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Please use uppercase 'NOT' together with RFC 2119 keywords (if that is what you mean). Found 'SHOULD not' in this paragraph: If the (trailer or header based) IP encapsulation method is used, the First SDU Length (FSL) field SHOULD be included in the GMA trailer (or header) to indicate the length of the first SDU. Otherwise, the FSL field SHOULD not be included. -- The document date (May 14, 2020) is 1437 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 INTAREA/Network Working Group J. Zhu 2 Internet Draft Intel 3 Intended status: Informational S. Kanugovi 4 Expires: November 14,2020 Nokia 5 May 14, 2020 7 Generic Multi-Access (GMA) Encapsulation Protocol 8 draft-zhu-intarea-gma-07 10 Abstract 12 Today, a device can be simultaneously connected to multiple 13 networks, e.g. Wi-Fi, LTE, 5G, and DSL. It is desirable to combine 14 them seamlessly to improve quality of experience. Such 15 optimization requires additional control information, e.g. 16 Sequence Number, in each (IP) data packet. This document presents 17 a new light-weight and flexible encapsulation protocol for this 18 need. The solution has been developed by the authors based on 19 their experiences in multiple standards bodies including the IETF 20 and 3GPP, is not an Internet Standard and does not represent the 21 consensus opinion of the IETF. This document will enable other 22 developers to build interoperable implementations. 24 Status of this Memo 26 This Internet-Draft is submitted in full conformance with the 27 provisions of BCP 78 and BCP 79. 29 Internet-Drafts are working documents of the Internet Engineering 30 Task Force (IETF), its areas, and its working groups. Note that 31 other groups may also distribute working documents as Internet- 32 Drafts. 34 Internet-Drafts are draft documents valid for a maximum of six 35 months and may be updated, replaced, or obsoleted by other 36 documents at any time. It is inappropriate to use Internet-Drafts 37 as reference material or to cite them other than as "work in 38 progress." 40 The list of current Internet-Drafts can be accessed at 41 http://www.ietf.org/ietf/1id-abstracts.txt 43 The list of Internet-Draft Shadow Directories can be accessed at 44 http://www.ietf.org/shadow.html 46 This Internet-Draft will expire on November 14, 2020. 48 Copyright Notice 50 Copyright (c) 2020 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (http://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with 58 respect to this document. Code Components extracted from this 59 document must include Simplified BSD License text as described in 60 Section 4.e of the Trust Legal Provisions and are provided without 61 warranty as described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction ................................................. 2 66 2. Conventions used in this document ............................ 4 67 3. Use Case ..................................................... 4 68 4. GMA Encapsulation Formats .................................... 5 69 5. Fragmentation ................................................ 9 70 6. Concatenation ............................................... 11 71 7. Security Considerations ..................................... 12 72 8. IANA Considerations ......................................... 12 73 9. References .................................................. 12 74 9.1. Normative References ..................................12 75 9.2. Informative References ................................12 77 1. Introduction 79 Figure 1 shows the Multi-Access Management Service (MAMS) user- 80 plane protocol stack [MAMS], which has been used in today's multi- 81 access solutions [ATSSS] [LWIPEP] [GRE]. It consists of two 82 layers: convergence and adaptation. 84 The convergence layer is responsible for multi-access operations, 85 including multi-link (path) aggregation, splitting/reordering, 86 lossless switching/retransmission, fragmentation, concatenation, 87 etc. It operates on top of the adaptation layer in the protocol 88 stack. From the Transmitter perspective, a User Payload (e.g. IP 89 packet) is processed by the convergence layer first, and then by 90 the adaptation layer before being transported over a delivery 91 connection; from the Receiver perspective, an IP packet received 92 over a delivery connection is processed by the adaptation layer 93 first, and then by the convergence layer. 95 +-----------------------------------------------------+ 96 | User Payload, e.g., IP Protocol Data Unit (PDU) | 97 +-----------------------------------------------------+ 98 +-----------------------------------------------------------+ 99 | +-----------------------------------------------------+ | 100 | | Multi-Access (MX) Convergence Layer | | 101 | +-----------------------------------------------------+ | 102 | +-----------------------------------------------------+ | 103 | | MX Adaptation | MX Adaptation | MX Adaptation | | 104 | | Layer | Layer | Layer | | 105 | | (optional) | (optional) | (optional) | | 106 | +-----------------+-----------------+-----------------+ | 107 | | Access #1 IP | Access #2 IP | Access #3 IP | | 108 | +-----------------------------------------------------+ | 109 | MAMS User-Plane Protocol Stack | 110 +-----------------------------------------------------------+ 112 Figure 1: MAMS User-Plane Protocol Stack [MAMS] 114 Today, GRE is used [LWIPEP] [GRE]as the encapsulation protocol at 115 the convergence layer to encode additional control information, 116 e.g. Key, Sequence Number. However, there are two main drawbacks 117 with this approach: 119 o IP-over-IP tunnelling (required for GRE) leads to higher 120 overhead especially for small packet; 121 o It is difficult to introduce new control fields. 123 For example, the overhead of IP-over-IP/GRE tunnelling with both 124 Key and Sequence Number is 32 Bytes (20 Bytes IP header + 12 Bytes 125 GRE header), which is 80% of a 40 Bytes TCP ACK packet; 127 This document presents a light-weight GMA encapsulation protocol 128 for the convergence layer. It supports three encapsulation 129 methods: trailer-based IP encapsulation, header-based IP 130 encapsulation, and non-IP encapsulation. Particularly, the IP 131 encapsulation methods avoid IP-over-IP tunneling overhead (20 132 Bytes), which is 50% of a 40 Bytes TCP ACK packet. Moreover, it 133 introduces new control fields to support fragmentation and 134 concatenation, which are not available in today's GRE-based 135 solutions [LWIPEP] [GRE]. 137 GMA protocol SHALL only operate between endpoints that have been 138 configured to operate with GMA through additional control messages 139 and procedures, for example [MAMS]. Moreover, UDP or IPSec 140 tunneling MAY be used at the adaptation sublayer to protect GMA 141 operation from intermediate nodes. 143 2. Conventions used in this document 145 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL 146 NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", 147 "MAY", and "OPTIONAL" in this document are to be interpreted as 148 described in BCP 14 [RFC2119] [RFC8174] when, and only when, they 149 appear in all capitals, as shown here. 151 3. Use Case 153 Multi-Access Aggregation 155 +---+ +---+ 156 | |A|--- LTE Connection -----|C| | 157 |U|-| |-|S| Internet 158 | |B|--- Wi-Fi Connection ---|D| | 159 +---+ +---+ 160 Client Multi-Access Gateway 162 A: The adaptation layer endpoint of the LTE connection 163 resides in the client 165 B: The adaptation layer endpoint of the Wi-Fi connection 166 resides in the client 168 C: The adaptation layer endpoint of the LTE connection 169 resides in the Multi-Access Gateway, aka N-MADP (Network 170 Multi-Access Data Proxy) in [MAMS] 172 D: The adaptation layer endpoint of the Wi-Fi connection 173 resides in the Multi-Access Gateway 175 U: The convergence layer endpoint resides in the client 177 S: The convergence layer endpoint resides in the Multi- 178 Access Gateway 180 Figure 2: GMA-based Multi-Access Aggregation 182 As shown in Figure 2, a client device (e.g. Smartphone, Laptop, 183 etc.) may connect to Internet via both Wi-Fi and LTE connections, 184 one of which (e.g. LTE) may operate as the anchor connection, and 185 the other (e.g. Wi-Fi) may operate as the delivery connection. The 186 anchor connection provides the IP address and connectivity for 187 end-to-end Internet access, and the delivery connection provides 188 additional path between client and Multi-Access Gateway for multi- 189 access optimizations. 191 For example, per-packet aggregation allows a single IP flow to use 192 the combined bandwidth of the two connections. In another example, 193 packets lost due to temporarily link outage may be retransmitted. 194 Moreover, packets may be duplicated over multiple connections to 195 achieve high reliability and low latency, and duplicated packets 196 should be eliminated by the receiving side. Such multi-access 197 optimization requires additional control information, e.g. 198 Sequence Number, in each IP data packet, which can be supported by 199 the GMA encapsulation protocol described in this document. 201 The GMA protocol in this document is designed for multiple 202 connections, but it may also be used when there is only one 203 connection between two end-points. For example, it may be used for 204 loss detection and recovery. In another example, it may be used to 205 concatenate multiple small packets and reduce per packet overhead. 207 4. GMA Encapsulation Formats 209 The GMA encapsulation protocols support the following three 210 formats: 212 o Trailer-based IP Encapsulation 213 o Header-based IP Encapsulation 214 o Header-based non-IP Encapsulation 216 |<---------------------GMA PDU ----------------------->| 217 +------------------------------------------------------+ 218 | IP hdr | IP payload | GMA Trailer | 219 +------------------------------------------------------+ 220 |<------- GMA SDU (user payload)-------->| 222 Figure 3: Trailer-based IP Encapsulation Format 224 Figure 3 shows the trailer-based encapsulation GMA PDU (protocol 225 data unit) format. A (GMA) PDU may carry one or multiple IP 226 packets, aka (GMA) SDUs (service data unit), in the payload, or a 227 fragment of the SDU. 229 The Protocol Type field in the IP header of the GMA PDU MUST be 230 changed to 114 (Any 0-Hop Protocol) [IANA] to indicate the 231 presence of the GMA trailer. The following three IP header fields 232 SHOULD also be changed: 234 o IP Length: add the length of "GMA Trailer" to the length of 235 the original IP packet 236 o Time To Live (TTL) or Hop-Limit (HL): set the HL field to "0" 237 if the original IP packet is IPv6, and set the TTL field to "1" 238 if the original IP packet is IPv4. 239 o IP checksum: recalculate after changing "Protocol Type", "TTL 240 or HL" and "IP Length" 242 However, if UDP tunnelling is used at the adaptation layer to 243 carry the GMA PDU, the above three IP header fields SHOULD remain 244 unchanged, and the receiver will determine the GMA PDU length 245 based on the UDP packet length. 247 The GMA (Generic Multi-Access) trailer MUST consist of two 248 mandatory fields: Flags and Next Header: 250 o Next Header (1 Byte): the IP protocol type of the (first) SDU 251 in a PDU, and it stores the value before it was overwritten to 252 114. 253 o Flags (2 Bytes): Bit 0 is the most significant bit (MSB), and 254 Bit 15 is the least significant bit (LSB) 255 + Checksum Present (bit 0): If the Checksum Present bit is set 256 to 1, then the Checksum field is present; 257 + Concatenation Present (bit 1): If the Concatenation Present 258 bit is set to 1, then the PDU carries multiple SDUs, and the 259 First SDU Length field is present; 260 + Connection ID Present (bit 2): If the Connection ID Present 261 bit is set to 1, then the Connection ID field is present; 262 + Flow ID Present (bit 3): If the Flow ID Present bit is set 263 to 1, then the Flow ID field is present; 264 + Fragmentation Present (bit 4): If the Fragmentation Present 265 bit is set to 1, then the PDU carry a fragment of the SDU and 266 the Fragmentation Control field is present; 267 + Delivery SN Present (bit 5): If the Delivery SN (Sequence 268 Number) Present bit is set to 1, then the Delivery SN field is 269 present and contains the valid information; 270 + Flow SN Present (bit 6): If the Flow SN Present bit is set 271 to 1, then the Sequence Number field is present; 272 + Timestamp Present (bit 7): If the Timestamp Present bit is 273 set to 1, then the Timestamp field is present; 274 + TTL Present (bit 8): If the TTL Present bit is set to 1, 275 then the TTL field is present; 276 + Reserved (bit 9-12): set to "0" and ignored on receipt; 277 + Version (bit 13~15): GMA version number, set to 0 for the 278 GMA encapsulation protocol specified in this document. 280 The Flags field is at the end of the PDU, and the Next Header 281 field is the second last. The Receiver SHOULD first decode the 282 Flags field to determine the length of the GMA trailer, and then 283 decode each optional field accordingly. The GMA (Generic Multi- 284 Access) trailer MAY consist of the following optional fields: 286 o Checksum (1 Byte): to contain the (one's complement) checksum 287 sum of all the 8 bits in the trailer. For purposes of 288 computing the checksum, the value of the checksum field is 289 zero. This field is present only if the Checksum Present bit 290 is set to one. 291 o First SDU Length (2 Bytes): the length of the first IP packet 292 in the PDU, only included if a PDU contains multiple IP 293 packets. This field is present only if the Concatenation 294 Present bit is set to one. 295 o Connection ID (1 Byte): an unsigned integer to identify the 296 anchor and delivery connection of the GMA PDU. This field is 297 present only if the Connection ID Present bit is set to one. 298 + Anchor Connection ID (MSB 4 Bits): an unsigned integer to 299 identify the anchor connection 300 + Delivery Connection ID (LSB 4 Bits): an unsigned integer to 301 identify the delivery connection 302 o Flow ID (1 Byte): an unsigned integer to identify the IP flow 303 that a PDU belongs to, for example Data Radio Bearer (DRB) ID 304 [LWIPEP] for a cellular (e.g. LTE) connection. This field is 305 present only if the Flow ID Present bit is set to one. 306 o Fragmentation Control (FC) (e.g. 1 Byte): to provide necessary 307 information for re-assembly, only needed if a PDU carries 308 fragments. This field is present only if the Fragmentation 309 Present bit is set to one. Please refer to section 5 for its 310 detailed format and usage. 311 o Delivery SN (1 Byte): an auto-incremented integer to indicate 312 the GMA PDU transmission order on a delivery connection. 313 Delivery SN is needed to measure packet loss of each delivery 314 connection and therefore generated per delivery connection per 315 flow. This field is present only if the Delivery SN Present 316 bit is set to one. 317 o Flow SN (3 Bytes): an auto-incremented integer to indicate the 318 GMA SDU (IP packet) order of a flow. Flow SN is needed for 319 retransmission, reordering, and fragmentation. It SHALL be 320 generated per flow. This field is present only if the Flow SN 321 Present bit is set to one. 322 o Timestamp (4 Bytes): to contain the current value of the 323 timestamp clock of the transmitter in the unit of 1 324 millisecond. This field is present only if the Timestamp 325 Present bit is set to one. 326 o TTL (1 Byte): to contain the TTL value of the original IP 327 header if the GMA SDU is IPv4, or the Hop-Limit value of the 328 IP header if the GMA SDU is IPv6. This field is present only 329 if the TTL Present bit is set to one. 331 Figure 4 shows the GMA trailer format with all the fields present, 332 and the order of the GMA control fields SHALL follow the bit order 333 in the Flags field. For example, Bit 0 (the MSB) of the Flags 334 field is the Checksum Present bit, and the Checksum field is the 335 last in the trailer except of the two mandatory fields. Bit 1 is 336 the Concatenation present bit, and the FSL field is the second 337 last. 339 The trailer-based IP encapsulation method SHOULD be used as long 340 as implementation allows. However, if the GMA control fields can't 341 be added at the end due to any reason, e.g. implementation 342 constraints, one may use the header-based encapsulation. 344 0 1 2 3 345 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 1 346 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 347 | TTL | Timestamp 348 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 349 | Flow SN | 350 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 351 | Delivery SN | FC | Flow ID | Connection ID | 352 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 353 | First SDU Length (FSL) | Checksum | Next Header | 354 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 355 | Flags | 356 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 358 Figure 4: GMA Trailer Format 360 +-----------------------------------------------------+ 361 |GMA Header | IP hdr | IP payload | 362 +-----------------------------------------------------+ 363 Figure 5: Header-based Non-IP Encapsulation Format 365 Figure 5 shows the header-based non-IP encapsulation format, and 366 Figure 6 shows the GMA header format. Herein, "Flags" is moved to 367 the front. Moreover, "TTL", "FSL", and "Next Header" are removed 368 from the GMA control fields since the IP header fields of the GMA 369 SDU remain unchanged during encapsulation. The order of other GMA 370 control fields is the same as shown in Figure 4. 372 +--------------------------------------------------+ 373 | Flags | GMA control fields | 374 +--------------------------------------------------+ 375 Figure 6: GMA Header Format 377 If the adaptation layer, e.g. UDP tunnelling, supports non-IP 378 packet format, the GMA PDU format as shown in Figure 5 SHOULD be 379 used without any modification. 381 If the adaptation layer only supports IP packet format, the 382 header-based IP encapsulation method MAY be used, and Figure 7 383 shows its format. Herein, the IP header of the GMA SDU is moved to 384 the front so that the GMA PDU becomes an IP packet, and the IP 385 header fields of the GMA PDU SHOULD be changed in the same way as 386 the trailered-based IP encapsulation method. 388 +-----------------------------------------------------+ 389 |IP hdr | GMA Header | IP payload | 390 +-----------------------------------------------------+ 391 Figure 7: Header-based IP Encapsulation Format 393 If the non-IP encapsulation method is configured, the GMA header 394 SHOULD always be present. In comparison, the (header or trailer 395 based) IP encapsulation (Figure 3 and 7) method may be used 396 dynamically on per-packet basis, and setting the protocol type of 397 the GMA PDU to "114" indicates the presence of GMA header (or 398 trailer) in an IP packet. 400 The GMA endpoints SHOULD configure the encapsulation method 401 through control signalling or pre-configuration. For example, the 402 "MX UP Setup Configuration Request" message as specified in Multi- 403 Access Management Service[MAMS] includes "MX Convergence Method 404 Parameters", which provides the list of parameters to configure 405 the convergence layer. Here, a new "GMA encapsulation format" 406 parameter SHOULD be included to indicate one of the following 407 three GMA encapsulation formats: 409 o Trailer-based IP Encapsulation (Figure 3) 410 o Header-based non-IP Encapsulation (Figure 5) 411 o Header-based IP Encapsulation (Figure 7) 413 5. Fragmentation 415 The convergence layer MAY support fragmentation if a delivery 416 connection has a smaller maximum transmission unit (MTU) than the 417 original IP packet (SDU). The fragmentation procedure at the 418 convergence sublayer is similar to IP fragmentation [RFC791] in 419 principle, but with the following two differences for less 420 overhead: 422 o The fragment offset field is expressed in number of fragments 423 o The maximum number of fragments per SDU is 2^7 (=128) 425 The Fragmentation Control (FC) field in the GMA trailer (or 426 header) contains the following bits: 428 o Bit #7: a More Fragment (MF) flag to indicate if the fragment 429 is the last one (0) or not (1) 430 o Bit #0~#6: Fragment Offset (in units of fragments) to specify 431 the offset of a particular fragment relative to the beginning 432 of the SDU 434 A PDU carries a whole SDU without fragmentation if the FC field is 435 set to all "0"s or the FC field is not present in the trailer. 436 Otherwise, the PDU contains a fragment of the SDU. 438 The Flow SN field in the trailer is used to distinguish the 439 fragments of one SDU from those of another. The Fragment Offset 440 (FO) field tells the receiver the position of a fragment in the 441 original SDU. The More Fragment (MF) flag indicates the last 442 fragment. 444 To fragment a long SDU, the transmitter creates n PDUs and copies 445 the content of the IP header fields from the long PDU into the IP 446 header of all the PDUs. The length field in the IP header of PDU 447 SHOULD be changed to the length of the PDU, and the protocol type 448 SHOULD be changed to 114. 450 The data of the long SDU is divided into n portions based on the 451 MTU size of the delivery connection. The first portion of the data 452 is placed in the first PDU. The MF flag is set to "1", and the FO 453 field is set to "0". The i-th portion of the data is placed in the 454 i-th PDU. The MF flag is set to "0" if it is the last fragment and 455 set to "1" otherwise. The FO field is set to i-1. 457 To assemble the fragments of a SDU, the receiver combines PDUs 458 that all have the same Flow SN. The combination is done by placing 459 the data portion of each fragment in the relative order indicated 460 by the Fragment Offset in that fragment's GMA trailer (or 461 trailer). The first fragment will have the Fragment Offset set to 462 "0", and the last fragment will have the More-Fragments flag set 463 to "0". 465 6. Concatenation 467 The convergence sublayer MAY support concatenation if a delivery 468 connection has a larger maximum transmission unit (MTU) than the 469 original IP packet (SDU). Only the SDUs with the same client IP 470 address, and the same Flow ID MAY be concatenated. 472 If the (trailer or header based) IP encapsulation method is used, 473 the First SDU Length (FSL) field SHOULD be included in the GMA 474 trailer (or header) to indicate the length of the first SDU. 475 Otherwise, the FSL field SHOULD not be included. 477 +-----------------------------------------------------------+ 478 |IP hdr| IP payload |IP hdr| IP payload | GMA Trailer | 479 +-----------------------------------------------------------+ 480 Figure 8: Example of GMA PDU Format with Concatenation and 481 Trailer-based IP Encapsulation 483 To concatenate two or more SDUs, the transmitter creates one PDU 484 and copies the content of the IP header field from the first SDU 485 into the IP header of the PDU. The data of the first SDU is placed 486 in the first portion of the data of the PDU. The whole second SDU 487 is then placed in the second portion of the data of the PDU 488 (Figure 8). The procedure continues till the PDU size reaches the 489 MTU of the delivery connection. If the FSL field is present, the 490 IP length field of the PDU SHOULD be updated to include all 491 concatenated SDUs and the trailer (or header), and the IP checksum 492 field SHOULD be recalculated. However, if the non-IP encapsulation 493 method is used, both the IP Length field and the checksum field of 494 the PDU SHOULD remain unchanged, and the receiver will determine 495 the GMA PDU length based on the UDP packet length. 497 To disaggregate a PDU, if the (header or trailer based) IP 498 encapsulation method is used, the receiver first obtains the 499 length of the first SDU from the FSL field and decodes the first 500 SDU. The receiver then obtains the length of the second SDU based 501 on the length field in the second SDU IP header and decodes the 502 second SDU. The procedure continues till no byte is left in the 503 PDU. If the non-IP encapsulation method (Figure 5) is used, the IP 504 header of the first SDU will not change during the encapsulation 505 process, and the receiver obtains the length of the first SDU 506 directly from its IP header. 508 If a PDU contains multiple SDUs, the Flow SN field is for the last 509 SDU, and the Flow SN of other SDU carried by the same PDU can be 510 obtained according to its order in the PDU. For example, if the SN 511 field is 6 and a PDU contains 3 SDUs (IP packets), the SN is 4, 5, 512 and 6 for the first, second, and last SDU respectively. 514 7. Security Considerations 516 Security in a network using GMA should be relatively similar to 517 security in a normal IP network. The GMA protocol at the 518 convergence sublayer is a 0-hop protocol and relies on the 519 security of the underlying network transport paths. When this 520 cannot be assumed, appropriate security protocols (IPsec, DTLS, 521 etc.) SHOULD be configured at the adaptation sublayer. On the 522 other hand, packet filtering requires either that a firewall looks 523 inside the GMA packet or that the filtering is done on the GMA 524 endpoints. In those environments in which this is considered to be 525 a security issue it may be desirable to terminate the GMA 526 operation at the firewall. 528 Local-only packet leak prevention (HL=0, TTL=1) SHOULD be on 529 preventing the leak of the local-only GMA PDUs outside the "local 530 domain" to the Internet or to another domain which could use the 531 same IP protocol type, i.e. 114. 533 8. IANA Considerations 535 This draft makes no requests of IANA 537 9. References 539 9.1. Normative References 541 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 542 Requirement Levels", BCP 14, RFC 2119, DOI 543 10.17487/RFC2119, March 1997, . 546 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 547 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174 548 May 2017, . 550 9.2. Informative References 552 [MAMS] S. Kanugovi, F. Baboescu, J. Zhu, and S. Seo "Multi-Access 553 Management Services 554 (MAMS)https://tools.ietf.org/rfc/rfc8743.txt 556 [IANA] https://www.iana.org/assignments/protocol- 557 numbers/protocol-numbers.xhtml 559 [LWIPEP] 3GPP TS 36.361, "Evolved Universal Terrestrial Radio 560 Access (E-UTRA); LTE-WLAN Radio Level Integration Using 561 Ipsec Tunnel (LWIP) encapsulation; Protocol 562 specification" 564 [RFC791] Internet Protocol, September 1981 566 [ATSSS] 3GPP TR 23.793, Study on access traffic steering, switch 567 and splitting support in the 5G system architecture. 569 [GRE] RFC 8157, Huawei's GRE Tunnel Bonding Protocol, May 2017 571 Authors' Addresses 573 Jing Zhu 575 Intel 577 Email: jing.z.zhu@intel.com 579 Satish Kanugovi 581 Nokia 583 Email: satish.k@nokia.com