papers/draft-gsenger-secure-anycast-tunneling-protocol-02.html

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 143 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 144 <table summary="layout" width="66%" border="0" cellpadding="0" cellspacing="0"><tr><td><table summary="layout" width="100%" border="0" cellpadding="2" cellspacing="1">
 145 <tr><td class="header">Network Working Group</td><td class="header">O. Gsenger</td></tr>
 146 <tr><td class="header">Internet-Draft</td><td class="header">May 6, 2008</td></tr>
 147 <tr><td class="header">Expires: November 7, 2008</td><td class="header">&nbsp;</td></tr>
 148 </table></td></tr></table>
 149 <h1><br />secure anycast tunneling protocol (SATP)<br />draft-gsenger-secure-anycast-tunneling-protocol-02</h1>
 150
 151 <h3>Status of this Memo</h3>
 152 <p>
 153 By submitting this Internet-Draft,
 154 each author represents that any applicable patent or other IPR claims of which
 155 he or she is aware have been or will be disclosed,
 156 and any of which he or she becomes aware will be disclosed,
 157 in accordance with Section&nbsp;6 of BCP&nbsp;79.</p>
 158 <p>
 159 Internet-Drafts are working documents of the Internet Engineering
 160 Task Force (IETF), its areas, and its working groups.
 161 Note that other groups may also distribute working documents as
 162 Internet-Drafts.</p>
 163 <p>
 164 Internet-Drafts are draft documents valid for a maximum of six months
 165 and may be updated, replaced, or obsoleted by other documents at any time.
 166 It is inappropriate to use Internet-Drafts as reference material or to cite
 167 them other than as &ldquo;work in progress.&rdquo;</p>
 168 <p>
 169 The list of current Internet-Drafts can be accessed at
 170 <a href='http://www.ietf.org/ietf/1id-abstracts.txt'>http://www.ietf.org/ietf/1id-abstracts.txt</a>.</p>
 171 <p>
 172 The list of Internet-Draft Shadow Directories can be accessed at
 173 <a href='http://www.ietf.org/shadow.html'>http://www.ietf.org/shadow.html</a>.</p>
 174 <p>
 175 This Internet-Draft will expire on November 7, 2008.</p>
 176
 177 <h3>Copyright Notice</h3>
 178 <p>
 179 Copyright &copy; The IETF Trust (2008).</p>
 180
 181 <h3>Abstract</h3>
 182
 183 <p>The secure anycast tunneling protocol (SATP) defines a protocol used for communication between any combination of unicast and anycast tunnel endpoints. It allows tunneling of every ETHER TYPE protocol (ethernet, ip ...). SATP directly includes cryptography and message authentication based on the methods used by the <a class='info' href='#RFC3711'>Secure Real-time Transport Protocol(SRTP)<span> (</span><span class='info'>Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;The Secure Real-time Transport Protocol (SRTP),&rdquo; March&nbsp;2004.</span><span>)</span></a> [1]. It can be used as an encrypted alternative to <a class='info' href='#RFC2003'>IP Encapsulation within IP<span> (</span><span class='info'>Perkins, C., &ldquo;IP Encapsulation within IP,&rdquo; October&nbsp;1996.</span><span>)</span></a> [3] and <a class='info' href='#RFC2784'>Generic Routing Encapsulation (GRE)<span> (</span><span class='info'>Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, &ldquo;Generic Routing Encapsulation (GRE),&rdquo; March&nbsp;2000.</span><span>)</span></a> [4]. Both anycast receivers and senders are supported.
 184
 185 </p><a name="toc"></a><br /><hr />
 186 <h3>Table of Contents</h3>
 187 <p class="toc">
 188 <a href="#anchor1">1.</a>&nbsp;
 189 Introduction<br />
 190 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor2">1.1.</a>&nbsp;
 191 Notational Conventions<br />
 192 <a href="#anchor3">2.</a>&nbsp;
 193 Motivation and usage scenarios<br />
 194 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor4">2.1.</a>&nbsp;
 195 Usage scenarions<br />
 196 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor5">2.1.1.</a>&nbsp;
 197 Tunneling from unicast hosts over anycast routers to other unicast hosts<br />
 198 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor6">2.1.2.</a>&nbsp;
 199 Tunneling from unicast hosts to anycast networks<br />
 200 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor7">2.1.3.</a>&nbsp;
 201 Redundant tunnel connection of 2 networks<br />
 202 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor8">2.2.</a>&nbsp;
 203 Encapsulation<br />
 204 <a href="#anchor9">3.</a>&nbsp;
 205 Using SATP on top of IP<br />
 206 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor10">3.1.</a>&nbsp;
 207 Fragmentation<br />
 208 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor11">3.2.</a>&nbsp;
 209 ICMP messages<br />
 210 <a href="#anchor12">4.</a>&nbsp;
 211 Protocol specification<br />
 212 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor13">4.1.</a>&nbsp;
 213 Header format<br />
 214 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor14">4.2.</a>&nbsp;
 215 sequence number<br />
 216 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor15">4.3.</a>&nbsp;
 217 sender ID<br />
 218 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor16">4.4.</a>&nbsp;
 219 MUX<br />
 220 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor17">4.5.</a>&nbsp;
 221 payload type<br />
 222 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor18">4.6.</a>&nbsp;
 223 payload<br />
 224 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor19">4.7.</a>&nbsp;
 225 padding (OPTIONAL)<br />
 226 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor20">4.8.</a>&nbsp;
 227 padding count (OPTIONAL)<br />
 228 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor21">4.9.</a>&nbsp;
 229 MKI (OPTIONAL)<br />
 230 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor22">4.10.</a>&nbsp;
 231 authentication tag (RECOMMENDED)<br />
 232 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor23">4.11.</a>&nbsp;
 233 Encryption<br />
 234 <a href="#anchor24">5.</a>&nbsp;
 235 Security Considerations<br />
 236 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor25">5.1.</a>&nbsp;
 237 Replay protection<br />
 238 <a href="#anchor26">6.</a>&nbsp;
 239 IANA Considerations<br />
 240 <a href="#rfc.references1">7.</a>&nbsp;
 241 References<br />
 242 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#rfc.references1">7.1.</a>&nbsp;
 243 Normative References<br />
 244 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#rfc.references2">7.2.</a>&nbsp;
 245 Informational References<br />
 246 <a href="#rfc.authors">&#167;</a>&nbsp;
 247 Author's Address<br />
 248 <a href="#rfc.copyright">&#167;</a>&nbsp;
 249 Intellectual Property and Copyright Statements<br />
 250 </p>
 251 <br clear="all" />
 252
 253 <a name="anchor1"></a><br /><hr />
 254 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 255 <a name="rfc.section.1"></a><h3>1.&nbsp;
 256 Introduction</h3>
 257
 258 <p>SATP is a mixture of a generic encapsulation protocol like <a class='info' href='#RFC2784'>GRE<span> (</span><span class='info'>Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, &ldquo;Generic Routing Encapsulation (GRE),&rdquo; March&nbsp;2000.</span><span>)</span></a> [4] and a secure tunneling protocol as <a class='info' href='#RFC2401'>IPsec<span> (</span><span class='info'>Kent, S. and R. Atkinson, &ldquo;Security Architecture for the Internet Protocol,&rdquo; November&nbsp;1998.</span><span>)</span></a> [5] in tunnel mode.  It can be used to build redundant virtual private network (VPN) connections.  It supports peer-to-peer tunnels, where tunnel endpoints can be any combination of unicast, multicast or anycast hosts, so it defines a <a class='info' href='#RFC1546'>Host Anycast Service<span> (</span><span class='info'>Partridge, C., Mendez, T., and W. Milliken, &ldquo;Host Anycasting Service,&rdquo; November&nbsp;1993.</span><span>)</span></a> [6]. Encryption is done per packet, so the protocol is robust against packet loss and routing changes.
 259                                 To reduce header overhead ncryption techniques of <a class='info' href='#RFC3711'>SRTP<span> (</span><span class='info'>Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;The Secure Real-time Transport Protocol (SRTP),&rdquo; March&nbsp;2004.</span><span>)</span></a> [1] are being used.
 260
 261 </p>
 262 <a name="anchor2"></a><br /><hr />
 263 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 264 <a name="rfc.section.1.1"></a><h3>1.1.&nbsp;
 265 Notational Conventions</h3>
 266
 267 <p>The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in  <a class='info' href='#RFC2119'>RFC2119<span> (</span><span class='info'>Bradner, S., &ldquo;Key words for use in RFCs to Indicate Requirement Levels,&rdquo; March&nbsp;1997.</span><span>)</span></a> [2].
 268 </p>
 269 <a name="anchor3"></a><br /><hr />
 270 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 271 <a name="rfc.section.2"></a><h3>2.&nbsp;
 272 Motivation and usage scenarios</h3>
 273
 274 <p>This section gives an overview of possible usage scenarios. Please note that the protocols used in the figures are only examples and that SATP itself does not care about either transport protocols or encapsulated protocols. Routing is not done by SATP and each implemetation MAY choose it's own way of doing this task (e.g. using functions provided by the operating system). SATP is used only to encapsulate and encrypt data.
 275 </p>
 276 <a name="anchor4"></a><br /><hr />
 277 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 278 <a name="rfc.section.2.1"></a><h3>2.1.&nbsp;
 279 Usage scenarions</h3>
 280
 281 <a name="anchor5"></a><br /><hr />
 282 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 283 <a name="rfc.section.2.1.1"></a><h3>2.1.1.&nbsp;
 284 Tunneling from unicast hosts over anycast routers to other unicast hosts</h3>
 285 <br /><hr class="insert" />
 286 <a name="tunnel_mode"></a>
 287
 288 <p>An example of SATP used to tunnel in a unicast client - anycast server model
 289 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 290                     --------- router -----------
 291                    /                            \
 292     unicast ------+---------- router ------------+------ unicast
 293     host           \                            /        host
 294                     --------- router -----------
 295
 296   unicast  | encrypted     |  anycast  | encrypted     |  unicast
 297   tunnel   | communication |  tunnel   | communication |  tunnel
 298   endpoint | using SATP    |  endpoint | using SATP    |  endpoint
 299 </pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b>&nbsp;Figure&nbsp;1&nbsp;</b></font><br /></td></tr></table><hr class="insert" />
 300
 301 <p>In this scenario the payload is encapsuleted into a SATP packet by a unicast host and gets transmitted to one of the anycast routers. After transmisson the packet gets decapsulated by the router. This router makes a routing descision based on the underlying protocol and transmits a new SATP package to one or more unicast hosts depending on this decision.
 302 </p>
 303 <a name="anchor6"></a><br /><hr />
 304 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 305 <a name="rfc.section.2.1.2"></a><h3>2.1.2.&nbsp;
 306 Tunneling from unicast hosts to anycast networks</h3>
 307 <br /><hr class="insert" />
 308 <a name="open_tunnel_mode"></a>
 309
 310 <p>An example of SATP used to encrypt data between a unicast host and anycast networks
 311 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 312                        -------Router -+---- DNS Server
 313                       /                \
 314                      /                  --- 6to4 Router
 315                     /
 316     unicast -------+----------Router --+--- DNS Server
 317     host            \                   \
 318                      \                   --- 6to4 Router
 319                       \
 320                        -------Router -+---- DNS Server
 321                                        \
 322                                         --- 6to4 Router
 323
 324   unicast  | encrypted     |  anycast  | plaintext
 325   tunnel   | communication |  tunnel   | anycast
 326   endpoint | using SATP    |  endpoint | services
 327
 328 </pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b>&nbsp;Figure&nbsp;2&nbsp;</b></font><br /></td></tr></table><hr class="insert" />
 329
 330 <p>When the unicast hosts wants to transmit data to one of the anycast DNS servers, it encapsulates the data and sends a SATP packet to the anycast address of the routers. The packet arrives at one of the routers, gets decapsulated and is then forwarded to the DNS server. This method can be used to tunnel between clients and networks providing anycast services. It can also be used the other way to virtually locate a unicast service within anycasted networks.
 331 </p>
 332 <a name="anchor7"></a><br /><hr />
 333 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 334 <a name="rfc.section.2.1.3"></a><h3>2.1.3.&nbsp;
 335 Redundant tunnel connection of 2 networks</h3>
 336 <br /><hr class="insert" />
 337 <a name="connect_networks"></a>
 338
 339 <p>An example of SATP used to connect 2 networks
 340 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 341               Router -----------   ---------------Router
 342             /                   \ /                     \
 343     Network - Router ------------x                       Network
 344        A    \                   / \                     /   B
 345               Router -----------   ---------------Router
 346
 347             | packets       |  packets  |  packets      |
 348  plaintext  | get           |  take a   |  get          | plaintext
 349  packets    | de/encrypted  |  random   |  de/encrypted | packets
 350             |de/encapsulated|   path    |de/encapsulated|
 351
 352 </pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b>&nbsp;Figure&nbsp;3&nbsp;</b></font><br /></td></tr></table><hr class="insert" />
 353
 354 <p>Network A has multiple routers which act as gateway/tunnel endpoints to another network B. This way a redundant encrypted tunnel connection between the two networks is built up. All tunnel endpoints of network A share the same anycast address and all tunnel endpoints of network B share another anycast address. When a packet from network A is transmitted to network B, it first arrives on one of network A's border routers. Which router is used is determined by network A's internal routing. This router encapsulates the package and sends it to the anycast address of network B's routers. After arrival the SATP packet gets decapsulated and routed to its destination within network B.
 355 </p>
 356 <a name="anchor8"></a><br /><hr />
 357 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 358 <a name="rfc.section.2.2"></a><h3>2.2.&nbsp;
 359 Encapsulation</h3>
 360
 361 <p>SATP does not depend on which lower layer protocol is used. This section only gives an example of how packets could look like.
 362
 363 </p><br /><hr class="insert" />
 364 <a name="transport_udp"></a>
 365
 366 <p>Examples of SATP used with different lower layer and payload protocols
 367 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 368     +------+-----+-------------------------------+
 369     |      |     |      +----------------+-----+ |
 370     | IPv6 | UDP | SATP | Ethernet 802.3 | ... | |
 371     |      |     |      +----------------+-----+ |
 372     +------+-----+-------------------------------+
 373
 374 Tunneling of Ethernet over UDP/IPv6
 375
 376     +------+-----+---------------------------+
 377     |      |     |      +------+-----+-----+ |
 378     | IPv4 | UDP | SATP | IPv6 | UDP | RTP | |
 379     |      |     |      +------+-----+-----+ |
 380     +------+-----+---------------------------+
 381
 382 Tunneling of IPv6 over UDP/IPv4 with RTP payload
 383
 384     +------+-------------------------------+
 385     |      |      +----------------+-----+ |
 386     | IPv6 | SATP | Ethernet 802.3 | ... | |
 387     |      |      +----------------+-----+ |
 388     +------+-------------------------------+
 389
 390 Tunneling of Ethernet over IPv6
 391
 392     +------+---------------------------+
 393     |      |      +------+-----+-----+ |
 394     | IPv4 | SATP | IPv6 | UDP | RTP | |
 395     |      |      +------+-----+-----+ |
 396     +------+---------------------------+
 397
 398 Tunneling of IPv6 over IPv4 with RTP payload
 399 </pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b>&nbsp;Figure&nbsp;4&nbsp;</b></font><br /></td></tr></table><hr class="insert" />
 400
 401 <a name="anchor9"></a><br /><hr />
 402 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 403 <a name="rfc.section.3"></a><h3>3.&nbsp;
 404 Using SATP on top of IP</h3>
 405
 406 <a name="anchor10"></a><br /><hr />
 407 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 408 <a name="rfc.section.3.1"></a><h3>3.1.&nbsp;
 409 Fragmentation</h3>
 410
 411 <p>
 412            The only way of fully supporting fragmentation would be to synchronise fragments between all anycast servers. This is considered to be too much overhead, so there are two non-perfect solutions for these problems. Either fragmentation HAS TO be disabled or if not all fragments arrive at the same server the IP datagramm HAS TO be discarded. As routing changes are not expected to occur very frequently, the encapsulated protocol can do a retransmission and all fragments will arrive at the new server.
 413
 414 </p>
 415 <p>If the payload type is IP and the IP headers' Don't Fragment (DF) bit is set, then the DF bit of the outer IP header HAS TO be set as well.
 416 </p>
 417 <a name="anchor11"></a><br /><hr />
 418 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 419 <a name="rfc.section.3.2"></a><h3>3.2.&nbsp;
 420 ICMP messages</h3>
 421
 422 <p>ICMP messages MUST be relayed according to <a class='info' href='#RFC2003'>rfc2003 section 4<span> (</span><span class='info'>Perkins, C., &ldquo;IP Encapsulation within IP,&rdquo; October&nbsp;1996.</span><span>)</span></a> [3]. This is needed for path MTU detection.
 423 </p>
 424 <a name="anchor12"></a><br /><hr />
 425 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 426 <a name="rfc.section.4"></a><h3>4.&nbsp;
 427 Protocol specification</h3>
 428
 429 <a name="anchor13"></a><br /><hr />
 430 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 431 <a name="rfc.section.4.1"></a><h3>4.1.&nbsp;
 432 Header format</h3>
 433 <br /><hr class="insert" />
 434 <a name="prot_header_table"></a>
 435
 436 <p>Protocol Format
 437 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 438       0                   1                   2                   3
 439       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
 440      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 441      |                         sequence number                       | |
 442      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 443      |           sender ID           |              MUX              | |
 444    +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+ |
 445    | |         payload type          |                               | |
 446    | +-------------------------------+                               | |
 447    | |              ....        payload        ...                   | |
 448    | |                               +-------------------------------+ |
 449    | |                               | padding (OPT) | pad count(OPT)| |
 450    +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+-+
 451    | ~                          MKI (OPTIONAL)                       ~ |
 452    | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 453    | :                 authentication tag (RECOMMENDED)              : |
 454    | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 455    |                                                                   |
 456    +- Encrypted Portion                       Authenticated Portion ---+
 457 </pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b>&nbsp;Figure&nbsp;5&nbsp;</b></font><br /></td></tr></table><hr class="insert" />
 458
 459 <p>
 460 </p>
 461 <a name="anchor14"></a><br /><hr />
 462 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 463 <a name="rfc.section.4.2"></a><h3>4.2.&nbsp;
 464 sequence number</h3>
 465
 466 <p>The sequence number is a 32 bit unsigned integer in network byte order. It starts with a random value and is increased by 1 for every sent packet. After the maximum value it starts over from 0. This overrun causes the ROC to be increased.
 467 </p>
 468 <a name="anchor15"></a><br /><hr />
 469 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 470 <a name="rfc.section.4.3"></a><h3>4.3.&nbsp;
 471 sender ID</h3>
 472
 473 <p>The sender ID is a 16 bit unsigned integer. It HAS TO be unique for every sender sharing the same anycast address.
 474 </p>
 475 <a name="anchor16"></a><br /><hr />
 476 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 477 <a name="rfc.section.4.4"></a><h3>4.4.&nbsp;
 478 MUX</h3>
 479
 480 <p>The MUX (multiplex) field is a 16 bit unsigned integer. It is used to distinguish multiple tunnel connections.
 481 </p>
 482 <a name="anchor17"></a><br /><hr />
 483 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 484 <a name="rfc.section.4.5"></a><h3>4.5.&nbsp;
 485 payload type</h3>
 486
 487 <p>The payload type field defines the payload protocol. ETHER TYPE protocol numbers are used. <a href='http://www.iana.org/assignments/ethernet-numbers'>See IANA assigned ethernet numbers</a> . The values 0000-05DC are reserverd and MUST NOT be used.
 488         <br /><hr class="insert" />
 489 <a name="prot_type_table"></a>
 490
 491 <p>Some examples for protocol numbers
 492 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 493 HEX
 494 0000 Reserved
 495 .... Reserved
 496 05DC Reserved
 497 0800 Internet IP (IPv4)
 498 6558 transparent ethernet bridging
 499 86DD IPv6
 500 </pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b>&nbsp;Figure&nbsp;6&nbsp;</b></font><br /></td></tr></table><hr class="insert" />
 501
 502
 503
 504 <a name="anchor18"></a><br /><hr />
 505 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 506 <a name="rfc.section.4.6"></a><h3>4.6.&nbsp;
 507 payload</h3>
 508
 509 <p>A packet of type payload type (e.g. an IP packet).
 510 </p>
 511 <a name="anchor19"></a><br /><hr />
 512 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 513 <a name="rfc.section.4.7"></a><h3>4.7.&nbsp;
 514 padding (OPTIONAL)</h3>
 515
 516 <p>Padding of max 255 octets.
 517 None of the pre-defined encryption transforms uses any padding; for
 518    these, the plaintext and encrypted payload sizes match exactly. Transforms are based on transforms of the SRTP protocol and therefore might use the RTP padding format, so a RTP-like padding is supported. If the padding count field is present, the padding count field MUST be set to the padding length.
 519 </p>
 520 <a name="anchor20"></a><br /><hr />
 521 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 522 <a name="rfc.section.4.8"></a><h3>4.8.&nbsp;
 523 padding count (OPTIONAL)</h3>
 524
 525 <p>The number of octets of the padding field. This field is optional. Its presence is signaled by the key management and not by this protocol. If this field isn't present, the padding field MUST NOT be present as well.
 526 </p>
 527 <a name="anchor21"></a><br /><hr />
 528 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 529 <a name="rfc.section.4.9"></a><h3>4.9.&nbsp;
 530 MKI (OPTIONAL)</h3>
 531
 532 <p>The MKI (Master Key Identifier) is OPTIONAL and of configurable length. See <a class='info' href='#RFC3711'>SRTP Section 3.1<span> (</span><span class='info'>Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;The Secure Real-time Transport Protocol (SRTP),&rdquo; March&nbsp;2004.</span><span>)</span></a> [1] for details.
 533 </p>
 534 <a name="anchor22"></a><br /><hr />
 535 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 536 <a name="rfc.section.4.10"></a><h3>4.10.&nbsp;
 537 authentication tag (RECOMMENDED)</h3>
 538
 539 <p>The authentication tag is RECOMMENDED and of configurable length. It contains a cryptographic checksum of the sender ID, sequence number and the encrypted portion, but not of the MKI. On transmitter side encryption HAS TO be done before calculating the authentication tag. A receiver HAS TO calculate the authentication tag before decrypting the encrypted portion.
 540 </p>
 541 <a name="anchor23"></a><br /><hr />
 542 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 543 <a name="rfc.section.4.11"></a><h3>4.11.&nbsp;
 544 Encryption</h3>
 545
 546 <p>Encryption is done in the same way as for <a class='info' href='#RFC3711'>SRTP<span> (</span><span class='info'>Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;The Secure Real-time Transport Protocol (SRTP),&rdquo; March&nbsp;2004.</span><span>)</span></a> [1]. This section will only discuss some small changes that HAVE TO be made. Please read  <a class='info' href='#RFC3711'>SRTP RFC3711 section 3-9<span> (</span><span class='info'>Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;The Secure Real-time Transport Protocol (SRTP),&rdquo; March&nbsp;2004.</span><span>)</span></a> [1] for details.
 547 </p>
 548 <p>The least significant bits of SSRC are replaced by the sender ID and the most significant bits are replaced by the MUX. For the SRTP SEQ the 16 least significant bits of the SATP sequence number are used and the 16 most significant bits of the sequence number replace the 16 least significant bits of the SRTP ROC.
 549 </p><br /><hr class="insert" />
 550 <a name="srtp_vs_satp"></a>
 551
 552 <p>Difference between SRTP and SATP
 553 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 554       0                   1                   2                   3
 555       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
 556      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 557      |                     SATP    sequence number                   |
 558      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 559                                      =
 560      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 561      |  SRTP ROC least significant   |           SRTP SEQ            |
 562      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 563
 564
 565       0                   1                   2                   3
 566       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
 567      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 568      |           SATP  MUX           |       SATP sender ID          |
 569      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 570                                      =
 571      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 572      |                           SRTP SSRC                           |
 573      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 574 </pre></div><table border="0" cellpadding="0" cellspacing="2" align="center"><tr><td align="center"><font face="monaco, MS Sans Serif" size="1"><b>&nbsp;Figure&nbsp;7&nbsp;</b></font><br /></td></tr></table><hr class="insert" />
 575
 576 <a name="anchor24"></a><br /><hr />
 577 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 578 <a name="rfc.section.5"></a><h3>5.&nbsp;
 579 Security Considerations</h3>
 580
 581 <p>As SATP uses the same encryption techniques as <a class='info' href='#RFC3711'>SRTP<span> (</span><span class='info'>Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;The Secure Real-time Transport Protocol (SRTP),&rdquo; March&nbsp;2004.</span><span>)</span></a> [1], it shares the same security issues. This section will only discuss some small changes. Please read  <a class='info' href='#RFC3711'>SRTP RFC3711 section 9<span> (</span><span class='info'>Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;The Secure Real-time Transport Protocol (SRTP),&rdquo; March&nbsp;2004.</span><span>)</span></a> [1] for details.
 582 </p>
 583 <a name="anchor25"></a><br /><hr />
 584 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 585 <a name="rfc.section.5.1"></a><h3>5.1.&nbsp;
 586 Replay protection</h3>
 587
 588 <p>Replay protection is done by a replay list. Every anycast receiver has its own replay list, which SHOULDN'T be syncronised because of massive overhead. This leads to an additional possible attack. An attacker is able to replay a captured packet once to every anycast receiver. This attack is considered be very unlikely because multiple attack hosts in different locations are needed to reach seperate anycast receivers and the number of replays is limited to count of receivers - 1. Such replays might also happen because of routing problems, so a payload protocol HAS TO be robust against a small number of duplicated packages. The window size and position HAS TO be syncronised between multiple anycast receivers to limit this attack.
 589 </p>
 590 <a name="anchor26"></a><br /><hr />
 591 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 592 <a name="rfc.section.6"></a><h3>6.&nbsp;
 593 IANA Considerations</h3>
 594
 595 <p>The protocol is intended to be used on top of IP or on top of UDP (to be compatible with NAT routers), so UDP and IP protocol numbers have to be assiged by IANA.
 596 </p>
 597 <a name="rfc.references"></a><br /><hr />
 598 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 599 <a name="rfc.section.7"></a><h3>7.&nbsp;
 600 References</h3>
 601
 602 <a name="rfc.references1"></a><br /><hr />
 603 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 604 <h3>7.1.&nbsp;Normative References</h3>
 605 <table width="99%" border="0">
 606 <tr><td class="author-text" valign="top"><a name="RFC3711">[1]</a></td>
 607 <td class="author-text">Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;<a href="ftp://ftp.isi.edu/in-notes/rfc3711.txt">The Secure Real-time Transport Protocol (SRTP)</a>,&rdquo; RFC&nbsp;3711, March&nbsp;2004.</td></tr>
 608 <tr><td class="author-text" valign="top"><a name="RFC2119">[2]</a></td>
 609 <td class="author-text"><a href="mailto:sob@harvard.edu">Bradner, S.</a>, &ldquo;<a href="ftp://ftp.isi.edu/in-notes/rfc2119.txt">Key words for use in RFCs to Indicate Requirement Levels</a>,&rdquo; BCP&nbsp;14, RFC&nbsp;2119, March&nbsp;1997 (<a href="ftp://ftp.isi.edu/in-notes/rfc2119.txt">TXT</a>, <a href="http://xml.resource.org/public/rfc/html/rfc2119.html">HTML</a>, <a href="http://xml.resource.org/public/rfc/xml/rfc2119.xml">XML</a>).</td></tr>
 610 <tr><td class="author-text" valign="top"><a name="RFC2003">[3]</a></td>
 611 <td class="author-text"><a href="mailto:perk@watson.ibm.com">Perkins, C.</a>, &ldquo;<a href="ftp://ftp.isi.edu/in-notes/rfc2003.txt">IP Encapsulation within IP</a>,&rdquo; RFC&nbsp;2003, October&nbsp;1996 (<a href="ftp://ftp.isi.edu/in-notes/rfc2003.txt">TXT</a>, <a href="http://xml.resource.org/public/rfc/html/rfc2003.html">HTML</a>, <a href="http://xml.resource.org/public/rfc/xml/rfc2003.xml">XML</a>).</td></tr>
 612 </table>
 613
 614 <a name="rfc.references2"></a><br /><hr />
 615 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 616 <h3>7.2.&nbsp;Informational References</h3>
 617 <table width="99%" border="0">
 618 <tr><td class="author-text" valign="top"><a name="RFC2784">[4]</a></td>
 619 <td class="author-text"><a href="mailto:dino@procket.com">Farinacci, D.</a>, <a href="mailto:tony1@home.net">Li, T.</a>, <a href="mailto:stan_hanks@enron.net">Hanks, S.</a>, <a href="mailto:dmm@cisco.com">Meyer, D.</a>, and <a href="mailto:pst@juniper.net">P. Traina</a>, &ldquo;<a href="ftp://ftp.isi.edu/in-notes/rfc2784.txt">Generic Routing Encapsulation (GRE)</a>,&rdquo; RFC&nbsp;2784, March&nbsp;2000.</td></tr>
 620 <tr><td class="author-text" valign="top"><a name="RFC2401">[5]</a></td>
 621 <td class="author-text"><a href="mailto:kent@bbn.com">Kent, S.</a> and <a href="mailto:rja@corp.home.net">R. Atkinson</a>, &ldquo;<a href="ftp://ftp.isi.edu/in-notes/rfc2401.txt">Security Architecture for the Internet Protocol</a>,&rdquo; RFC&nbsp;2401, November&nbsp;1998 (<a href="ftp://ftp.isi.edu/in-notes/rfc2401.txt">TXT</a>, <a href="http://xml.resource.org/public/rfc/html/rfc2401.html">HTML</a>, <a href="http://xml.resource.org/public/rfc/xml/rfc2401.xml">XML</a>).</td></tr>
 622 <tr><td class="author-text" valign="top"><a name="RFC1546">[6]</a></td>
 623 <td class="author-text"><a href="mailto:craig@bbn.com">Partridge, C.</a>, <a href="mailto:tmendez@bbn.com">Mendez, T.</a>, and <a href="mailto:milliken@bbn.com">W. Milliken</a>, &ldquo;<a href="ftp://ftp.isi.edu/in-notes/rfc1546.txt">Host Anycasting Service</a>,&rdquo; RFC&nbsp;1546, November&nbsp;1993.</td></tr>
 624 </table>
 625
 626 <a name="rfc.authors"></a><br /><hr />
 627 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 628 <h3>Author's Address</h3>
 629 <table width="99%" border="0" cellpadding="0" cellspacing="0">
 630 <tr><td class="author-text">&nbsp;</td>
 631 <td class="author-text">Othmar Gsenger</td></tr>
 632 <tr><td class="author-text">&nbsp;</td>
 633 <td class="author-text">Puerstingerstr 32</td></tr>
 634 <tr><td class="author-text">&nbsp;</td>
 635 <td class="author-text">Saalfelden  5760</td></tr>
 636 <tr><td class="author-text">&nbsp;</td>
 637 <td class="author-text">AT</td></tr>
 638 <tr><td class="author" align="right">Phone:&nbsp;</td>
 639 <td class="author-text"></td></tr>
 640 <tr><td class="author" align="right">Email:&nbsp;</td>
 641 <td class="author-text"><a href="mailto:satp@gsenger.com">satp@gsenger.com</a></td></tr>
 642 <tr><td class="author" align="right">URI:&nbsp;</td>
 643 <td class="author-text"><a href="http://www.gsenger.com/satp/">http://www.gsenger.com/satp/</a></td></tr>
 644 </table>
 645 <a name="rfc.copyright"></a><br /><hr />
 646 <table summary="layout" cellpadding="0" cellspacing="2" class="TOCbug" align="right"><tr><td class="TOCbug"><a href="#toc">&nbsp;TOC&nbsp;</a></td></tr></table>
 647 <h3>Full Copyright Statement</h3>
 648 <p class='copyright'>
 649 Copyright &copy; The IETF Trust (2008).</p>
 650 <p class='copyright'>
 651 This document is subject to the rights,
 652 licenses and restrictions contained in BCP&nbsp;78,
 653 and except as set forth therein,
 654 the authors retain all their rights.</p>
 655 <p class='copyright'>
 656 This document and the information contained herein are provided
 657 on an &ldquo;AS IS&rdquo; basis and THE CONTRIBUTOR,
 658 THE ORGANIZATION HE/SHE REPRESENTS
 659 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST
 660 AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
 661 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
 662 THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
 663 IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
 664 PURPOSE.</p>
 665 <h3>Intellectual Property</h3>
 666 <p class='copyright'>
 667 The IETF takes no position regarding the validity or scope of any
 668 Intellectual Property Rights or other rights that might be claimed
 669 to pertain to the implementation or use of the technology
 670 described in this document or the extent to which any license
 671 under such rights might or might not be available; nor does it
 672 represent that it has made any independent effort to identify any
 673 such rights.
 674 Information on the procedures with respect to
 675 rights in RFC documents can be found in BCP&nbsp;78 and BCP&nbsp;79.</p>
 676 <p class='copyright'>
 677 Copies of IPR disclosures made to the IETF Secretariat and any
 678 assurances of licenses to be made available,
 679 or the result of an attempt made to obtain a general license or
 680 permission for the use of such proprietary rights by implementers or
 681 users of this specification can be obtained from the IETF on-line IPR
 682 repository at <a href='http://www.ietf.org/ipr'>http://www.ietf.org/ipr</a>.</p>
 683 <p class='copyright'>
 684 The IETF invites any interested party to bring to its attention
 685 any copyrights,
 686 patents or patent applications,
 687 or other
 688 proprietary rights that may cover technology that may be required
 689 to implement this standard.
 690 Please address the information to the IETF at <a href='mailto:ietf-ipr@ietf.org'>ietf-ipr@ietf.org</a>.</p>
 691 <h3>Acknowledgment</h3>
 692 <p class='copyright'>
 693 Funding for the RFC Editor function is provided by
 694 the IETF Administrative Support Activity (IASA).</p>
 695 </body></html>