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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 BESS Workgroup J. Rabadan, Ed. 3 Internet Draft S. Sathappan 4 K. Nagaraj 5 Intended status: Standards Track Nokia 7 W. Lin 8 Juniper 10 Expires: October 27, 2019 April 25, 2019 12 Propagation of ARP/ND Flags in EVPN 13 draft-ietf-bess-evpn-na-flags-03 15 Abstract 17 An EVPN MAC/IP Advertisement route can optionally carry an IPv4 or 18 IPv6 addresses associated with a MAC address. Remote PEs can use this 19 information to reply locally (act as proxy) to IPv4 ARP requests and 20 IPv6 Neighbor Solicitation messages and reduce/suppress the flooding 21 produced by the Address Resolution procedure. The information 22 conveyed in the MAC/IP route may not be enough for the remote PE to 23 reply to local ARP or ND requests. For example, if a PE learns an 24 IPv6->MAC ND entry via EVPN, the PE would not know if that particular 25 IPv6->MAC pair belongs to a host, a router or a host with an anycast 26 address, as this information is not carried in the MAC/IP route 27 advertisements. Similarly, other information relevant to the IP->MAC 28 ARP/ND entries may be needed. This document proposes an OPTIONAL 29 extended community that is advertised along with an EVPN MAC/IP 30 Advertisement route and carries information relevant to the ARP/ND 31 resolution, so that an EVPN PE implementing a proxy-ARP/ND function 32 can reply to ARP Requests or Neighbor Solicitations with the correct 33 information. 35 Status of this Memo 37 This Internet-Draft is submitted in full conformance with the 38 provisions of BCP 78 and BCP 79. 40 Internet-Drafts are working documents of the Internet Engineering 41 Task Force (IETF), its areas, and its working groups. Note that 42 other groups may also distribute working documents as Internet- 43 Drafts. 45 Internet-Drafts are draft documents valid for a maximum of six months 46 and may be updated, replaced, or obsoleted by other documents at any 47 time. It is inappropriate to use Internet-Drafts as reference 48 material or to cite them other than as "work in progress." 50 The list of current Internet-Drafts can be accessed at 51 http://www.ietf.org/ietf/1id-abstracts.txt 53 The list of Internet-Draft Shadow Directories can be accessed at 54 http://www.ietf.org/shadow.html 56 This Internet-Draft will expire on October 27, 2019. 58 Copyright Notice 60 Copyright (c) 2019 IETF Trust and the persons identified as the 61 document authors. All rights reserved. 63 This document is subject to BCP 78 and the IETF Trust's Legal 64 Provisions Relating to IETF Documents 65 (http://trustee.ietf.org/license-info) in effect on the date of 66 publication of this document. Please review these documents 67 carefully, as they describe your rights and restrictions with respect 68 to this document. Code Components extracted from this document must 69 include Simplified BSD License text as described in Section 4.e of 70 the Trust Legal Provisions and are provided without warranty as 71 described in the Simplified BSD License. 73 Table of Contents 75 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 76 1.1 Terminology and Conventions . . . . . . . . . . . . . . . . 3 77 2. The EVPN ARP/ND Extended Community . . . . . . . . . . . . . . 4 78 3. Use of the EVPN ARP/ND Extended Community . . . . . . . . . . . 5 79 4. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 80 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 81 6. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 82 6.1. Normative References . . . . . . . . . . . . . . . . . . . 7 83 6.2. Informative References . . . . . . . . . . . . . . . . . . 7 84 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . 7 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8 87 1. Introduction 89 An EVPN MAC/IP Advertisement route can optionally carry an IPv4 or 90 IPv6 addresses associated with a MAC address. Remote PEs can use this 91 information to reply locally (act as proxy) to IPv4 ARP requests and 92 IPv6 Neighbor Solicitation messages and reduce/suppress the flooding 93 produced by the Address Resolution procedure. The information 94 conveyed in the MAC/IP route may not be enough for the remote PE to 95 reply to local ARP or ND requests. For example, if a PE learns an 96 IPv6->MAC ND entry via EVPN, the PE would not know if that particular 97 IPv6->MAC pair belongs to a host, a router or a host with an anycast 98 address, as this information is not carried in the MAC/IP route 99 advertisements. Similarly, other information relevant to the host 100 advertised in the MAC/IP Advertisement route may be needed. 102 This document proposes an OPTIONAL extended community that is 103 advertised along with an EVPN MAC/IP Advertisement route and carries 104 information relevant to the ARP/ND resolution, so that an EVPN PE 105 implementing a proxy-ARP/ND function can reply to ARP Requests or 106 Neighbor Solicitations with the correct information. In particular, 107 the Flags defined in [RFC4861] can now be conveyed along with a 108 MAC/IP Advertisement route, so that an egress EVPN PE can issue 109 Neighbor Advertisement messages with the correct Flag information. 111 The Flags are carried in the EVPN Address Resolution Protocol (ARP) 112 and Neighbor Discovery (ND) Extended Community, as described in the 113 following sections. 115 1.1 Terminology and Conventions 117 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 118 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 119 "OPTIONAL" in this document are to be interpreted as described in BCP 120 14 [RFC2119] [RFC8174] when, and only when, they appear in all 121 capitals, as shown here. 123 EVPN: Ethernet Virtual Private Networks, as in [RFC7432]. 125 BD: Broadcast Domain, also described in [RFC7432]. 127 IP->MAC: refers to an IP address and MAC address combination that 128 represents a given host and is added to an Address Resolution 129 Protocol table or Neighbor Discovery table. This document uses IP- 130 >MAC generically for IPv4 and IPv6 addresses. When something is 131 specific to IPv4, the document will use IPv4->MAC and likewise, IPv6- 132 >MAC will be used when something is specific to IPv6 entries only. 134 Proxy-ARP/ND: refers to a function on the EVPN PEs by which received 135 Address Resolution Protocol (ARP) Requests or Neighbor Discovery (ND) 136 - or Neighbor Solicitation (NS) - messages are replied locally by the 137 PE, without the need to flood the requests to remote PEs in the BD. 138 In order to reply to ARP Requests or NS messages, the PE does a 139 lookup on an ARP/ND table, that is a collection of IP->MAC entries 140 learned by the PE. 142 Familiarity with the terminology in [RFC7432] and [RFC4861] is 143 expected. 145 2. The EVPN ARP/ND Extended Community 147 This document defines a new EVPN Extended Community with a Type field 148 value of 0x06 and a Sub-Type 0x08, as allocated by IANA. It MAY be 149 advertised along with EVPN MAC/IP Advertisement routes that carry an 150 IPv4 or IPv6 address. 152 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 1 153 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 154 | Type=0x06 | Sub-Type= TBD |Flags (1 octet)| Reserved=0 | 155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 | Reserved=0 | 157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 159 Flags field: 161 0 1 2 3 4 5 6 7 162 +-+-+-+-+-+-+-+-+ 163 | |I| |O|R| 164 +-+-+-+-+-+-+-+-+ 166 The following Flags are defined in the Flags field, third octet of 167 the Extended Community: 169 R - Router Flag (corresponds to Bit 23 of the extended community) 171 Bit 7 of the Flags octet is defined as the "Router flag". When set, 172 the R-bit indicates that the IPv6->MAC pair advertised in the MAC/IP 173 Advertisement route along with the extended community belongs to a 174 router. If the R-bit is zero, the IPv6->MAC pair belongs to a "host". 175 The receiving PE implementing the ND function will use this 176 information in Neighbor Advertisement messages for the associated 177 IPv6 address. This flag is ignored when the extended community is 178 advertised with a MAC/IP route for an IPv4->MAC pair. 180 O - Override Flag (corresponds to Bit 22 of the extended community) 181 Bit 6 of the Flags octet is defined as the "Override flag". An egress 182 PE will normally advertise IPv6->MAC pairs with the O-bit set, and 183 only when IPv6 "anycast" is enabled in the BD, the PE will send an 184 IPv6->MAC pair with the O-bit = 0. The ingress PE will install the ND 185 entry with the received O-bit and will use this information when 186 replying to a Neighbor Solicitation for the IPv6 address. This flag 187 is ignored when the extended community is advertised with a MAC/IP 188 route for an IPv4->MAC pair. 190 I - Immutable ARP/ND Binding Flag (corresponds to Bit 20 of the 191 extended community) 193 Bit 4 of the Flags octet is defined as the "Immutable ARP/ND binding 194 flag". When set, the egress PE indicates that the IP->MAC pair sent 195 in a MAC/IP route along with the extended community is a configured 196 ARP/ND entry, and the IP address in the MAC/IP route can only be 197 bound together with the MAC address specified in the same route. 199 Bits 0-3 and 5 are not assigned by this document. 201 3. Use of the EVPN ARP/ND Extended Community 203 An EVPN PE supporting a ND/ARP function and implementing the 204 propagation of the ARP/ND Flags will follow this procedure: 206 a) Transmission of the EVPN ARP/ND Extended Community 208 A PE may learn the IPv6->MAC pair and its associated ND Flags in the 209 management plane or snooping Neighbor Advertisement messages coming 210 from the CE. Either way, the PE SHOULD send a MAC/IP Advertisement 211 route including the learned IPv6->MAC pair and MAY send the ARP/ND 212 Extended Community carrying its associated "R" and "O" Flags. 214 If an IPv4->MAC or IPv6->MAC pair has been learned in the management 215 plane (it has been configured) the corresponding MAC/IP Advertisement 216 route SHOULD be sent along with an ARP/ND extended community with the 217 flag I set. 219 This Extended Community does not have any impact on the rest of the 220 procedures described in [RFC7432], including the advertisement of the 221 MAC Mobility Extended Community along with the MAC/IP Advertisement 222 route. 224 b) Reception of the EVPN ARP/ND Extended Community 226 In addition to the procedures specified in [RFC7432] a PE receiving a 227 MAC/IP Advertisement route containing an IPv6 address and the ND 228 Extended Community SHOULD add the R and O Flags to the ND entry for 229 the IPv6->MAC entry and use that information in Neighbor 230 Advertisements when replying to a Solicitation for the IPv6 address. 232 A PE that implements a proxy-ND function SHOULD have an 233 administrative option to define the default Flag to be used in case 234 no EVPN ND Extended Community is received for a given IPv6->MAC 235 entry. A PE MUST ignore the received R and O Flags for a MAC/IP route 236 that contains an IPv4 address. 238 A PE receiving a MAC/IP Advertisement route containing an IPv4 or 239 IPv6 address and the I flag set, SHOULD install the IP->MAC entry in 240 the ARP/ND table as "Immutable binding" entry. 242 In a situation where a host (with a IP->MAC configured as Immutable 243 binding) is allowed to move between PEs (that is, the associated MAC 244 is non-static), PEs can receive multiple MAC/IP advertisement routes 245 for the same IP->MAC. In such situations, MAC mobility procedures 246 dictate the reachability of the MAC. Receiving multiple MAC/IP routes 247 with I=1 for the same IP but different MAC is considered a 248 misconfiguration. 250 For example, consider PE1, PE2 and PE3 are attached to the same BD. 251 PE1 originates a MAC/IP route for IP1->MAC1 with I=1; later on, PE2 252 also originates a MAC/IP route IP1->MAC1 with a higher sequence 253 number and I=1. Then all the EVPN PEs attached to the same BD SHOULD 254 retain their IP1->MAC1 ARP/ND binding but update MAC1's forwarding 255 destination to PE2. If for some reason, PE3 originates a MAC/IP route 256 for IP1->MAC2 (even with a higher sequence number), then the EVPN PEs 257 in the BD SHOULD NOT update their IP1->MAC1 ARP/ND bindings, since 258 IP1 is bound to MAC1 (MAC2 SHOULD still be programmed in the layer-2 259 BDs). This is considered a misconfiguration in PE3. 261 A PE originating a MAC/IP route for IP1->MAC1 with I=1 may also 262 originate the route with the Static bit set (in the MAC Mobility 263 extended community). In such a case, the IP1->MAC1 binding is not 264 only immutable but it cannot move as well. 266 The flags SHOULD be ignored if they are advertised along with a 267 MAC/IP Advertisement route that does not contain an IP address. 269 4. Security Considerations 271 The same security considerations described in [RFC7432] apply to this 272 document. 274 5. IANA Considerations 275 This document requests the registration of a new EVPN Extended 276 Community sub-type: 278 Sub-Type Name Reference 280 0x08 ARP/ND Extended Community [this document] 282 This document also requests the creation of a registry called "ARP/ND 283 Extended Community Flags octet" where the following allocations are 284 made: 286 Flag position Name Reference 288 0-3 Unassigned 289 4 Immutable ARP/ND Binding Flag (I) [this document] 290 5 Unassigned 291 6 Override Flag (O) [this document] 292 7 Router Flag (R) [this document] 294 6. References 296 6.1. Normative References 298 [RFC4861] Narten, T., Nordmark, E., Simpson, W., and H. Soliman, 299 "Neighbor Discovery for IP version 6 (IPv6)", RFC 4861, DOI 300 10.17487/RFC4861, September 2007, . 303 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 304 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet 305 VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, 306 . 308 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 309 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, March 310 1997, . 312 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC2119 313 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 2017, 314 . 316 6.2. Informative References 318 7. Acknowledgments 319 Authors' Addresses 321 Jorge Rabadan (Editor) 322 Nokia 323 777 E. Middlefield Road 324 Mountain View, CA 94043 USA 325 Email: jorge.rabadan@nokia.com 327 Senthil Sathappan 328 Nokia 329 701 E. Middlefield Road 330 Mountain View, CA 94043 USA 331 Email: senthil.sathappan@nokia.com 333 Kiran Nagaraj 334 Nokia 335 701 E. Middlefield Road 336 Mountain View, CA 94043 USA 337 Email: kiran.nagaraj@nokia.com 339 Wen Lin 340 Juniper Networks 341 Email: wlin@juniper.net