Internet DRAFT - draft-cheng-idr-redirection-risks-ps
draft-cheng-idr-redirection-risks-ps
idr W. Cheng, Ed.
Internet-Draft China Mobile
Intended status: Standards Track D. li
Expires: 14 September 2023 Tsinghua University
Y. liu
China Mobile
M. Huang
Huawei
F. Gao
Zhongguancun Laboratory
S. Chen
Huawei
13 March 2023
Problem statement of Inter-domain Traffic Redirection Risks
draft-cheng-idr-redirection-risks-ps-02
Abstract
Redirection of network traffic on the Internet is a common
technology. In operator network, there are complex scenarios, such
as multi-domain interconnection and large scale network topology.
Typo, limitation of out-of-band tool capabilities for configuration
verification, network adjustment or failure may cause risks, such as
traffic detour, traffic exposure, traffic black hole and traffic
loops. This draft describes these risks.
Status of This Memo
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This Internet-Draft will expire on 14 September 2023.
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Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Risks Description . . . . . . . . . . . . . . . . . . . . . . 3
3. Valuable Scenarios and Potential Solutions . . . . . . . . . 5
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
5. Security Considerations . . . . . . . . . . . . . . . . . . . 6
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6
7. Normative References . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
1. Introduction
There are many network traffic redirection technologies[RFC1102],
such as Policy Based Routing[RFC1104] and BGP Flow Specification
Rules[RFC8955] etc. These technologies are widely used in carrier
networks.
For example, BGP Flow Specification provides various filtering
conditions and processing actions to implement traffic
control[RFC9117]. This function is used not only to protect the
device against denial-of-service (DoS) and distributed DoS (DDoS)
attacks, but also used for network traffic optimization.
As reliability and effectiveness of traffic redirection are
artificially guaranteed, there are risks, such as traffic detour,
traffic exposure, traffic black hole, traffic loop, as well as
inconsistent traffic paths between the control plane and data plane.
Currently, operators have applied the redirection technologies, such
as BGP Flowspec, on a large scale. How to deal with these risks
needs further discussion.
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2. Risks Description
The operation and maintenance of redirection in the long run is a big
challenge. Typo, limitation of out-of-band tool capabilities for
configuration verification, network adjustment or failure may cause
potential problems without system awareness.
The following figure shows the risks of traffic redirection.
Take the topology in Figure 1 as an example, In this application
scenario, one campus network inter-connects to two providers Network.
AS 65003 and AS 65500, AS 65105 and AS 65500 form a provider-customer
adjacency relationship. Assume that the user needs to transmit data
to the server. According to the routing information on the control
plane, the traffic is transmitted through the path [User -- AS65001
-- AS65003 -- AS65104 -- AS65106 -- Server].
+---------------------+ +--------------------+
| ISP1 | | ISP2 |
+----+ | ,-. | | ,-. |
|user| | / \ | | / \ |
| |-----| AS | | | | AS | |
+----+ | |65001\ | | |65106| | +------+
| \ / \ ,-. | | ,-. .\ / -----|server|
| '-' \ / \ | | / \ ' '-' | | |
| | '| AS | | | | AS |-` | +------+
| ,-. .|65003|-----------|65104| ,-. |
| / \ ' \ / | | \ / `. / \ |
| | AS -` '\' | | '-' '| AS | |
| |65002| \ | | |65105| |
| \ / , | | \ / |
| '-' \ | | '-' |
+------------------\--+ +------------/-------+
\ Provider /
\ /
\ Customer /
+------+--------+---+
| '.-, |
| / \ |
| | AS | |
| |65500 | |
| \ / |
| `--` |
| ISP3(Campus) |
+-------------------+
Figure 1: Example of the risks of traffic redirection
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Risk 1: Violation of the valley-free principle[RFC7908] leads to
traffic detour and exposure.
Assume ISP1 configures wrong traffic redirection rule, as a result,
AS 65003 redirects traffic from AS 65104 to AS 65500. In this case,
valley-free principle is violated as AS 65003 and AS 65500 form a
provider-customer adjacency relationship. Traffic passes through the
AS 65500 and exposes itself to the campus network.
Risk 2: The traffic is redirected to a network node that has no
route, which leads to a traffic black hole
After traffic is redirected from AS 65003 to the AS 65500, the AS
65500 may not have a route to the destination server. In this case,
the traffic is discarded, resulting in a traffic black hole.
Assume traffic is redirected from AS65003 to AS65500, and AS65500
learns the route to server from AS65105. After the traffic is
redirected to the AS65500, it is forwarded to the server according to
the route. If the link between AS 65500 and AS 65105 fails, as a
result, the route is lost. The traffic is redirected to AS 65500
anyway, which also causes a traffic black hole.
Risk 3: One or more traffic redirections on the traffic transmission
path may cause a traffic loop.
Assume that traffic is redirected from AS 65104 to AS 65105. In AS
65105, the traffic is transmitted to AS 65500, or the traffic is
redirected to AS 65500. In this case, if the traffic on AS 65500 is
transmitted to AS 65003, then traffic loop occurs.
Assume traffic is redirected from AS 65003 to AS 65500, and AS 65500
learns the route to server from AS 65105. After receiving the
redirected traffic, the AS65500 forwards the traffic to the server
according to the route. If the link between AS6500 and AS65105
fails, AS 65500 learns that the next hop of the route to the server
is AS65003 through routing protocols. If the traffic is still
redirected to AS 65500 at this time, AS 65500 will send packets back
to AS65003, then traffic loop occurs.
Risk 4: inconsistent paths on the control plane and data plane may
cause O&M risks.
The traffic owner expects traffic to be transmitted along the AS path
carried in the route, but the actual transmission path is different
from the AS path.
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If the network O&M control system does not obtain traffic redirection
information on the network, unpredictable risks may occur during
traffic optimization, for example, network congestion.
For the risks mentioned above, it is not sufficient to rely on manual
operation or automated management. Traffic redirection increases
management difficulties and effectiveness requirements. It is
necessary to explore technical solutions, such as redirection
configuration verification, protocol extension, or path
visualization, to reduce risks mentioned above.
3. Valuable Scenarios and Potential Solutions
Since BGP cannot perceive the AS_path generated by the inter-domain
traffic redirection, the security of traffic redirection only relies
on human decision, which inevitably increases the risks. Below is
three potential solutions.
Solution 1: AS path validation
BGP flowspec only considers the verification of the source of the
flow specification.A potential solutions is to add a redirection path
perception capability to BGP, and verify the validity of the
redirection path before actually configuring the redirection. If the
redirection could lead to the above risks, alert the operator
explicitly.
Solution 2: Considerate routing
Traffic redirection may generate unexpected traffic models, causing
some SLAs to be unguaranteed. A potential solution is to extend BGP
to allow redirection rules and the next hop to be advertised to other
peers for routing decision.
Solution 3: Network visualization
Inter-domain redirection also hinders network visualization, making
it impossible to determine the forwarding path of packets solely
based on routing protocols. A potential solution is to extend the
BMP protocol to allow redirection rules and redirected forwarding
paths to be sent to the BMP server, improving administrators' ability
to visualize and plan their own traffic.
4. IANA Considerations
This document makes no request of IANA.
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5. Security Considerations
TBD
6. Acknowledgements
The authors would like to thank Hao Li.
7. Normative References
[RFC1102] Clark, D., "Policy routing in Internet protocols",
RFC 1102, DOI 10.17487/RFC1102, May 1989,
<https://www.rfc-editor.org/info/rfc1102>.
[RFC1104] Braun, H., "Models of policy based routing", RFC 1104,
DOI 10.17487/RFC1104, June 1989,
<https://www.rfc-editor.org/info/rfc1104>.
[RFC7908] Sriram, K., Montgomery, D., McPherson, D., Osterweil, E.,
and B. Dickson, "Problem Definition and Classification of
BGP Route Leaks", RFC 7908, DOI 10.17487/RFC7908, June
2016, <https://www.rfc-editor.org/info/rfc7908>.
[RFC8955] Loibl, C., Hares, S., Raszuk, R., McPherson, D., and M.
Bacher, "Dissemination of Flow Specification Rules",
RFC 8955, DOI 10.17487/RFC8955, December 2020,
<https://www.rfc-editor.org/info/rfc8955>.
[RFC9117] Uttaro, J., Alcaide, J., Filsfils, C., Smith, D., and P.
Mohapatra, "Revised Validation Procedure for BGP Flow
Specifications", RFC 9117, DOI 10.17487/RFC9117, August
2021, <https://www.rfc-editor.org/info/rfc9117>.
Authors' Addresses
Weiqiang Cheng (editor)
China Mobile
China
Email: chengweiqiang@chinamobile.com
Dan Li
Tsinghua University
China
Email: tolidan@tsinghua.edu.cn
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Yasi Liu
China Mobile
China
Email: liuyasi@chinamobile.com
Mingqing Huang
Huawei
China
Email: huangmingqing@huawei.com
Fang Gao
Zhongguancun Laboratory
China
Email: gaofang@zgclab.edu.cn
Shuanglong Chen
Huawei
China
Email: chenshuanglong@huawei.com
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