Network Working Group S. Hyun Internet-Draft J. Jeong Intended status: Standards Track Sungkyunkwan University Expires: January 4, 2018 J. Park ETRI S. Hares Huawei July 3, 2017 Service Function Chaining-Enabled I2NSF Architecture draft-hyun-i2nsf-nsf-triggered-steering-03 Abstract This document describes an architecture of the I2NSF framework using security function chaining for securiy policy enforcement. Security function chaining enables composite inspection of network traffic by steering the traffic through multiple types of network security functions according to the information model for NSFs capabilities in the I2NSF framework. This document explains the additional components integrated into the I2NSF framework and their functionalities to achieve security function chaining. It also describes representative use cases to address major benefits from the proposed architecture. Status of This Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 4, 2018. Hyun, et al. Expires January 4, 2018 [Page 1] Internet-Draft SFC-enabled I2NSF Architecture July 2017 Copyright Notice Copyright (c) 2017 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Objective . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 4. Architecture . . . . . . . . . . . . . . . . . . . . . . . . . 5 4.1. SFC Policy Manager . . . . . . . . . . . . . . . . . . . . 8 4.2. SFC Catalog Manager . . . . . . . . . . . . . . . . . . . 8 4.3. Developer's Management System . . . . . . . . . . . . . . 9 4.4. Classifier . . . . . . . . . . . . . . . . . . . . . . . . 9 4.5. Service Function Forwarder (SFF) . . . . . . . . . . . . . 9 5. Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5.1. Dynamic Path Alternation . . . . . . . . . . . . . . . . . 10 5.2. Enforcing Different SFPs Depending on Trust Levels . . . . 11 5.3. Effective Load Balancing with Dynamic SF Instantiation . . 12 6. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 13 7. Security Considerations . . . . . . . . . . . . . . . . . . . 14 8. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 14 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 15 9.1. Normative References . . . . . . . . . . . . . . . . . . . 15 9.2. Informative References . . . . . . . . . . . . . . . . . . 15 Appendix A. Changes from draft-hyun-i2nsf-nsf-triggered-steering-02 . . . . . 16 Hyun, et al. Expires January 4, 2018 [Page 2] Internet-Draft SFC-enabled I2NSF Architecture July 2017 1. Introduction To effectively cope with emerging sophisticated network attacks, it is necessary that various security functions cooperatively analyze network traffic [RFC7498][i2nsf-problem][nsf-capability-im]. In addition, depending on the characteristics of network traffic and their suspiciousness level, the different types of network traffic need to be analyzed through the different sets of security functions. In order to meet such requirements, besides security policy rules for individual security functions, we need an additional policy about service function chaining (SFC) for network security which determines a set of security functions through which network traffic packets should pass for inspection. In addition, [nsf-capability-im] proposes an information model for NSFs capabilities that enables a security function to trigger further inspection by executing additional security functions based on its own analysis results [i2nsf-framework]. However, the current design of the I2NSF framework does not consider network traffic steering fully in order to enable such chaining between security functions. In this document, we propose an architecture that integrates additional components from Service Function Chaining (SFC) into the I2NSF framework to support security function chaining. We extend the security controller's functionalities such that it can interpret a high-level policy of security function chaining into a low-level policy and manage them. It also keeps the track of the available service function (SF) instances for security functions and their information (e.g., network information and workload), and makes a decision on which SF instances to use for a given security function chain/path. Based on the forwarding information provided by the security controller, the service function forwarder (SFF) performs network traffic steering through various required security functions. A classifier is deployed for the enforcement of SFC policies given by the security controller. It performs traffic classification based on the polices so that the traffic passes through the required security function chain/path by the SFF. 2. Objective o Policy configuration for security function chaining: SFC-enabled I2NSF architecture allows policy configuration and management of security function chaining. Based on the chaining policy, relevant network traffic can be analyzed through various security functions in a composite, cooperative manner. o Network traffic steering for security function chaining: SFC- enabled I2NSF architecture allows network traffic to be steered through multiple required security functions based on the SFC Hyun, et al. Expires January 4, 2018 [Page 3] Internet-Draft SFC-enabled I2NSF Architecture July 2017 policy. Moreover, the I2NSF information model for NSFs capabilities [nsf-capability-im] requires a security function to call another security function for further inspection based on its own inspection result. To meet this requirement, SFC-enabled I2NSF architecture also enables traffic forwarding from one security function to another security function. o Load balancing over security function instances: SFC-enabled I2NSF architecture provides load balancing of incoming traffic over available security function instances by leveraging the flexible traffic steering mechanism. For this objective, it also performs dynamic instantiation of a security function when there are an excessive amount of requests for that security function. 3. Terminology This document uses the following terminology described in [RFC7665], [RFC7665][i2nsf-terminology][ONF-SFC-Architecture]. o Service Function/Security Function (SF): A function that is responsible for specific treatment of received packets. A Service Function can act at various layers of a protocol stack (e.g., at the network layer or other OSI layers) [RFC7665]. In this document, SF is used to represent both Service Function and Security Function. Sample Security Service Functions are as follows: Firewall, Intrusion Prevention/Detection System (IPS/ IDS), Deep Packet Inspection (DPI), Application Visibility and Control (AVC), network virus and malware scanning, sandbox, Data Loss Prevention (DLP), Distributed Denial of Service (DDoS) mitigation and TLS proxy. o Classifier: An element that performs Classification. It uses a given policy from SFC Policy Manager. o Service Function Chain (SFC): A service function chain defines an ordered set of abstract service functions and ordering constraints that must be applied to packets and/or frames and/or flows selected as a result of classification [RFC7665]. o Service Function Forwarder (SFF): A service function forwarder is responsible for forwarding traffic to one or more connected service functions according to information carried in the SFC encapsulation, as well as handling traffic coming back from the SF. Additionally, an SFF is responsible for delivering traffic to a classifier when needed and supported, transporting traffic to another SFF (in the same or the different type of overlay), and terminating the Service Function Path (SFP) [RFC7665]. Hyun, et al. Expires January 4, 2018 [Page 4] Internet-Draft SFC-enabled I2NSF Architecture July 2017 o Service Function Path (SFP): The service function path is a constrained specification of where packets assigned to a certain service function path must be forwarded. While it may be so constrained as to identify the exact locations for packet processing, it can also be less specific for such locations [RFC7665]. o SFC Policy Manager: It is responsible for translating a high-level policy into a low-level policy, and performing the configuration for SFC-aware nodes, passing the translated policy and configuration to SFC-aware nodes, and maintaining a stabilized network. o SFC Catalog Manager: It is responsible for keeping the track of the information of available SF instances. For example, the information includes the supported transport protocols, IP addresses, and locations for the SF instances. o Control Nodes: It collectively refer to SFC Policy Manager, SFC Catalog Manager, SFF, and Classifier. o Service Path Identifier (SPI): It identifies a service path. The classifier MUST use this identifier for path selection and the Control Nodes MUST use this identifier to find the next hop [sfc-nsh]. o Service Index (SI): It provides a location within the service path. SI MUST be decremented by service functions or proxy nodes after performing the required services [sfc-nsh]. o Network Service Header (NSH): The header is used to carry SFC related information. Basically, SPI and SI should be conveyed to the Control Nodes of SFC via this header. o SF Forwarding Table: SFC Policy Manager maintains this table. It contains all the forwarding information on SFC-enabled I2NSF architecture. Each entry includes SFF identifier, SPI, SI, and next hop information. For example, an entry ("SFF: 1", "SPI: 1", "SI: 1", "IP: 192.168.xx.xx") is interpreted as follows: "SFF 1" should forword the traffic containing "SPI 1" and "SI 1" to "IP=192.168.xx.xx". 4. Architecture This section describes an SFC-enabled I2NSF architecture and the basic operations of service chaining. It also includes details about each component of the architecture. Hyun, et al. Expires January 4, 2018 [Page 5] Internet-Draft SFC-enabled I2NSF Architecture July 2017 Figure 1 describes the components of SFC-enabled I2NSF architecture. Our architecture is designed to support a composite inspection of traffic packets in transit. According to the inspection result of each SF, the traffic packets could be steered to another SF for futher detailed analysis. It is also possible to reflect a high- level SFC-related policy and a configuration from I2NSF Client on the components of the original I2NSF framwork. Moreover, the proposed architecture provides load balancing, auto supplementary SF generation, and the elimination of unused SFs. In order to achieve these design purposes, we integrate several components to the original I2NSF framwork. In the following sections, we explain the details of each component. Hyun, et al. Expires January 4, 2018 [Page 6] Internet-Draft SFC-enabled I2NSF Architecture July 2017 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | I2NSF User | | +-+-+-+-+-+-+-+-+ | | |I2NSF User | | | | | | | +-+-+-+^+-+-+-+-+ | | | | | | | +-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Consumer-Facing Interface | +-+-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Security Management System | | | | | +-+-+-+-+-+-+-v-+-+-+-+-+ | | |Security Controller | | | | +-+-+-+-+ +-+-+-+-+ | Registration | | | |SFC | |SFC | | Interface +-+-+-+-++-+-+-+-+ | | | |Policy | |Catalog| |<----------->| Developer's | | | | |Manager| |Manager| | | Mgnt System | | | | +-+-+-+-+ +-+-+-+-+ | +-+-+-+-++-+-+-+-+ | | +-+-+-+-+-+-^-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | NSF-Facing Interface | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Security Network | | | +------------------------------------------------+ | | | | | | | | +-+-+-v-+-+-+ +-+-+-+-+v+-+-+ | | +-+-+-v-++-+ | +-+-+-+ | | +-+-+-+ | | | | | | |SFF1 |<-|---------------->| SF1 | | | | |Classifier|<------> | +-+-+-+< | | +-+-+-+ | | | | | | \| | +-+-+-+ | | | +-+-+-+-++-+ | +-+-+-+ \---------------->| SF2 | | | | | |SFF2 |<-|---------------/ +-+-+-+ | | | | +-+-+-+<-|-------------\ +-+-+-+ | | | +-+-+-+-+-+-+ \->| SF3 | | | | | +-+-+-+ | | | +-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: SFC-enabled I2NSF Hyun, et al. Expires January 4, 2018 [Page 7] Internet-Draft SFC-enabled I2NSF Architecture July 2017 4.1. SFC Policy Manager SFC Policy Manager is a core component in our system. It is responsible for the following two things: (1) Interpreting a high- level SFC policy (or configuration) into a low-level SFC policy (or configuration), which is given by I2NSF Client, and delivering the interpreted policy to Classifiers for security function chaining. (2) Generating an SF forwarding table and distributing the fowarding information to SFF(s) by consulting with SFC Catalog Manager. As Figure 1 describes, SFC Policy Manager performs these additional functionalities through Consumer-Facing Interface and NSF-Facing Interface. Given a high-level SFC policy/configuration from I2NSF Client via Consumer-Facing Interface, SFC Policy Manager interprets it into a low-level policy/configuration comprehensible to Classifier(s), and then delivers the resulting low-level policy to them. Moreover, SFC Policy Manager possibly generates new policies for the flexible change of traffic steering to rapidly react to the current status of SFs. For instance, it could generate new rules to forward all subsequent packets to "Firewall Instance 2" instead of "Firewall Instance 1" in the case where "Firewall Instance 1" is under congestion. SFC Policy Manager gets information about SFs from SFC Catalog Manager to generate SF forwarding table. In the table generation process, SFC Policy Manager considers various criteria such as SFC policies, SF load status, SF physical location, and supported transport protocols. An entry of the SF forwarding table consists of SFF Identifier, SFP, SI, and next hop information. The examples of next hop information includes the IP address and supported transport protocols (e.g., VxLAN and GRE). These forwarding table updates are distributed to SFFs with either push or pull methods. 4.2. SFC Catalog Manager In Figure 1, SFC Catalog Manager is a component integrated into Security Controller. It is responsible for the following three things: (1) Maintaining the information of every available SF instance such as IP address, supported transport protocol, service name, and load status. (2) Responding to the queries of available SF instances from SFC Policy Manager so as to help to generate a forwarding table entry relevant to a given SFP. (3) Requesting Developer's Management System to dynamically instantiate supplementary SF instances to avoid service congestion or the elimination of an existing SF instance to avoid resource waste. Whenever a new SF instance is registered, Developer's Management Hyun, et al. Expires January 4, 2018 [Page 8] Internet-Draft SFC-enabled I2NSF Architecture July 2017 System passes the information of the registered SF instance to SFC Catalog Manager, so SFC Catalog Manager maintains a list of the information of every available SF instance. Once receiving a query of a certain SFP from SFC Policy Manager, SFC Catalog Manager searches for all the available SF instances applicable for that SFP and then returns the search result to SFC Policy Manager. In our system, each SF instance periodically reports its load status to SFC Catalog Manager. Based on such reports, SFC Catalog Manager updates the information of the SF instances and manages the pool of SF instances by requesting Developer's Management System for the additional instantiation or elimination of the SF instances. Consequently, SFC Catalog Manager enables efficient resource utilization by avoiding congestion and resource waste. 4.3. Developer's Management System We extend Developer's Management System for additional functionalities as follows. As mentioned above, the SFC Catalog Manager requests the Developer's Management System to create additional SF instances when the existing instances of that service function are congested. On the other hand, when there are an excessive number of instances for a certain service function, the SFC Policy Manager requests the Developer's Management System to eliminate some of the SF instances. As a response to such requests, the Developer's Management System creates and/or removes SF instances. Once it creates a new SF instance or removes an existing SF instance, the changes must be notified to the SFC Catalog Manager. 4.4. Classifier Classifier is a logical component that may exist as a standalone component or a submodule of another component. In our system, the initial classifier is typically located at an entry point like a border router of the network domain, and performs the initial classification of all incoming packets according to the SFC policies, which are given by SFC policy manager. The classification means determining the SFP through which a given packet should pass. Once the SFP is decided, the classifier constructs an NSH that specifies the corresponding SPI and SI, and attaches it to the packet. The packet will then be forwarded through the determined SFP on the basis of the NSH information. 4.5. Service Function Forwarder (SFF) It is responsible for the following two functionalities: (1) Forwarding the packets to the next SFF/SF. (2) Handling re- classification request from SF. Hyun, et al. Expires January 4, 2018 [Page 9] Internet-Draft SFC-enabled I2NSF Architecture July 2017 An SFF basically takes forwarding functionality, so it needs to find the next SF/SFF for the incoming traffic. It will search its forwarding table to find the next hop information that corresponds to the given traffic. In the case where the SFF finds a target entry on its forwarding table, it just forwards the traffic to the next SF/SFF specified in the next hop information. If an SFF does not have an entry for a given packet, it will request the next hop information to SFC Policy Manager with SFF identifier, SPI, and SI information. The SFC Policy Manager will respond to the SFF with next hop information, and then the SFF updates its forwarding table with the response, forwarding the traffic to the next hop. Sometimes an SF may want to forward a packet, which is highly suspicious, to another SF for futher security inspection. This is referred to as advanced security action in I2NSF. In this situation, if the next SF may not be the one on the current SFP of the packet, re-classification is required to change the SFP of the packet. If the current SF is capable of re-classifying the packet by itself, the SF updates the SPI field in the NSH in the packet to serve the advanced secuity action. Otherwise, if the classifier exists as a standalone, the SF appends the inspection result of the packet to the MetaData field of the NSH and delivers it to the source SFF. The attached MetaData includes a re-classification request to change the SFP of the packet to another SFP for stronger inspection. When the SFF receives the traffic requiring re-classification, it forwards the traffic to the Classifier where re-classification will be eventually performed. SFC defines Rendered Service Path (RSP), which represents the sequence of actual visits by a packet to SFFs and SFs [RFC7665]. If the RSP information of a packet is available, the SFF could check this RSP information to detect whether undesired looping happened on the packet. If the SFF detects looping, it could notify the Security Controller of this looping, and the Security Controller could modify relevant security policy rules to resolve this looping. 5. Use Cases This section introduces three use cases for the SFC-enabled I2NSF architecture : (1) Dynamic Path Alternation, (2) Enforcing Different SFPs Depending on Trust Levels, and (3) Effective Load Balancing with Dynamic SF Instantiation. 5.1. Dynamic Path Alternation In SFC-enabled I2NSF architecture, a Classifier determines the initial SFP of incoming traffic according to the SFC policies. The classifier then attaches an NSH specifying the determined SFP of the Hyun, et al. Expires January 4, 2018 [Page 10] Internet-Draft SFC-enabled I2NSF Architecture July 2017 packets, and they are analyzed through the SFs of the initial SFP. However, SFP is not a static property, so it could be changed dynamically through re-classification. A typical example is for a certain SF in the initial SFP to detect that the traffic is highly suspicious (likely to be malicious). In this case, the traffic needs to take stronger inspection through a different SFP which consists of more sophisticated SFs. Figure 2 illustrates an example of such dynamic SFP alternation in a DDoS attack scenario. SFP-1 represents the default Service Function Path that the traffic initially follows, and SFP-1 consists of AVC, Firewall, and IDS/IPS. If the IDS/IPS suspects that the traffic is attempting DDoS attacks, it will change the SFP of the traffic from the default to SFP-2 so that the DDoS attack mitigator can execute a proper countermeasure against the attack. Such SFP alternation is possible in the proposed architecture with re-classification. In Figure 1, to initiate re-classification, the IDS/IPS appends its own inspection result to the MetaData field of NSH and deliver it to the SFF from which it has originally received the traffic. The SFF then forwards the received traffic including the inspection result from the IDS/IPS to Classifier for re- classification. Classifier checks the inspection result and determines the new SFP (SFP-2) associated with the inspection result in the SFC policy, and updates the NSH with the SPI of SFP-2. The traffic is forwarded to the DDoS attack mitigator. SFP-1. AVC:Firewall:IDS/IPS ------------------------------------------------------------------> +-+-+-+-+ +-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+-+-+ | Source|---| AVC |---| Firewall|-----| IDS/IPS |---| Destination | +-+-+-+-+ +-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+-+-+ ----------------------------------------, ,------> \ +-+-+-+-+ / \ | DDoS | / \ +-+-+-+-+ / '----------' SFP-2. AVC:Firewall:DDoS:IDS/IPS Figure 2: Dynamic SFP Alternation Example 5.2. Enforcing Different SFPs Depending on Trust Levels Because the traffic coming from a trusted source is highly likely to be harmless, it does not need to be inspected excessively. On the other hand, the traffic coming from an untrusted source requires an Hyun, et al. Expires January 4, 2018 [Page 11] Internet-Draft SFC-enabled I2NSF Architecture July 2017 in-depth inspection. By applying minimum required security functions to the traffic from a trusted source, it is possible to prevent the unnecessary waste of resources. In addition, we can concentrate more resources on potential malicious traffic. In the SFC-enabled I2NSF architecture, by configuring an SFC Policy to take into account the levels of trust of traffic sources, we can apply different SFPs to the traffic coming from different sources. Figure 3(a) and Figure 3(b) represent SFPs applicable to traffic from trusted and untrusted sources, respectively. In Figure 3(a), we assume a lightweight IDS/IPS which is configured to perform packet header inspection only. In this scenario, when receiving the traffic from a trusted source, the classifier determines the SFP in Figure 3(a) such that the traffic passes through just a simple analysis by the lightweight IDS/IPS. On the other hand, traffic from an untrusted source passes more thorough examination through the SFP in Figure 3(b) which consists of three different types of SFs. +-+-+-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+-+-+ | Source |----------->| IDS/IPS |----------->| Destination | +-+-+-+-+-+ +-+-+-+-+-+ +-+-+-+-+-+-+-+ (a) Traffic flow of trusted source +-+-+-+-+-+ +-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+ | Source | | Anti-Spoofing | | Destination | +-+-+-+-+-+ | function | +-+-+-+^+-+-+-+ | +-+^+-+-+-+-+-+-+ | | | | | | +-+-+-+-+-+-+ | | +-+-+-+-+-+ | ------->| Firewall |-- ---->| DPI |-- +-+-+-+-+-+-+ +-+-+-+-+-+ (b) Traffic flow of untrusted source Figure 3: Different path allocation depending on source of traffic 5.3. Effective Load Balancing with Dynamic SF Instantiation In a large-scale network domain, there typically exist a large number of SF instances that provide various security services. It is possible that a specific SF instance experiences an excessive amount of traffic beyond its capacity. In this case, it is required to allocate some of the traffic to another available instance of the Hyun, et al. Expires January 4, 2018 [Page 12] Internet-Draft SFC-enabled I2NSF Architecture July 2017 same security function. If there are no additional instances of the same security function available, we need to create a new SF instance and then direct the subsequent traffic to the new instance. In this way, we can avoid service congestion and achieve more efficient resource utilization. This process is commonly called load balancing. In the SFC-enabled I2NSF architecture, SFC Catalog Manager performs periodic monitoring of the load status of available SF instances. In addition, it is possible to dynamically generate a new SF instance through Developer's Management System. With these functionalities along with the flexible traffic steering mechanism, we can eventually provide load balancing service. The following describes the detailed process of load balancing when congestion occurs at the firewall instance: 1. SFC Catalog Manager detects that the firewall instance is receiving too much requests. Currently, there are no additional firewall instances available. 2. SFC Catalog Manager requests Developer's Management System to create a new firewall instance. 3. Developer's Management System creates a new firewall instance and then registers the information of the new firewall instance to SFC Catalog Manager. 4. SFC Catalog Manager updates the SFC Information Table to reflect the new firewall instance, and notifies SFC Policy Manager of this update. 5. Based on the received information, SFC Policy Manager updates the forwarding information for traffic steering and sends the new forwarding information to the SFF. 6. According to the new forwarding information, the SFF forwards the subsequent traffic to the new firewall instance. As a result, we can effecively alleviate the burden of the existing firewall instance. 6. Discussion The information model and data model of security policy rules in the I2NSF framework defines an advanced security action as a type of action to be taken on a packet [nsf-capability-im][nsf-facing-inf-dm]. Through the advanced security action, a basic NSF (e.g., firewall) can call a different Hyun, et al. Expires January 4, 2018 [Page 13] Internet-Draft SFC-enabled I2NSF Architecture July 2017 type of NSF for more in-depth security analysis of a packet. If an NSF triggers an advanced security action on a given packet, the packet should be forwarded to the NSF dedicated to the advanced action. That is, the advanced action dynamically determines the next NSF where the packet should go through. So if a forwarding component is configured with the network access information (e.g., IP address, port number) of the next required NSF, it can forward the packet to the NSF. With this advanced security action, it is possible to avoid the overhead for configuring and managing the information of security function chains and paths. In SFC, re-classification is required to support the situation where the security function path of a packet changes dynamically, and the classifier is responsible for re-classification tasks to change the security function path of a packet. But if the classifier exists as a separate component from an NSF, the packet should be first delivered from the NSF to the classifier for re-classification, and this introduces an additional delay. As already mentioned, the advanced security action in the i2nsf framework can omit the requirement of pre-defined security function chain configuration. If there exists no security function chain/path configurations, there is no need of re-classification as well. That is, the forwarder can simply forward the packet to the next required NSF according to the advanced action determiend by the predesessor NSF, without re- classification through the classifier. 7. Security Considerations To enable security function chaining in the I2NSF framework, we adopt the additional components in the SFC architecture. Thus, this document shares the security considerations of the SFC architecture that are specified in [RFC7665] for the purpose of achieving secure communication among components in the proposed architecture. 8. Acknowledgements This work was supported by Institute for Information and communications Technology Promotion(IITP) grant funded by the Korea government(MSIP) (No.R-20160222-002755, Cloud based Security Intelligence Technology Development for the Customized Security Service Provisioning). This document has greatly benefited from inputs by Sanguk Woo, Yunsuk Yeo, Taekyun Roh, and Sarang Wee. 9. References Hyun, et al. Expires January 4, 2018 [Page 14] Internet-Draft SFC-enabled I2NSF Architecture July 2017 9.1. Normative References [RFC7665] Halpern, J. and C. Pignataro, "Service Function Chaining (SFC) Architecture", RFC 7665, October 2015. [sfc-nsh] Quinn, P. and U. Elzur, "Network Service Header", draft-ietf-sfc-nsh-12 (work in progress), February 2017. 9.2. Informative References [RFC7498] Quinn, P. and T. Nadeau, "Problem Statement for Service Function Chaining", RFC 7498, April 2015. [nsf-capability-im] Xia, L., Strassner, J., Basile, C., and D. Lopez, "Information Model of NSFs Capabilities", draft-xibassnez-i2nsf-capability-01 (work in progress), March 2017. [nsf-facing-inf-dm] Kim, J., Jeong, J., Park, J., Hares, S., and L. Xia, "I2NSF Network Security Functions- Facing Interface YANG Data Model", draft-kim- i2nsf-nsf-facing-interface-data-model-02 (work in progress), July 2017. [i2nsf-framework] Lopez, D., Lopez, E., Dunbar, L., Strassner, J., and R. Kumar, "Framework for Interface to Network Security Functions", draft-ietf-i2nsf-framework-05 (work in progress), May 2017. [i2nsf-problem] Hares, S., Lopez, D., Zarny, M., Jacquenet, C., Kumar, R., and J. Jeong, "I2NSF Problem Statement and Use cases", draft-ietf-i2nsf-problem-and-use-cases-16 (work in progress), May 2017. [i2nsf-terminology] Hares, S., Strassner, J., Lopez, D., Xia, L., and H. Birkholz, "Interface to Network Security Functions (I2NSF) Terminology", draft-ietf-i2nsf-terminology-03 (work in progress), March 2017. [ONF-SFC-Architecture] ONF, "L4-L7 Service Function Chaining Solution Architecture", June 2015. Hyun, et al. Expires January 4, 2018 [Page 15] Internet-Draft SFC-enabled I2NSF Architecture July 2017 Appendix A. Changes from draft-hyun-i2nsf-nsf-triggered-steering-02 The following changes have been made from draft-hyun-i2nsf-nsf-triggered-steering-02: o Sections 3, 4, and 5 have been revised to describe an architecture, which integrates additional components of service function chaining (SFC) into the I2NSF framework in order to support packet forwarding between NSFs. o Section 6 has been added to discuss some drawbacks when SFC is used for packet forwarding between NSFs in the I2NSF framework. Authors' Addresses Sangwon Hyun Department of Software Sungkyunkwan University 2066 Seobu-Ro, Jangan-Gu Suwon, Gyeonggi-Do 16419 Republic of Korea Phone: +82 31 290 7222 Fax: +82 31 299 6673 EMail: swhyun77@skku.edu URI: http://imtl.skku.ac.kr/ Jaehoon Paul Jeong Department of Software Sungkyunkwan University 2066 Seobu-Ro, Jangan-Gu Suwon, Gyeonggi-Do 16419 Republic of Korea Phone: +82 31 299 4957 Fax: +82 31 290 7996 EMail: pauljeong@skku.edu URI: http://iotlab.skku.edu/people-jaehoon-jeong.php Hyun, et al. Expires January 4, 2018 [Page 16] Internet-Draft SFC-enabled I2NSF Architecture July 2017 Jung-Soo Park Electronics and Telecommunications Research Institute 218 Gajeong-Ro, Yuseong-Gu Daejeon 305-700 Republic of Korea Phone: +82 42 860 6514 EMail: pjs@etri.re.kr Susan Hares Huawei 7453 Hickory Hill Saline, MI 48176 USA Phone: +1 734 604 0332 EMail: shares@ndzh.com Hyun, et al. Expires January 4, 2018 [Page 17]