| Internet Engineering Task Force | L. Fang, Ed. |
| Internet-Draft | Cisco Systems Inc. |
| Intended status: Informational | B. Niven-Jenkins, Ed. |
| Expires: November 14, 2011 | Velocix |
| S. Mansfield, Ed. | |
| Ericsson | |
| R. Zhang | |
| British Telecom | |
| N. Bitar | |
| Verizon | |
| M. Daikoku | |
| KDDI Corporation | |
| L. Wang | |
| Telenor | |
| H. Yu | |
| TW Telecom | |
| May 13, 2011 |
MPLS-TP Security Framework
draft-fang-mpls-tp-security-framework-05
This document provides a security framework for Multiprotocol Label Switching Transport Profile (MPLS-TP). Extended from MPLS technologies, MPLS-TP introduces new OAM capabilities, transport oriented path protection mechanism, and strong emphasis on static provisioning supported by network management systems. This document addresses the security aspects that are relevant in the context of MPLS-TP specifically. It describes the security requirements for MPLS-TP; potential securities threats and migration procedures for MPLS-TP networks and MPLS-TP inter-connection to MPLS and GMPLS networks.
This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network.
This Informational Internet-Draft is aimed at achieving IETF Consensus before publication as an RFC and will be subject to an IETF Last Call.
[RFC Editor, please remove this note before publication as an RFC and insert the correct Streams Boilerplate to indicate that the published RFC has IETF Consensus.]
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 http://datatracker.ietf.org/drafts/current/.
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This Internet-Draft will expire on November 14, 2011.
Copyright (c) 2011 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 (http://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 Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License.
This document provides a security framework for Multiprotocol Label Switching Transport Profile (MPLS-TP).
MPLS-TP Requirements and MPLS-TP Framework are defined in [RFC5654] and [RFC5921] respectively. The intent of MPLS-TP development is to address the needs for transport evolution, the fast growing bandwidth demand accelerated by new packet based services and multimedia applications, from Ethernet Services, Layer 2 and Layer 3 VPNS, triple play to Mobile Access Network (RAN) backhaul, etc. MPLS-TP is based on MPLS technologies to take advantage of the technology maturity, and it is required to maintain the transport characteristics.
Focused on meeting transport requirements, MPLS-TP uses a subset of MPLS features, and introduces extensions to reflect the transport technology characteristics. The added functionalities include in-band OAM, transport oriented path protection and recovery mechanisms, etc. There is strong emphasis on static provisioning supported by Network Management System (NMS) or Operation Support System (OSS). There are also needs for MPLS-TP and MPLS interworking.
The security aspects for the new extensions which are particularly designed for MPLS-TP need to be addressed. The security models, requirements, threat and defense techniques previously defined in [RFC5921] can be used for the re-use of the existing functionalities in MPLS and GMPLS, but not sufficient to cover the new extensions.
This document is a product of a joint Internet Engineering Task Force (IETF) / International Telecommunication Union Telecommunication Standardization Sector (ITU-T) effort to include an MPLS Transport Profile within the IETF MPLS and PWE3 architectures to support the capabilities and functionalities of a packet transport network.
This document addresses the security aspects that are specific to MPLS-TP. It intends to provide the security requirements for MPLS-TP; define security models which apply to various MPLS-TP deployment scenarios; identify the potential security threats and mitigation procedures for MPLS-TP networks and MPLS-TP inter-connection to MPLS or GMPLS networks. Inter-AS and Inter-provider security for MPLS-TP to MPLS-TP connections or MPLS-TP to MPLS connections are discussed, where connections present higher security risk factors than connections for Intra-AS MPLS-TP.
The general security analysis and guidelines for MPLS and GMPLS are addressed in [RFC5920], the content which has no new impact to MPLS-TP will not be repeated in this document. Other general security issues regarding transport networks that are not specific to MPLS-TP are also out of scope. Readers may also refer to the "Security Best Practices Efforts and Documents" Opsec Effort [opsec-efforts] and "Security Mechanisms for the Internet" [RFC3631] (if there are linkages to the Internet in the applications) for general network operation security considerations. This document does not intend to define the specific mechanisms/methods that must be implemented to satisfy the security requirements.
Issues/Areas to be addressed:
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]. Although this document is not a protocol specification, the use of this language clarifies the instructions to protocol designers producing solutions that satisfy the requirements set out in this document.
This document uses MPLS, MPLS-TP, and Security specific terminology. Detailed definitions and additional terminology for MPLS-TP may be found in [RFC5654], [RFC5921], and MPLS/GMPLS security related terminology in [RFC5920].
Section 1: Introduction
Section 2: MPLS-TP Security Reference Models
Section 3: Security Requirements
Section 4: Security Threats
Section 5: Defensive/Mitigation techniques/procedures
This section defines a reference model for security in MPLS-TP networks.
The models are built on the architecture of MPLS-TP defined in [RFC5921]. The Service Provider (SP) boundaries play an important role in determining the security models for any particular deployment.
This document defines a trusted zone as being where a single SP has the total operational control over that part of the network. A primary concern is about security aspects that relate to breaches of security from the "outside" of a trusted zone to the "inside" of this zone.
In the reference model 1, a single SP has total control of PE/T-PE to PE/T-PE of the MPLS-TP network.
Security reference model 1(a)
An MPLS-TP network with Single Segment Pseudowire (SS-PW) from PE to PE. The trusted zone is PE1 to PE2 as illustrated in MPLS-TP Security Model 1 (a) [secref-1a].
|<-------------- Emulated Service ---------------->|
| |
| |<------- Pseudo Wire ------>| |
| | | |
| | |<-- PSN Tunnel -->| | |
| V V V V |
V AC +----+ +----+ AC V
+-----+ | | PE1|==================| PE2| | +-----+
| |----------|............PW1.............|----------| |
| CE1 | | | | | | | | CE2 |
| |----------|............PW2.............|----------| |
+-----+ ^ | | |==================| | | ^ +-----+
^ | +----+ +----+ | | ^
| | Provider Edge 1 Provider Edge 2 | |
| | | |
Customer | | Customer
Edge 1 | | Edge 2
| |
Native service Native service
----Untrusted--- >|<------- Trusted Zone ----- >|<---Untrusted----
MPLS-TP Security Model 1 (a)
Security reference model 1(b)
An MPLS-TP network with Multi-Segment Pseudowire (MS-PW) from T-PE to T-PE. The trusted zone is T-PE1 to T-PE2 in this model as illustrated in MPLS-TP Security Model 1 (b) [secref-1b].
Native |<------------Pseudowire-------------->| Native
Service | PSN PSN | Service
(AC) | |<--cloud->| |<-cloud-->| | (AC)
| V V V V V V |
| +----+ +-----+ +----+ |
+----+ | |TPE1|===========|SPE1 |==========|TPE2| | +----+
| |------|..... PW.Seg't1.........PW.Seg't3.....|-------| |
| CE1| | | | | | | | | |CE2 |
| |------|..... PW.Seg't2.........PW.Seg't4.....|-------| |
+----+ | | |===========| |==========| | | +----+
^ +----+ ^ +-----+ ^ +----+ ^
| | | |
| TP LSP TP LSP |
| |
| |
|<---------------- Emulated Service ----------------->|
-Untrusted >|<----------- Trusted Zone ---------- >|< Untrusted-
MPLS-TP Security Model 1 (b)
In the reference model 2, a single SP does not have the total control of PE/T-PE to PE/T-PE of the MPLS-TP network, S-PE and T-PE may be under the control of different SPs or their customers or may not be trusted for some other reason. The MPLS-TP network is not contained within a single trusted zone.
Security Reference Model 2(a)
An MPLS-TP network with Multi-Segment Pseudowire (MS-PW) from T-PE to T-PE. The trusted zone is T-PE1 to S-PE, as illustrated in MPLS-TP Security Model 2 (a) [secref-2a].
Native |<------------Pseudowire-------------->| Native
Service | PSN PSN | Service
(AC) | |<cloud->| |<-cloud-->| | (AC)
| V V V V V V |
| +----+ +----+ +----+ |
+----+ | |TPE1|=========|SPE1|==========|TPE2| | +----+
| |------|.....PW.Seg't1......PW.Seg't3.... .|-------| |
| CE1| | | | | | | | | |CE2 |
| |------|.....PW.Seg't2......PW.Seg't4..... |-------| |
+----+ | | |=========| |==========| | | +----+
^ +----+ ^ +----+ ^ +----+ ^
| | | |
| TP LSP TP LSP |
| |
|<---------------- Emulated Service -------------->|
--Untrusted-- >|<-- Trusted Zone -->|< ------Untrusted--------
MPLS-TP Security Model 2 (a)
Security Reference Model 2(b)
An MPLS-TP network with Multi-Segment Pseudowire (MS-PW) from T-PE to T-PE. The trusted zone is the S-PE, as illustrated in MPLS-TP Security Model 2 (b) [secref-2b].
Native |<------------Pseudowire-------------->| Native
Service | PSN PSN | Service
(AC) | |<cloud->| |<-cloud-->| | (AC)
| V V V V V V |
| +----+ +----+ +----+ |
+----+ | |TPE1|=========|SPE1|==========|TPE2| | +----+
| |------|.....PW.Seg't1......PW.Seg't3.... .|-------| |
| CE1| | | | | | | | | |CE2 |
| |------|.....PW.Seg't2......PW.Seg't4..... |-------| |
+----+ | | |=========| |==========| | | +----+
^ +----+ ^ +----+ ^ +----+ ^
| | | |
| TP LSP TP LSP |
| |
|<---------------- Emulated Service -------------->|
--------Untrusted----------->|<--->|< ------Untrusted--------
Trusted
Zone
MPLS-TP Security Model 2 (b)
Security Reference Model 2(c)
An MPLS-TP network with Multi-Segment Pseudowire (MS-PW) from different Service Providers with inter-provider PW connections. The trusted zone is T-PE1 to S-PE3, as illustrated in MPLS-TP Security Model 2 (c) [secref-2c].
Native |<-------------------- PW15 --------------------->| Native
Layer | | Layer
Service | |<-PSN13->| |<-PSN3X->| |<-PSNXZ->| | Service
(AC1) V V LSP V V LSP V V LSP V V (AC2)
+----+ +-+ +----+ +----+ +-+ +----+
+---+ |TPE1| | | |SPE3| |SPEX| | | |TPEZ| +---+
| | | |=========| |=========| |=========| | | |
|CE1|----|........PW1........|...PW3...|........PW5........|---|CE2|
| | | |=========| |=========| |=========| | | |
+---+ | 1 | |2| | 3 | | X | |Y| | Z | +---+
+----+ +-+ +----+ +----+ +-+ +----+
|<- Subnetwork 123->| |<- Subnetwork XYZ->|
Untrusted->|<- Trusted Zone - >| <-------------Untrusted------------
MPLS-TP Security Model 2 (c)
An MPLS-TP network with a Transport LSP from PE1 to PE2. The trusted zone is PE1 to PE2 as illustrated in MPLS-TP Security Model 3 (a) [secref-3a].
|<------------- Client Network Layer --------------->|
| |
| |<----------- Packet --------->| |
| | Transport Service | |
| | | |
| | | |
| | Transport | |
| | |<------ LSP ------->| | |
| V V V V |
V AC +----+ +-----+ +----+ AC V
+-----+ | | PE1|=======\ /========| PE2| | +-----+
| |----------|..Svc LSP1.| \ / |............|----------| |
| CE1 | | | | | X | | | | | CE2 |
| |----------|..Svc LSP2.| / \ |............|----------| |
+-----+ ^ | | |=======/ \========| | | ^ +-----+
^ | +----+ ^ +-----+ +----+ | | ^
| | Provider | ^ Provider | |
| | Edge 1 | | Edge 2 | |
Customer | | P Router | Customer
Edge 1 | TE LSP | Edge 2
| |
| |
Native service Native service
-----Untrusted---- >|< ----- Trusted Zone ----- >|<----Untrusted----
MPLS-TP Security Model 3 (a)
The boundaries of a trusted zone should be carefully defined when analyzing the security properties of each individual network, as illustrated from the above, the security boundaries determine which reference model should be applied to the use case analysis.
A key requirement of MPLS-TP networks is that the security of the trusted zone MUST NOT be compromised by interconnecting one SP's MPLS-TP or MPLS infrastructure with another SP's core, T-PE devices, or end users.
In addition, neighboring nodes in the network may be trusted or untrusted. Neighbors may also be authorized or unauthorized. Even though a neighbor may be authorized for communication, it may not be trusted. For example, when connecting with another provider's S-PE to set up Inter-AS LSPs, the other provider is considered to be untrusted but may be authorized for communication.
+---------------+ +----------------+
| | | |
| MPLS-TP S-PE1----S-PE3 MPLS-TP |
CE1--T-PE1 Network | | Network T-PE2--CE2
| Provider S-PE2----S-PE4 Provider |
| A | | B |
+---------------+ +----------------+
For Provider A:
Trusted Zone: Provider A MPLS-TP network
Trusted neighbors: T-PE1, S-PE1, S-PE2
Authorized but untrusted neighbor: Provider B
Unauthorized neighbors: CE2
MPLS-TP trusted zone and authorized neighbor
This section covers security requirements for securing MPLS-TP network infrastructure. The MPLS-TP network can be operated without a control plane or via dynamic control planes protocols. The security requirements related to new MPLS-TP OAM, recovery mechanisms, MPLS-TP and MPLS interconnection, and MPLS-TP specific operational requirements will be addressed in this section.
A service provider may choose the implementation options which are the best fit for his/her network operation. This document does not state that a MPLS/GMPLS network must fulfill all security requirements listed to be secure.
These requirements are focused on: 1) how to protect the MPLS-TP network from various attacks originating outside the trusted zone including those from network users, both accidental and malicious; 2) prevention of operational errors resulting from misconfiguration within the trusted zone.
This section discusses the various network security threats that may endanger MPLS-TP networks. The discussion is limited to those threats that are unique to MPLS-TP networks or that affect MPLS-TP networks in unique ways.
A successful attack on a particular MPLS-TP network or on a SP's MPLS-TP infrastructure may cause one or more of the following ill effects:
It is useful to consider that threats, whether malicious or accidental, may come from different categories of sources. For example they may come from:
Given that security is generally a tradeoff between expense and risk, it is also useful to consider the likelihood of different attacks occurring. There is at least a perceived difference in the likelihood of most types of attacks being successfully mounted in different environments, such as:
Most types of attacks become easier to mount and hence more likely as the shared infrastructure via which service is provided expands from a single SP to multiple cooperating SPs to the global Internet. Attacks that may not be of sufficient likeliness to warrant concern in a closely controlled environment often merit defensive measures in broader, more open environments. In closed communities, it is often practical to deal with misbehavior after the fact: an employee can be disciplined, for example.
The following sections discuss specific types of exploits that threaten MPLS-TP networks.
This category encompasses attacks on the provider's or end user's data. Note that from the MPLS-TP network end user's point of view, some of this might be control plane traffic, e.g. routing protocols running from user site A to user site B via IP or non-IP connections, which may be some type of VPN.
The defensive techniques discussed in this document are intended to describe methods by which some security threats can be addressed. They are not intended as requirements for all MPLS-TP implementations. The MPLS-TP provider should determine the applicability of these techniques to the provider's specific service offerings, and the end user may wish to assess the value of these techniques to the user's service requirements. The operational environment determines the security requirements. Therefore, protocol designers need to provide a full set of security services, which can be used where appropriate.
The techniques discussed here include encryption, authentication, filtering, firewalls, access control, isolation, aggregation, and others.
To prevent security issues arising from some DoS attacks or from malicious or accidental misconfiguration, it is critical that devices in the MPLS-TP should only accept connections or control messages from valid sources. Authentication refers to methods to ensure that message sources are properly identified by the MPLS-TP devices with which they communicate. This section focuses on identifying the scenarios in which sender authentication is required and recommends authentication mechanisms for these scenarios.
Management system authentication includes the authentication of a PE to a centrally-managed network management or directory server when directory-based "auto-discovery" is used. It also includes authentication of a CE to the configuration server, when a configuration server system is used.
Authentication should be bi-directional, including PE or CE to configuration server authentication for PE or CE to be certain it is communicating with the right server.
Peer-to-peer authentication includes peer authentication for network control protocols and other peer authentication (i.e., authentication of one IPsec security gateway by another).
Authentication should be bi-directional, including S-PE, T-PE, PE or CE to configuration server authentication for PE or CE to be certain it is communicating with the right server.
Cryptographic techniques offer several mechanisms for authenticating the identity of devices or individuals. These include the use of shared secret keys, one-time keys generated by accessory devices or software, user-ID and password pairs, and a range of public-private key systems. Another approach is to use a hierarchical Certification Authority system to provide digital certificates.
Most of the security issues related to management interfaces can be addressed through the use of authentication techniques as described in the section on authentication. However, additional security may be provided by controlling access to management interfaces in other ways.
The Optical Internetworking Forum has done relevant work on protecting such interfaces with TLS, SSH, Kerberos, IPsec, WSS, etc. See Security for Management Interfaces to Network Elements [OIF-SMI-01.0], and Addendum to the Security for Management Interfaces to Network Elements [OIF-SMI-02.1]. See also the work in the ISMS WG.
Management interfaces, especially console ports on MPLS-TP devices, may be configured so they are only accessible out-of-band, through a system which is physically or logically separated from the rest of the MPLS-TP infrastructure.
Where management interfaces are accessible in-band within the MPLS-TP domain, filtering or firewalling techniques can be used to restrict unauthorized in-band traffic from having access to management interfaces. Depending on device capabilities, these filtering or firewalling techniques can be configured either on other devices through which the traffic might pass, or on the individual MPLS-TP devices themselves.
One way to protect the infrastructure used for support of MPLS-TP is to separate the resources for support of MPLS-TP services from the resources used for other purposes.
In general, it is not feasible to use a completely separate set of resources for support of each service. In fact, one of the main reasons for MPLS-TP enabled services is to allow sharing of resources between multiple services and multiple users. Thus, even if certain services use a separate network from Internet services, nonetheless there will still be multiple MPLS-TP users sharing the same network resources.
In general, the use of aggregated infrastructure allows the service provider to benefit from stochastic multiplexing of multiple bursty flows, and also may in some cases thwart traffic pattern analysis by combining the data from multiple users. However, service providers must minimize security risks introduced from any individual service or individual users.
In order to protect against deliberate or accidental misconnection, mechanisms can be put in place to verify both end-to-end connectivity and hop-by-hop resources. These mechanisms can trace the routes of LSPs in both the control plane and the data plane.
MPLS-TP network and service may be subject to attacks from a variety of security threats. Many threats are described in the Security Requirements [Security-Requirements] Section of this document. Many of the defensive techniques described in this document and elsewhere provide significant levels of protection from a variety of threats. However, in addition to employing defensive techniques silently to protect against attacks, MPLS-TP services can also add value for both providers and customers by implementing security monitoring systems to detect and report on any security attacks, regardless of whether the attacks are effective.
Attackers often begin by probing and analyzing defenses, so systems that can detect and properly report these early stages of attacks can provide significant benefits.
Information concerning attack incidents, especially if available quickly, can be useful in defending against further attacks. It can be used to help identify attackers or their specific targets at an early stage. This knowledge about attackers and targets can be used to strengthen defenses against specific attacks or attackers, or to improve the defenses for specific targets on an as-needed basis. Information collected on attacks may also be useful in identifying and developing defenses against novel attack types.
Security considerations constitute the sole subject of this memo and hence are discussed throughout.
The document describes a variety of defensive techniques that may be used to counter the suspected threats. All of the techniques presented involve mature and widely implemented technologies that are practical to implement.
The document evaluates MPLS-TP security requirements from a customer's perspective as well as from a service provider's perspective. These sections re-evaluate the identified threats from the perspectives of the various stakeholders and are meant to assist equipment vendors and service providers, who must ultimately decide what threats to protect against in any given configuration or service offering.
This document contains no new IANA considerations.
| [RFC2119] | Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. |
| [RFC3871] | Jones, G., "Operational Security Requirements for Large Internet Service Provider (ISP) IP Network Infrastructure", RFC 3871, September 2004. |
| [RFC4732] | Handley, M., Rescorla, E., IAB, "Internet Denial-of-Service Considerations", RFC 4732, December 2006. |
| [RFC5654] | Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N. and S. Ueno, "Requirements of an MPLS Transport Profile", RFC 5654, September 2009. |
| [RFC5951] | Lam, K., Mansfield, S. and E. Gray, "Network Management Requirements for MPLS-based Transport Networks", RFC 5951, September 2010. |
| [RFC3631] | Bellovin, S., Schiller, J. and C. Kaufman, "Security Mechanisms for the Internet", RFC 3631, December 2003. |
| [RFC5920] | Fang, L., "Security Framework for MPLS and GMPLS Networks", RFC 5920, July 2010. |
| [RFC5921] | Bocci, M., Bryant, S., Frost, D., Levrau, L. and L. Berger, "A Framework for MPLS in Transport Networks", RFC 5921, July 2010. |
| [opsec-efforts] | Security Best Practices Efforts and Documents", IETF draft-ietf-opsec-efforts-08.txt, June 2008. | , "
| [OIF-SMI-01.0] | Optical Internetworking Forum, "Security for Management Interfaces to Network Elements", OIF OIF-SMI-01.0, Sept 2003. |
| [OIF-SMI-02.1] | Optical Internetworking Forum, "Addendum to the Security for Management Interfaces to Network Elements", OIF OIF-SMI-02.1, March 2006. |