--- 1/draft-ietf-bess-nsh-bgp-control-plane-08.txt 2019-03-06 16:13:15.604890285 -0800 +++ 2/draft-ietf-bess-nsh-bgp-control-plane-09.txt 2019-03-06 16:13:15.732893414 -0800 @@ -1,24 +1,24 @@ BESS Working Group A. Farrel Internet-Draft Old Dog Consulting Intended status: Standards Track J. Drake -Expires: September 2, 2019 E. Rosen +Expires: September 7, 2019 E. Rosen Juniper Networks J. Uttaro AT&T L. Jalil Verizon - March 1, 2019 + March 6, 2019 BGP Control Plane for NSH SFC - draft-ietf-bess-nsh-bgp-control-plane-08 + draft-ietf-bess-nsh-bgp-control-plane-09 Abstract This document describes the use of BGP as a control plane for networks that support Service Function Chaining (SFC). The document introduces a new BGP address family called the SFC AFI/SAFI with two route types. One route type is originated by a node to advertise that it hosts a particular instance of a specified service function. This route type also provides "instructions" on how to send a packet to the hosting node in a way that indicates that the service function @@ -38,21 +38,21 @@ 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 https://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 2, 2019. + This Internet-Draft will expire on September 7, 2019. Copyright Notice Copyright (c) 2019 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 (https://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents @@ -63,79 +63,79 @@ described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 4 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 2. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Overview of Service Function Chaining . . . . . . . . . . 6 2.2. Control Plane Overview . . . . . . . . . . . . . . . . . 7 - 3. BGP SFC Routes . . . . . . . . . . . . . . . . . . . . . . . 10 - 3.1. Service Function Instance Route (SFIR) . . . . . . . . . 11 - 3.1.1. SFI Pool Identifier Extended Community . . . . . . . 12 - 3.1.2. MPLS Mixed Swapping/Stacking Extended Community . . . 13 - 3.2. Service Function Path Route (SFPR) . . . . . . . . . . . 13 - 3.2.1. The SFP Attribute . . . . . . . . . . . . . . . . . . 14 - 3.2.2. General Rules For The SFP Attribute . . . . . . . . . 19 - 4. Mode of Operation . . . . . . . . . . . . . . . . . . . . . . 20 - 4.1. Route Targets . . . . . . . . . . . . . . . . . . . . . . 20 - 4.2. Service Function Instance Routes . . . . . . . . . . . . 20 + 3. BGP SFC Routes . . . . . . . . . . . . . . . . . . . . . . . 11 + 3.1. Service Function Instance Route (SFIR) . . . . . . . . . 12 + 3.1.1. SFI Pool Identifier Extended Community . . . . . . . 13 + 3.1.2. MPLS Mixed Swapping/Stacking Extended Community . . . 14 + 3.2. Service Function Path Route (SFPR) . . . . . . . . . . . 14 + 3.2.1. The SFP Attribute . . . . . . . . . . . . . . . . . . 15 + 3.2.2. General Rules For The SFP Attribute . . . . . . . . . 20 + 4. Mode of Operation . . . . . . . . . . . . . . . . . . . . . . 21 + 4.1. Route Targets . . . . . . . . . . . . . . . . . . . . . . 21 + 4.2. Service Function Instance Routes . . . . . . . . . . . . 21 4.3. Service Function Path Routes . . . . . . . . . . . . . . 21 4.4. Classifier Operation . . . . . . . . . . . . . . . . . . 23 - 4.5. Service Function Forwarder Operation . . . . . . . . . . 23 - 4.5.1. Processing With 'Gaps' in the SI Sequence . . . . . . 24 - 5. Selection in Service Function Paths . . . . . . . . . . . . . 25 - 6. Looping, Jumping, and Branching . . . . . . . . . . . . . . . 27 - 6.1. Protocol Control of Looping, Jumping, and Branching . . . 27 - 6.2. Implications for Forwarding State . . . . . . . . . . . . 28 + 4.5. Service Function Forwarder Operation . . . . . . . . . . 24 + 4.5.1. Processing With 'Gaps' in the SI Sequence . . . . . . 25 + 5. Selection in Service Function Paths . . . . . . . . . . . . . 26 + 6. Looping, Jumping, and Branching . . . . . . . . . . . . . . . 28 + 6.1. Protocol Control of Looping, Jumping, and Branching . . . 28 + 6.2. Implications for Forwarding State . . . . . . . . . . . . 29 7. Advanced Topics . . . . . . . . . . . . . . . . . . . . . . . 29 - 7.1. Preserving Entropy . . . . . . . . . . . . . . . . . . . 29 - 7.2. Correlating Service Function Path Instances . . . . . . . 29 - 7.3. Considerations for Stateful Service Functions . . . . . . 30 - 7.4. VPN Considerations and Private Service Functions . . . . 31 - 7.5. Flow Spec for SFC Classifiers . . . . . . . . . . . . . . 31 - 7.6. Choice of Data Plane SPI/SI Representation . . . . . . . 33 - 7.6.1. MPLS Representation of the SPI/SI . . . . . . . . . . 34 - 7.7. MPLS Label Swapping/Stacking Operation . . . . . . . . . 34 - 7.8. Support for MPLS-Encapsulated NSH Packets . . . . . . . . 34 + 7.1. Correlating Service Function Path Instances . . . . . . . 29 + 7.2. Considerations for Stateful Service Functions . . . . . . 30 + 7.3. VPN Considerations and Private Service Functions . . . . 31 + 7.4. Flow Spec for SFC Classifiers . . . . . . . . . . . . . . 32 + 7.5. Choice of Data Plane SPI/SI Representation . . . . . . . 33 + 7.5.1. MPLS Representation of the SPI/SI . . . . . . . . . . 34 + + 7.6. MPLS Label Swapping/Stacking Operation . . . . . . . . . 34 + 7.7. Support for MPLS-Encapsulated NSH Packets . . . . . . . . 35 8. Examples . . . . . . . . . . . . . . . . . . . . . . . . . . 35 - 8.1. Example Explicit SFP With No Choices . . . . . . . . . . 36 + 8.1. Example Explicit SFP With No Choices . . . . . . . . . . 37 8.2. Example SFP With Choice of SFIs . . . . . . . . . . . . . 37 8.3. Example SFP With Open Choice of SFIs . . . . . . . . . . 38 8.4. Example SFP With Choice of SFTs . . . . . . . . . . . . . 38 8.5. Example Correlated Bidirectional SFPs . . . . . . . . . . 39 8.6. Example Correlated Asymmetrical Bidirectional SFPs . . . 39 8.7. Example Looping in an SFP . . . . . . . . . . . . . . . . 40 8.8. Example Branching in an SFP . . . . . . . . . . . . . . . 41 8.9. Examples of SFPs with Stateful Service Functions . . . . 41 8.9.1. Forward and Reverse Choice Made at the SFF . . . . . 42 8.9.2. Parallel End-to-End SFPs with Shared SFF . . . . . . 43 - 8.9.3. Parallel End-to-End SFPs with Separate SFFs . . . . . 44 - 8.9.4. Parallel SFPs Downstream of the Choice . . . . . . . 46 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 49 - 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 50 - 10.1. New BGP AF/SAFI . . . . . . . . . . . . . . . . . . . . 50 - 10.2. New BGP Path Attribute . . . . . . . . . . . . . . . . . 50 - 10.3. New SFP Attribute TLVs Type Registry . . . . . . . . . . 50 - 10.4. New SFP Association Type Registry . . . . . . . . . . . 51 - 10.5. New Service Function Type Registry . . . . . . . . . . . 51 + 8.9.3. Parallel End-to-End SFPs with Separate SFFs . . . . . 45 + 8.9.4. Parallel SFPs Downstream of the Choice . . . . . . . 47 + 9. Security Considerations . . . . . . . . . . . . . . . . . . . 50 + 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 51 + 10.1. New BGP AF/SAFI . . . . . . . . . . . . . . . . . . . . 51 + 10.2. New BGP Path Attribute . . . . . . . . . . . . . . . . . 51 + 10.3. New SFP Attribute TLVs Type Registry . . . . . . . . . . 51 + 10.4. New SFP Association Type Registry . . . . . . . . . . . 52 + 10.5. New Service Function Type Registry . . . . . . . . . . . 53 10.6. New Generic Transitive Experimental Use Extended - Community Sub-Types . . . . . . . . . . . . . . . . . . 52 - 10.7. New BGP Transitive Extended Community Types . . . . . . 52 - 10.8. SPI/SI Representation . . . . . . . . . . . . . . . . . 53 - 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 53 - 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 53 - 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 53 - 13.1. Normative References . . . . . . . . . . . . . . . . . . 54 - 13.2. Informative References . . . . . . . . . . . . . . . . . 55 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 55 + Community Sub-Types . . . . . . . . . . . . . . . . . . 54 + 10.7. New BGP Transitive Extended Community Types . . . . . . 54 + 10.8. SPI/SI Representation . . . . . . . . . . . . . . . . . 54 + 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 54 + 12. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 55 + 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 55 + 13.1. Normative References . . . . . . . . . . . . . . . . . . 55 + 13.2. Informative References . . . . . . . . . . . . . . . . . 56 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 56 1. Introduction As described in [RFC7498], the delivery of end-to-end services can require a packet to pass through a series of Service Functions (SFs) (e.g., WAN and application accelerators, Deep Packet Inspection (DPI) engines, firewalls, TCP optimizers, and server load balancers) in a specified order: this is termed "Service Function Chaining" (SFC). There are a number of issues associated with deploying and maintaining service function chaining in production networks, which @@ -268,32 +268,34 @@ sets the SI to the value of the SI for the first hop in the SFP, and then prepends a Network Services Header (NSH) [RFC8300] containing the assigned SPI/SI to that packet. Note that the Classifier and the node that hosts the first Service Function in a Service Function Path need not be located at the same point in the service function overlay network. Note that the presence of the NSH can make it difficult for nodes in the underlay network to locate the fields in the original packet that would normally be used to constrain equal cost multipath (ECMP) - forwarding. Therefore, it is recommended, as described in - Section 7.1, that the node prepending the NSH also provide some form - of entropy indicator that can be used in the underlay network. + forwarding. Therefore, it is recommended that the node prepending + the NSH also provide some form of entropy indicator that can be used + in the underlay network. How this indicator is generated and + supplied, and how an SFF generates a new entropy indicator when it + forwards a packet to the next SFF are out of scope of this document. The Service Function Forwarder (SFF) receives a packet from the previous node in a Service Function Path, removes the packet's link layer or tunnel encapsulation and hands the packet and the NSH to the Service Function Instance for processing. The SFI has no knowledge of the SFP. When the SFF receives the packet and the NSH back from the SFI it - MUST select the next SFI along the path using the SPI and SI in the + must select the next SFI along the path using the SPI and SI in the NSH and potentially choosing between multiple SFIs (possibly of different Service Function Types) as described in Section 5. In the normal case the SPI remains unchanged and the SI will have been decremented to indicate the next SF along the path. But other possibilities exist if the SF makes other changes to the NSH through a process of re-classification: o The SI in the NSH may indicate: * A previous SF in the path: known as "looping" (see Section 6). @@ -315,20 +317,23 @@ An SFF receiving an SI that is unknown in the context of the SPI can reduce the value to the next meaningful SI value in the SFP indicated by the SPI. If no such value exists or if the SFF does not support this function, the SFF drops the packet and should log the event: such logs are also subject to rate limits. The SFF then selects an SFI that provides the SF denoted by the SPI/ SI, and forwards the packet to the SFF that supports that SFI. + [RFC8300] makes it clear that the intended scope is for use within a + single provider's operational domain. + 2.2. Control Plane Overview To accomplish the function described in Section 2.1, this document introduces the Service Function Type (SFT) that is the category of SF that is supported by an SFF (such as "firewall"). An IANA registry of Service Function Types is introduced in Section 10. An SFF may support SFs of multiple different SFTs, and may support multiple SFIs of each SF. This document also introduces a new BGP AFI/SAFI (values to be @@ -362,91 +367,102 @@ When choosing the next SFI in a path, the SFF uses the SPI and SI as well as the SFT to choose among the SFIs, applying, for example, a load balancing algorithm or direct knowledge of the underlay network topology as described in Section 4. The SFF then encapsulates the packet using the encapsulation specified by the SFIR of the selected SFI and forwards the packet. See Figure 1. - Thus the SFF can be seen as a gateway in the underlay network through + Thus the SFF can be seen as a portal in the underlay network through which a particular SFI is reached. Figure 1 shows a reference model for the SFC architecture. There are four SFFs (SFF-1 through SFF-4) connected by tunnels across the underlay network. Packets arrive at a Classifier and are channelled along SFPs to destinations reachable through SFF-4. SFF-1 and SFF-4 each have one instance of one SF attached (SFa and SFe). SFF-2 has two types of SF attached: there is one instance of one (SFc), and three instances of the other (SFb). SFF-3 has just one instance of an SF (SFd), but it in this case the type of SFd is the same type as SFb (SFTx). - This figure demonstrates how load balancing can be achieved. Suppose - an SFC needs to include SFa, an SF of type SFTx, and SFd. A number - of SFPs can be constructed using any instance of SFb or using SFd. + This figure demonstrates how load balancing can be achieved by + creating several SFPs that satisfy the same SFC. Suppose an SFC + needs to include SFa, an SF of type SFTx, and SFc. A number of SFPs + can be constructed using any instance of SFb or using SFd. Load + balancing may be applied at two places: + + o The Classifier may distribute different flows onto different SFPs + to share the load in the network and across SFIs. + + o SFF-2 may distribute different flows (on the same SFP) to + different instances of SFb to share the processing load. + + Note that, for convenience and clarity, Figure 1 shows only a few + tunnels between SFFs. There could be a full mesh of such tunnels, or + more likely, a selection of tunnels connecting key SFFs to enable the + construction of SFPs and to balance load and traffic in the network. Packets | | | - | | | - | | | ------------ | | | Classifier | | | - ------------ - | + ------+----- | - ------- --------- ------- + ---+--- --------- ------- | | Tunnel | | | | | SFF-1 |===============| SFF-2 |=========| SFF-4 | | | | | | | | | -+-----+- | | | | ,,,,,,,,,,,,,,/,, \ | | | | ' .........../. ' ..\...... | | | | ' : SFb / : ' : \ SFc : | | | | ' : ---+- : ' : --+-- : | | | | ' : -| SFI | : ' : | SFI | : | | | | ' : -| ----- : ' : ----- : | | | | ' : | ----- : ' ......... | | | | ' : ----- : ' | | | | ' ............. ' | |--- Dests | | ' ' | |--- Dests - | | ' ' | | | | ' ......... ' | | | | ' : ----- : ' | | | | ' : | SFI | : ' | | | | ' : --+-- : ' | | | | ' :SFd | : ' | | | | ' ....|.... ' | | | | ' | ' | | | | ' SFTx | ' | | | | ',,,,,,,,|,,,,,,,,' | | | | | | | - | | | | | | | ---+--- | | | | | | | | | |======| SFF-3 |====================| | ---+--- | | ---+--- | ------- | - ....|.... ....|.... : | SFa: : | SFe: : --+-- : : --+-- : : | SFI | : : | SFI | : : ----- : : ----- : ......... ......... Figure 1: The SFC Architecture Reference Model + As previously noted, [RFC8300] makes it clear that the mechanisms it + defines are intended for use within a single provider's operational + domain. This reduces the requirements on the control plane function. + 3. BGP SFC Routes This document defines a new AFI/SAFI for BGP, known as "SFC", with an NLRI that is described in this section. The format of the SFC NLRI is shown in Figure 2. +---------------------------------------+ | Route Type (2 octets) | +---------------------------------------+ @@ -482,20 +498,23 @@ and a Subsequent Address Family Identifier (SAFI) of TBD2. The NLRI field in the MP_REACH_NLRI/MP_UNREACH_NLRI attribute contains the SFC NLRI, encoded as specified above. In order for two BGP speakers to exchange SFC NLRIs, they MUST use BGP Capabilities Advertisements to ensure that they both are capable of properly processing such NLRIs. This is done as specified in [RFC4760], by using capability code 1 (Multiprotocol BGP) with an AFI of TBD1 and a SAFI of TBD2. + The nexthop field of the MP_REACH_NLRI attribute of the SFC NLRI MUST + be set to loopback address of the advertising SFF. + 3.1. Service Function Instance Route (SFIR) Figure 3 shows the Route Type specific NLRI of the SFIR. +--------------------------------------------+ | Route Distinguisher (RD) (8 octets) | +--------------------------------------------+ | Service Function Type (2 octets) | +--------------------------------------------+ @@ -503,29 +522,30 @@ Per [RFC4364] the RD field comprises a two byte Type field and a six byte Value field. Two SFIs of the same SFT MUST be associated with different RDs, where the association of an SFI with an RD is determined by provisioning. If two SFIRs are originated from different administrative domains, they MUST have different RDs. In particular, SFIRs from different VPNs (for different service function overlay networks) MUST have different RDs, and those RDs MUST be different from any non-VPN SFIRs. - The Service Function Type identifies a service function type, e.g., - classifier, firewall, load balancer, etc. There may be several SFIs - that can perform a given Service Function. Each node hosting an SFI - MUST originate an SFIR for each type of SF that it hosts, and it may - advertise an SFIR for each instance of each type of SF. The minimal - advertisement allows construction of valid SFPs and leaves the - selection of SFIs to the local SFF; the detailed advertisement may - have scaling concerns, but allows a Controller that constructs an SFP - to make an explicit choice of SFI. + The Service Function Type identifies the functions/features of + service function can offer, e.g., classifier, firewall, load + balancer, etc. There may be several SFIs that can perform a given + Service Function. Each node hosting an SFI MUST originate an SFIR + for each type of SF that it hosts, and it may advertise an SFIR for + each instance of each type of SF. The minimal advertisement allows + construction of valid SFPs and leaves the selection of SFIs to the + local SFF; the detailed advertisement may have scaling concerns, but + allows a Controller that constructs an SFP to make an explicit choice + of SFI. The SFIR representing a given SFI will contain an NLRI with RD field set to an RD as specified above, and with SFT field set to identify that SFI's Service Function Type. The values for the SFT field are taken from a registry administered by IANA (see Section 10). A BGP Update containing one or more SFIRs MUST also include a Tunnel Encapsulation attribute [I-D.ietf-idr-tunnel-encaps]. If a data packet needs to be sent to an SFI identified in one of the SFIRs, it will be encapsulated as specified by the Tunnel Encapsulation attribute, and then transmitted through the underlay network. @@ -590,21 +610,21 @@ Figure 5: The MPLS Mixed Swapping/Stacking Extended Community Note that it is assumed that each SFF has one or more globally unique SFC Context Labels and that the context label space and the SPI address space are disjoint. If an SFF supports SFP Traversal with an MPLS Label Stack it MUST include this extended community with the SFIRs that it advertises. - See Section 7.7 for a description of how this extended community is + See Section 7.6 for a description of how this extended community is used. 3.2. Service Function Path Route (SFPR) Figure 6 shows the Route Type specific NLRI of the SFPR. +-----------------------------------------------+ | Route Distinguisher (RD) (8 octets) | +-----------------------------------------------+ | Service Path Identifier (SPI) (3 octets) | @@ -673,29 +693,30 @@ o The SFP attribute contains a sequence of one or more Hop TLVs. Each Hop TLV contains all of the information about a single hop in the SFP. o Each Hop TLV contains an SI value and a sequence of one or more SFT TLVs. Each SFT TLV contains an SFI reference for each instance of an SF that is allowed at this hop of the SFP for the specific SFT. Each SFI is indicated using the RD with which it is advertised (we say the SFIR-RD to avoid ambiguity). - Malformed SFP attributes, or those that in error in some way, MUST be - handled as described in Section 6 of [RFC4271]. + Malformed SFP attributes, or those that are in error in some way, + MUST be handled as described in Section 6 of [RFC4271]. 3.2.1.1. The Association TLV The Association TLV is an optional TLV in the SFP attribute. It MAY be present multiple times. Each occurrence provides an association with another SFP as advertised in another SFPR. The format of the Association TLV is shown in Figure 7 + +--------------------------------------------+ | Type = 1 (1 octet) | +--------------------------------------------| | Length (2 octets) | +--------------------------------------------| | Association Type (1 octet) | +--------------------------------------------| | Associated SFPR-RD (8 octets) | +--------------------------------------------| | Associated SPI (3 octets) | @@ -729,26 +750,25 @@ Association TLVs with unknown Association Type values SHOULD be ignored. Association TLVs that contain an Associated SFPR-RD value equal to the RD of the SFPR in which they are contained SHOULD be ignored. If the Associated SPI is not equal to the SPI advertised in the SFPR indicated by the Associated SFPR-RD then the Association TLV SHOULD be ignored. Note that when two SFPRs reference each other using the Association TLV, one SFPR advertisement will be received before the other. - Therefore, processing of an association MUST NOT be rejected simply because the Associated SFPR-RD is unknown. Further discussion of correlation of SFPRs is provided in - Section 7.2. + Section 7.1. 3.2.1.2. The Hop TLV There is one Hop TLV in the SFP attribute for each hop in the SFP. The format of the Hop TLV is shown in Figure 8. At least one Hop TLV MUST be present in an SFP attribute. +--------------------------------------------+ | Type = 2 (1 octet) | +--------------------------------------------| @@ -827,24 +847,24 @@ RD of each SFIR advertised with that SFI Pool Identifier. An SFIR-RD of value zero has special meaning as described in Section 5. Each entry in the list is eight octets long, and the number of entries in the list can be deduced from the value of the Length field. 3.2.1.4. MPLS Swapping/Stacking TLV The MPLS Swapping/Stacking TLV (Type value 4) is a zero length sub- TLV that is optionally present in the Hop TLV and is used when the - data representation is MPLS (see Section 7.6). When present it + data representation is MPLS (see Section 7.5). When present it indicates to the Classifier imposing an MPLS label stack that the current hop is to use an {SFC Context Label, SF label} rather than an - {SPI, SF} label pair. See Section 7.7 for more details. + {SPI, SF} label pair. See Section 7.6 for more details. 3.2.1.5. SFP Traversal With MPLS Label Stack TLV The SFP Traversal With MPLS Label Stack TLV (Type value 5) is a zero length sub-TLV that can be carried in the SFP Attribute and indicates to the Classifier and the SFFs on the SFP that an MPLS labels stack with label swapping/stacking is to be used for packets traversing the SFP. All of the SFF specified at each the SFP's hops MUST have advertised an MPLS Mixed Swapping/Stacking Extended Community (see Section 3.1.2) for the SFP to be considered usable. @@ -897,24 +917,24 @@ Targets (RTs) [RFC4364]. Every BGP UPDATE containing an SFIR or SFPR carries one or more RTs. The RT carried by a particular SFIR or SFPR is determined by the provisioning of the route's originator. Every node in a service function overlay network is configured with one or more import RTs. Thus, each SFF will import only the SFPRs with matching RTs allowing the construction of multiple service function overlay networks or the instantiation of Service Function - Chains within an L3VPN or EVPN instance (see Section 7.4). An SFF + Chains within an L3VPN or EVPN instance (see Section 7.3). An SFF that has a presence in multiple service function overlay networks - (i.e., imports more than one RT) may find it helpful to maintain - separate forwarding state for each overlay network. + (i.e., imports more than one RT) will usually maintain separate + forwarding state for each overlay network. 4.2. Service Function Instance Routes The SFIR (see Section 3.1) is used to advertise the existence and location of a specific Service Function Instance and consists of: o The RT as just described. o A Service Function Type (SFT) that is the type of service function that is provided (such as "firewall"). @@ -1021,23 +1040,20 @@ 4.4. Classifier Operation As shown in Figure 1, the Classifier is a component that is used to assign packets to an SFP. The Classifier is responsible for determining to which packet flow a packet belongs (usually by inspecting the packet header), imposing an NSH, and initializing the NSH with the SPI of the selected SFP and the SI of its first hop. - The Classifier may also provide an entropy indicator as described in - Section 7.1. - 4.5. Service Function Forwarder Operation Each packet sent to an SFF is transmitted encapsulated in an NSH. The NSH includes an SPI and SI: the SPI indicates the SFPR advertisement that announced the Service Function Path; the tuple SPI/SI indicates a specific hop in a specific path and maps to the RD/SFT of a particular SFIR advertisement. When an SFF gets an SFPR advertisement it will first determine whether to import the route by examining the RT. If the SFPR is @@ -1137,21 +1153,21 @@ 5. Selection in Service Function Paths As described in Section 2 the SPI/SI in the NSH passed back from an SFI to the SFF may leave the SFF with a choice of next hop SFTs, and a choice of SFIs for each SFT. That is, the SPI indicates an SFPR, and the SI indicates an entry in that SFPR. Each entry in an SFPR is a set of one or more SFT/SFIR-RD pairs. The SFF MUST choose one of these, identify the SFF that supports the chosen SFI, and send the packet to that next hop SFF. - The choice may offered for load balancing across multiple SFIs, or + The choice be may offered for load balancing across multiple SFIs, or for discrimination between different actions necessary at a specific hop in the SFP. Different SFT values may exist at a given hop in an SFP to support several cases: o There may be multiple instances of similar service functions that are distinguished by different SFT values. For example, firewalls made by vendor A and vendor B may need to be identified by different SFT values because, while they have similar functionality, their behavior is not identical. Then, some SFPs may limit the choice of SF at a given hop by specifying the SFT @@ -1301,48 +1318,21 @@ needed to create the forwarding state. This is a matter of local configuration and implementation: for example, an implementation could be configured to install forwarding state for specific branching (identified by SPI and SI). 7. Advanced Topics This section highlights several advanced topics introduced elsewhere in this document. -7.1. Preserving Entropy - - Forwarding decisions in the underlay network in the presence of equal - cost multipath (ECMP) are usually made by inspecting key invariant - fields in a packet header so that all packets from the same packet - flow receive the same forwarding treatment. However, when an NSH is - included in a packet, those key fields may be inaccessible. For - example, the fields may be too far inside the packet for a forwarding - engine to quickly find them and extract their values, or the node - performing the examination may be unaware of the format and meaning - of the NSH and so unable to parse far enough into the packet. - - Various mechanisms exist within forwarding technologies to include an - "entropy indicator" within a forwarded packet. For example, in MPLS - there is the entropy label [RFC6790], while for encapsulations in UDP - the source port field is often used to carry an entropy indicator - (such as for MPLS in UDP [RFC7510]). - - Implementations of this specification are RECOMMENDED to include an - entropy indicator within the packet's underlay network header, and - SHOULD preserve any entropy indicator from a received packet for use - on the same packet when it is forwarded along the path but MAY choose - to generate a new entropy indicator so long as the method used is - constant for all packets. Note that preserving per packet entropy - may require that the entropy indicator is passed to and returned by - the SFI to prevent the SFF from having to maintain per-packet state. - -7.2. Correlating Service Function Path Instances +7.1. Correlating Service Function Path Instances It is often useful to create bidirectional SFPs to enable packet flows to traverse the same set of SFs, but in the reverse order. However, packets on SFPs in the data plane (per [RFC8300]) do not contain a direction indicator, so each direction must use a different SPI. As described in Section 3.2.1.1 an SFPR can contain one or more correlators encoded in Association TLVs. If the Association Type indicates "Bidirectional SFP" then the SFP advertised in the SFPR is @@ -1368,21 +1358,21 @@ log this situation because it represents a Controller error. Usage of a bidirectional SFP may be programmed into the Classifiers by the Controller. Alternatively, a Classifier may look at incoming packets on a bidirectional packet flow, extract the SPI from the received NSH, and look up the SFPR to find the reverse direction SFP to use when it sends packets. See Section 8 for an example of how this works. -7.3. Considerations for Stateful Service Functions +7.2. Considerations for Stateful Service Functions Some service functions are stateful. That means that they build and maintain state derived from configuration or from the packet flows that they handle. In such cases it can be important or necessary that all packets from a flow continue to traverse the same instance of a service function so that the state can be leveraged and does not need to be regenerated. In the case of bidirectional SFPs, it may be necessary to traverse the same instances of a stateful service function in both directions. @@ -1414,34 +1404,34 @@ that makes the choice in both directions. Note that this approach necessarily increases the amount of SFP state in the network (i.e., there are more SFPs). It is possible to mitigate this effect by careful construction of SFPs built from a concatenation of other SFPs. Section 8.9 includes some simple examples of SFPs for stateful service functions. -7.4. VPN Considerations and Private Service Functions +7.3. VPN Considerations and Private Service Functions Likely deployments include reserving specific instances of Service Functions for specific customers or allowing customers to deploy their own Service Functions within the network. Building Service Functions in such environments requires that suitable identifiers are used to ensure that SFFs distinguish which SFIs can be used and which cannot. This problem is similar to how VPNs are supported and is solved in a similar way. The RT field is used to indicate a set of Service Functions from which all choices must be made. -7.5. Flow Spec for SFC Classifiers +7.4. Flow Spec for SFC Classifiers [RFC5575] defines a set of BGP routes that can be used to identify the packets in a given flow using fields in the header of each packet, and a set of actions, encoded as extended communities, that can be used to disposition those packets. This document enables the use of RFC 5575 mechanisms by SFC Classifiers by defining a new action extended community called "Flow Spec for SFC classifiers" identified by the value TBD4. Note that other action extended communities may also be present. @@ -1487,23 +1477,24 @@ * If there is a choice of SFT in the hop indicated by the value of the SI (including SI = 0) then SFT = 0 means there is a free choice according to local policy of which SFT to use). * If there is no choice of SFT in the hop indicated by the value of SI, then SFT = 0 means that the value of the SFT at that hop as indicated in the SPFR for the indicated SPI MUST be used. Note that each FlowSpec update MUST be tagged with the route target - of the overlay or VPN network for which it is intended. + of the overlay or VPN network for which it is intended to put the + indicated SPI into context. -7.6. Choice of Data Plane SPI/SI Representation +7.5. Choice of Data Plane SPI/SI Representation This document ties together the control and data planes of an SFC overlay network through the use of the SPI/SI which is nominally carried in the NSH of a given packet. However, in order to handle situations in which the NSH is not ubiquitously deployed, it is also possible to use alternative data plane representations of the SPI/SI by carrying the identical semantics in other protocol fields such as MPLS labels [I-D.ietf-mpls-sfc]. This document defines a new sub-TLV for the Tunnel Encapsulation @@ -1514,21 +1505,21 @@ of which describes how the originating SFF expects to see the SPI/SI represented in the data plane for packets carried in the tunnels described by the Tunnel TLV. The following bits are defined by this document: Bit 0: If this bit is set the NSH is to be used to carry the SPI/SI in the data plane. Bit 1: If this bit is set two labels in an MPLS label stack are to - be used as described in Section 7.6.1. + be used as described in Section 7.5.1. If a given Tunnel TLV does not contain an SPI/SI Representation sub- TLV then it MUST be processed as if such a sub-TLV is present with Bit 0 set and no other bits set. That is, the absence of the sub-TLV SHALL be interpreted to mean that the NSH is to be used. If a given Tunnel TLV contains an SPI/SI Representation sub-TLV with value field that has no flag set then the tunnel indicated by the Tunnel TLV MUST NOT be used for forwarding SFC packets. If a given Tunnel TLV contains an SPI/SI Representation sub-TLV with both bit 0 @@ -1543,57 +1534,56 @@ instances MUST be ignored. Note that the MPLS representation of the logical NSH may be used even if the tunnel is not an MPLS tunnel. Conversely, MPLS tunnels may be used to carry other encodings of the logical NSH (specifically, the NSH itself). It is a requirement that both ends of a tunnel over the underlay network know that the tunnel is used for SFC and know what form of NSH representation is used. The signaling mechanism described here allows coordination of this information. -7.6.1. MPLS Representation of the SPI/SI +7.5.1. MPLS Representation of the SPI/SI If bit 1 is set in the in the SPI/SI Representation sub-TLV then labels in the MPLS label stack are used to indicate SFC forwarding and processing instructions to achieve the semantics of a logical NSH. The label stack is encoded as shown in [I-D.ietf-mpls-sfc]. -7.7. MPLS Label Swapping/Stacking Operation +7.6. MPLS Label Swapping/Stacking Operation When a classifier constructs an MPLS label stack for an SFP it starts with that SFP' last hop. If the last hop requires an {SPI, SI} label pair for label swapping, it pushes the SI (set to the SI value of the last hop) and the SFP's SPI onto the MPLS label stack. If the last hop requires a {context label, SFI label} label pair for label stacking it selects a specific SFIR and pushes that SFIR's SFI label and context label onto the MPLS label stack. The classifier then moves sequentially back through the SFP one hop at a time. For each hop, if the hop requires an {SPI, SI]} and there is an {SPI, SI} at the top of the MPLS label stack, the SI is set to the SI value of the current hop. If there is not an {SPI, SI} at the top of the MPLS label stack, it pushes the SI (set to the SI value of the current hop) and the SFP's SPI onto the MPLS label stack. If the hop requires a {context label, SFI label}, it selects a specific SFIR and pushes that SFIR's SFI label and context label onto the MPLS label stack. -7.8. Support for MPLS-Encapsulated NSH Packets +7.7. Support for MPLS-Encapsulated NSH Packets [I-D.ietf-mpls-sfc-encapsulation] describes how to transport SFC packets using the NSH over an MPLS transport network. Signaling MPLS encapsulation of SFC packets using the NSH is also supported by this document by using the "BGP Tunnel Encapsulation Attribute Sub-TLV" with the codepoint 10 (representing "MPLS Label Stack") from the "BGP Tunnel Encapsulation Attribute Sub-TLVs" registry defined in - [I-D.ietf-idr-tunnel-encaps], and also using the "SFP Traversal With MPLS Label Stack TLV" and the "SPI/SI Representation sub-TLV" with bit 0 set and bit 1 cleared. In this case the MPLS label stack constructed by the SFF to forward a packet to the next SFF on the SFP will consist of the labels needed to reach that SFF, and if label stacking is used it will also include the labels advertised in the MPLS Label Stack sub-TLV and the labels remaining in the stack needed to traverse the remainder of the SFP. @@ -1641,84 +1631,84 @@ ------ ------ ------ ------ | SFI | | SFI | | SFI | | SFI | |SFT=42| |SFT=44| |SFT=43| |SFT=44| ------ ------ ------ ------ Figure 11: Example Service Function Overlay Network The SFFs advertise routes to the SFIs they support. So we see the following SFIRs: - RD = 192.0.2.1,1, SFT = 41 - RD = 192.0.2.1,2, SFT = 42 - RD = 192.0.2.2,1, SFT = 41 - RD = 192.0.2.2,2, SFT = 43 - RD = 192.0.2.3,7, SFT = 42 - RD = 192.0.2.3,8, SFT = 44 - RD = 192.0.2.4,5, SFT = 43 - RD = 192.0.2.4,6, SFT = 44 + RD = 192.0.2.1:1, SFT = 41 + RD = 192.0.2.1:2, SFT = 42 + RD = 192.0.2.2:1, SFT = 41 + RD = 192.0.2.2:2, SFT = 43 + RD = 192.0.2.3:7, SFT = 42 + RD = 192.0.2.3:8, SFT = 44 + RD = 192.0.2.4:5, SFT = 43 + RD = 192.0.2.4:6, SFT = 44 Note that the addressing used for communicating between SFFs is taken from the Tunnel Encapsulation attribute of the SFIR and not from the SFIR-RD. 8.1. Example Explicit SFP With No Choices Consider the following SFPR. - SFP1: RD = 198.51.100.1,101, SPI = 15, - [SI = 255, SFT = 41, RD = 192.0.2.1,1], - [SI = 250, SFT = 43, RD = 192.0.2.2,2] + SFP1: RD = 198.51.100.1:101, SPI = 15, + [SI = 255, SFT = 41, RD = 192.0.2.1:1], + [SI = 250, SFT = 43, RD = 192.0.2.2:2] The Service Function Path consists of an SF of type 41 located at SFF1 followed by an SF of type 43 located at SFF2. This path is fully explicit and each SFF is offered no choice in forwarding packet along the path. SFF1 will receive packets on the path from the Classifier and will identify the path from the SPI (15). The initial SI will be 255 and so SFF1 will deliver the packets to the SFI for SFT 41. When the packets are returned to SFF1 by the SFI the SI will be decreased to 250 for the next hop. SFF1 has no flexibility in the choice of SFF to support the next hop SFI and will forward the packet to SFF2 which will send the packets to the SFI that supports SFT 43 before forwarding the packets to their destinations. 8.2. Example SFP With Choice of SFIs - SFP2: RD = 198.51.100.1,102, SPI = 16, - [SI = 255, SFT = 41, RD = 192.0.2.1,], - [SI = 250, SFT = 43, {RD = 192.0.2.2,2, - RD = 192.0.2.4,5 } ] + SFP2: RD = 198.51.100.1:102, SPI = 16, + [SI = 255, SFT = 41, RD = 192.0.2.1:1], + [SI = 250, SFT = 43, {RD = 192.0.2.2:2, + RD = 192.0.2.4:5 } ] In this example the path also consists of an SF of type 41 located at SFF1 and this is followed by an SF of type 43, but in this case the SI = 250 contains a choice between the SFI located at SFF2 and the SFI located at SFF4. SFF1 will receive packets on the path from the Classifier and will identify the path from the SPI (16). The initial SI will be 255 and so SFF1 will deliver the packets to the SFI for SFT 41. When the packets are returned to SFF1 by the SFI the SI will be decreased to 250 for the next hop. SFF1 now has a choice of next hop SFF to execute the next hop in the path. It can either forward packets to SFF2 or SFF4 to execute a function of type 43. It uses its local load balancing algorithm to make this choice. The chosen SFF will send the packets to the SFI that supports SFT 43 before forwarding the packets to their destinations. 8.3. Example SFP With Open Choice of SFIs - SFP3: RD = 198.51.100.1,103, SPI = 17, - [SI = 255, SFT = 41, RD = 192.0.2.1,1], + SFP3: RD = 198.51.100.1:103, SPI = 17, + [SI = 255, SFT = 41, RD = 192.0.2.1:1], [SI = 250, SFT = 44, RD = 0] In this example the path also consists of an SF of type 41 located at SFF1 and this is followed by an SI with an RD of zero and SF of type 44. This means that a choice can be made between any SFF that supports an SFI of type 44. SFF1 will receive packets on the path from the Classifier and will identify the path from the SPI (17). The initial SI will be 255 and so SFF1 will deliver the packets to the SFI for SFT 41. @@ -1727,24 +1717,24 @@ decreased to 250 for the next hop. SFF1 now has a free choice of next hop SFF to execute the next hop in the path selecting between all SFFs that support SFs of type 44. Looking at the SFIRs it has received, SFF1 knows that SF type 44 is supported by SFF3 and SFF4. SFF1 uses its local load balancing algorithm to make this choice. The chosen SFF will send the packets to the SFI that supports SFT 44 before forwarding the packets to their destinations. 8.4. Example SFP With Choice of SFTs - SFP4: RD = 198.51.100.1,104, SPI = 18, - [SI = 255, SFT = 41, RD = 192.0.2.1,1], - [SI = 250, {SFT = 43, RD = 192.0.2.2,2, - SFT = 44, RD = 192.0.2.3,8 } ] + SFP4: RD = 198.51.100.1:104, SPI = 18, + [SI = 255, SFT = 41, RD = 192.0.2.1:1], + [SI = 250, {SFT = 43, RD = 192.0.2.2:2, + SFT = 44, RD = 192.0.2.3:8 } ] This example provides a choice of SF type in the second hop in the path. The SI of 250 indicates a choice between SF type 43 located through SF2 and SF type 44 located at SF3. SFF1 will receive packets on the path from the Classifier and will identify the path from the SPI (18). The initial SI will be 255 and so SFF1 will deliver the packets to the SFI for SFT 41. When the packets are returned to SFF1 by the SFI the SI will be @@ -1756,70 +1746,70 @@ functions identified with different type identifiers (such as firewalls from different vendors). SFF1 uses its local policy and load balancing algorithm to make this choice, and may use additional information passed back from the local SFI to help inform its selection. The chosen SFF will send the packets to the SFI that supports the chose SFT before forwarding the packets to their destinations. 8.5. Example Correlated Bidirectional SFPs - SFP5: RD = 198.51.100.1,105, SPI = 19, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,106, Assoc-SPI = 20, - [SI = 255, SFT = 41, RD = 192.0.2.1,1], - [SI = 250, SFT = 43, RD = 192.0.2.2,2] + SFP5: RD = 198.51.100.1:105, SPI = 19, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:106, Assoc-SPI = 20, + [SI = 255, SFT = 41, RD = 192.0.2.1:1], + [SI = 250, SFT = 43, RD = 192.0.2.2:2] - SFP6: RD = 198.51.100.1,106, SPI = 20, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,105, Assoc-SPI = 19, - [SI = 254, SFT = 43, RD = 192.0.2.2,2], - [SI = 249, SFT = 41, RD = 192.0.2.1,1] + SFP6: RD = 198.51.100.1:106, SPI = 20, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:105, Assoc-SPI = 19, + [SI = 254, SFT = 43, RD = 192.0.2.2:2], + [SI = 249, SFT = 41, RD = 192.0.2.1:1] This example demonstrates correlation of two SFPs to form a - bidirectional SFP as described in Section 7.2. + bidirectional SFP as described in Section 7.1. Two SFPRs are advertised by the Controller. They have different SPIs (19 and 20) so they are known to be separate SFPs, but they both have Association TLVs with Association Type set to 1 indicating bidirectional SFPs. Each has an Associated SFPR-RD fields containing the value of the other SFPR-RD to correlated the two SFPs as a bidirectional pair. As can be seen from the SFPRs in this example, the paths are symmetric: the hops in SFP5 appear in the reverse order in SFP6. 8.6. Example Correlated Asymmetrical Bidirectional SFPs - SFP7: RD = 198.51.100.1,107, SPI = 21, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,108, Assoc-SPI = 22, - [SI = 255, SFT = 41, RD = 192.0.2.1,1], - [SI = 250, SFT = 43, RD = 192.0.2.2,2] + SFP7: RD = 198.51.100.1:107, SPI = 21, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:108, Assoc-SPI = 22, + [SI = 255, SFT = 41, RD = 192.0.2.1:1], + [SI = 250, SFT = 43, RD = 192.0.2.2:2] - SFP8: RD = 198.51.100.1,108, SPI = 22, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,107, Assoc-SPI = 21, - [SI = 254, SFT = 44, RD = 192.0.2.4,6], - [SI = 249, SFT = 41, RD = 192.0.2.1,1] + SFP8: RD = 198.51.100.1:108, SPI = 22, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:107, Assoc-SPI = 21, + [SI = 254, SFT = 44, RD = 192.0.2.4:6], + [SI = 249, SFT = 41, RD = 192.0.2.1:1] Asymmetric bidirectional SFPs can also be created. This example shows a pair of SFPs with distinct SPIs (21 and 22) that are correlated in the same way as in the example in Section 8.5. However, unlike in that example, the SFPs are different in each direction. Both paths include a hop of SF type 41, but SFP7 includes a hop of SF type 43 supported at SFF2 while SFP8 includes a hop of SF type 44 supported at SFF4. 8.7. Example Looping in an SFP - SFP9: RD = 198.51.100.1,109, SPI = 23, - [SI = 255, SFT = 41, RD = 192.0.2.1,1], - [SI = 250, SFT = 44, RD = 192.0.2.4,5], + SFP9: RD = 198.51.100.1:109: SPI = 23, + [SI = 255, SFT = 41, RD = 192.0.2.1:1], + [SI = 250, SFT = 44, RD = 192.0.2.4:5], [SI = 245, SFT = 1, RD = {SPI=23, SI=255, Rsv=0}], - [SI = 245, SFT = 42, RD = 192.0.2.3,7] + [SI = 245, SFT = 42, RD = 192.0.2.3:7] Looping and jumping are described in Section 6. This example shows an SFP that contains an explicit loop-back instruction that is presented as a choice within an SFP hop. The first two hops in the path (SI = 255 and SI = 250) are normal. That is, the packets will be delivered to SFF1 and SFF4 in turn for execution of SFs of type 41 and 44 respectively. The third hop (SI = 245) presents SFF4 with a choice of next hop. It @@ -1836,26 +1826,26 @@ SFF4 must make a choice between these two next hops. Either the packets will be forwarded to SFF3 with the NSH SI decreased to 245 or looped back to SFF1 with the NSH SI reset to 255. This choice will be made according to local policy, information passed back by the local SFI, and details in the packets' metadata that are used to prevent infinite looping. 8.8. Example Branching in an SFP - SFP10: RD = 198.51.100.1,110, SPI = 24, - [SI = 254, SFT = 42, RD = 192.0.2.3,7], - [SI = 249, SFT = 43, RD = 192.0.2.2,2] + SFP10: RD = 198.51.100.1:110, SPI = 24, + [SI = 254, SFT = 42, RD = 192.0.2.3:7], + [SI = 249, SFT = 43, RD = 192.0.2.2:2] - SFP11: RD = 198.51.100.1,111, SPI = 25, - [SI = 255, SFT = 41, RD = 192.0.2.1,1], + SFP11: RD = 198.51.100.1:111, SPI = 25, + [SI = 255, SFT = 41, RD = 192.0.2.1:1], [SI = 250, SFT = 1, RD = {SPI=24, SI=254, Rsv=0}] Branching follows a similar procedure to that for looping (and jumping) as shown in Section 8.7 however there are two SFPs involved. SFP10 shows a normal path with packets forwarded to SFF3 and SFF2 for execution of service functions of type 42 and 43 respectively. SFP11 starts as normal (SFF1 for an SF of type 41), but then SFF1 processes the next hop in the path and finds a "Change Sequence" @@ -1864,21 +1854,21 @@ so SFF1 knows that it must set the SPI/SI in the NSH to 24/254 and send the packets to the appropriate SFF as advertised in the SFPR for SFP10 (that is, SFF3). 8.9. Examples of SFPs with Stateful Service Functions This section provides some examples to demonstrate establishing SFPs when there is a choice of service functions at a particular hop, and where consistency of choice is required in both directions. The scenarios that give rise to this requirement are discussed in - Section 7.3. + Section 7.2. 8.9.1. Forward and Reverse Choice Made at the SFF Consider the topology shown in Figure 12. There are three SFFs arranged neatly in a line, and the middle one (SFF2) supports three SFIs all of SFT 42. These three instances can be used by SFF2 to load balance so that no one instance is swamped. ------ ------ ------ ------ ------ | SFI | | SFIa | | SFIb | | SFIc | | SFI | @@ -1889,110 +1879,122 @@ ---------- | SFF1 | | SFF2 | | SFF3 | --> | |..|192.0.2.1|...|192.0.2.2|...|192.0.2.3|--> --> |Classifier| --------- --------- --------- | | ---------- Figure 12: Example Where Choice is Made at the SFF This leads to the following SFIRs being advertised. - RD = 192.0.2.1,11, SFT = 41 - RD = 192.0.2.2,11, SFT = 42 (for SFIa) - RD = 192.0.2.2,12, SFT = 42 (for SFIb) - RD = 192.0.2.2,13, SFT = 42 (for SFIc) - RD = 192.0.2.3,11, SFT = 43 + RD = 192.0.2.1:11, SFT = 41 + RD = 192.0.2.2:11, SFT = 42 (for SFIa) + RD = 192.0.2.2:12, SFT = 42 (for SFIb) + RD = 192.0.2.2:13, SFT = 42 (for SFIc) + RD = 192.0.2.3:11, SFT = 43 The controller can create a single forward SFP giving SFF2 the choice of which SFI to use to provide function of SFT 42 as follows. The load-balancing choice between the three available SFIs is assumed to be within the capabilities of the SFF and if the SFs are stateful it is assumed that the SFF knows this and arranges load balancing in a stable, flow-dependent way. - SFP12: RD = 198.51.100.1,112, SPI = 26, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,113, Assoc-SPI = 27, - [SI = 255, SFT = 41, RD = 192.0.2.1,11], - [SI = 254, SFT = 42, {RD = 192.0.2.2,11, - 192.0.2.2,12, - 192.0.2.2,13 }], - [SI = 253, SFT = 43, RD = 192.0.2.3,11] + SFP12: RD = 198.51.100.1:112, SPI = 26, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:113, Assoc-SPI = 27, + [SI = 255, SFT = 41, RD = 192.0.2.1:11], + [SI = 254, SFT = 42, {RD = 192.0.2.2:11, + 192.0.2.2:12, + 192.0.2.2:13 }], + [SI = 253, SFT = 43, RD = 192.0.2.3:11] The reverse SFP in this case may also be created as shown below using association with the forward SFP and giving the load-balancing choice to SFF2. This is safe, even in the case that the SFs of type 42 are stateful because SFF2 is doing the load balancing in both directions and can apply the same algorithm to ensure that packets associated with the same flow use the same SFI regardless of the direction of travel. - SFP13: RD = 198.51.100.1,113, SPI = 27, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,112, Assoc-SPI = 26, - [SI = 255, SFT = 43, RD = 192.0.2.3,11], - [SI = 254, SFT = 42, {RD = 192.0.2.2,11, - 192.0.2.2,12, - 192.0.2.2,13 }], - [SI = 253, SFT = 41, RD = 192.0.2.1,11] + How an SFF knows that an attached SFI is stateful is is out of scope + of this document. It is assumed that this will form part of the + process by which SFIs are registered as local to SFFs. Section 7.2 + provides additional observations about the coordination of the use of + stateful SFIs in the case of bidirecitonal SFPs. + + In general, the problems of load balancing and the selection of the + same SFIs in both directions of a bidirectional SPF can be addressed + by using sufficiently precisely specified SFPs (specifying the exact + SFIs to use) and suitable programming of the Classifiers at each end + of the SFPs to make sure that the matching pair of SFPs are used. + + SFP13: RD = 198.51.100.1:113, SPI = 27, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:112, Assoc-SPI = 26, + [SI = 255, SFT = 43, RD = 192.0.2.3:11], + [SI = 254, SFT = 42, {RD = 192.0.2.2:11, + 192.0.2.2:12, + 192.0.2.2:13 }], + [SI = 253, SFT = 41, RD = 192.0.2.1:11] 8.9.2. Parallel End-to-End SFPs with Shared SFF The mechanism described in Section 8.9.1 might not be desirable because of the functional assumptions it places on SFF2 to be able to load balance with suitable flow identification, stability, and equality in both directions. Instead, it may be desirable to place the responsibility for flow classification in the Classifier and let it determine load balancing with the implied choice of SFIs. Consider the network graph as shown in Figure 12 and with the same set of SFIRs as listed in Section 8.9.1. In this case the controller could specify three forward SFPs with their corresponding associated reverse SFPs. Each bidirectional pair of SFPs uses a different SFI for the SF of type 42. The controller can instruct the Classifier how to place traffic on the three bidirectional SFPs, or can treat them as a group leaving the Classifier responsible for balancing the load. - SFP14: RD = 198.51.100.1,114, SPI = 28, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,117, Assoc-SPI = 31, - [SI = 255, SFT = 41, RD = 192.0.2.1,11], - [SI = 254, SFT = 42, RD = 192.0.2.2,11], - [SI = 253, SFT = 43, RD = 192.0.2.3,11] + SFP14: RD = 198.51.100.1:114, SPI = 28, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:117, Assoc-SPI = 31, + [SI = 255, SFT = 41, RD = 192.0.2.1:11], + [SI = 254, SFT = 42, RD = 192.0.2.2:11], + [SI = 253, SFT = 43, RD = 192.0.2.3:11] - SFP15: RD = 198.51.100.1,115, SPI = 29, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,118, Assoc-SPI = 32, - [SI = 255, SFT = 41, RD = 192.0.2.1,11], - [SI = 254, SFT = 42, RD = 192.0.2.2,12], - [SI = 253, SFT = 43, RD = 192.0.2.3,11] + SFP15: RD = 198.51.100.1:115, SPI = 29, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:118, Assoc-SPI = 32, + [SI = 255, SFT = 41, RD = 192.0.2.1:11], + [SI = 254, SFT = 42, RD = 192.0.2.2:12], + [SI = 253, SFT = 43, RD = 192.0.2.3:11] - SFP16: RD = 198.51.100.1,116, SPI = 30, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,119, Assoc-SPI = 33, - [SI = 255, SFT = 41, RD = 192.0.2.1,11], - [SI = 254, SFT = 42, RD = 192.0.2.2,13], - [SI = 253, SFT = 43, RD = 192.0.2.3,11] + SFP16: RD = 198.51.100.1:116, SPI = 30, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:119, Assoc-SPI = 33, + [SI = 255, SFT = 41, RD = 192.0.2.1:11], + [SI = 254, SFT = 42, RD = 192.0.2.2:13], + [SI = 253, SFT = 43, RD = 192.0.2.3:11] - SFP17: RD = 198.51.100.1,117, SPI = 31, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,114, Assoc-SPI = 28, - [SI = 255, SFT = 43, RD = 192.0.2.3,11], - [SI = 254, SFT = 42, RD = 192.0.2.2,11], - [SI = 253, SFT = 41, RD = 192.0.2.1,11] + SFP17: RD = 198.51.100.1:117, SPI = 31, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:114, Assoc-SPI = 28, + [SI = 255, SFT = 43, RD = 192.0.2.3:11], + [SI = 254, SFT = 42, RD = 192.0.2.2:11], + [SI = 253, SFT = 41, RD = 192.0.2.1:11] - SFP18: RD = 198.51.100.1,118, SPI = 32, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,115, Assoc-SPI = 29, - [SI = 255, SFT = 43, RD = 192.0.2.3,11], - [SI = 254, SFT = 42, RD = 192.0.2.2,12], - [SI = 253, SFT = 41, RD = 192.0.2.1,11] + SFP18: RD = 198.51.100.1:118, SPI = 32, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:115, Assoc-SPI = 29, + [SI = 255, SFT = 43, RD = 192.0.2.3:11], + [SI = 254, SFT = 42, RD = 192.0.2.2:12], + [SI = 253, SFT = 41, RD = 192.0.2.1:11] - SFP19: RD = 198.51.100.1,119, SPI = 33, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,116, Assoc-SPI = 30, - [SI = 255, SFT = 43, RD = 192.0.2.3,11], - [SI = 254, SFT = 42, RD = 192.0.2.2,13], - [SI = 253, SFT = 41, RD = 192.0.2.1,11] + SFP19: RD = 198.51.100.1:119, SPI = 33, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:116, Assoc-SPI = 30, + [SI = 255, SFT = 43, RD = 192.0.2.3:11], + [SI = 254, SFT = 42, RD = 192.0.2.2:13], + [SI = 253, SFT = 41, RD = 192.0.2.1:11] 8.9.3. Parallel End-to-End SFPs with Separate SFFs While the examples in Section 8.9.1 and Section 8.9.2 place the choice of SFI as subtended from the same SFF, it is also possible that the SFIs are each subtended from a different SFF as shown in Figure 13. In this case it is harder to coordinate the choices for forward and reverse paths without some form of coordination between SFF1 and SFF3. Therefore it would be normal to consider end-to-end parallel SFPs as described in Section 8.9.2. @@ -2023,68 +2025,68 @@ | ------ | SFIc | |SFT=42| ------ Figure 13: Second Example With Parallel End-to-End SFPs In this case, five SFIRs are advertised as follows: - RD = 192.0.2.1,11, SFT = 41 - RD = 192.0.2.5,11, SFT = 42 (for SFIa) - RD = 192.0.2.6,11, SFT = 42 (for SFIb) - RD = 192.0.2.7,11, SFT = 42 (for SFIc) - RD = 192.0.2.3,11, SFT = 43 + RD = 192.0.2.1:11, SFT = 41 + RD = 192.0.2.5:11, SFT = 42 (for SFIa) + RD = 192.0.2.6:11, SFT = 42 (for SFIb) + RD = 192.0.2.7:11, SFT = 42 (for SFIc) + RD = 192.0.2.3:11, SFT = 43 In this case the controller could specify three forward SFPs with their corresponding associated reverse SFPs. Each bidirectional pair of SFPs uses a different SFF and SFI for middle hop (for an SF of type 42). The controller can instruct the Classifier how to place traffic on the three bidirectional SFPs, or can treat them as a group leaving the Classifier responsible for balancing the load. - SFP20: RD = 198.51.100.1,120, SPI = 34, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,123, Assoc-SPI = 37, - [SI = 255, SFT = 41, RD = 192.0.2.1,11], - [SI = 254, SFT = 42, RD = 192.0.2.5,11], - [SI = 253, SFT = 43, RD = 192.0.2.3,11] + SFP20: RD = 198.51.100.1:120, SPI = 34, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:123, Assoc-SPI = 37, + [SI = 255, SFT = 41, RD = 192.0.2.1:11], + [SI = 254, SFT = 42, RD = 192.0.2.5:11], + [SI = 253, SFT = 43, RD = 192.0.2.3:11] - SFP21: RD = 198.51.100.1,121, SPI = 35, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,124, Assoc-SPI = 38, - [SI = 255, SFT = 41, RD = 192.0.2.1,11], - [SI = 254, SFT = 42, RD = 192.0.2.6,11], - [SI = 253, SFT = 43, RD = 192.0.2.3,11] + SFP21: RD = 198.51.100.1:121, SPI = 35, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:124, Assoc-SPI = 38, + [SI = 255, SFT = 41, RD = 192.0.2.1:11], + [SI = 254, SFT = 42, RD = 192.0.2.6:11], + [SI = 253, SFT = 43, RD = 192.0.2.3:11] - SFP22: RD = 198.51.100.1,122, SPI = 36, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,125, Assoc-SPI = 39, - [SI = 255, SFT = 41, RD = 192.0.2.1,11], - [SI = 254, SFT = 42, RD = 192.0.2.7,11], - [SI = 253, SFT = 43, RD = 192.0.2.3,11] + SFP22: RD = 198.51.100.1:122, SPI = 36, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:125, Assoc-SPI = 39, + [SI = 255, SFT = 41, RD = 192.0.2.1:11], + [SI = 254, SFT = 42, RD = 192.0.2.7:11], + [SI = 253, SFT = 43, RD = 192.0.2.3:11] - SFP23: RD = 198.51.100.1,123, SPI = 37, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,120, Assoc-SPI = 34, - [SI = 255, SFT = 43, RD = 192.0.2.3,11], - [SI = 254, SFT = 42, RD = 192.0.2.5,11], - [SI = 253, SFT = 41, RD = 192.0.2.1,11] + SFP23: RD = 198.51.100.1:123, SPI = 37, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:120, Assoc-SPI = 34, + [SI = 255, SFT = 43, RD = 192.0.2.3:11], + [SI = 254, SFT = 42, RD = 192.0.2.5:11], + [SI = 253, SFT = 41, RD = 192.0.2.1:11] - SFP24: RD = 198.51.100.1,124, SPI = 38, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,121, Assoc-SPI = 35, - [SI = 255, SFT = 43, RD = 192.0.2.3,11], - [SI = 254, SFT = 42, RD = 192.0.2.6,11], - [SI = 253, SFT = 41, RD = 192.0.2.1,11] + SFP24: RD = 198.51.100.1:124, SPI = 38, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:121, Assoc-SPI = 35, + [SI = 255, SFT = 43, RD = 192.0.2.3:11], + [SI = 254, SFT = 42, RD = 192.0.2.6:11], + [SI = 253, SFT = 41, RD = 192.0.2.1:11] - SFP25: RD = 198.51.100.1,125, SPI = 39, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,122, Assoc-SPI = 36, - [SI = 255, SFT = 43, RD = 192.0.2.3,11], - [SI = 254, SFT = 42, RD = 192.0.2.7,11], - [SI = 253, SFT = 41, RD = 192.0.2.1,11] + SFP25: RD = 198.51.100.1:125, SPI = 39, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:122, Assoc-SPI = 36, + [SI = 255, SFT = 43, RD = 192.0.2.3:11], + [SI = 254, SFT = 42, RD = 192.0.2.7:11], + [SI = 253, SFT = 41, RD = 192.0.2.1:11] 8.9.4. Parallel SFPs Downstream of the Choice The mechanism of parallel SFPs demonstrated in Section 8.9.3 is perfectly functional and may be practical in many environments. However, there may be scaling concerns because of the large amount of state (knowledge of SFPs, i.e., SFPR advertisements retained) if there is a very large amount of choice of SFIs (for example, tens of instances of the same stateful SF), or if there are multiple choices of stateful SF along a path. This situation may be mitigated using @@ -2120,82 +2122,82 @@ | ------ | SFIc | |SFT=43| ------ Figure 14: Example With Parallel SFPs Downstream of Choice The six SFIs are advertised as follows: - RD = 192.0.2.1,11, SFT = 41 - RD = 192.0.2.2,11, SFT = 42 - RD = 192.0.2.5,11, SFT = 43 (for SFIa) - RD = 192.0.2.6,11, SFT = 43 (for SFIb) - RD = 192.0.2.7,11, SFT = 43 (for SFIc) - RD = 192.0.2.3,11, SFT = 44 + RD = 192.0.2.1:11, SFT = 41 + RD = 192.0.2.2:11, SFT = 42 + RD = 192.0.2.5:11, SFT = 43 (for SFIa) + RD = 192.0.2.6:11, SFT = 43 (for SFIb) + RD = 192.0.2.7:11, SFT = 43 (for SFIc) + RD = 192.0.2.3:11, SFT = 44 SFF2 is the point at which a load balancing choice must be made. So "tail-end" SFPs are constructed as follows. Each takes in a different SFF that provides access to an SF of type 43. - SFP26: RD = 198.51.100.1,126, SPI = 40, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,130, Assoc-SPI = 44, - [SI = 255, SFT = 43, RD = 192.0.2.5,11], - [SI = 254, SFT = 44, RD = 192.0.2.3,11] + SFP26: RD = 198.51.100.1:126, SPI = 40, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:130, Assoc-SPI = 44, + [SI = 255, SFT = 43, RD = 192.0.2.5:11], + [SI = 254, SFT = 44, RD = 192.0.2.3:11] - SFP27: RD = 198.51.100.1,127, SPI = 41, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,131, Assoc-SPI = 45, - [SI = 255, SFT = 43, RD = 192.0.2.6,11], - [SI = 254, SFT = 44, RD = 192.0.2.3,11] + SFP27: RD = 198.51.100.1:127, SPI = 41, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:131, Assoc-SPI = 45, + [SI = 255, SFT = 43, RD = 192.0.2.6:11], + [SI = 254, SFT = 44, RD = 192.0.2.3:11] - SFP28: RD = 198.51.100.1,128, SPI = 42, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,132, Assoc-SPI = 46, - [SI = 255, SFT = 43, RD = 192.0.2.7,11], - [SI = 254, SFT = 44, RD = 192.0.2.3,11] + SFP28: RD = 198.51.100.1:128, SPI = 42, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:132, Assoc-SPI = 46, + [SI = 255, SFT = 43, RD = 192.0.2.7:11], + [SI = 254, SFT = 44, RD = 192.0.2.3:11] Now an end-to-end SFP with load balancing choice can be constructed as follows. The choice made by SFF2 is expressed in terms of entering one of the three "tail end" SFPs. - SFP29: RD = 198.51.100.1,129, SPI = 43, - [SI = 255, SFT = 41, RD = 192.0.2.1,11], - [SI = 254, SFT = 42, RD = 192.0.2.2,11], + SFP29: RD = 198.51.100.1:129, SPI = 43, + [SI = 255, SFT = 41, RD = 192.0.2.1:11], + [SI = 254, SFT = 42, RD = 192.0.2.2:11], [SI = 253, {SFT = 1, RD = {SPI=40, SI=255, Rsv=0}, RD = {SPI=41, SI=255, Rsv=0}, RD = {SPI=42, SI=255, Rsv=0} } ] Now, despite the load balancing choice being made other than at the initial classifier, it is possible for the reverse SFPs to be well- constructed without any ambiguity. The three reverse paths appear as follows. - SFP30: RD = 198.51.100.1,130, SPI = 44, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,126, Assoc-SPI = 40, - [SI = 255, SFT = 44, RD = 192.0.2.4,11], - [SI = 254, SFT = 43, RD = 192.0.2.5,11], - [SI = 253, SFT = 42, RD = 192.0.2.2,11], - [SI = 252, SFT = 41, RD = 192.0.2.1,11] + SFP30: RD = 198.51.100.1:130, SPI = 44, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:126, Assoc-SPI = 40, + [SI = 255, SFT = 44, RD = 192.0.2.4:11], + [SI = 254, SFT = 43, RD = 192.0.2.5:11], + [SI = 253, SFT = 42, RD = 192.0.2.2:11], + [SI = 252, SFT = 41, RD = 192.0.2.1:11] - SFP31: RD = 198.51.100.1,131, SPI = 45, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,127, Assoc-SPI = 41, - [SI = 255, SFT = 44, RD = 192.0.2.4,11], - [SI = 254, SFT = 43, RD = 192.0.2.6,11], - [SI = 253, SFT = 42, RD = 192.0.2.2,11], - [SI = 252, SFT = 41, RD = 192.0.2.1,11] + SFP31: RD = 198.51.100.1:131, SPI = 45, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:127, Assoc-SPI = 41, + [SI = 255, SFT = 44, RD = 192.0.2.4:11], + [SI = 254, SFT = 43, RD = 192.0.2.6:11], + [SI = 253, SFT = 42, RD = 192.0.2.2:11], + [SI = 252, SFT = 41, RD = 192.0.2.1:11] - SFP32: RD = 198.51.100.1,132, SPI = 46, - Assoc-Type = 1, Assoc-RD = 198.51.100.1,128, Assoc-SPI = 42, - [SI = 255, SFT = 44, RD = 192.0.2.4,11], - [SI = 254, SFT = 43, RD = 192.0.2.7,11], - [SI = 253, SFT = 42, RD = 192.0.2.2,11], - [SI = 252, SFT = 41, RD = 192.0.2.1,11] + SFP32: RD = 198.51.100.1:132, SPI = 46, + Assoc-Type = 1, Assoc-RD = 198.51.100.1:128, Assoc-SPI = 42, + [SI = 255, SFT = 44, RD = 192.0.2.4:11], + [SI = 254, SFT = 43, RD = 192.0.2.7:11], + [SI = 253, SFT = 42, RD = 192.0.2.2:11], + [SI = 252, SFT = 41, RD = 192.0.2.1:11] 9. Security Considerations This document inherits all the security considerations discussed in the documents that specify BGP, the documents that specify BGP Multiprotocol Extensions, and the documents that define the attributes that are carried by BGP UPDATEs of the SFC AFI/SAFI. For more information look in [RFC4271], [RFC4760], and [I-D.ietf-idr-tunnel-encaps]. @@ -2205,21 +2207,39 @@ are instantiated in software can be subverted. However, this specification does not change the existence of Service Function Chaining and security issues specific to Service Function Chaining are covered in [RFC7665] and [RFC8300]. This document defines a control plane for Service Function Chaining. Clearly, this provides an attack vector for a Service Function Chaining system as an attack on this control plane could be used to make the system misbehave. Thus, the security of the BGP system is critically important to the security of the whole Service Function - Chaining system. + Chaining system. The control plane mechanisms are very similar to + those used for BGP/MPLS IP VPNs as described in [RFC4364], and so the + security considerations in that document (Section 23) provide good + guidance for securing SFC systems reliant on this specification. + Section 19 of [RFC7432] also provides useful guidance on the use of + BGP in a similar environment. + + Note that a component of an SFC system that uses the procedures + described in this document also requires communications between a + controller and the SFC network elements. This communication covers + instructing the Classifiers using BGP mechanisms (see Section 7.4) + which is covered by BGP security. But it also covers other + mechanisms for programming the Classifier and instructing the SFFs + and SFs (for example, to bind SFs to an SFF, and to cause the + estblishment of tunnels between SFFs). This document does not cover + these latter mechanisms and so their security is out of scope, but it + should be noted that these communications provide an attack vector on + the SFC system and so attention must be paid to ensuring that they + are secure. 10. IANA Considerations 10.1. New BGP AF/SAFI IANA maintains a registry of "Address Family Numbers". IANA is requested to assign a new Address Family Number from the "Standards Action" range called "BGP SFC" (TBD1 in this document) with this document as a reference. @@ -2385,23 +2404,24 @@ Email: ar977m@att.com 12. Acknowledgements Thanks to Tony Przygienda, Jeff Haas, and Andy Malis for helpful comments, and to Joel Halpern for discussions that improved this document. Yuanlong Jiang provided a useful review and caught some important issues. Stephane Litkowski did an exceptionally good and detailed document shepherd review. - Andy Malis contributed text that formed the basis of Section 7.8. + Andy Malis contributed text that formed the basis of Section 7.7. 13. References + 13.1. Normative References [I-D.ietf-idr-tunnel-encaps] Rosen, E., Patel, K., and G. Velde, "The BGP Tunnel Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-11 (work in progress), February 2019. [I-D.ietf-mpls-sfc] Farrel, A., Bryant, S., and J. Drake, "An MPLS-Based Forwarding Plane for Service Function Chaining", draft- @@ -2430,20 +2450,25 @@ [RFC4760] Bates, T., Chandra, R., Katz, D., and Y. Rekhter, "Multiprotocol Extensions for BGP-4", RFC 4760, DOI 10.17487/RFC4760, January 2007, . [RFC5575] Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J., and D. McPherson, "Dissemination of Flow Specification Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009, . + [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., + Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based + Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February + 2015, . + [RFC7665] Halpern, J., Ed. and C. Pignataro, Ed., "Service Function Chaining (SFC) Architecture", RFC 7665, DOI 10.17487/RFC7665, October 2015, . [RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 8126, DOI 10.17487/RFC8126, June 2017, . @@ -2451,35 +2476,25 @@ 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, . [RFC8300] Quinn, P., Ed., Elzur, U., Ed., and C. Pignataro, Ed., "Network Service Header (NSH)", RFC 8300, DOI 10.17487/RFC8300, January 2018, . 13.2. Informative References - [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and - L. Yong, "The Use of Entropy Labels in MPLS Forwarding", - RFC 6790, DOI 10.17487/RFC6790, November 2012, - . - [RFC7498] Quinn, P., Ed. and T. Nadeau, Ed., "Problem Statement for Service Function Chaining", RFC 7498, DOI 10.17487/RFC7498, April 2015, . - [RFC7510] Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black, - "Encapsulating MPLS in UDP", RFC 7510, - DOI 10.17487/RFC7510, April 2015, - . - Authors' Addresses Adrian Farrel Old Dog Consulting Email: adrian@olddog.co.uk John Drake Juniper Networks