messages signaling to xTR2 that xTR1 is now the preferred path
toward the aircraft.
4. xTR3 has a map-cache which still points to xTR2, therefore xTR3
still sends traffic via xTR2. xTR2 sends Solicit-Map-Request
(SMR) to xTR3 who queries the LISP mapping system again. This
results in updating the map-cache on xTR3 which now points to
XTR1 so ground-to-air traffic now flows on the SATCOM radio link.
The procedure for mobility is derived from
[I-D.ietf-lisp-eid-mobility].
6. Convergence
When traffic is flowing on a radio link and that link goes down, the
network has to converge rapidly on the other link available for that
aircraft.
For air-to-ground traffic, once the A-R detects the failure it can
switch immediatly to the other radio link.
For ground-to-air traffic, when a radio link fails, the corresponding
AC-R sends a reachability update that the IPv6 EID prefixes are not
reachable anymore. This leads to the A/G-R (also an xTR) in that
region to unregister the IPv6 EID prefixes with the MS/MR. This
indicates that the xTR in question has no reachability to the EID
prefixes. The notification of the failure should reach all relevant
xTRs as soon as possible. For example, if the LDACS radio link
fails, xTR3 and xTR4 need to learn about the failure so that they
stop sending traffic via xTR2 and use xTR1 instead.
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In the sub-sections below, we the use of RLOC-probing, Solicit-Map-
Request, and LISP pub-sub as alternative mechanisms for link failure
notification.
6.1. Use of RLOC-probing
RLOC-probing is described in section 6.3.2 of [RFC9300].
At regular intervals xTR3 sends Map-Request to xTR2 for the
aircraft's EID prefixes. When xTR3 detects via RLOC-probing that it
can not use xTR2 anymore, it sends a Map-Request for the aircraft's
EID prefixes. The corresponding Map-Reply indicates that xTR1 should
now be used. The map-cache on xTR3 is updated and air-to-ground
traffic now goes through xTR1 to use the SATCOM radio link to the
aircraft.
The disadvantage of RLOC-probing is that fast detection becomes more
difficult when the number of EID prefixes is large.
6.2. Use of Solicit-Map-Request
Solicit-Map-Request is used as described in Section 5:
1. xTR3 is still sending traffic to xTR2 since its map-cache has not
been updated yet.
2. Upon detecting that the link is down, and receiving data plane
traffic from the ground network, xTR2 sends an SMR to xTR3 that
sends a Map-Request to update its map-cache. The corresponding
Map-Reply indicates that xTR1 should now be used.
The disadvantage of this approach is that the traffic is delayed
pending control-plane resolution. This method also depends on data
traffic being continuous, in many cases data traffic may be sporadic,
leading to very slow convergence.
6.3. Use of LISP pub-sub
As specified in [I-D.ietf-lisp-pubsub], ITRs can subscribe to changes
in the LISP mapping system. So if all ITRs subscribe to the EID
prefixes for which they have traffic, the ITRs will be notified when
there is mapping change.
In the example where the LDACS radio link fails, when xTR2
unregisters the EID prefixes with the MS/MR, xTR3 would be notified
via LISP pub-sub (assuming xTR3 has a map-cache entry for these EID
prefixes).
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This mechanism provides the fastest convergence at the cost of more
state in the LISP mapping system.
7. Multi-domain structure of the ATN/IPS
The overlay on the ATN/IPS can be structured as a collection of
independent administrative domains following the model defined in
[I-D.moreno-lisp-uberlay]. In this model, the different
administrative domains are interconnected by a transit area referred
to as an uberlay. Each administrative domain is independent from the
perspective of the control, data and administrative planes.
Structuring the ATN/IPS in this manner allows the combination of
different implementations and even different mobility methods in the
ATN/IPS. The structure proposed also improves resiliency by
isolating events and failures across the different administrative
domains and improves the scale of the ATN/IPS by distributing the
responsibility of maintaining granular aircraft state across the
different administrative domains.
The uberlay may be a BGP network as defined in [I-D.templin-atn-bgp].
Following the definitions put forth in [I-D.templin-atn-bgp], the
uberlay transit is the core autonomous system and the different
administrative domains that conform the ATN/IPS are what
[I-D.templin-atn-bgp] defines as stub autonomous systems.
8. Security Considerations
For LISP control-plane message security, please refer to
[I-D.ietf-lisp-sec]. This addresses the control-plane threats that
target EID-to-RLOC mappings, including manipulations of Map-Request
and Map-Reply messages, and malicious ETR EID prefix overclaiming.
8.1. LISP Basic Security Mechanisms
The LISP specification, documented in [RFC6830bis] and [RFC6833bis],
includes basic security mechanisms for the control plane. The base
mechanisms are designed to prevent rogue unauthorized ETRs from
registering mappings into the Mapping System and to protect ITRs from
receiving unsolicited mapping information. To authenticate EID-to-
RLOC mapping registrations and ensure that they are from an
authorized ETR, LISP uses shared secret keys between ETRs and the
Mapping System. Only ETRs that have the shared secret key are able
to register EID-to-RLOC mappings to the Mapping System. Without the
correct key, the authenticity of the map-register message cannot be
verified, and the Mapping System must reject the map-register. The
shared keys used to authenticate map-registers are distributed across
ETRs and MS/MRs by the orchestration/configuration infrastructure.
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The shared keys need to be distributed between the xTR and the
Mapping System. Since these components will be in the same
administrative domain in GB-LISP, it would be feasible to implement a
method for this key exchange (see Clause 6.5 in [LISP-SEC]. In
addition to authenticating EID registrations, it is recommended that
the Mapping System restricts EID registrations to configured EID
prefix ranges. Thus, an authorized ETR is allowed to register EID
prefixes only within the EID prefix range configured in the Map-
Server. The confidentiality of the LISP control plane messages can
be ensured by protecting the transport of control messages with DTLS
(over UDP) [RFC6347] or LISP-crypto [RFC8061]. DTLS is also proposed
in Clause 6.7 of [LISP-SEC] for providing message privacy.
8.2. Control Plane overload protection
Data-plane gleaning [Clause 9 in RFC6830bis] might need to be turned
off for avoiding potential attacks by forged data plane packets that
could overload the control plane. Another approach is data fusion
between multiple reachability verification mechanisms. Generic
control plane protection mechanism, such as packet filtering and rate
control, should be also deployed for GB-LISP nodes based on a risk
assessment. This could mitigate such attacks that try to misuse the
Map-Versioning mechanism in the data-plane for overloading the
control-plane.
8.3. Protecting the LISP control plane from overclaim attacks
The Internet Draft [LISP-SEC] defines a set of security mechanisms
(usually referred as LISP-SEC) to provide origin authentication,
integrity, and antireplay protection to the EID-to-RLOC mapping data
conveyed in the map-resolution process. It includes the usage of
multiple one-time-keys (OTK) and hash based message authentication.
LISP-SEC also enables authorization verification on EID-prefixes
claims made by ETRs, preventing so-called “overclaiming attacks” in
which an ETR attempts to claim EID-prefixes for which it is not
authoritative. A LISP-SEC protected map-reply, in fact, includes
metadata authenticated by the map-server that specify which
8.4. LISP Reliable Transport
The communication with the Mappin Systems is originally proposed
based on UDP that is not a reliable transport. For a proper
synchronization between the ETR and the Map-Servers periodic message
transmission would be needed. Usually, Map-Register messages are
retransmitted every minute by the ETR. The Map-Server removes the
EID entries if they are not refreshed for three successive periods.
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In mobility solutions, typically a large number of EID entries needs
to be registered. Because of packet size limitations these entries
can be transported only by a significant number of Map-Register
messages in each period. A new reliable transport option has been
defined in [LISP-RELT] to solve these issues. Although this Internet
Draft has been expired, the new method is used in the latest widely
deployed LISP solution for Software Defined Access (SDA) by Cisco
Systems. The reliable transport is composed by new message formats
and the support for other then UDP as a transport in the control
plane. Both TCP and SCTP is addressed by the specification. The TCP
implementation could be traced in the labs. The messages are based
on a TLV format where a type filed support the future extensions of
the protocol. A message end marker provides extra integrity check
possibility for complex aggregated messages. Error notification
messages are also specified for notifying situations when the
receiver does not recognize or cannot parse message contents. The
following message types are specified for the reliable transport
mechanism: • Map-Register, • Registration acknowledgement, •
Registration rejection, • Registration refresh, • Mapping
notification, The session establishment has to be backward
compatible. The Map Server authenticates the ETR first using UDP
based messages. Once the ETR is authenticated, the Map Server
performs a passive open by listening on TCP port 4342. TCP
connections are accepted only from the already authenticated ETRs.
The ETR has to open the TCP connection actively towards the Map
Server one it has received the Map-Notify message on the UDP
transport. If the TCP session goes down, the same UDP based
procedure has to be repeated. The Map-Server will also revert to the
expiration mechanism used for UDP transport until the TCP based
session would be fully restored. A single TCP session is built up
for all subsequent control plane messages. This applies even when
multiple address families are used in the EID space. Once the
reliable transport can be used, the periodic refresh is not needed
anymore. Mapping information is sent only when there is new
information to share. Time-out based removal of registrations are
not used in this case. An explicit de-registration is needed by
carrying a zero TTL. The reliable transport session should be
authenticated. In the simpler case, it could be an RLOC spoofing
mitigation. If this is not reliable, then the TCP Authentication
Option [RFC5925], or the SCTP Authenticated Chunks [RFC4895] are
recommended.
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8.5. Reachability Control
The communication with the Mappin Systems is originally proposed
based on UDP that is not a reliable transport. For a proper
synchronization between the ETR and the Map-Servers periodic message
transmission would be needed. Usually, Map-Register messages are
retransmitted every minute by the ETR. The Map-Server removes the
EID entries if they are not refreshed for three successive periods.
In mobility solutions, typically a large number of EID entries needs
to be registered. Because of packet size limitations these entries
can be transported only by a significant number of Map-Register
messages in each period. A new reliable transport option has been
defined in [LISP-RELT] to solve these issues. Although this Internet
Draft has been expired, the new method is used in the latest widely
deployed LISP solution for Software Defined Access (SDA) by Cisco
Systems. The reliable transport is composed by new message formats
and the support for other then UDP as a transport in the control
plane. Both TCP and SCTP is addressed by the specification. The TCP
implementation could be traced in the labs. The messages are based
on a TLV format where a type filed support the future extensions of
the protocol. A message end marker provides extra integrity check
possibility for complex aggregated messages. Error notification
messages are also specified for notifying situations when the
receiver does not recognize or cannot parse message contents. The
following message types are specified for the reliable transport
mechanism: • Map-Register, • Registration acknowledgement, •
Registration rejection, • Registration refresh, • Mapping
notification, The session establishment has to be backward
compatible. The Map Server authenticates the ETR first using UDP
based messages. Once the ETR is authenticated, the Map Server
performs a passive open by listening on TCP port 4342. TCP
connections are accepted only from the already authenticated ETRs.
The ETR has to open the TCP connection actively towards the Map
Server one it has received the Map-Notify message on the UDP
transport. If the TCP session goes down, the same UDP based
procedure has to be repeated. The Map-Server will also revert to the
expiration mechanism used for UDP transport until the TCP based
session would be fully restored. A single TCP session is built up
for all subsequent control plane messages. This applies even when
multiple address families are used in the EID space. Once the
reliable transport can be used, the periodic refresh is not needed
anymore. Mapping information is sent only when there is new
information to share. Time-out based removal of registrations are
not used in this case. An explicit de-registration is needed by
carrying a zero TTL. The reliable transport session should be
authenticated. In the simpler case, it could be an RLOC spoofing
mitigation. If this is not reliable, then the TCP Authentication
Option [RFC5925], or the SCTP Authenticated Chunks [RFC4895] are
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recommended.
8.6. Data Plane Security
8.6.1. Segmentation
LISP inherently delivers segmentation by using extended endpoint
identifiers (EIDs) and Instance-IDs to partition the EID space,
segment the map-caches, and color the control and data plane messages
to create virtual networks. These virtual networks are a seamless
extension of the way EIDs are normally handled in LISP and therefore
enjoy all the benefits of scale, mobility, and address family
independence that LISP provides.
8.6.2. Automated RLOC Filtering
The communication on between the xTRs and Map-Servers use the RLOC
space data plane. Only those communications attempts shall be
accepted that are coming from valid RLOC addresses. Manual
configuration of such access lists would be too difficult to manage.
An automated RLOC membership mechanism is proposed in [LISP-RFIL].
Although this Internet Draft has been expired, it is still included
in some LISP implementations. The Map-Server can authenticate each
xTR that wants to communicate. It will build up a list of xTRs that
are valid members of this LISP administrative domain. An xTR can
specifically subscribe to this membership information. Membership
can be maintained by address family and instance ID (VPN). This
allows an easy management of both RLOC and EID space segmentation by
VPNs. It also supports gateway functions between separated RLOC
spaces. Only valid xTR members can apply for notifications of
membership information. The xTR receiving the membership information
might use it for building internal access control lists
automatically. Proxy xTR information is not included in the
membership list, so communication with such nodes need to be
configured manually. A membership message format is defined in
[LISP-RFIL]. The following message type are specified: • Membership
subscribe, • Membership subscribe acknowledgement, • Membership
subscribe negative acknowledgement, • Membership unsubscribe, •
Membership element add, • Membership element delete, • Membership
refresh request, • Membership refresh begin, • Membership refresh
end. The membership information could be used by the xTR for other
future functions, too. Automated RLOC filtering is just one example.
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8.6.3. Confidentiality, Integrity and Anti-replay protection
In those sections of the ATN/IPS network where data plane
confidentiality, integrity and anti-replay protection may be
required, the LISP data plane can be secured as any other IP traffic
by leveraging IPsec. The provisioning of an IPsec VPN to secure IP
encapsulated LISP frames is orthogonal to deployment of LISP and can
be done using well known IPsec key negotiation mechanisms such as
IKEv2 [RFC7296].
IKEv2 uses X.509 certificates for authentication. A PKI is needed
for managing the certificates. The certificates are used for
generating the exchanged symmetric encryption keys.
9. IANA Considerations
No IANA considerations.
10. Acknowledgements
The original authors would like to thank Dino Farinacci and Bela
Varkonyi for their review of the document and deep insights.
The following people have contributed, over time, to the autorship of
this document: Bernhard Haindl, Manfred Lindner, Reshad Rahman, Marc
Portoles-Comeras, Victor Moreno, Fabio Maino, Balaji
Venkatachalapathy.
11. References
11.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[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>.
11.2. Informative References
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[GBL] Frequentis, "Ground Based LISP for Multilink Operation,
https://www.icao.int/safety/acp/ACPWGF/CP WG-I 19/WP06
Ground_Based_LISP 2016-01-14.pdf", January 2016.
[I-D.ermagan-lisp-nat-traversal]
Ermagan, V., Farinacci, D., Lewis, D., Maino, F.,
Portoles-Comeras, M., Skriver, J., White, C., Brescó, A.
L., and A. Cabellos-Aparicio, "NAT traversal for LISP",
Work in Progress, Internet-Draft, draft-ermagan-lisp-nat-
traversal-19, 7 May 2021,
<https://datatracker.ietf.org/doc/html/draft-ermagan-lisp-
nat-traversal-19>.
[I-D.ietf-lisp-eid-mobility]
Portoles-Comeras, M., Ashtaputre, V., Maino, F., Moreno,
V., and D. Farinacci, "LISP L2/L3 EID Mobility Using a
Unified Control Plane", Work in Progress, Internet-Draft,
draft-ietf-lisp-eid-mobility-11, 10 January 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-lisp-
eid-mobility-11>.
[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-15, 28 February 2023,
<https://datatracker.ietf.org/doc/html/draft-ietf-lisp-
pubsub-15>.
[I-D.ietf-lisp-sec]
Maino, F., Ermagan, V., Cabellos-Aparicio, A., and D.
Saucez, "Locator/ID Separation Protocol Security (LISP-
SEC)", Work in Progress, Internet-Draft, draft-ietf-lisp-
sec-29, 7 July 2022,
<https://datatracker.ietf.org/doc/html/draft-ietf-lisp-
sec-29>.
[I-D.moreno-lisp-uberlay]
Moreno, V., Farinacci, D., Rodriguez-Natal, A., Portoles-
Comeras, M., Maino, F., and S. Hooda, "Uberlay
Interconnection of Multiple LISP overlays", Work in
Progress, Internet-Draft, draft-moreno-lisp-uberlay-06, 28
September 2022, <https://datatracker.ietf.org/doc/html/
draft-moreno-lisp-uberlay-06>.
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[I-D.templin-atn-bgp]
Templin, F., Saccone, G., Dawra, G., Lindem, A., and V.
Moreno, "A Simple BGP-based Mobile Routing System for the
Aeronautical Telecommunications Network", Work in
Progress, Internet-Draft, draft-templin-atn-bgp-08, 16
August 2018, <https://datatracker.ietf.org/doc/html/draft-
templin-atn-bgp-08>.
Authors' Addresses
Bernhard Haindl
Frequentis
Email: bernhard.haindl@frequentis.com
Manfred Lindner
Frequentis
Email: manfred.lindner@frequentis.com
Victor Moreno
Google
Email: vimoreno@google.com
Marc Portoles Comeras
Cisco Systems
Email: mportole@cisco.com
Fabio Maino
Cisco Systems
Email: fmaino@cisco.com
Balaji Venkatachalapathy
Cisco Systems
Email: bvenkata@cisco.com
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