Generic Delivery Functions
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|Authors||Zhaohui (Jeffrey) Zhang , Ron Bonica , Kireeti Kompella , Greg Mirsky|
|Stream||Stream state||(No stream defined)|
|RFC Editor Note||(None)|
|IESG||IESG state||I-D Exists|
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intarea Z. Zhang Internet-Draft R. Bonica Intended status: Standards Track K. Kompella Expires: October 23, 2021 Juniper Networks G. Mirsky ZTE April 21, 2021 Generic Delivery Functions draft-zzhang-intarea-generic-delivery-functions-01 Abstract Some functionalities (e.g., fragmentation/reassembly and Encapsulating Security Payload) provided by IPv6 can be viewed as delivery functions independent of IPv6 or even IP entirely. This document proposes to provide those functionalities at different layers (e.g., MPLS, BIER or even Ethernet) independent of IP. 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 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 October 23, 2021. Copyright Notice Copyright (c) 2021 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 carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Zhang, et al. Expires October 23, 2021 [Page 1] Internet-Draft Generic Delivery Functions April 2021 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 2. Specifications . . . . . . . . . . . . . . . . . . . . . . . 4 2.1. Generic Delivery Function Header . . . . . . . . . . . . 4 2.2. Generic Fragmentation Header . . . . . . . . . . . . . . 5 2.3. Payload Type Header . . . . . . . . . . . . . . . . . . . 6 2.4. Generic ESP/Authentication Header . . . . . . . . . . . . 6 2.5. GDFH in an MPLS Data Plane . . . . . . . . . . . . . . . 6 3. Security Considerations . . . . . . . . . . . . . . . . . . . 6 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 5. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 5.1. Normative References . . . . . . . . . . . . . . . . . . 6 5.2. Informative References . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction Consider an operator providing Ethernet services such as EVPN. The Ethernet frames that a Provider Edge (PE) device receives from a Customer Edge (CE) device may have a larger size than the PE-PE path MTU (PMTU) in the provider network. This could be because 1. the provider network is built upon virtual connections (e.g., pseudowires) provided by another infrastructure provider, or 2. the customer network uses jumbo frames while the provider network does not, or 3. the provider-side overhead for transporting customer packets across the network pushes past the PMTU. In any case, the provider cannot simply require its customers to change their MTU. To get those large frames across the provider network, currently, the only workaround is to encapsulate the frames in IP (with or without GRE) and then fragment the IP packets. Even if MPLS is used for service delimiting, IP is used for transportation (MPLS over IP/GRE). This may not be desirable in certain deployment scenarios, where MPLS is the preferred transport or IP encapsulation overhead is deemed excessive. Zhang, et al. Expires October 23, 2021 [Page 2] Internet-Draft Generic Delivery Functions April 2021 IPv6 fragmentation and reassembly are based on the IPv6 Fragmentation header below [RFC8200]: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Next Header | Reserved | Fragment Offset |Res|M| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1: IPv6 Fragmentation Header This document proposes adapting this header for use in non-IP contexts since the fragmentation/reassembly function is actually independent of IPv6 except for the following aspects: o The fragment header is identified as such by the "previous" header. o The "Next Header" value is from the "Internet Protocol Numbers" registry. o The "Identification" value is unique in the (source, destination) context provided by the IPv6 header. The "Identification" field, in conjunction with the IPv6 source and destination addresses identifies fragments of the original packet for the purpose of reassembly. Therefore, the fragmentation/reassembly function can be applied at other layers as long as a) the fragment header is identified as such; and b) the context for packet identification is provided. Examples of such layers include MPLS, BIER, and Ethernet (if IEEE determines it is so desired). For the same consideration, the IP Encapsulating Security Payload (ESP) [RFC4303] could also be applied at other layers if ESP is desired there. For example, if for whatever reason the Ethernet service provider wants to provide ESP between its PEs, it could do so without requiring IP encapsulation if ESP is applied at non-IP layers. We refer to these as Generic Delivery Functions (GDFs), which could be achieved at a shim layer between a source and destination delivery points, for example: o Source and destination IP/Ethernet nodes o Ingress and egress nodes of MPLS Label Switch Paths (LSPs) Zhang, et al. Expires October 23, 2021 [Page 3] Internet-Draft Generic Delivery Functions April 2021 o BIER Forwarding Ingress Routers (BFIRs) and BIER Forwarding Egress Routers (BFERs) It is not the intended to apply the GDFs hop by hop between the source and destination delivery points. The possibility of applying some other IP functions (e.g., Authentication Header [RFC4302]) is for further study. 2. Specifications 2.1. Generic Delivery Function Header The following Generic Delivery Function Header (GDFH) is defined: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0| Rsved | Header Length | Next Header | This Header | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ ~ Variable field per "This header" ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: Generic Delivery Function Header 0000 nibble: Prevents the GDFH from being mistaken for an IP header by a router doing deep packet inspection for ECMP hashing purposes. Header Length: The length of header in the number of 4-octet units. Next Header: The type of next header. For functions that IETF is concerned with, the "Next Header" values are from the "Internet Protocol Numbers" registry (e.g., the next header could be a TCP or UDP or MPLS header). The next header could be another GDFH, and a value for GDFH will be assigned by IANA from that registry. This Header: The type of this GDFH header. For example, TBD1 for generic fragmentation, TBD2 for generic ESP. The values are from a space independent of the "Next Header". The outer header MUST identify that a GDFH follows. Encoding "This Header" in the GDFH allows a single outer header encoding to be used for different GDFHs. If the outer header is BIER, a TBD value for the "proto" field in the BIER header identifies that a GDFH follows. If the outer header is MPLS, the label preceding the GDFH indicates that a GDFH follows (see Section 2.5). Zhang, et al. Expires October 23, 2021 [Page 4] Internet-Draft Generic Delivery Functions April 2021 If the outer header is Ethernet (if IEEE would decide to provide the generic delivery functions on top of Ethernet directly), then a new Ethertype would be assigned by IEEE. 2.2. Generic Fragmentation Header For generic fragmentation/reassembly functionality, the GDFH takes the following Generic Fragmentation Header (GFH) format: +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0| Rsved | Header Length | Next Header | TBD1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Fragment Offset |R|S|M| Identification (variable) ~ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Identification | | (continues) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 3: Generic Fragmentation Header The "Fragment Offset" and "M" flag bit fields are as defined for the IPv6 Fragmentation Header in Section 4.5 [RFC8200]. R: The "R" flag bit is reserved. It MUST be set to 0 on transmit and ignored on receive. Identification: at least 4-octet long. // would 2-octet be ok as a minimum? S: If the "S" flag bit is clear, the context for the Identification field is provided by the outer header, and only the source- identifying information in the outer header is used. If the "S" flag bit is set, the variable Identification field encodes both source-identifying information (e.g., the IP address of the node adding the GFH) and an identification number unique within that source. When a GFH is used together with other GDFHs, the GFH SHOULD be the first GDFH. If the outer header is BIER and the "S" flag bit is clear, the "BFIR- id" field in the BIER header provides the context for the "Identification" field. If the outer header is MPLS, the "S" flag bit MAY be clear if the label preceding the GFH identifies the sending node in addition to indicating that a GFH follows (see Section 2.5). Zhang, et al. Expires October 23, 2021 [Page 5] Internet-Draft Generic Delivery Functions April 2021 2.3. Payload Type Header While originally it is not the intention to provide a way to identify the payload type after an MPLS label stack, it has been pointed out that the GFH now provides the payload-identifying functionality as a by-product - even when fragmentation is not needed, a GFH can be inserted, with the Fragmentation Offset, the M-bit and Identification fields set to 0, and the Next Header set appropriately. If the payload-identifying functionality is deemed as desired, a dedicated header type could be assigned for this purpose, with a smaller header compared to GFH. +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0| Rsved |Header Length:1| Next Header | TBD3 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 4: Generic Payload Type Header 2.4. Generic ESP/Authentication Header To be specified in future revisions. 2.5. GDFH in an MPLS Data Plane When GDFH is used in a network with MPLS data plane, the BoS label indicates that a GDFH immediately follows. The label can be either a special purpose label or a regular label signaled via BGP or IGP. The details will be provided in future revisions. 3. Security Considerations To be provided. 4. Acknowledgements The authors thank Stewart Bryant and Tony Przygienda for their valuable comments and suggestions. 5. References 5.1. Normative References [RFC4303] Kent, S., "IP Encapsulating Security Payload (ESP)", RFC 4303, DOI 10.17487/RFC4303, December 2005, <https://www.rfc-editor.org/info/rfc4303>. Zhang, et al. Expires October 23, 2021 [Page 6] Internet-Draft Generic Delivery Functions April 2021 [RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi Topology (MT) Routing in Intermediate System to Intermediate Systems (IS-ISs)", RFC 5120, DOI 10.17487/RFC5120, February 2008, <https://www.rfc-editor.org/info/rfc5120>. [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, DOI 10.17487/RFC5305, October 2008, <https://www.rfc-editor.org/info/rfc5305>. [RFC5308] Hopps, C., "Routing IPv6 with IS-IS", RFC 5308, DOI 10.17487/RFC5308, October 2008, <https://www.rfc-editor.org/info/rfc5308>. [RFC7684] Psenak, P., Gredler, H., Shakir, R., Henderickx, W., Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute Advertisement", RFC 7684, DOI 10.17487/RFC7684, November 2015, <https://www.rfc-editor.org/info/rfc7684>. [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 (IPv6) Specification", STD 86, RFC 8200, DOI 10.17487/RFC8200, July 2017, <https://www.rfc-editor.org/info/rfc8200>. [RFC8362] Lindem, A., Roy, A., Goethals, D., Reddy Vallem, V., and F. Baker, "OSPFv3 Link State Advertisement (LSA) Extensibility", RFC 8362, DOI 10.17487/RFC8362, April 2018, <https://www.rfc-editor.org/info/rfc8362>. 5.2. Informative References [RFC4302] Kent, S., "IP Authentication Header", RFC 4302, DOI 10.17487/RFC4302, December 2005, <https://www.rfc-editor.org/info/rfc4302>. [RFC6514] Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP Encodings and Procedures for Multicast in MPLS/BGP IP VPNs", RFC 6514, DOI 10.17487/RFC6514, February 2012, <https://www.rfc-editor.org/info/rfc6514>. Authors' Addresses Zhaohui Zhang Juniper Networks Email: email@example.com Zhang, et al. Expires October 23, 2021 [Page 7] Internet-Draft Generic Delivery Functions April 2021 Ron Bonica Juniper Networks Email: firstname.lastname@example.org Kireeti Kompella Juniper Networks Email: email@example.com Gregory Mirsky ZTE Email: firstname.lastname@example.org Zhang, et al. Expires October 23, 2021 [Page 8]