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 141 </head>
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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">June 21, 2007</td></tr>
 147 <tr><td class="header">Expires: December 23, 2007</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-00</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 December 23, 2007.</p>
 176
 177 <h3>Copyright Notice</h3>
 178 <p>
 179 Copyright &copy; The IETF Trust (2007).</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 methodes used by SRTP. 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]. It supports both anycast receivers and senders.
 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 sender ID<br />
 216 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor15">4.3.</a>&nbsp;
 217 sequence number<br />
 218 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor16">4.4.</a>&nbsp;
 219 payload<br />
 220 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor17">4.5.</a>&nbsp;
 221 padding (OPTIONAL)<br />
 222 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor18">4.6.</a>&nbsp;
 223 padding count (OPTIONAL)<br />
 224 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor19">4.7.</a>&nbsp;
 225 payload type field<br />
 226 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor20">4.7.1.</a>&nbsp;
 227 MKI (OPTIONAL)<br />
 228 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor21">4.7.2.</a>&nbsp;
 229 authentication tag (RECOMMENDED)<br />
 230 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor22">4.8.</a>&nbsp;
 231 Encryption<br />
 232 <a href="#anchor23">5.</a>&nbsp;
 233 Security Considerations<br />
 234 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor24">5.1.</a>&nbsp;
 235 Replay protection<br />
 236 <a href="#anchor25">6.</a>&nbsp;
 237 IANA Considerations<br />
 238 <a href="#rfc.references1">7.</a>&nbsp;
 239 References<br />
 240 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#rfc.references1">7.1.</a>&nbsp;
 241 Normative References<br />
 242 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#rfc.references2">7.2.</a>&nbsp;
 243 Informational References<br />
 244 <a href="#rfc.authors">&#167;</a>&nbsp;
 245 Author's Address<br />
 246 <a href="#rfc.copyright">&#167;</a>&nbsp;
 247 Intellectual Property and Copyright Statements<br />
 248 </p>
 249 <br clear="all" />
 250
 251 <a name="anchor1"></a><br /><hr />
 252 <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>
 253 <a name="rfc.section.1"></a><h3>1.&nbsp;
 254 Introduction</h3>
 255
 256 <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.
 257                                 To save some header overhead it uses the encryption 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].
 258
 259 </p>
 260 <a name="anchor2"></a><br /><hr />
 261 <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>
 262 <a name="rfc.section.1.1"></a><h3>1.1.&nbsp;
 263 Notational Conventions</h3>
 264
 265 <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].
 266 </p>
 267 <a name="anchor3"></a><br /><hr />
 268 <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>
 269 <a name="rfc.section.2"></a><h3>2.&nbsp;
 270 Motivation and usage scenarios</h3>
 271
 272 <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.
 273 </p>
 274 <a name="anchor4"></a><br /><hr />
 275 <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>
 276 <a name="rfc.section.2.1"></a><h3>2.1.&nbsp;
 277 Usage scenarions</h3>
 278
 279 <a name="anchor5"></a><br /><hr />
 280 <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>
 281 <a name="rfc.section.2.1.1"></a><h3>2.1.1.&nbsp;
 282 Tunneling from unicast hosts over anycast routers to other unicast hosts</h3>
 283 <br /><hr class="insert" />
 284 <a name="tunnel_mode"></a>
 285
 286 <p>An example of SATP used to tunnel in a unicast client - anycast server model
 287 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 288                     --------- router -----------
 289                    /                            \
 290     unicast ------+---------- router ------------+------ unicast
 291     host           \                            /        host
 292                     --------- router -----------
 293
 294   unicast  | encrypted     |  anycast  | encrypted     |  unicast
 295   tunnel   | communication |  tunnel   | communication |  tunnel
 296   endpoint | using SATP    |  endpoint | using SATP    |  endpoint
 297 </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" />
 298
 299 <p>In this scenario the payload gets encapsuleted into a SATP packet by a unicast host and gets transmitted to one of the anycast routers. It than 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 the routing descition.
 300 </p>
 301 <a name="anchor6"></a><br /><hr />
 302 <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>
 303 <a name="rfc.section.2.1.2"></a><h3>2.1.2.&nbsp;
 304 Tunneling from unicast hosts to anycast networks</h3>
 305 <br /><hr class="insert" />
 306 <a name="open_tunnel_mode"></a>
 307
 308 <p>An example of SATP used to encrypt data between a unicast host and anycast networks
 309 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 310                        -------Router -+---- DNS Server
 311                       /                \
 312                      /                  --- 6to4 Router
 313                     /
 314     unicast -------+----------Router --+--- DNS Server
 315     host            \                   \
 316                      \                   --- 6to4 Router
 317                       \
 318                        -------Router -+---- DNS Server
 319                                        \
 320                                         --- 6to4 Router
 321
 322   unicast  | encrypted     |  anycast  | plaintext
 323   tunnel   | communication |  tunnel   | anycast
 324   endpoint | using SATP    |  endpoint | services
 325
 326 </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" />
 327
 328 <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 routed to the DNS server. This method can be used to tunnel between a clients and networks providing anycast services. It can also be used the other way to virtually locate a unicast service within anycasted networks.
 329 </p>
 330 <a name="anchor7"></a><br /><hr />
 331 <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>
 332 <a name="rfc.section.2.1.3"></a><h3>2.1.3.&nbsp;
 333 Redundant tunnel connection of 2 networks</h3>
 334 <br /><hr class="insert" />
 335 <a name="connect_networks"></a>
 336
 337 <p>An example of SATP used to connect 2 networks
 338 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 339               Router -----------   ---------------Router
 340             /                   \ /                     \
 341     Network - Router ------------x                       Network
 342        A    \                   / \                     /   B
 343               Router -----------   ---------------Router
 344
 345             | packets       |  packets  |  packets      |
 346  plaintext  | get           |  take a   |  get          | plaintext
 347  packets    | de/encrypted  |  random   |  de/encrypted | packets
 348             |de/encapsulated|   path    |de/encapsulated|
 349
 350 </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" />
 351
 352 <p>Network A has multiple routers, that act as gateway/tunnel endpoints to another network B. This is done to build a redundant encrypted tunnel connection between the two networks. 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 gets 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 the network B routers. The SATP packet arrives at one of network B's routers and gets decapsulated and routed to it's destination within network B.
 353 </p>
 354 <a name="anchor8"></a><br /><hr />
 355 <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>
 356 <a name="rfc.section.2.2"></a><h3>2.2.&nbsp;
 357 Encapsulation</h3>
 358
 359 <p>SATP does not depend on which lower layer protocols is used, but this section gives an example of how packets could look like.
 360
 361 </p><br /><hr class="insert" />
 362 <a name="transport_udp"></a>
 363
 364 <p>Examples of SATP used with different lower layer and payload protocols
 365 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 366     +------+-----+-------------------------------+
 367     |      |     |      + ---------------+------ |
 368     | IPv6 | UDP | SATP | Ethernet 802.3 | ... | |
 369     |      |     |      +----------------+-----+ |
 370     +------+-----+-------------------------------+
 371
 372 Tunneling of Ethernet over UDP/IPv6
 373
 374     +------+-----+---------------------------+
 375     |      |     |      +------+-----+-----+ |
 376     | IPv4 | UDP | SATP | IPv6 | UDP | RTP | |
 377     |      |     |      +------+-----+-----+ |
 378     +------+-----+---------------------------+
 379
 380 Tunneling of IPv6 over UDP/IPv4 with RTP payload
 381
 382     +------+-------------------------------+
 383     |      |      + ---------------+------ |
 384     | IPv6 | SATP | Ethernet 802.3 | ... | |
 385     |      |      +----------------+-----+ |
 386     +------+-------------------------------+
 387
 388 Tunneling of Ethernet over IPv6
 389
 390     +------+---------------------------+
 391     |      |      +------+-----+-----+ |
 392     | IPv4 | SATP | IPv6 | UDP | RTP | |
 393     |      |      +------+-----+-----+ |
 394     +------+---------------------------+
 395
 396 Tunneling of IPv6 over IPv4 with RTP payload
 397 </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" />
 398
 399 <a name="anchor9"></a><br /><hr />
 400 <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>
 401 <a name="rfc.section.3"></a><h3>3.&nbsp;
 402 Using SATP on top of IP</h3>
 403
 404 <a name="anchor10"></a><br /><hr />
 405 <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>
 406 <a name="rfc.section.3.1"></a><h3>3.1.&nbsp;
 407 Fragmentation</h3>
 408
 409 <p>
 410            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 occure very frequently, the encapsulated protocol can do a retransmission and all fragments will arrive at the new server.
 411
 412 </p>
 413 <p>If the payload type is IP and the ip headers's Don't Fragment (DF) bit is set, than the DF bit of the outer IP header HAS TO be set as well.
 414 </p>
 415 <a name="anchor11"></a><br /><hr />
 416 <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>
 417 <a name="rfc.section.3.2"></a><h3>3.2.&nbsp;
 418 ICMP messages</h3>
 419
 420 <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.
 421 </p>
 422 <a name="anchor12"></a><br /><hr />
 423 <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>
 424 <a name="rfc.section.4"></a><h3>4.&nbsp;
 425 Protocol specification</h3>
 426
 427 <a name="anchor13"></a><br /><hr />
 428 <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>
 429 <a name="rfc.section.4.1"></a><h3>4.1.&nbsp;
 430 Header format</h3>
 431 <br /><hr class="insert" />
 432 <a name="prot_header_table"></a>
 433
 434 <p>Protocol Format
 435 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 436         0                   1                   2                   3
 437       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
 438      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 439      |                         sequence number                       | |
 440      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+ |
 441      |           sender ID           #                               | |
 442    +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+                               + |
 443    | |              ....        payload        ...                   | |
 444    | |-------------------------------+-------------------------------+ |
 445    | | padding (OPT) | pad count(OPT)|         payload type          | |
 446    +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+-+
 447    | ~                          MKI (OPTIONAL)                       ~ |
 448    | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 449    | :                 authentication tag (RECOMMENDED)              : |
 450    | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 451    |                                                                   |
 452    +- Encrypted Portion                       Authenticated Portion ---+
 453 </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" />
 454
 455 <p>
 456 </p>
 457 <a name="anchor14"></a><br /><hr />
 458 <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>
 459 <a name="rfc.section.4.2"></a><h3>4.2.&nbsp;
 460 sender ID</h3>
 461
 462 <p>The sender ID is a 16 bit unsigned integer. It HAS TO be unique for every sender sharing the same anycast address
 463 </p>
 464 <a name="anchor15"></a><br /><hr />
 465 <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>
 466 <a name="rfc.section.4.3"></a><h3>4.3.&nbsp;
 467 sequence number</h3>
 468
 469 <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.
 470 </p>
 471 <a name="anchor16"></a><br /><hr />
 472 <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>
 473 <a name="rfc.section.4.4"></a><h3>4.4.&nbsp;
 474 payload</h3>
 475
 476 <p>A packet of the type payload type (e.g. an IP packet).
 477 </p>
 478 <a name="anchor17"></a><br /><hr />
 479 <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>
 480 <a name="rfc.section.4.5"></a><h3>4.5.&nbsp;
 481 padding (OPTIONAL)</h3>
 482
 483 <p>Padding of max 255 octets.
 484 None of the pre-defined encryption transforms uses any padding; for
 485    these, the plaintext and encrypted payload sizes match exactly. Transforms are based on transforms of the SRTP protocol and these transforms might use the RTP padding format, so a RTP like padding is supported. If the padding count field is present, than the padding count field MUST be set to the padding lenght.
 486 </p>
 487 <a name="anchor18"></a><br /><hr />
 488 <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>
 489 <a name="rfc.section.4.6"></a><h3>4.6.&nbsp;
 490 padding count (OPTIONAL)</h3>
 491
 492 <p>The number of octets of the padding field. This field is optional. It's 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.
 493 </p>
 494 <a name="anchor19"></a><br /><hr />
 495 <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>
 496 <a name="rfc.section.4.7"></a><h3>4.7.&nbsp;
 497 payload type field</h3>
 498
 499 <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.
 500         <br /><hr class="insert" />
 501 <a name="prot_type_table"></a>
 502
 503 <p>Some examples for protocol types
 504 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 505 HEX
 506 0000 Reserved
 507 .... Reserved
 508 05DC Reserved
 509 0800 Internet IP (IPv4)
 510 6558 transparent ethernet bridging
 511 86DD IPv6
 512 </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" />
 513
 514
 515 <a name="anchor20"></a><br /><hr />
 516 <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>
 517 <a name="rfc.section.4.7.1"></a><h3>4.7.1.&nbsp;
 518 MKI (OPTIONAL)</h3>
 519
 520 <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
 521 </p>
 522
 523 <a name="anchor21"></a><br /><hr />
 524 <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>
 525 <a name="rfc.section.4.7.2"></a><h3>4.7.2.&nbsp;
 526 authentication tag (RECOMMENDED)</h3>
 527
 528 <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 sender side encryption HAS TO be done before calculating the authentication tag. A receiver HAS TO calculate the authentication tag before decrypting the encrypted portion.
 529 </p>
 530
 531
 532 <a name="anchor22"></a><br /><hr />
 533 <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>
 534 <a name="rfc.section.4.8"></a><h3>4.8.&nbsp;
 535 Encryption</h3>
 536
 537 <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.
 538 </p>
 539 <p>The least significant bits of SSRC are replaced by the sender ID and the rest is filled with zeros. 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.
 540 </p><br /><hr class="insert" />
 541 <a name="srtp_vs_satp"></a>
 542
 543 <p>Difference between SRTP and SATP
 544 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 545         0                   1                   2                   3
 546       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
 547      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 548      |                     SATP    sequence number                   |
 549      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 550                                     =
 551      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 552      | SRTP ROC least significant   |         SRTP SEQ               |
 553      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 554
 555
 556         0                   1                   2                   3
 557       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
 558      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 559      |0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0|       SATP sender ID          |
 560      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 561                                     =
 562      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 563      |                           SRTP SSRC                           |
 564      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 565 </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" />
 566
 567 <a name="anchor23"></a><br /><hr />
 568 <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>
 569 <a name="rfc.section.5"></a><h3>5.&nbsp;
 570 Security Considerations</h3>
 571
 572 <p>As SATP uses the same encrytion technics 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.
 573 </p>
 574 <a name="anchor24"></a><br /><hr />
 575 <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>
 576 <a name="rfc.section.5.1"></a><h3>5.1.&nbsp;
 577 Replay protection</h3>
 578
 579 <p>Replay protection is done by a replay list. Every anycast receiver has it's own replay list, which SHOULDN'T be syncronised, because of massive overhead. This leads to an additional possible attack. A attacker is able to replay a captured packet once to every anycast receiver. This attack is considered of be very unlikely, because multiple attack hosts in different loactions are needed to reach the seperate anycast receivers and the number of replays is limited to the 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 multible anycast receivers to limit this attack.
 580 </p>
 581 <a name="anchor25"></a><br /><hr />
 582 <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>
 583 <a name="rfc.section.6"></a><h3>6.&nbsp;
 584 IANA Considerations</h3>
 585
 586 <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.
 587 </p>
 588 <a name="rfc.references"></a><br /><hr />
 589 <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>
 590 <a name="rfc.section.7"></a><h3>7.&nbsp;
 591 References</h3>
 592
 593 <a name="rfc.references1"></a><br /><hr />
 594 <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>
 595 <h3>7.1.&nbsp;Normative References</h3>
 596 <table width="99%" border="0">
 597 <tr><td class="author-text" valign="top"><a name="RFC3711">[1]</a></td>
 598 <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>
 599 <tr><td class="author-text" valign="top"><a name="RFC2119">[2]</a></td>
 600 <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>
 601 <tr><td class="author-text" valign="top"><a name="RFC2003">[3]</a></td>
 602 <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/xml/rfc2003.xml">XML</a>).</td></tr>
 603 </table>
 604
 605 <a name="rfc.references2"></a><br /><hr />
 606 <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>
 607 <h3>7.2.&nbsp;Informational References</h3>
 608 <table width="99%" border="0">
 609 <tr><td class="author-text" valign="top"><a name="RFC2784">[4]</a></td>
 610 <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>
 611 <tr><td class="author-text" valign="top"><a name="RFC2401">[5]</a></td>
 612 <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>
 613 <tr><td class="author-text" valign="top"><a name="RFC1546">[6]</a></td>
 614 <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>
 615 </table>
 616
 617 <a name="rfc.authors"></a><br /><hr />
 618 <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>
 619 <h3>Author's Address</h3>
 620 <table width="99%" border="0" cellpadding="0" cellspacing="0">
 621 <tr><td class="author-text">&nbsp;</td>
 622 <td class="author-text">Othmar Gsenger</td></tr>
 623 <tr><td class="author-text">&nbsp;</td>
 624 <td class="author-text">Puerstingerstr 32</td></tr>
 625 <tr><td class="author-text">&nbsp;</td>
 626 <td class="author-text">Saalfelden  5760</td></tr>
 627 <tr><td class="author-text">&nbsp;</td>
 628 <td class="author-text">AT</td></tr>
 629 <tr><td class="author" align="right">Phone:&nbsp;</td>
 630 <td class="author-text"></td></tr>
 631 <tr><td class="author" align="right">Email:&nbsp;</td>
 632 <td class="author-text"><a href="mailto:satp@gsenger.com">satp@gsenger.com</a></td></tr>
 633 <tr><td class="author" align="right">URI:&nbsp;</td>
 634 <td class="author-text"><a href="http://www.gsenger.com/satp/">http://www.gsenger.com/satp/</a></td></tr>
 635 </table>
 636 <a name="rfc.copyright"></a><br /><hr />
 637 <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>
 638 <h3>Full Copyright Statement</h3>
 639 <p class='copyright'>
 640 Copyright &copy; The IETF Trust (2007).</p>
 641 <p class='copyright'>
 642 This document is subject to the rights,
 643 licenses and restrictions contained in BCP&nbsp;78,
 644 and except as set forth therein,
 645 the authors retain all their rights.</p>
 646 <p class='copyright'>
 647 This document and the information contained herein are provided
 648 on an &ldquo;AS IS&rdquo; basis and THE CONTRIBUTOR,
 649 THE ORGANIZATION HE/SHE REPRESENTS
 650 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST
 651 AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
 652 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
 653 THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
 654 IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
 655 PURPOSE.</p>
 656 <h3>Intellectual Property</h3>
 657 <p class='copyright'>
 658 The IETF takes no position regarding the validity or scope of any
 659 Intellectual Property Rights or other rights that might be claimed
 660 to pertain to the implementation or use of the technology
 661 described in this document or the extent to which any license
 662 under such rights might or might not be available; nor does it
 663 represent that it has made any independent effort to identify any
 664 such rights.
 665 Information on the procedures with respect to
 666 rights in RFC documents can be found in BCP&nbsp;78 and BCP&nbsp;79.</p>
 667 <p class='copyright'>
 668 Copies of IPR disclosures made to the IETF Secretariat and any
 669 assurances of licenses to be made available,
 670 or the result of an attempt made to obtain a general license or
 671 permission for the use of such proprietary rights by implementers or
 672 users of this specification can be obtained from the IETF on-line IPR
 673 repository at <a href='http://www.ietf.org/ipr'>http://www.ietf.org/ipr</a>.</p>
 674 <p class='copyright'>
 675 The IETF invites any interested party to bring to its attention
 676 any copyrights,
 677 patents or patent applications,
 678 or other
 679 proprietary rights that may cover technology that may be required
 680 to implement this standard.
 681 Please address the information to the IETF at <a href='mailto:ietf-ipr@ietf.org'>ietf-ipr@ietf.org</a>.</p>
 682 <h3>Acknowledgment</h3>
 683 <p class='copyright'>
 684 Funding for the RFC Editor function is provided by
 685 the IETF Administrative Support Activity (IASA).</p>
 686 </body></html>