Network Working Group P. Quinn, Ed. Internet-Draft Cisco Systems, Inc. Intended status: Standards Track U. Elzur, Ed. Expires: September 25, 2015 Intel March 24, 2015 Network Service Header draft-ietf-sfc-nsh-00.txt Abstract This draft describes a Network Service Header (NSH) inserted onto encapsulated packets or frames to realize service function paths. NSH also provides a mechanism for metadata exchange along the instantiated service path. Quinn & Elzur Expires September 25, 2015 [Page 1] Internet-Draft Network Service Header March 2015 1. 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/. 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." This Internet-Draft will expire on September 25, 2015. Copyright Notice Copyright (c) 2015 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. Quinn & Elzur Expires September 25, 2015 [Page 2] Internet-Draft Network Service Header March 2015 Table of Contents 1. Requirements Language . . . . . . . . . . . . . . . . . . . . 2 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Definition of Terms . . . . . . . . . . . . . . . . . . . 4 2.2. Problem Space . . . . . . . . . . . . . . . . . . . . . . 6 3. Network Service Header . . . . . . . . . . . . . . . . . . . . 8 3.1. Network Service Header Format . . . . . . . . . . . . . . 8 3.2. NSH Base Header . . . . . . . . . . . . . . . . . . . . . 8 3.3. Service Path Header . . . . . . . . . . . . . . . . . . . 10 3.4. NSH MD-type 1 . . . . . . . . . . . . . . . . . . . . . . 10 3.4.1. Mandatory Context Header Allocation Guidelines . . . . 11 3.5. NSH MD-type 2 . . . . . . . . . . . . . . . . . . . . . . 12 3.5.1. Optional Variable Length Metadata . . . . . . . . . . 13 4. NSH Actions . . . . . . . . . . . . . . . . . . . . . . . . . 15 5. NSH Encapsulation . . . . . . . . . . . . . . . . . . . . . . 17 6. NSH Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 18 7. NSH Proxy Nodes . . . . . . . . . . . . . . . . . . . . . . . 19 8. Fragmentation Considerations . . . . . . . . . . . . . . . . . 20 9. Service Path Forwarding with NSH . . . . . . . . . . . . . . . 21 9.1. SFFs and Overlay Selection . . . . . . . . . . . . . . . . 21 9.2. Mapping NSH to Network Overlay . . . . . . . . . . . . . . 23 9.3. Service Plane Visibility . . . . . . . . . . . . . . . . . 24 9.4. Service Graphs . . . . . . . . . . . . . . . . . . . . . . 24 10. Policy Enforcement with NSH . . . . . . . . . . . . . . . . . 26 10.1. NSH Metadata and Policy Enforcement . . . . . . . . . . . 26 10.2. Updating/Augmenting Metadata . . . . . . . . . . . . . . . 27 10.3. Service Path ID and Metadata . . . . . . . . . . . . . . . 29 11. NSH Encapsulation Examples . . . . . . . . . . . . . . . . . . 30 11.1. GRE + NSH . . . . . . . . . . . . . . . . . . . . . . . . 30 11.2. VXLAN-gpe + NSH . . . . . . . . . . . . . . . . . . . . . 30 11.3. Ethernet + NSH . . . . . . . . . . . . . . . . . . . . . . 31 12. Security Considerations . . . . . . . . . . . . . . . . . . . 32 13. Open Items for WG Discussion . . . . . . . . . . . . . . . . . 33 14. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 34 15. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 37 16. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 38 16.1. NSH EtherType . . . . . . . . . . . . . . . . . . . . . . 38 16.2. Network Service Header (NSH) Parameters . . . . . . . . . 38 16.2.1. NSH Base Header Reserved Bits . . . . . . . . . . . . 38 16.2.2. MD Type Registry . . . . . . . . . . . . . . . . . . . 38 16.2.3. TLV Class Registry . . . . . . . . . . . . . . . . . . 39 16.2.4. NSH Base Header Next Protocol . . . . . . . . . . . . 39 17. References . . . . . . . . . . . . . . . . . . . . . . . . . . 40 17.1. Normative References . . . . . . . . . . . . . . . . . . . 40 17.2. Informative References . . . . . . . . . . . . . . . . . . 40 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 42 Quinn & Elzur Expires September 25, 2015 [Page 3] Internet-Draft Network Service Header March 2015 2. Introduction Service functions are widely deployed and essential in many networks. These service functions provide a range of features such as security, WAN acceleration, and server load balancing. Service functions may be instantiated at different points in the network infrastructure such as the wide area network, data center, campus, and so forth. The current service function deployment models are relatively static, and bound to topology for insertion and policy selection. Furthermore, they do not adapt well to elastic service environments enabled by virtualization. New data center network and cloud architectures require more flexible service function deployment models. Additionally, the transition to virtual platforms requires an agile service insertion model that supports elastic service delivery; the movement of service functions and application workloads in the network and the ability to easily bind service policy to granular information such as per-subscriber state are necessary. The approach taken by NSH is composed of the following elements: 1. Service path identification 2. Transport independent per-packet/frame service metadata. 3. Optional variable TLV metadata. NSH is designed to be easy to implement across a range of devices, both physical and virtual, including hardware platforms. An NSH aware control plane is outside the scope of this document. The SFC Architecture document [SFC-arch] provides an overview of a service chaining architecture that clearly defines the roles of the various elements and the scope of a service function chaining encapsulation. 2.1. Definition of Terms Classification: Locally instantiated policy and customer/network/ service profile matching of traffic flows for identification of appropriate outbound forwarding actions. Quinn & Elzur Expires September 25, 2015 [Page 4] Internet-Draft Network Service Header March 2015 SFC Network Forwarder (NF): SFC network forwarders provide network connectivity for service functions forwarders and service functions. SFC network forwarders participate in the network overlay used for service function chaining as well as in the SFC encapsulation. Service Function Forwarder (SFF): A service function forwarder is responsible for delivering traffic received from the NF to one or more connected service functions, and from service functions to the NF. Service Function (SF): A function that is responsible for specific treatment of received packets. A service function can act at the network layer or other OSI layers. A service function can be a virtual instance or be embedded in a physical network element. One of multiple service functions can be embedded in the same network element. Multiple instances of the service function can be enabled in the same administrative domain. Service Node (SN): Physical or virtual element that hosts one or more service functions and has one or more network locators associated with it for reachability and service delivery. Service Function Chain (SFC): A service function chain defines an ordered set of service functions that must be applied to packets and/or frames selected as a result of classification. The implied order may not be a linear progression as the architecture allows for nodes that copy to more than one branch. The term service chain is often used as shorthand for service function chain. Service Function Path (SFP): The instantiation of a SFC in the network. Packets follow a service function path from a classifier through the requisite service functions Network Node/Element: Device that forwards packets or frames based on outer header information. In most cases is not aware of the presence of NSH. Network Overlay: Logical network built on top of existing network (the underlay). Packets are encapsulated or tunneled to create the overlay network topology. Network Service Header: Data plane header added to frames/packets. The header contains information required for service chaining, as well as metadata added and consumed by network nodes and service elements. Quinn & Elzur Expires September 25, 2015 [Page 5] Internet-Draft Network Service Header March 2015 Service Classifier: Function that performs classification and imposes an NSH. Creates a service path. Non-initial (i.e. subsequent) classification can occur as needed and can alter, or create a new service path. Service Hop: NSH aware node, akin to an IP hop but in the service overlay. Service Path Segment: A segment of a service path overlay. NSH Proxy: Acts as a gateway: removes and inserts NSH on behalf of a service function that is not NSH aware. 2.2. Problem Space Network Service Header (NSH) addresses several limitations associated with service function deployments today. 1. Topological Dependencies: Network service deployments are often coupled to network topology. Such dependency imposes constraints on the service delivery, potentially inhibiting the network operator from optimally utilizing service resources, and reduces the flexibility. This limits scale, capacity, and redundancy across network resources. 2. Service Chain Construction: Service function chains today are most typically built through manual configuration processes. These are slow and error prone. With the advent of newer service deployment models the control/management planes provide not only connectivity state, but will also be increasingly utilized for the creation of network services. Such a control/management planes could be centralized, or be distributed. 3. Application of Service Policy: Service functions rely on topology information such as VLANs or packet (re) classification to determine service policy selection, i.e. the service function specific action taken. Topology information is increasingly less viable due to scaling, tenancy and complexity reasons. The topological information is often stale, providing the operator with inaccurate placement that can result in suboptimal resource utilization. Furthermore topology-centric information often does not convey adequate information to the service functions, forcing functions to individually perform more granular classification. 4. Per-Service (re)Classification: Classification occurs at each service function independent from previously applied service functions. More importantly, the classification functionality often differs per service function and service functions may not Quinn & Elzur Expires September 25, 2015 [Page 6] Internet-Draft Network Service Header March 2015 leverage the results from other service functions. 5. Common Header Format: Various proprietary methods are used to share metadata and create service paths. An open header provides a common format for all network and service devices. 6. Limited End-to-End Service Visibility: Troubleshooting service related issues is a complex process that involve both network- specific and service-specific expertise. This is especially the case when service function chains span multiple DCs, or across administrative boundaries. Furthermore, the physical and virtual environments (network and service) can be highly divergent in terms of topology and that topological variance adds to these challenges. 7. Transport Dependence: Service functions can and will be deployed in networks with a range of transports requiring service functions to support and participate in many transports (and associated control planes) or for a transport gateway function to be present. Please see the Service Function Chaining Problem Statement [SFC-PS] for a more detailed analysis of service function deployment problem areas. Quinn & Elzur Expires September 25, 2015 [Page 7] Internet-Draft Network Service Header March 2015 3. Network Service Header A Network Service Header (NSH) contains metadata and service path information that are added to a packet or frame and used to create a service plane. The packets and the NSH are then encapsulated in an outer header for transport. The service header is added by a service classification function - a device or application - that determines which packets require servicing, and correspondingly which service path to follow to apply the appropriate service. 3.1. Network Service Header Format An NSH is composed of a 4-byte base header, a 4-byte service path header and context headers, as shown in Figure 1 below. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Base Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Path Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Context Headers ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: Network Service Header Base header: provides information about the service header and the payload protocol. Service Path Header: provide path identification and location within a path. Context headers: carry opaque metadata and variable length encoded information. 3.2. NSH Base Header 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Ver|O|C|R|R|R|R|R|R| Length | MD Type | Next Protocol | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Quinn & Elzur Expires September 25, 2015 [Page 8] Internet-Draft Network Service Header March 2015 Figure 2: NSH Base Header Base Header Field Descriptions Version: The version field is used to ensure backward compatibility going forward with future NSH updates. O bit: Indicates that this packet is an operations and management (OAM) packet. SFF and SFs nodes MUST examine the payload and take appropriate action (e.g. return status information). OAM message specifics and handling details are outside the scope of this document. C bit: Indicates that a critical metadata TLV is present (see Section 3.4.2). This bit acts as an indication for hardware implementers to decide how to handle the presence of a critical TLV without necessarily needing to parse all TLVs present. The C bit MUST be set to 1 if one or more critical TLVs are present. All other flag fields are reserved. Length: total length, in 4-byte words, of the NSH header, including optional variable TLVs. MD Type: indicates the format of NSH beyond the base header and the type of metadata being carried. This typing is used to describe the use for the metadata. A new registry will be requested from IANA for the MD Type. NSH defines two MD types: 0x1 which indicates that the format of the header includes fixed length context headers. 0x2 which does not mandate any headers beyond the base header and service path header, and may contain optional variable length context information. The format of the base header is invariant, and not described by MD Type. NSH implementations MUST support MD-Type 0x1, and SHOULD support MD- Type 0x2. Next Protocol: indicates the protocol type of the original packet. A new IANA registry will be created for protocol type. Quinn & Elzur Expires September 25, 2015 [Page 9] Internet-Draft Network Service Header March 2015 This draft defines the following Next Protocol values: 0x1 : IPv4 0x2 : IPv6 0x3 : Ethernet 3.3. Service Path Header 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Path ID | Service Index | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Service path ID (SPI): 24 bits Service index (SI): 8 bits Figure 3: NSH Service Path Header Service Path Identifier (SPI): identifies a service path. Participating nodes MUST use this identifier for path selection. An administrator can use the service path value for reporting and troubleshooting packets along a specific path. Service Index (SI): provides location within the service path. Service index MUST be decremented by service functions or proxy nodes after performing required services. MAY be used in conjunction with service path for path selection. Service Index is also valuable when troubleshooting/reporting service paths. In addition to location within a path, SI can be used for loop detection. 3.4. NSH MD-type 1 When the base header specifies MD Type 1, NSH defines four 4-byte mandatory context headers, as per Figure 4. These headers must be present and the format is opaque as depicted in Figure 5. Quinn & Elzur Expires September 25, 2015 [Page 10] Internet-Draft Network Service Header March 2015 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Ver|O|C|R|R|R|R|R|R| Length | MD-type=0x1 | Next Protocol | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Path ID | Service Index | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mandatory Context Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mandatory Context Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mandatory Context Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Mandatory Context Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: NSH MD-type=0x1 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Context data | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: Context Header 3.4.1. Mandatory Context Header Allocation Guidelines 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Network Platform Context | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Network Shared Context | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Platform Context | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Shared Context | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Quinn & Elzur Expires September 25, 2015 [Page 11] Internet-Draft Network Service Header March 2015 Figure 6: Context Data Significance Figure 6, above, and the following examples of context header allocation are guidelines that illustrate how various forms of information can be carried and exchanged via NSH. Network platform context: provides platform-specific metadata shared between network nodes. Examples include (but are not limited to) ingress port information, forwarding context and encapsulation type. Network shared context: metadata relevant to any network node such as the result of edge classification. For example, application information, identity information or tenancy information can be shared using this context header. Service platform context: provides service platform specific metadata shared between service functions. This context header is analogous to the network platform context, enabling service platforms to exchange platform-centric information such as an identifier used for load balancing decisions. Service shared context: metadata relevant to, and shared, between service functions. As with the shared network context, classification information such as application type can be conveyed using this context. The data center[dcalloc] and mobility[moballoc] context header allocation drafts provide guidelines for the semantics of NSH fixed context headers in each respective environment. 3.5. NSH MD-type 2 When the base header specifies MD Type 2, NSH defines variable length only context headers. There may be zero or more of these headers as per the length field. 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |Ver|O|C|R|R|R|R|R|R| Length | MD-type=0x2 | Next Protocol | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Service Path ID | Service Index | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | ~ Optional Variable Length Context Headers ~ | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Quinn & Elzur Expires September 25, 2015 [Page 12] Internet-Draft Network Service Header March 2015 Figure 7: NSH MD-type=0x2 3.5.1. Optional Variable Length Metadata NSH MD Type 2 MAY contain optional variable length context headers. The format of these headers is as described below. 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | TLV Class | Type |R|R|R| Len | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Variable Metadata | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: Variable Context Headers TLV Class: describes the scope of the "Type" field. In some cases, the TLV Class will identify a specific vendor, in others, the TLV Class will identify specific standards body allocated types. Type: the specific type of information being carried, within the scope of a given TLV Class. Value allocation is the responsibility of the TLV Class owner. The most significant bit of the Type field indicates whether the TLV is mandatory for the receiver to understand/process. This effectively allocates Type values 0 to 127 for non-critical options and Type values 128 to 255 for critical options. Figure 7 below illustrates the placement of the Critical bit within the Type field. +-+-+-+-+-+-+-+-+ |C| Type | +-+-+-+-+-+-+-+-+ Figure 9: Critical Bit Placement Within the TLV Type Field Encoding the criticality of the TLV within the Type field is consistent with IPv6 option types. If a receiver receives an encapsulated packet containing a TLV with the Critical bit set in the Type field and it does not understand how to process the Type, it MUST drop the packet. Transit devices MUST NOT drop packets based on the setting of this bit. Reserved bits: three reserved bit are present for future use. The Quinn & Elzur Expires September 25, 2015 [Page 13] Internet-Draft Network Service Header March 2015 reserved bits MUST be zero. Length: Length of the variable metadata, in 4-byte words. Quinn & Elzur Expires September 25, 2015 [Page 14] Internet-Draft Network Service Header March 2015 4. NSH Actions Service header aware nodes - service classifiers, SFF, SF and NSH proxies, have several possible header related actions: 1. Insert or remove service header: These actions can occur at the start and end respectively of a service path. Packets are classified, and if determined to require servicing, a service header imposed. The last node in a service path, an SFF, removes the NSH. A service classifier MUST insert an NSH. At the end of a service function chain, the last node operating on the service header MUST remove it. A service function can re-classify data as required and that re- classification might result in a new service path. In this case, the SF acts as a logical classifier as well. When the logical classifier performs re-classification that results in a change of service path, it MUST remove the existing NSH and MUST impose a new NSH with the base header reflecting the new path. 2. Select service path: The base header provides service chain information and is used by SFFs to determine correct service path selection. SFFs MUST use the base header for selecting the next service in the service path. 3. Update a service header: NSH aware service functions MUST decrement the service index. A service index = 0 indicates that a packet MUST be dropped by the SFF performing NSH-based forwarding. Service functions MAY update context headers if new/updated context is available. If an NSH proxy (see Section 7) is in use (acting on behalf of a non-NSH-aware service function for NSH actions), then the proxy MUST update service index and MAY update contexts. When an NSH proxy receives an NSH-encapsulated packet, it removes the NSH before forwarding it to an NSH unaware SF. When it receives a packet back from an NSH unaware SF, it re-encapsulates it with the NSH, decrementing the service index. 4. Service policy selection: Service function instances derive policy selection from the service header. Context shared in the service header can provide a range of service-relevant information such as traffic classification. Service functions SHOULD use NSH to select local service policy. Quinn & Elzur Expires September 25, 2015 [Page 15] Internet-Draft Network Service Header March 2015 Figure 10 maps each of the four actions above to the components in the SFC architecture that can perform it. +----------------+--------------------+-------+---------------+-------+ | | Insert or remove |Select | Update a |Service| | | service header |service|service header |Policy | | +------+------+------+ path +---------------+Select-| | |Insert|Remove|Remove| | Dec. |Update |ion | | | | | and | |Service|Context| | | Component | | |Insert| | Index |Header | | +----------------+------+------+------+-------+-------+-------+-------+ |Service Classif-| + | | | | | + | | |ication Function| | | | | | | | + -------------- + ---- + ---- + ---- + ----- + ----- + ----- + ----- + |Service Function| | + | | + | | + | | |Forwarder(SFF) | | | | | | | | + -------------- + ---- + ---- + ---- + ----- + ----- + ----- + ----- + |Service | | | | | + | + | + | |Function (SF) | | | | | | | | + -------------- + ---- + ---- + ---- + ----- + ----- + ----- + ----- + |NSH Proxy | + | + | | | + | + | | +----------------+------+------+------+-------+-------+-------+-------+ Figure 10: NSH Action and Role Mapping Quinn & Elzur Expires September 25, 2015 [Page 16] Internet-Draft Network Service Header March 2015 5. NSH Encapsulation Once NSH is added to a packet, an outer encapsulation is used to forward the original packet and the associated metadata to the start of a service chain. The encapsulation serves two purposes: 1. Creates a topologically independent services plane. Packets are forwarded to the required services without changing the underlying network topology. 2. Transit network nodes simply forward the encapsulated packets as is. The service header is independent of the encapsulation used and is encapsulated in existing transports. The presence of NSH is indicated via protocol type or other indicator in the outer encapsulation. See Section 11 for NSH encapsulation examples. Quinn & Elzur Expires September 25, 2015 [Page 17] Internet-Draft Network Service Header March 2015 6. NSH Usage The NSH creates a dedicated service plane, that addresses many of the limitations highlighted in Section 2.2. More specifically, NSH enables: 1. Topological Independence: Service forwarding occurs within the service plane, via a network overlay, the underlying network topology does not require modification. Service functions have one or more network locators (e.g. IP address) to receive/send data within the service plane, the NSH contains an identifier that is used to uniquely identify a service path and the services within that path. 2. Service Chaining: NSH contains path identification information needed to realize a service path. Furthermore, NSH provides the ability to monitor and troubleshoot a service chain, end-to-end via service-specific OAM messages. The NSH fields can be used by administrators (via, for example a traffic analyzer) to verify (account, ensure correct chaining, provide reports, etc.) the path specifics of packets being forwarded along a service path. 3. Metadata Sharing: NSH provides a mechanism to carry shared metadata between network devices and service function, and between service functions. The semantics of the shared metadata is communicated via a control plane to participating nodes. Examples of metadata include classification information used for policy enforcement and network context for forwarding post service delivery. 4. Transport Agnostic: NSH is transport independent and is carried in an overlay, over existing underlays. If an existing overlay topology provides the required service path connectivity, that existing overlay may be used. Quinn & Elzur Expires September 25, 2015 [Page 18] Internet-Draft Network Service Header March 2015 7. NSH Proxy Nodes In order to support NSH-unaware service functions, an NSH proxy is used. The proxy node removes the NSH header and delivers the original packet/frame via a local attachment circuit to the service function. Examples of a local attachment circuit include, but are not limited to: VLANs, IP in IP, GRE, VXLAN. When complete, the service function returns the packet to the NSH proxy via the same or different attachment circuit. NSH is re-imposed on packets returned to the proxy from the non-NSH- aware service. Typically, an SFF will act as an NSH-proxy when required. An NSH proxy MUST perform NSH actions as described in Section 4. Quinn & Elzur Expires September 25, 2015 [Page 19] Internet-Draft Network Service Header March 2015 8. Fragmentation Considerations Work in progress Quinn & Elzur Expires September 25, 2015 [Page 20] Internet-Draft Network Service Header March 2015 9. Service Path Forwarding with NSH 9.1. SFFs and Overlay Selection As described above, NSH contains a service path identifier (SPI) and a service index (SI). The SPI is, as per its name, an identifier. The SPI alone cannot be used to forward packets along a service path. Rather the SPI provide a level of indirection between the service path/topology and the network transport. Furthermore, there is no requirement, or expectation of an SPI being bound to a pre-determined or static network path. The service index provides an indication of location within a service path. The combination of SPI and SI provides the identification and location of a logical SF (locator and order). The logical SF may be a single SF, or a set of SFs that are equivalent. In the latter case, the SFF provides load distribution amongst the collection of SFs as needed. SI may also serve as a mechanism for loop detection with in a service path since each SF in the path decrements the index; an index of 0 indicates that a loop occurred and packet must be discarded. This indirection -- path ID to overlay -- creates a true service plane. That is the SFF/SF topology is constructed without impacting the network topology but more importantly service plane only participants (i.e. most SFs) need not be part of the network overlay topology and its associated infrastructure (e.g. control plane, routing tables, etc.). As mentioned above, an existing overlay topology may be used provided it offers the requisite connectivity. The mapping of SPI to transport occurs on an SFF. The SFF consults the SPI/ID values to determine the appropriate overlay transport protocol (several may be used within a given network) and next hop for the requisite SF. Figure 10 below depicts an SPI/SI to network overlay mapping. +-------------------------------------------------------+ | SPI | SI | NH | Transport | +-------------------------------------------------------+ | 10 | 3 | 1.1.1.1 | VXLAN-gpe | | 10 | 2 | 2.2.2.2 | nvGRE | | 245 | 12 | 192.168.45.3 | VXLAN-gpe | | 10 | 9 | 10.1.2.3 | GRE | | 40 | 9 | 10.1.2.3 | GRE | | 50 | 7 | 01:23:45:67:89:ab | Ethernet | | 15 | 1 | Null (end of path) | None | +-------------------------------------------------------+ Quinn & Elzur Expires September 25, 2015 [Page 21] Internet-Draft Network Service Header March 2015 Figure 11: SFF NSH Mapping Example Additionally, further indirection is possible: the resolution of the required SF function locator may be a localized resolution on an SFF,rather than a service function chain control plane responsibility, as per figures 11 and 12 below. +-------------------+ | SPI | SI | NH | +-------------------+ | 10 | 3 | SF2 | | 245 | 12 | SF34 | | 40 | 9 | SF9 | +-------------------+ Figure 12: NSH to SF Mapping Example +-----------------------------------+ | SF | NH | Transport | +-----------------------------------| | SF2 | 10.1.1.1 | VXLAN-gpe | | SF34| 192.168.1.1 | UDP | | SF9 | 1.1.1.1 | GRE | +-----------------------------------+ Figure 13: SF Locator Mapping Example Since the SPI is a representation of the service path, the lookup may return more than one possible next-hop within a service path for a given SF, essentially a series of weighted (equally or otherwise) overlay links to be used (for load distribution, redundancy or policy), see Figure 13. The metric depicted in Figure 13 is an example to help illustrated weighing SFs. In a real network, the metric will range from a simple preference (similar to routing next- hop), to a true dynamic composite metric based on some service function-centric state (including load, sessions sate, capacity, etc.) Quinn & Elzur Expires September 25, 2015 [Page 22] Internet-Draft Network Service Header March 2015 +----------------------------------+ | SPI | SI | NH | Metric | +----------------------------------+ | 10 | 3 | 10.1.1.1 | 1 | | | | 10.1.1.2 | 1 | | | | | | | 20 | 12 | 192.168.1.1 | 1 | | | | 10.2.2.2 | 1 | | | | | | | 30 | 7 | 10.2.2.3 | 10 | | | | 10.3.3.3 | 5 | +----------------------------------+ (encap type omitted for formatting) Figure 14: NSH Weighted Service Path 9.2. Mapping NSH to Network Overlay As described above, the mapping of SPI to network topology may result in a single overlay path, or it might result in a more complex topology. Furthermore, the SPIx to overlay mapping occurs at each SFF independently. Any combination of topology selection is possible. Examples of mapping for a topology: 1. Next SF is located at SFFb with locator 10.1.1.1 SFFa mapping: SPI=10 --> VXLAN-gpe, dst-ip: 10.1.1.1 2. Next SF is located at SFFc with multiple locator for load distribution purposes: SFFb mapping: SPI=10 --> VXLAN-gpe, dst_ip:10.2.2.1, 10.2.2.2, 10.2.2.3, equal cost 3. Next SF is located at SFFd with two path to SFFc, one for redundancy: SFFc mapping: SPI=10 --> VXLAN-gpe, dst_ip:10.1.1.1 cost=10, 10.1.1.2, cost=20 In the above example, each SFF makes an independent decision about the network overlay path and policy for that path. In other words, there is no a priori mandate about how to forward packets in the network (only the order of services that must be traversed). The network operator retains the ability to engineer the overlay paths as required. For example, the overlay path between service functions forwarders may utilize traffic engineering, QoS marking, or Quinn & Elzur Expires September 25, 2015 [Page 23] Internet-Draft Network Service Header March 2015 ECMP, without requiring complex configuration and network protocol support to be extended to the service path explicitly. In other words, the network operates as expected, and evolves as required, as does the service function plane. 9.3. Service Plane Visibility The SPI and SI serve an important function for visibility into the service topology. An operator can determine what service path a packet is "on", and its location within that path simply by viewing the NSH information (packet capture, IPFIX, etc.). The information can be used for service scheduling and placement decisions, troubleshooting and compliance verification. 9.4. Service Graphs In some cases, a service path is exactly that -- a linear list of service functions that must be traversed. However, increasingly, the "path" is actually a true directed graph. Furthermore, within a given service topology several directed graphs may exist with packets moving between graphs based on non-initial classification (usually performed by a service function). Note: strictly speaking a path is a form of graph; the intent is to distinguish between a directed graph and a path. ,---. ,---. ,---. / \ / \ / \ ( SF2 ) ( SF7 ) ( SF3 ) ,------\ +. \ / \ / ; |---' `-. `---'\ `-+-' | : : \ ; | \ | : ; ,-+-. `. ,+--. : | / \ '---+ \ \ ; ( SF1 ) ( SF6 ) \ / \ / \ +--. : / `---' `---' `-. ,-+-. / `+ +' ( SF4 ) \ / `---' Figure 15: Service Graph Example The SPI/SI combination provides a simple representation of a directed graph, the SPI represents a graph ID; and the SI a node ID. The Quinn & Elzur Expires September 25, 2015 [Page 24] Internet-Draft Network Service Header March 2015 service topology formed by SPI/SI support cycles, weighting, and alternate topology selection, all within the service plane. The realization of the network topology occurs as described above: SPI/ID mapping to an appropriate transport and associated next network hops. NSH-aware services receive the entire header, including the SPI/SI. An SF can now, based on local policy, alter the SPI, which in turn effects both the service graph, and in turn the selection of overlay at the SFF. The figure below depicts the policy associated with the graph in Figure 14 above. Note: this illustrates multiple graphs and their representation; it does not depict the use of metadata within a single service function graph. +---------------------------------------------------------------------+ | SPI: 21 Bob: SF7 | | SPI: 20 Bad : SF2 --> SF6 --> SF4 | |SPI: 10 SF1 --> SF2 --> SF6 SPI: 22 Alice: SF3 | | SPI: 30 Good: SF4 | | SPI:31 Bob: SF7 | | SPI:32 Alice: SF3 | +---------------------------------------------------------------------+ Figure 16: Service Graphs Using SPI This example above does not show the mapping of the service topology to the network overlay topology. As discussed in the sections above, the overlay selection occurs as per network policy. Quinn & Elzur Expires September 25, 2015 [Page 25] Internet-Draft Network Service Header March 2015 10. Policy Enforcement with NSH 10.1. NSH Metadata and Policy Enforcement As described in Section 3, NSH provides the ability to carry metadata along a service path. This metadata may be derived from several sources, common examples include: Network nodes: Information provided by network nodes can indicate network-centric information (such as VRF or tenant) that may be used by service functions, or conveyed to another network node post-service pathing. External (to the network) systems: External systems, such as orchestration systems, often contain information that is valuable for service function policy decisions. In most cases, this information cannot be deduced by network nodes. For example, a cloud orchestration platform placing workloads "knows" what application is being instantiated and can communicate this information to all NSH nodes via metadata. Service functions: Service functions often perform very detailed and valuable classification. In some cases they may terminate, and be able to inspect encrypted traffic. SFs may update, alter or impose metadata information. Regardless of the source, metadata reflects the "result" of classification. The granularity of classification may vary. For example, a network switch might only be able to classify based on a 5-tuple, whereas, a service function may be able to inspect application information. Regardless of granularity, the classification information can be represented in NSH. Once the data is added to NSH, it is carried along the service path, NSH-aware SFs receive the metadata, and can use that metadata for local decisions and policy enforcement. The following two examples highlight the relationship between metadata and policy: Quinn & Elzur Expires September 25, 2015 [Page 26] Internet-Draft Network Service Header March 2015 +-------------------------------------------------+ | ,---. ,---. ,---. | | / \ / \ / \ | | ( SCL )-------->( SF1 )--------->( SF2 ) | | \ / \ / \ / | | `---' `---' `---' | |5-tuple: Permit Inspect | |Tenant A Tenant A AppY | |AppY | +-------------------------------------------------+ Figure 17: Metadata and Policy +-------------------------------------------------+ | ,---. ,---. ,---. | | / \ / \ / \ | | ( SCL )-------->( SF1 )--------->( SF2 ) | | \ / \ / \ / | | `-+-' `---' `---' | | | Permit Deny AppZ | | +---+---+ employees | | | | | | +-------+ | | external | | system: | | Employee | | App Z | +-------------------------------------------------+ Figure 18: External Metadata and Policy In both of the examples above, the service functions perform policy decisions based on the result of the initial classification: the SFs did not need to perform re-classification, rather they relied on a antecedent classification for local policy enforcement. 10.2. Updating/Augmenting Metadata Post-initial metadata imposition (typically performed during initial service path determination), metadata may be augmented or updated: 1. Metadata Augmentation: Information may be added to NSH's existing metadata, as depicted in Figure 18. For example, if the initial classification returns the tenant information, a secondary classification (perhaps a DPI or SLB) may augment the tenant classification with application information. The tenant Quinn & Elzur Expires September 25, 2015 [Page 27] Internet-Draft Network Service Header March 2015 classification is still valid and present, but additional information has been added to it. 2. Metadata Update: Subsequent classifiers may update the initial classification if it is determined to be incorrect or not descriptive enough. For example, the initial classifier adds metadata that describes the trafic as "internet" but a security service function determines that the traffic is really "attack". Figure 19 illustrates an example of updating metadata. +-------------------------------------------------+ | ,---. ,---. ,---. | | / \ / \ / \ | | ( SCL )-------->( SF1 )--------->( SF2 ) | | \ / \ / \ / | | `-+-' `---' `---' | | | Inspect Deny | | +---+---+ employees employee+ | | | | Class=AppZ appZ | | +-------+ | | external | | system: | | Employee | | | +-------------------------------------------------+ Figure 19: Metadata Augmentation +-------------------------------------------------+ | ,---. ,---. ,---. | | / \ / \ / \ | | ( SCL )-------->( SF1 )--------->( SF2 ) | | \ / \ / \ / | | `---' `---' `---' | |5-tuple: Inspect Deny | |Tenant A Tenant A attack | | --> attack | +-------------------------------------------------+ Figure 20: Metadata Update Quinn & Elzur Expires September 25, 2015 [Page 28] Internet-Draft Network Service Header March 2015 10.3. Service Path ID and Metadata Metadata information may influence the service path selection since the service path identifier can represent the result of classification. A given SPI can represent all or some of the metadata, and be updated based on metadata classification results. This relationship provides the ability to create a dynamic services plane based on complex classification without requiring each node to be capable of such classification, or requiring a coupling to the network topology. This yields service graph functionality as described in Section 9.4. Figure 20 illustrates an example of this behavior. +----------------------------------------------------+ | ,---. ,---. ,---. | | / \ / \ / \ | | ( SCL )-------->( SF1 )--------->( SF2 ) | | \ / \ / \ / | | `---' `---' \ `---' | |5-tuple: Inspect \ Original | |Tenant A Tenant A \ next SF | | --> DoS \ | | \ | | ,---. | | / \ | | ( SF10 ) | | \ / | | `---' | | DoS | | "Scrubber" | +----------------------------------------------------+ Figure 21: Path ID and Metadata Specific algorithms for mapping metadata to an SPI are outside the scope of this draft. Quinn & Elzur Expires September 25, 2015 [Page 29] Internet-Draft Network Service Header March 2015 11. NSH Encapsulation Examples 11.1. GRE + NSH IPv4 Packet: +----------+--------------------+--------------------+ |L2 header | L3 header, proto=47|GRE header,PT=0x894F| +----------+--------------------+--------------------+ --------------+----------------+ NSH, NP=0x1 |original packet | --------------+----------------+ L2 Frame: +----------+--------------------+--------------------+ |L2 header | L3 header, proto=47|GRE header,PT=0x894F| +----------+--------------------+--------------------+ ---------------+---------------+ NSH, NP=0x3 |original frame | ---------------+---------------+ Figure 22: GRE + NSH 11.2. VXLAN-gpe + NSH IPv4 Packet: +----------+------------------------+---------------------+ |L2 header | IP + UDP dst port=4790 |VXLAN-gpe NP=0x4(NSH)| +----------+------------------------+---------------------+ --------------+----------------+ NSH, NP=0x1 |original packet | --------------+----------------+ L2 Frame: +----------+------------------------+---------------------+ |L2 header | IP + UDP dst port=4790 |VXLAN-gpe NP=0x4(NSH)| +----------+------------------------+---------------------+ ---------------+---------------+ NSH,NP=0x3 |original frame | ---------------+---------------+ Figure 23: VXLAN-gpe + NSH Quinn & Elzur Expires September 25, 2015 [Page 30] Internet-Draft Network Service Header March 2015 11.3. Ethernet + NSH IPv4 Packet: +-------------------------------+---------------+--------------------+ |Outer Ethernet, ET=0x894F | NSH, NP = 0x1 | original IP Packet | +-------------------------------+---------------+--------------------+ L2 Frame: +-------------------------------+---------------+----------------+ |Outer Ethernet, ET=0x894F | NSH, NP = 0x3 | original frame | +-------------------------------+---------------+----------------+ Figure 24: Ethernet + NSH Quinn & Elzur Expires September 25, 2015 [Page 31] Internet-Draft Network Service Header March 2015 12. Security Considerations As with many other protocols, NSH data can be spoofed or otherwise modified. In many deployments, NSH will be used in a controlled environment, with trusted devices (e.g. a data center) thus mitigating the risk of unauthorized header manipulation. NSH is always encapsulated in a transport protocol and therefore, when required, existing security protocols that provide authenticity (e.g. RFC 2119 [RFC6071]) can be used. Similarly if confidentiality is required, existing encryption protocols can be used in conjunction with encapsulated NSH. Quinn & Elzur Expires September 25, 2015 [Page 32] Internet-Draft Network Service Header March 2015 13. Open Items for WG Discussion 1. MD type 1 metadata semantics specifics 2. Bypass bit in NSH. 3. Rendered Service Path ID (RSPID). Quinn & Elzur Expires September 25, 2015 [Page 33] Internet-Draft Network Service Header March 2015 14. Contributors This WG document originated as draft-quinn-sfc-nsh and had the following co-authors and contributors. The editors of this document would like to thank and recognize them and their contributions. These co-authors and contributors provided invaluable concepts and content for this document's creation. Surendra Kumar Cisco Systems smkumar@cisco.com Michael Smith Cisco Systems michsmit@cisco.com Jim Guichard Cisco Systems jguichar@cisco.com Rex Fernando Cisco Systems Email: rex@cisco.com Navindra Yadav Cisco Systems Email: nyadav@cisco.com Wim Henderickx Alcatel-Lucent wim.henderickx@alcatel-lucent.com Andrew Dolganow Alcaltel-Lucent Email: andrew.dolganow@alcatel-lucent.com Praveen Muley Alcaltel-Lucent Email: praveen.muley@alcatel-lucent.com Tom Nadeau Brocade tnadeau@lucidvision.com Puneet Agarwal puneet@acm.org Rajeev Manur Quinn & Elzur Expires September 25, 2015 [Page 34] Internet-Draft Network Service Header March 2015 Broadcom rmanur@broadcom.com Abhishek Chauhan Citrix Abhishek.Chauhan@citrix.com Joel Halpern Ericsson joel.halpern@ericsson.com Sumandra Majee F5 S.Majee@f5.com David Melman Marvell davidme@marvell.com Pankaj Garg Microsoft Garg.Pankaj@microsoft.com Brad McConnell Rackspace bmcconne@rackspace.com Chris Wright Red Hat Inc. chrisw@redhat.com Kevin Glavin Riverbed kevin.glavin@riverbed.com Hong (Cathy) Zhang Huawei US R&D cathy.h.zhang@huawei.com Louis Fourie Huawei US R&D louis.fourie@huawei.com Ron Parker Affirmed Networks ron_parker@affirmednetworks.com Myo Zarny Quinn & Elzur Expires September 25, 2015 [Page 35] Internet-Draft Network Service Header March 2015 Goldman Sachs myo.zarny@gs.com Quinn & Elzur Expires September 25, 2015 [Page 36] Internet-Draft Network Service Header March 2015 15. Acknowledgments The authors would like to thank Nagaraj Bagepalli, Abhijit Patra, Peter Bosch, Darrel Lewis, Pritesh Kothari, Tal Mizrahi and Ken Gray for their detailed review, comments and contributions. A special thank you goes to David Ward and Tom Edsall for their guidance and feedback. Additionally the authors would like to thank Carlos Pignataro and Larry Kreeger for their invaluable ideas and contributions which are reflected throughout this draft. Lastly, Reinaldo Penno deserves a particular thank you for his architecture and implementation work that helped guide the protocol concepts and design. Quinn & Elzur Expires September 25, 2015 [Page 37] Internet-Draft Network Service Header March 2015 16. IANA Considerations 16.1. NSH EtherType An IEEE EtherType, 0x894F, has been allocated for NSH. 16.2. Network Service Header (NSH) Parameters IANA is requested to create a new "Network Service Header (NSH) Parameters" registry. The following sub-sections request new registries within the "Network Service Header (NSH) Parameters " registry. 16.2.1. NSH Base Header Reserved Bits There are ten bits at the beginning of the NSH Base Header. New bits are assigned via Standards Action [RFC5226]. Bits 0-1 - Version Bit 2 - OAM (O bit) Bits 2-9 - Reserved 16.2.2. MD Type Registry IANA is requested to set up a registry of "MD Types". These are 8-bit values. MD Type values 0, 1, 2, 254, and 255 are specified in this document. Registry entries are assigned by using the "IETF Review" policy defined in RFC 5226 [RFC5226]. +---------+--------------+---------------+ | MD Type | Description | Reference | +---------+--------------+---------------+ | 0 | Reserved | This document | | | | | | 1 | NSH | This document | | | | | | 2 | NSH | This document | | | | | | 3..253 | Unassigned | | | | | | | 254 | Experiment 1 | This document | | | | | | 255 | Experiment 2 | This document | +---------+--------------+---------------+ Table 1 Quinn & Elzur Expires September 25, 2015 [Page 38] Internet-Draft Network Service Header March 2015 16.2.3. TLV Class Registry IANA is requested to set up a registry of "TLV Types". These are 16- bit values. Registry entries are assigned by using the "IETF Review" policy defined in RFC 5226 [RFC5226]. 16.2.4. NSH Base Header Next Protocol IANA is requested to set up a registry of "Next Protocol". These are 8-bit values. Next Protocol values 0, 1, 2 and 3 are defined in this draft. New values are assigned via Standards Action [RFC5226]. +---------------+-------------+---------------+ | Next Protocol | Description | Reference | +---------------+-------------+---------------+ | 0 | Reserved | This document | | | | | | 1 | IPv4 | This document | | | | | | 2 | IPv6 | This document | | | | | | 3 | Ethernet | This document | | | | | | 4..253 | Unassigned | | +---------------+-------------+---------------+ Table 2 Quinn & Elzur Expires September 25, 2015 [Page 39] Internet-Draft Network Service Header March 2015 17. References 17.1. Normative References [RFC0791] Postel, J., "Internet Protocol", STD 5, RFC 791, September 1981. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. 17.2. Informative References [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, March 2000. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. [RFC6071] Frankel, S. and S. Krishnan, "IP Security (IPsec) and Internet Key Exchange (IKE) Document Roadmap", RFC 6071, February 2011. [SFC-PS] Quinn, P., Ed. and T. Nadeau, Ed., "Service Function Chaining Problem Statement", 2014, . [SFC-arch] Quinn, P., Ed. and J. Halpern, Ed., "Service Function Chaining (SFC) Architecture", 2014, . [VXLAN-gpe] Quinn, P., Agarwal, P., Kreeger, L., Lewis, D., Maino, F., Yong, L., Xu, X., Elzur, U., and P. Garg, "Generic Protocol Extension for VXLAN", . [dcalloc] Guichard, J., Smith, M., and S. Kumar, "Network Service Header (NSH) Context Header Allocation (Data Center)", 2014, . [moballoc] Napper, J. and S. Kumar, "NSH Context Header Allocation -- Mobility", 2014, . Quinn & Elzur Expires September 25, 2015 [Page 41] Internet-Draft Network Service Header March 2015 Authors' Addresses Paul Quinn (editor) Cisco Systems, Inc. Email: paulq@cisco.com Uri Elzur (editor) Intel Email: uri.elzur@intel.com Quinn & Elzur Expires September 25, 2015 [Page 42]