SFC M. Boucadair Internet-Draft C. Jacquenet Intended status: Informational France Telecom Expires: April 06, 2014 Y. Jiang Huawei Technologies Co., Ltd. R. Parker Affirmed Networks C. Pignataro Cisco Systems, Inc. October 03, 2013 Requirements for Service Function Chaining draft-boucadair-sfc-requirements-00 Abstract This document identifies the requirements for the Service Function Chaining (SFC). 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 RFC 2119 [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 http://datatracker.ietf.org/drafts/current/. 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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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 3. Detailed Requirements List . . . . . . . . . . . . . . . . . 2 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 5. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 8.1. Normative References . . . . . . . . . . . . . . . . . . 9 8.2. Informative References . . . . . . . . . . . . . . . . . 9 1. Introduction This document identifies the requirements for the Service Function Chaining (SFC). The overall problem space is described in [I-D.quinn-nsc-problem-statement]. The Service Function Chaining Framework is documented in [I-D.boucadair-service-chaining-framework]. 2. Terminology The reader should be familiar with the terms defined in [I-D.boucadair-service-chaining-framework] and [I-D.quinn-nsc-problem-statement]. 3. Detailed Requirements List The following set of functional requirements should be considered for the design of the Service Function Chaining solution: Boucadair, et al. Expires April 06, 2014 [Page 2] Internet-Draft SFC Requirements October 2013 REQ#1: The solution MUST NOT make any assumption on whether Service Functions (SF) are deployed directly on physical hardware, as one or more Virtual Machines, or any combination thereof. REQ#2: The solution MUST NOT make any assumption on whether Service Functions each reside on a separate addressable Network Element, horizontal scaling of Service Functions, are co- resident on a single addressable Network Element, or any combination thereof. Note: Communications between Service Functions co- resident on same Network Element are considered implementation-specific. These considerations are out of scope of the SFC specification effort. REQ#3: The solution MUST NOT require any IANA registry for Service Functions. REQ#4: The solution MUST NOT assume predefined order of Service Functions. In particular, the solution MUST NOT require any IANA registry to store typical Service Function Chains. REQ#5: The identification of instantiated Service Function Chains is local to each administrative domain; it is policy-based and deployment-specific. REQ#6: The solution MUST allow multiple instances of a given Service Function ( i.e., a Service Function can be embedded in multiple Network Elements). a. This is used for load-balancing, load-sharing, prevent from failures (e.g., hot or cold standby protection mechanism), accommodate planned maintenance operations, etc. b. How these multiple devices are involved in the service delivery is deployment-specific. REQ#7: The solution MUST allow for multiple Service Chains to be simultaneously enforced within an administrative domain. REQ#8: The solution MUST allow the same Service Function to be involved in multiple Service Function Chains. REQ#9: The solution MUST support multiple SFC-enabled domains be deployed within the same administrative domain. Boucadair, et al. Expires April 06, 2014 [Page 3] Internet-Draft SFC Requirements October 2013 REQ#10: The solution MUST be able to associate the same or distinct Service Function Chains for each direction (inbound/ outbound) of the traffic. In particular, unidirectional Service Function Chains, bi-directional Service Function Chains, or any combination thereof MUST be supported. REQ#11: The solution MUST be able to dynamically enforce Service Function Chains. In particular, the solution MUST allow the update or the withdrawal of existing Service Function Chains, the definition of a new Service Function Chain, the addition of new Service Functions without having any impact on other existing Service Functions or other Service Function Chains. REQ#12: The solution MUST provide means to control the SF-inferred information to be leaked outside an SFC-enabled domain. In particular, an administrative entity MUST be able to prevent Service Function Chaining logic and related policies from being exposed outside its administrative domain. REQ#13: The solution SHOULD minimize fragmentation; in particular a minimal set of SFC-specific information should be conveyed in the data packet. a. The per-SF Map forwarding MUST be undertaken without relying on dedicated resources to treat fragments. In particular, Out of order fragments MUST be forwarded on a per-SF Map basis without relying on any state. b. Of course, some SFs (e.g., NAT) may require dedicated resources (e.g., resources to store fragmented packets) or specific behavior (e.g, limit the time interval to accept fragments). The solution MUST NOT interfere with such practices. REQ#14: The solution MUST NOT make any assumption on how RIBs (Routing Information Bases) and FIBs (Forwarding Information Bases) are populated. Particularly, the solution does not make any assumption on protocols and mechanisms used to build these tables. REQ#15: The solution MUST be transport independent. a. The Service Function Chaining should operate regardless of the network transport used by the administrative entity. In particular, the solution can be used whatever the switching technologies deployed in the underlying transport infrastructure. Boucadair, et al. Expires April 06, 2014 [Page 4] Internet-Draft SFC Requirements October 2013 b. Techniques such as MPLS are neither required nor excluded. REQ#16: The solution MUST allow for chaining logics where involved Service Functions are not within the same layer 3 subnet. REQ#17: The solution MUST NOT exclude Service Functions to be within the same IP subnet (this is deployment-specific). REQ#18: An administrative entity, grouping its Service Functions within the same IP subnet, SHOULD be able to avoid encapsulation overhead . REQ#19: The solution MUST NOT make any assumption on how the traffic is to be bound to a given chaining policy. In other words, classification rules are deployment-specific and policy- based. For instance, classification can rely on a subset of the information carried in a received packet such as 5-tuple classification. REQ#20: The solution MUST support classifying traffic into Service Function Chains. REQ#21: The solution MUST NOT require every Service Function be co- located with a SFC Classifier; this is a deployment-specific decision. REQ#22: The solution MAY allow reclassification at the Service Functions (i.e., a Service Function can also be co-located with a classifier). The configuration of classification rules in such context are the responsibility of the administrative entity managing that SFC-enabled domain. REQ#23: The solution MUST be able to forward the traffic between two Service Functions (involved in the same Service Function Chain) without relying on the original destination address in a data packet. REQ#24: The solution MUST allow for the association of a context with the data packets. In particular: a. The solution MUST support the ability to invoke differentiated sets of policies for a Service Function (called Profiles). A profile denotes a set of policies configured to a local Service Function (e.g., content- filter-child, content-filter-adult). Boucadair, et al. Expires April 06, 2014 [Page 5] Internet-Draft SFC Requirements October 2013 a. Few profiles should be assumed per Service Function to accommodate the need for scalable solutions. b. Finer-grained of policies should be configured directly to each Service Function; no need to overload the design of Service Function Chains with policies of low-level granularity. REQ#25: The solution MUST allow for Operations, Administration, and Maintenance (OAM) features [RFC6291]. In particular, a. Support means to verify the completion of the forwarding actions derived from the contents of the SF Map until the Border Node is reached (see Section 3.4.1 of [RFC5706]). b. Support means to ensure coherent classification rules are installed to all SFC Classifiers. c. Support means to correlate between the classification policies and observed forwarding actions. d. Support in-band liveness and functionality checking of instantiated Service Function Chains. REQ#26: The solution MUST prevent the same Service Function to be invoked multiple times in the context of the same Service Function Chain (at the risk of generating Service Function Loop). REQ#27: The solution MUST allow for load-balancing. a. Load-balancing may be provided by legacy technologies or protocols (e.g., make use of load-balancers) b. Load-balancing may be part of the Service Function itself. c. Load-balancer may be considered as a Service Function element. d. Because of the possible complications, load balancing SHOULD NOT be driven by the SFC Classifier. REQ#28: The solution MUST separate provisioning-related aspects from the actual handling of packets (including forwarding decisions). Boucadair, et al. Expires April 06, 2014 [Page 6] Internet-Draft SFC Requirements October 2013 REQ#29: The solution SHOULD means to detect the liveness of involved Service Functions. REQ#30: Means to dynamically discover Service Functions SHOULD be supported. REQ#31: Service Functions may be reachable using IPv4 and/or IPv6. The administrative domain entity MUST be able to define and enforce policies with regards to the address family to be used when invoking a Service Function. a. A SF Map may be composed of IPv4 addresses, IPv6 addresses, or a mix of both IPv4 and IPv6 addresses. b. Multiple Service Functions can be reachable using the same IP address. Each of these Service Functions is unambiguously identified with a Service Function Identifier. REQ#32: The solution MUST allow for gradual deployment in legacy infrastructures, and therefore coexist with legacy technologies that cannot support SFC-specific capabilities, such as SFC Map interpretation and processing. The solution MUST be able to work in a domain that may be partly composed of opaque elements, i.e., elements that do not support SFC- specific capabilities. REQ#33: The solution MUST be able to provide different SLAs (Service Level Agreements, [I-D.boucadair-connectivity-provisioning-profile]). In particular, a. The solution MUST allow for different levels of service to be provided for traffic streams (e.g., configure Classes of Service (CoSes)). b. The solution MUST be compatible with Diffserv [RFC2475]. c. The solution SHOULD support the two modes defined in [RFC2983]. REQ#34: ECN re-marking, when required, MUST be performed according to [RFC6040]. 4. IANA Considerations Authors of this document do not require any action from IANA. Boucadair, et al. Expires April 06, 2014 [Page 7] Internet-Draft SFC Requirements October 2013 5. Security Considerations Below are listed some security-related requirements to be taken into account when designing the Service Function Chaining solution: SEC_REQ#1: The solution MUST provide means to prevent leaking any information that would be used as a hint to guess internal engineering practices (e.g., network topology, service infrastructure topology, hints on the enabled mechanisms to protect internal service infrastructures, etc.). In particular, topology hiding means MUST supported to avoid exposing the topology of an SFC-enabled domain (including the set of involved Service Functions). SEC_REQ#2: The solution MUST support means to defend against denial- of-service and theft of service (e.g., illegitimate access to the service). For example, a user should not be granted access to connectivity services it didn't subscribed to such as illegitimate access to network resources. SEC_REQ#3: The solution MUST NOT interfere with IPsec [RFC4301] (in particular IPsec integrity checks). 6. Contributors The following individuals contributed text to the document: Hongyu Li Huawei Technologies Co., Ltd. Bantian, Longgang district Shenzhen 518129, China EMail: hongyu.lihongyu@huawei.com Jim Guichard Cisco Systems, Inc. USA EMail: jguichar@cisco.com Paul Quinn Cisco Systems, Inc. USA Boucadair, et al. Expires April 06, 2014 [Page 8] Internet-Draft SFC Requirements October 2013 Email: paulq@cisco.com 7. Acknowledgements Many thanks to K. Gray for his review. 8. References 8.1. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 8.2. Informative References [I-D.boucadair-connectivity-provisioning-profile] Boucadair, M., Jacquenet, C., and N. Wang, "IP/MPLS Connectivity Provisioning Profile", draft-boucadair- connectivity-provisioning-profile-02 (work in progress), September 2012. [I-D.boucadair-service-chaining-framework] Boucadair, M., Jacquenet, C., Parker, R., Lopez, D., Guichard, J., and C. Pignataro, "Differentiated Service Function Chaining Framework", draft-boucadair-service- chaining-framework-00 (work in progress), August 2013. [I-D.quinn-nsc-problem-statement] Quinn, P., Guichard, J., Surendra, S., Agarwal, P., Manur, R., Chauhan, A., Leymann, N., Boucadair, M., Jacquenet, C., Smith, M., Yadav, N., Nadeau, T., Gray, K., McConnell, B., and K. Kevin, "Network Service Chaining Problem Statement", draft-quinn-nsc-problem-statement-03 (work in progress), August 2013. [RFC2475] Blake, S., Black, D., Carlson, M., Davies, E., Wang, Z., and W. Weiss, "An Architecture for Differentiated Services", RFC 2475, December 1998. [RFC2983] Black, D., "Differentiated Services and Tunnels", RFC 2983, October 2000. [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. Boucadair, et al. Expires April 06, 2014 [Page 9] Internet-Draft SFC Requirements October 2013 [RFC5706] Harrington, D., "Guidelines for Considering Operations and Management of New Protocols and Protocol Extensions", RFC 5706, November 2009. [RFC6040] Briscoe, B., "Tunnelling of Explicit Congestion Notification", RFC 6040, November 2010. [RFC6291] Andersson, L., van Helvoort, H., Bonica, R., Romascanu, D., and S. Mansfield, "Guidelines for the Use of the "OAM" Acronym in the IETF", BCP 161, RFC 6291, June 2011. Authors' Addresses Mohamed Boucadair France Telecom Rennes 35000 France EMail: mohamed.boucadair@orange.com Christian Jacquenet France Telecom Rennes 35000 France EMail: christian.jacquenet@orange.com Yuanlong Jiang Huawei Technologies Co., Ltd. Bantian, Longgang district Shenzhen 518129, China EMail: jiangyuanlong@huawei.com Ron Parker Affirmed Networks Acton, MA USA EMail: Ron_Parker@affirmednetworks.com Boucadair, et al. Expires April 06, 2014 [Page 10] Internet-Draft SFC Requirements October 2013 Carlos Pignataro Cisco Systems, Inc. USA EMail: cpignata@cisco.com Boucadair, et al. Expires April 06, 2014 [Page 11]