Internet DRAFT - draft-jliu-savi-ipsa
draft-jliu-savi-ipsa
SAVNET Working Group J. Liu
Internet-Draft H. Li
Intended status: Informational T. Zhang
Expires: 31 August 2024 Q. Wu
Tsinghua University
28 February 2024
A SAVI Solution for IP based Satellite Access
draft-jliu-savi-ipsa-00
Abstract
This document presents the source address validation solution for for
IP based Satellite Access. This mechanism transfers user states
through end network collaboration to solve the impact of dynamic
handover of satellite-ground links on native SAVI. This document
mainly describes the operations involved in overcoming the dynamics
of the access link.
Status of This Memo
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Copyright Notice
Copyright (c) 2024 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. The threat of IP source address spoofing in satellite access
scenarios . . . . . . . . . . . . . . . . . . . . . . . . 4
3.1. Characteristics of Satellite Access Scenarios . . . . . . 4
3.2. source address validation for IP based satellite access
scenarios . . . . . . . . . . . . . . . . . . . . . . . . 4
3.3. Deterioration of existing mobility processing
mechanism . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Design requirements for source address validation for IP based
satellite access . . . . . . . . . . . . . . . . . . . . 6
4.1. The ability to effectively resist source address
spoofing . . . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Lightweight signaling interaction . . . . . . . . . . . . 6
4.3. High scalability . . . . . . . . . . . . . . . . . . . . 6
5. Specification of SAVI for for IP based satellite access . . . 6
5.1. Framework . . . . . . . . . . . . . . . . . . . . . . . . 6
5.2. The new binding anchor . . . . . . . . . . . . . . . . . 8
5.3. Semantic extension of IPv6 address based on satellite
characteristic . . . . . . . . . . . . . . . . . . . . . 9
5.4. Reliable binding migration . . . . . . . . . . . . . . . 9
5.5. Binding clearing . . . . . . . . . . . . . . . . . . . . 9
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
8.1. Normative References . . . . . . . . . . . . . . . . . . 10
8.2. Informative References . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
1. Introduction
Malicious source address spoofing is an important component of
Distributed Denial of Service (DDoS) attacks. Source Address
Validation Improvements (SAVI) [RFC7039][RFC7513][RFC8074] is a key
technology used in terrestrial Internet to prevent source address
spoofing. By listening to the control packets exchanged when the
host obtains the IP address, a binding relationship between the IP
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address and the unforgeable link layer attributes (Anchors) is
established for the terminal on the access device. And then source
address validation is performed on the IP data packets, Only packets
with matching source addresses and bound table entries will be
forwarded to ensure the authenticity of the source address of data
packets entering the internet. However, in the scenario of satellite
access, the high dynamism of Low Earth Orbit (LEO) satellites keeps
the anchor away from the user, resulting in the failure of anchor
binding information. Each time a handover is made, the satellite
storing binding information will move away from the corresponding
user. So the user needs to perform identity authentication and
anchor binding again. Frequent execution of this operation by a
massive number of global user nodes will generate a signaling storm,
leading to a sharp decline in the availability of SAVI.
This document describes the mechanism for the source address
validation method for IP based satellite access by end-network
collaboration, considering the dynamic characteristics of satellite
access scenarios. This technology requires the decomposition of user
states in source address validation into collaborative management
between the network side and user terminals. When handover occurs,
the end-network collaboration completes a low-cost secure transfer of
user states, avoiding anchor mobility caused by dynamic handover of
satellite-ground links, which leads to a sharp increase in source
address validation costs and a decrease in availability. This
technology requires only one hop signaling interaction between the
user terminal and the access satellite, without involving the ground
Network Control Center (NCC) and Inter Satellite Links (ISL)
[Starlink-ISL], significantly reducing the rebinding delay caused by
handover. In addition, due to the fact that the rebinding process
does not occupy any ISL bandwidth, this method has high scalability
for satellite access scenarios with a global massive number of users.
2. Terminology
Initial access satellite: the satellite that the user terminal
connects to the satellite Internet for the first time.
New access satellite: the user terminal reconnects to the satellite
connected to the satellite Internet after handover.
Binding anchor: "binding anchor" is defined as the physical and / or
link layer attributes of the additional device, as defined in
[RFC7039]. In this document, the binding anchor refers to the
communication key of the link layer.
Binding entry: the entry that associates the IP address and MAC
address with the binding anchor.
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3. The threat of IP source address spoofing in satellite access
scenarios
3.1. Characteristics of Satellite Access Scenarios
The satellite access scenario has many new network characteristics,
including the use of ISL, the dynamism of the access link (frequent
handover between user terminals and LEO satellites will inevitably
lead to frequent updates of IP addresses), and the openness of
satellite orbit information (accurate prediction of satellite motion
can be achieved through calculation). Due to the global movement of
satellites, they are mostly in an uncontrolled environment and face
threats from a large number of malicious hosts distributed around the
world. In addition, there is a significant performance gap between
satellite processors and the ground device, and many terrestrial
mature solutions are difficult to implement on satellites.
3.2. source address validation for IP based satellite access scenarios
The use of ISL in satellite access scenarios increases the
vulnerability of the network layer. DDoS attack is one of the most
common attacks at the network layer. Due to limited computing
resources, lack of traceability, and exposure to uncontrolled
environments, source address spoofing attacks in satellite access
scenarios are more severe than those in terrestrial networks. To
defend against such attacks, the most effective technique in
terrestrial networks is to filter address spoofing packets and ensure
that malicious users in the network are located through traceability
of the source address. SAVI and other source address validation
technologies have been deployed in terrestrial networks, and their
effectiveness has been proven to some extent. However, due to the
fragility of satellite constellations described above, SAVI
technology cannot be directly applied to satellite access scenarios.
The source address validation scenario for IP based satellite access
scenario is shown in Figure 1, which is divided into ground segment
and space segment. The ground segment includes user terminals,
authentication servers, and ground gateways connected to the
Internet. The space segment consists of satellites with access
capabilities (using ISL and supporting SAVI).
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+----------------------------------------+
|+---------+ +---------+ |
Space ||Satellite| ISLs |Satellite| |
Segment || (SAVI) | <-------------> | (SAVI) | |
|+----+----+ +-----+---+ |
+-----|----------------------------|-----+
| |
+-----|----------------------------|-----+
|+----+----++--------------+ +---+---+ | +--------+
Ground || User ||Authentication|<->|Gateway|<->|Internet|
Segment || Terminal|| Server | |Station| | +--------+
|+---------++--------------+ +-------+ |
+----------------------------------------+
Figure 1: The source address validation for IP based satellite access
scenarios.
3.3. Deterioration of existing mobility processing mechanism
A SAVI Solution for WLAN [draft-bi-savi-wlan-24] proposes to extend
CAPWAP protocol by introducing host IP message elements. When the
mobile host is disconnected from the original access device on the
network side, the new access device sends a request to the original
access device, and the original access device uses this message to
report the MAC address and IP address to the new access device, so as
to complete the migration of binding information. Related draft
describes that the movement of hosts between APs and ACs can be
applied to this extension.
This solution can work effectively in the ground WLAN scenario, but
it will fail in ISTN due to the extremely fast relative moving speed
(up to 27000km/hour) between the access device (LEO satellite) and
the host, and the large moving range (globally). This document
refers to the implementation of this solution in ISTN as the anchor
request.
Specifically, after the satellite handover, the newly accessed
satellite sends the anchor request to the satellite where the anchor
binding information is located. After obtaining the anchor binding
information, the binding relationship is added in the local data
plane, and then the source address validation operation is performed
locally. Because the handover frequency of access satellite is
minute level and the scale is all users, this method will make the
network face massive state migration signaling overhead.
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4. Design requirements for source address validation for IP based
satellite access
4.1. The ability to effectively resist source address spoofing
The source address validation for IP based satellite access can
effectively resist various attacks initiated by malicious users
through source address spoofing, such as DDoS. By matching and
validating the source address of user data packets with anchor
binding information on the access satellite, packets with forged
source addresses will be identified and discarded, thus avoiding
malicious packets from entering the network.
4.2. Lightweight signaling interaction
The cost of source address validation for IP based satellite access
must be within the acceptable range of the devices involved. When
satellite handover occurs, the signaling interaction required to
handle user state transitions should be sufficiently streamlined to
reduce additional latency and bandwidth waste. In addition, the
processing and computational costs of data should also take into
account the performance limitations of onboard processing devices.
4.3. High scalability
The source address validation for IP based satellite access should be
easy to deploy in a lightweight manner on a large number of globally
distributed users and satellites, with performance not deteriorating
with the growth of user and satellite scale, and support incremental
deployment.
5. Specification of SAVI for for IP based satellite access
5.1. Framework
SAVI for IP based satellite access provides a framework for low-cost
migration of anchor binding status information in wide area high-
speed dynamic network scenarios represented by IP based satellite
access. In the existing SAVI technology, the user state managed only
by the network side is decomposed into the collaborative management
of the user end and the network side, that is, the satellite sends
the user state (such as the user IP address, MAC address and binding
anchor) to the user terminal for maintenance, and when the handover
occurs, the user terminal and the network side infrastructure linkage
complete the user state transfer.
The core workflow of SAVI for based satellite access is briefly
described as follows:
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a. Tthe orbit deployment stage
The satellite uses encryption methods (such as asymmetric encryption
algorithm) to generate key pairs, binds satellite characteristic
information (such as satellite ID) with the satellite's own public
key to form a public key comparison table, distributes it to other
satellites in the constellation through earth stations or GEO
satellites, and requests to update the local public key comparison
table.
b. The identity authentication stage
The corresponding communication key is obtained after successful
authentication through a specific identity authentication mechanism
(such as 802.1x).
c. The address allocation stage
This document takes the StateLess Address Autoconfiguration (SLAAC)
as an example. The initial access satellite sends the address prefix
and satellite ID to the user terminal through the extended RA
message. The user terminal generates a temporary IPv6 address and
sends it back to the initial access satellite through the NS message
for duplicate address detection (DAD).
d. The initial binding stage
After the initial access satellite completes the duplicate address
detection of the temporary address, the communication key is used as
the anchor of the source address validation, bound with the user's
MAC address and IPv6 address to form the binding information, which
is added to the binding state table (BST) of the initial satellite,
and the lifetime of this entry is set. After signing the binding
information with its own private key, it is sent to the user terminal
through the extended Na message.
e. The rebinding stage
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After the user terminal switches the new access satellite, it sends
the signed binding information to the new satellite through the
extended RS message. The new access satellite queries the initial
satellite public key in the local public key comparison table through
the initial satellite ID parsed from the user's IPv6 address, obtains
the original binding information after verifying the signature of the
received information, and then queries the local BST. If the query
is successful, Explain that the user terminal has been connected to
the satellite, reset the lifetime of the entry. If the query fails,
match and verify the binding information with the MAC address and
IPv6 address of the current user terminal. If the matching passes,
add it as a new entry to the local BST and set the lifetime.
The new access satellite informs the user terminal that the
communication key will be used for subsequent data transmission
encryption.
5.2. The new binding anchor
Unlike existing SAVI solutions that use Ethernet ports or MAC
addresses as anchors, this document proposes to use the communication
key of the data link layer as an anchor. The communication key
conforms to the characteristic description of the anchor in the SAVI
framework. More importantly, the new access satellite can inherit
the communication key after completing the migration of the anchor
binding state information, so as to avoid reperforming identity
authentication and key negotiation to obtain the communication key
after handover, so that the user terminal only needs to authenticate
when it accesses the IP based satellite access for the first time.
The BST of SAVI for IP based satellite access mainly contains fields,
as shown in Figure 1.
+------+--------------+------------+---------------+
|Anchor| MAC Address | IPv6 Address |Lifetime|
+------+--------------+-------------------+--------+
| 1 |5489-98f6-16c0|2001:da8:26d:131::1| 6000 |
+------+--------------+-------------------+--------+
| 2 |21a5-3659-d721|2001:da8:26d:030::1| 300 |
+------+--------------+-------------------+--------+
Figure 2: Example Binding State Table for IP based satellite access.
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5.3. Semantic extension of IPv6 address based on satellite
characteristic
By embedding satellite characteristic information, such as satellite
ID, into the IPv6 address, it can be used as the stable
identification of the network side state maintenance equipment when
the user first accesses. Any new access satellite can resolve the
identification from the IP address of the user terminal, so as to
query the elements required to decrypt the user state of the
corresponding application.
The IPv6 address structure of the SAVI for IP based satellite access
embedded with satellite ID is shown in Figure 3.
| N bits | M bits | 128-N-M bits |
+-------------+--------+--------------+
|Global Prefix| SatID | Interface ID |
+-------------+--------+--------------+
Figure 3: The structure of IPv6 address expanded.
5.4. Reliable binding migration
Through encryption and decryption technologies such as asymmetric
encryption algorithm, the encrypted binding state information is
stored in the user terminal, and the terminal sends it to the new
access satellite for decryption verification and rebinding after each
handover, so as to ensure the security of the user state in the
process of transferring from the previous access satellite to the new
access satellite via the user terminal in the clear text
communication environment without performing identity authentication.
5.5. Binding clearing
In order to reduce the storage burden of satellite nodes, the entries
in the BST will be automatically deleted once the lifetime reaches to
zero.
6. Acknowledgements
7. IANA Considerations
This memo includes no request to IANA.
8. References
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8.1. Normative References
[RFC7039] Wu, J., Bi, J., Bagnulo, M., Baker, F., and C. Vogt, Ed.,
"Source Address Validation Improvement (SAVI) Framework",
RFC 7039, DOI 10.17487/RFC7039, October 2013,
<https://www.rfc-editor.org/info/rfc7039>.
[RFC7513] Bi, J., Wu, J., Yao, G., and F. Baker, "Source Address
Validation Improvement (SAVI) Solution for DHCP",
RFC 7513, DOI 10.17487/RFC7513, May 2015,
<https://www.rfc-editor.org/info/rfc7513>.
[RFC8074] Bi, J., Yao, G., Halpern, J., and E. Levy-Abegnoli, Ed.,
"Source Address Validation Improvement (SAVI) for Mixed
Address Assignment Methods Scenario", RFC 8074,
DOI 10.17487/RFC8074, February 2017,
<https://www.rfc-editor.org/info/rfc8074>.
8.2. Informative References
[draft-bi-savi-wlan-24]
Bi, J., "A SAVI Solution for WLAN", 2024,
<https://datatracker.ietf.org/doc/draft-bi-savi-wlan/>.
[Starlink-ISL]
"Starlink block v1.5",
<https://space.skyrocket.de/doc_sdat/starlink-v1-5.html>.
Authors' Addresses
Jun Liu
Tsinghua University
Beijing 100084
China
Email: juneliu@tsinghua.edu.cn
Hewu Li
Tsinghua University
Beijing 100084
China
Email: lihewu@cernet.edu.cn
Tianyu Zhang
Tsinghua University
Beijing 100084
China
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Email: ty-zhang20@tsinghua.org.cn
Qian Wu
Tsinghua University
Beijing 100084
China
Email: wuqian@cernet.edu.cn
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