Internet Engineering Task Force V. Govindan Internet-Draft Cisco Intended status: Experimental 21 February 2021 Expires: 25 August 2021 PIM Join/ Prune Attributes for LISP Environments using Underlay Multicast draft-vgovindan-pim-jp-extensions-lisp-00 Abstract This document specifies an extension to PIM Join/ Prune messages. This document defines one PIM Join/ Prune attribute that support the construction of multicast distribution trees where the root and receivers are located in different Locator/ID Separation Protocol (LISP) sites using underlay IP Multicast. This attribute allows the receiver site to signal the underlay multicast group to the control plane of the root ITR (Ingress Tunnel Router). 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 25 August 2021. Copyright Notice Copyright (c) 2021 IETF Trust and the persons identified as the document authors. All rights reserved. Govindan Expires 25 August 2021 [Page 1] Internet-Draft PIM Join Attributes for LISP Mcast February 2021 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 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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 2. The case for requiring a new PIM Join/ Prune Extension . . . 3 3. Receiver ETR Group Address Attribute . . . . . . . . . . . . 3 3.1. Receiver Group Address Attribute Format . . . . . . . . . 3 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4 5. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 4 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 8. Normative References . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 1. Introduction The construction of multicast distribution trees where the root and receivers are located in different LISP sites [RFC6830] is defined in [RFC6831]. [RFC6831] specifies that (root-EID,G) data packets are to be LISP- encapsulated into (root-RLOC,G) multicast packets. This document defines a TLV that facilitates the construction of trees for (root- RLOC, G). Specifically, the assignment of the underlay multicast group needs to be done in consonance with the downstream xTR nodes and avoid unnecessary replication or traffic hairpinning. Since the Receiver RLOC Attribute TLV defined in [RFC8059] only addresses the Ingress Replication case, an additional TLV is defined by this draft to include scenarios where the underlay uses Multicast transport. The TLV definition proposed here complies with the base specification [RFC5384]. This document uses terminology defined in [RFC6830], such as EID, RLOC, ITR, and ETR. Govindan Expires 25 August 2021 [Page 2] Internet-Draft PIM Join Attributes for LISP Mcast February 2021 1.1. 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]. 2. The case for requiring a new PIM Join/ Prune Extension When LISP based Multicast trees are built using IP Multicast in the underlay, the mapping between the overlay group address and the underlay group address becomes a very crucial. It is possible that under certain circumstances, differnt subsets of xTRs subscribing to the same overlay multicast stream would be constrained to use different underlay multicast mapping ranges. This definitely involves a trade-off between replication and the flexibility in assigning address ranges and could be required in certain situations as below: Inter-site PxTR: When multiple LISP sites are connected through a LISP based transit, the site border node interconnects the site-facing interfaces and the external LISP based core. Under such circumstances, there could be different ranges of multicast group addresses used for building the (S-RLOC, G) trees inside the LISP site and the external LISP based core. This is desired for various reasons: Other Use-cases: TBD Editorial Note: Comments from Stig: There should be some text indicating that the group address used should ideally only be used for LISP encapsulation (if ASM), and perhaps that it is preferrable to use an SSM group. Also, that the group obviously must be a group that the underlay supports/allows. I think it is also worth noting that ideally, different ETRs should request the same group. 3. Receiver ETR Group Address Attribute 3.1. Receiver Group Address Attribute Format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |F|E|Type=TBD | Length | Addr Family | Receiver Group +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-... Govindan Expires 25 August 2021 [Page 3] Internet-Draft PIM Join Attributes for LISP Mcast February 2021 Figure 1 F-bit: The Transitive bit. Specifies whether this attribute is transitive or non-transitive. MUST be set to zero. This attribute is ALWAYS non-transitive. E-bit: End-of-Attributes bit. Specifies whether this attribute is the last. Set to zero if there are more attributes. Set to 1 if this is the last attribute. Type: The Receiver Group Attribute type is TBD. Length: The length in octets of the attribute value. MUST be set to the length in octets of the receiver group address plus one octet to account for the Address Family field. Addr Family: The PIM Address Family of the receiver group as defined in [RFC7761]. Receiver Group: The Multicast Group address on which the receiver ETR wishes to receive the IP multicast encapsulated flow. 4. Acknowledgements The authors would like to thank Stig Venaas for his valuable comments. 5. Contributors Sankaralingam Cisco Email: sankt@cisco.com Amit Kumar Cisco Email: kumaram3@cisco.com Govindan Expires 25 August 2021 [Page 4] Internet-Draft PIM Join Attributes for LISP Mcast February 2021 6. IANA Considerations This memo includes the following request to IANA: One new PIM Join/ Prune attribute types have been requested: value TBD for the Receiver Group Attribute. 7. Security Considerations There is perhaps a new attack vector where an attacker can send a bunch of joins with different group addresses. It may interfere with other multicast traffic if those group addresses overlap. Also, it may take up a lot of resources if replication for thousands of groups are requested. However PIM authentication (?) should come to the rescue here. TBD Since explicit tracking would be done, perhaps it is worth enforcing that for each ETR RLOC (the RLOC used as the source of the overlay join), there should be only one group, whatever is in the last join would override what was there earlier? Or is it to strict to only allow a single group? Might there be reasons to maybe split different LISP payload into different groups in some cases. TBD. Ed Note: To be addressed - Comments from Stig: Regarding security considerations and PIM authentication. The only solution we have here is to use IP-Sec to sign the J/P messages. I don't know if anyone has tried to us IPSec between LISP RLOCs. Are there any LISP security mechanisms that would help here for authenticating LISP encapsulated messages between xTRs? 8. Normative References [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 1997, . [RFC5384] Boers, A., Wijnands, I., and E. Rosen, "The Protocol Independent Multicast (PIM) Join Attribute Format", RFC 5384, DOI 10.17487/RFC5384, November 2008, . [RFC6830] Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The Locator/ID Separation Protocol (LISP)", RFC 6830, DOI 10.17487/RFC6830, January 2013, . Govindan Expires 25 August 2021 [Page 5] Internet-Draft PIM Join Attributes for LISP Mcast February 2021 [RFC6831] Farinacci, D., Meyer, D., Zwiebel, J., and S. Venaas, "The Locator/ID Separation Protocol (LISP) for Multicast Environments", RFC 6831, DOI 10.17487/RFC6831, January 2013, . [RFC7761] Fenner, B., Handley, M., Holbrook, H., Kouvelas, I., Parekh, R., Zhang, Z., and L. Zheng, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification (Revised)", STD 83, RFC 7761, DOI 10.17487/RFC7761, March 2016, . [RFC8059] Arango, J., Venaas, S., Kouvelas, I., and D. Farinacci, "PIM Join Attributes for Locator/ID Separation Protocol (LISP) Environments", RFC 8059, DOI 10.17487/RFC8059, January 2017, . Author's Address Vengada Prasad Govindan Cisco Email: venggovi@cisco.com Govindan Expires 25 August 2021 [Page 6]