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 2008</td></tr>
 147 <tr><td class="header">Expires: November 2, 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 2, 2008.</p>
 176
 177 <h3>Abstract</h3>
 178
 179 <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> [RFC3711]. 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> [RFC2003] 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> [RFC2784]. Both anycast receivers and senders are supported.
 180
 181 </p><a name="toc"></a><br /><hr />
 182 <h3>Table of Contents</h3>
 183 <p class="toc">
 184 <a href="#anchor1">1.</a>&nbsp;
 185 Introduction<br />
 186 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor2">1.1.</a>&nbsp;
 187 Notational Conventions<br />
 188 <a href="#anchor3">2.</a>&nbsp;
 189 Motivation and usage scenarios<br />
 190 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor4">2.1.</a>&nbsp;
 191 Usage scenarions<br />
 192 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor5">2.1.1.</a>&nbsp;
 193 Tunneling from unicast hosts over anycast routers to other unicast hosts<br />
 194 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor6">2.1.2.</a>&nbsp;
 195 Tunneling from unicast hosts to anycast networks<br />
 196 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor7">2.1.3.</a>&nbsp;
 197 Redundant tunnel connection of 2 networks<br />
 198 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor8">2.2.</a>&nbsp;
 199 Encapsulation<br />
 200 <a href="#anchor9">3.</a>&nbsp;
 201 Using SATP on top of IP<br />
 202 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor10">3.1.</a>&nbsp;
 203 Fragmentation<br />
 204 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor11">3.2.</a>&nbsp;
 205 ICMP messages<br />
 206 <a href="#anchor12">4.</a>&nbsp;
 207 Protocol specification<br />
 208 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor13">4.1.</a>&nbsp;
 209 Header format<br />
 210 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor14">4.2.</a>&nbsp;
 211 sequence number<br />
 212 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor15">4.3.</a>&nbsp;
 213 sender ID<br />
 214 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor16">4.4.</a>&nbsp;
 215 MUX<br />
 216 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor17">4.5.</a>&nbsp;
 217 payload type<br />
 218 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor18">4.6.</a>&nbsp;
 219 payload<br />
 220 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor19">4.7.</a>&nbsp;
 221 padding (OPTIONAL)<br />
 222 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor20">4.8.</a>&nbsp;
 223 padding count (OPTIONAL)<br />
 224 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor21">4.9.</a>&nbsp;
 225 MKI (OPTIONAL)<br />
 226 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor22">4.10.</a>&nbsp;
 227 authentication tag (RECOMMENDED)<br />
 228 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor23">4.11.</a>&nbsp;
 229 Encryption<br />
 230 <a href="#anchor24">5.</a>&nbsp;
 231 Security Considerations<br />
 232 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor25">5.1.</a>&nbsp;
 233 Replay protection<br />
 234 <a href="#anchor26">6.</a>&nbsp;
 235 IANA Considerations<br />
 236 <a href="#rfc.references1">7.</a>&nbsp;
 237 References<br />
 238 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#rfc.references1">7.1.</a>&nbsp;
 239 Normative References<br />
 240 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#rfc.references2">7.2.</a>&nbsp;
 241 Informational References<br />
 242 <a href="#rfc.authors">&#167;</a>&nbsp;
 243 Author's Address<br />
 244 <a href="#rfc.copyright">&#167;</a>&nbsp;
 245 Intellectual Property and Copyright Statements<br />
 246 </p>
 247 <br clear="all" />
 248
 249 <a name="anchor1"></a><br /><hr />
 250 <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>
 251 <a name="rfc.section.1"></a><h3>1.&nbsp;
 252 Introduction</h3>
 253
 254 <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> [RFC2784] 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> [RFC2401] 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> [RFC1546]. Encryption is done per packet, so the protocol is robust against packet loss and routing changes.
 255                                 To reduce header overhead, 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> [RFC3711] are being used.
 256
 257 </p>
 258 <a name="anchor2"></a><br /><hr />
 259 <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>
 260 <a name="rfc.section.1.1"></a><h3>1.1.&nbsp;
 261 Notational Conventions</h3>
 262
 263 <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> [RFC2119].
 264 </p>
 265 <a name="anchor3"></a><br /><hr />
 266 <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>
 267 <a name="rfc.section.2"></a><h3>2.&nbsp;
 268 Motivation and usage scenarios</h3>
 269
 270 <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.
 271 </p>
 272 <a name="anchor4"></a><br /><hr />
 273 <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>
 274 <a name="rfc.section.2.1"></a><h3>2.1.&nbsp;
 275 Usage scenarions</h3>
 276
 277 <a name="anchor5"></a><br /><hr />
 278 <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>
 279 <a name="rfc.section.2.1.1"></a><h3>2.1.1.&nbsp;
 280 Tunneling from unicast hosts over anycast routers to other unicast hosts</h3>
 281 <br /><hr class="insert" />
 282 <a name="tunnel_mode"></a>
 283
 284 <p>An example of SATP used to tunnel in a unicast client - anycast server model
 285 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 286                     --------- router -----------
 287                    /                            \
 288     unicast ------+---------- router ------------+------ unicast
 289     host           \                            /        host
 290                     --------- router -----------
 291
 292   unicast  | encrypted     |  anycast  | encrypted     |  unicast
 293   tunnel   | communication |  tunnel   | communication |  tunnel
 294   endpoint | using SATP    |  endpoint | using SATP    |  endpoint
 295 </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" />
 296
 297 <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.
 298 </p>
 299 <a name="anchor6"></a><br /><hr />
 300 <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>
 301 <a name="rfc.section.2.1.2"></a><h3>2.1.2.&nbsp;
 302 Tunneling from unicast hosts to anycast networks</h3>
 303 <br /><hr class="insert" />
 304 <a name="open_tunnel_mode"></a>
 305
 306 <p>An example of SATP used to encrypt data between a unicast host and anycast networks
 307 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 308                        -------Router -+---- DNS Server
 309                       /                \
 310                      /                  --- 6to4 Router
 311                     /
 312     unicast -------+----------Router --+--- DNS Server
 313     host            \                   \
 314                      \                   --- 6to4 Router
 315                       \
 316                        -------Router -+---- DNS Server
 317                                        \
 318                                         --- 6to4 Router
 319
 320   unicast  | encrypted     |  anycast  | plaintext
 321   tunnel   | communication |  tunnel   | anycast
 322   endpoint | using SATP    |  endpoint | services
 323
 324 </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" />
 325
 326 <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.
 327 </p>
 328 <a name="anchor7"></a><br /><hr />
 329 <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>
 330 <a name="rfc.section.2.1.3"></a><h3>2.1.3.&nbsp;
 331 Redundant tunnel connection of 2 networks</h3>
 332 <br /><hr class="insert" />
 333 <a name="connect_networks"></a>
 334
 335 <p>An example of SATP used to connect 2 networks
 336 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 337               Router -----------   ---------------Router
 338             /                   \ /                     \
 339     Network - Router ------------x                       Network
 340        A    \                   / \                     /   B
 341               Router -----------   ---------------Router
 342
 343             | packets       |  packets  |  packets      |
 344  plaintext  | get           |  take a   |  get          | plaintext
 345  packets    | de/encrypted  |  random   |  de/encrypted | packets
 346             |de/encapsulated|   path    |de/encapsulated|
 347
 348 </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" />
 349
 350 <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.
 351 </p>
 352 <a name="anchor8"></a><br /><hr />
 353 <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>
 354 <a name="rfc.section.2.2"></a><h3>2.2.&nbsp;
 355 Encapsulation</h3>
 356
 357 <p>SATP does not depend on the lower layer protocol. This section only gives an example of how packets could look like.
 358
 359 </p><br /><hr class="insert" />
 360 <a name="transport_udp"></a>
 361
 362 <p>Examples of SATP used with different lower layer and payload protocols
 363 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 364     +------+-----+-------------------------------+
 365     |      |     |      +----------------+-----+ |
 366     | IPv6 | UDP | SATP | Ethernet 802.3 | ... | |
 367     |      |     |      +----------------+-----+ |
 368     +------+-----+-------------------------------+
 369
 370 Tunneling of Ethernet over UDP/IPv6
 371
 372     +------+-----+---------------------------+
 373     |      |     |      +------+-----+-----+ |
 374     | IPv4 | UDP | SATP | IPv6 | UDP | RTP | |
 375     |      |     |      +------+-----+-----+ |
 376     +------+-----+---------------------------+
 377
 378 Tunneling of IPv6 over UDP/IPv4 with RTP payload
 379
 380     +------+-------------------------------+
 381     |      |      +----------------+-----+ |
 382     | IPv6 | SATP | Ethernet 802.3 | ... | |
 383     |      |      +----------------+-----+ |
 384     +------+-------------------------------+
 385
 386 Tunneling of Ethernet over IPv6
 387
 388     +------+---------------------------+
 389     |      |      +------+-----+-----+ |
 390     | IPv4 | SATP | IPv6 | UDP | RTP | |
 391     |      |      +------+-----+-----+ |
 392     +------+---------------------------+
 393
 394 Tunneling of IPv6 over IPv4 with RTP payload
 395 </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" />
 396
 397 <a name="anchor9"></a><br /><hr />
 398 <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>
 399 <a name="rfc.section.3"></a><h3>3.&nbsp;
 400 Using SATP on top of IP</h3>
 401
 402 <a name="anchor10"></a><br /><hr />
 403 <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>
 404 <a name="rfc.section.3.1"></a><h3>3.1.&nbsp;
 405 Fragmentation</h3>
 406
 407 <p>
 408            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.
 409
 410 </p>
 411 <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.
 412 </p>
 413 <a name="anchor11"></a><br /><hr />
 414 <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>
 415 <a name="rfc.section.3.2"></a><h3>3.2.&nbsp;
 416 ICMP messages</h3>
 417
 418 <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> [RFC2003]. This is needed for path MTU detection.
 419 </p>
 420 <a name="anchor12"></a><br /><hr />
 421 <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>
 422 <a name="rfc.section.4"></a><h3>4.&nbsp;
 423 Protocol specification</h3>
 424
 425 <a name="anchor13"></a><br /><hr />
 426 <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>
 427 <a name="rfc.section.4.1"></a><h3>4.1.&nbsp;
 428 Header format</h3>
 429 <br /><hr class="insert" />
 430 <a name="prot_header_table"></a>
 431
 432 <p>Protocol Format
 433 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 434       0                   1                   2                   3
 435       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
 436      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 437      |                         sequence number                       | |
 438      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 439      |           sender ID           |              MUX              | |
 440    +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+ |
 441    | |         payload type          |                               | |
 442    | +-------------------------------+                               | |
 443    | |              ....        payload        ...                   | |
 444    | |                               +-------------------------------+ |
 445    | |                               | padding (OPT) | pad count(OPT)| |
 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 sequence number</h3>
 461
 462 <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.
 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 sender ID</h3>
 468
 469 <p>The sender ID is a 16 bit unsigned integer. It HAS TO be unique for every sender sharing the same anycast address.
 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 MUX</h3>
 475
 476 <p>The MUX (multiplex) field is a 16 bit unsigned integer. It is used to distinguish multiple tunnel connections.
 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 payload type</h3>
 482
 483 <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.
 484         <br /><hr class="insert" />
 485 <a name="prot_type_table"></a>
 486
 487 <p>Some examples for protocol numbers
 488 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 489 HEX
 490 0000 Reserved
 491 .... Reserved
 492 05DC Reserved
 493 0800 Internet IP (IPv4)
 494 6558 transparent ethernet bridging
 495 86DD IPv6
 496 </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" />
 497
 498
 499
 500 <a name="anchor18"></a><br /><hr />
 501 <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>
 502 <a name="rfc.section.4.6"></a><h3>4.6.&nbsp;
 503 payload</h3>
 504
 505 <p>A packet of type payload type (e.g. an IP packet).
 506 </p>
 507 <a name="anchor19"></a><br /><hr />
 508 <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>
 509 <a name="rfc.section.4.7"></a><h3>4.7.&nbsp;
 510 padding (OPTIONAL)</h3>
 511
 512 <p>Padding of max 255 octets.
 513 None of the pre-defined encryption transforms uses any padding; for
 514    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.
 515 </p>
 516 <a name="anchor20"></a><br /><hr />
 517 <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>
 518 <a name="rfc.section.4.8"></a><h3>4.8.&nbsp;
 519 padding count (OPTIONAL)</h3>
 520
 521 <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.
 522 </p>
 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.4.9"></a><h3>4.9.&nbsp;
 526 MKI (OPTIONAL)</h3>
 527
 528 <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> [RFC3711] for details.
 529 </p>
 530 <a name="anchor22"></a><br /><hr />
 531 <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>
 532 <a name="rfc.section.4.10"></a><h3>4.10.&nbsp;
 533 authentication tag (RECOMMENDED)</h3>
 534
 535 <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.
 536 </p>
 537 <a name="anchor23"></a><br /><hr />
 538 <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>
 539 <a name="rfc.section.4.11"></a><h3>4.11.&nbsp;
 540 Encryption</h3>
 541
 542 <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> [RFC3711]. 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> [RFC3711] for details.
 543 </p>
 544 <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.
 545 </p><br /><hr class="insert" />
 546 <a name="srtp_vs_satp"></a>
 547
 548 <p>Difference between SRTP and SATP
 549 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 550       0                   1                   2                   3
 551       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
 552      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 553      |                     SATP    sequence number                   |
 554      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 555                                      =
 556      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 557      |  SRTP ROC least significant   |           SRTP SEQ            |
 558      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 559
 560
 561       0                   1                   2                   3
 562       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
 563      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 564      |           SATP  MUX           |       SATP sender ID          |
 565      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 566                                      =
 567      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 568      |                           SRTP SSRC                           |
 569      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 570 </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" />
 571
 572 <a name="anchor24"></a><br /><hr />
 573 <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>
 574 <a name="rfc.section.5"></a><h3>5.&nbsp;
 575 Security Considerations</h3>
 576
 577 <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> [RFC3711], 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> [RFC3711] for details.
 578 </p>
 579 <a name="anchor25"></a><br /><hr />
 580 <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>
 581 <a name="rfc.section.5.1"></a><h3>5.1.&nbsp;
 582 Replay protection</h3>
 583
 584 <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.
 585 </p>
 586 <a name="anchor26"></a><br /><hr />
 587 <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>
 588 <a name="rfc.section.6"></a><h3>6.&nbsp;
 589 IANA Considerations</h3>
 590
 591 <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.
 592 </p>
 593 <a name="rfc.references"></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 <a name="rfc.section.7"></a><h3>7.&nbsp;
 596 References</h3>
 597
 598 <a name="rfc.references1"></a><br /><hr />
 599 <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>
 600 <h3>7.1.&nbsp;Normative References</h3>
 601 <table width="99%" border="0">
 602 <tr><td class="author-text" valign="top"><a name="RFC3711">[RFC3711]</a></td>
 603 <td class="author-text">Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, &ldquo;<a href="http://tools.ietf.org/html/rfc3711">The Secure Real-time Transport Protocol (SRTP)</a>,&rdquo; RFC&nbsp;3711, March&nbsp;2004 (<a href="ftp://ftp.isi.edu/in-notes/rfc3711.txt">TXT</a>).</td></tr>
 604 <tr><td class="author-text" valign="top"><a name="RFC2119">[RFC2119]</a></td>
 605 <td class="author-text"><a href="mailto:sob@harvard.edu">Bradner, S.</a>, &ldquo;<a href="http://tools.ietf.org/html/rfc2119">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>
 606 <tr><td class="author-text" valign="top"><a name="RFC2003">[RFC2003]</a></td>
 607 <td class="author-text"><a href="mailto:perk@watson.ibm.com">Perkins, C.</a>, &ldquo;<a href="http://tools.ietf.org/html/rfc2003">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>
 608 </table>
 609
 610 <a name="rfc.references2"></a><br /><hr />
 611 <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>
 612 <h3>7.2.&nbsp;Informational References</h3>
 613 <table width="99%" border="0">
 614 <tr><td class="author-text" valign="top"><a name="RFC2784">[RFC2784]</a></td>
 615 <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="http://tools.ietf.org/html/rfc2784">Generic Routing Encapsulation (GRE)</a>,&rdquo; RFC&nbsp;2784, March&nbsp;2000 (<a href="ftp://ftp.isi.edu/in-notes/rfc2784.txt">TXT</a>).</td></tr>
 616 <tr><td class="author-text" valign="top"><a name="RFC2401">[RFC2401]</a></td>
 617 <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="http://tools.ietf.org/html/rfc2401">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>
 618 <tr><td class="author-text" valign="top"><a name="RFC1546">[RFC1546]</a></td>
 619 <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="http://tools.ietf.org/html/rfc1546">Host Anycasting Service</a>,&rdquo; RFC&nbsp;1546, November&nbsp;1993 (<a href="ftp://ftp.isi.edu/in-notes/rfc1546.txt">TXT</a>).</td></tr>
 620 </table>
 621
 622 <a name="rfc.authors"></a><br /><hr />
 623 <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>
 624 <h3>Author's Address</h3>
 625 <table width="99%" border="0" cellpadding="0" cellspacing="0">
 626 <tr><td class="author-text">&nbsp;</td>
 627 <td class="author-text">Othmar Gsenger</td></tr>
 628 <tr><td class="author-text">&nbsp;</td>
 629 <td class="author-text">Puerstingerstr 32</td></tr>
 630 <tr><td class="author-text">&nbsp;</td>
 631 <td class="author-text">Saalfelden  5760</td></tr>
 632 <tr><td class="author-text">&nbsp;</td>
 633 <td class="author-text">AT</td></tr>
 634 <tr><td class="author" align="right">Phone:&nbsp;</td>
 635 <td class="author-text"></td></tr>
 636 <tr><td class="author" align="right">Email:&nbsp;</td>
 637 <td class="author-text"><a href="mailto:satp@gsenger.com">satp@gsenger.com</a></td></tr>
 638 <tr><td class="author" align="right">URI:&nbsp;</td>
 639 <td class="author-text"><a href="http://www.gsenger.com/satp/">http://www.gsenger.com/satp/</a></td></tr>
 640 </table>
 641 <a name="rfc.copyright"></a><br /><hr />
 642 <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>
 643 <h3>Full Copyright Statement</h3>
 644 <p class='copyright'>
 645 Copyright &copy; The IETF Trust (2008).</p>
 646 <p class='copyright'>
 647 This document is subject to the rights,
 648 licenses and restrictions contained in BCP&nbsp;78,
 649 and except as set forth therein,
 650 the authors retain all their rights.</p>
 651 <p class='copyright'>
 652 This document and the information contained herein are provided
 653 on an &ldquo;AS IS&rdquo; basis and THE CONTRIBUTOR,
 654 THE ORGANIZATION HE/SHE REPRESENTS
 655 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST
 656 AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES,
 657 EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT
 658 THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY
 659 IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR
 660 PURPOSE.</p>
 661 <h3>Intellectual Property</h3>
 662 <p class='copyright'>
 663 The IETF takes no position regarding the validity or scope of any
 664 Intellectual Property Rights or other rights that might be claimed
 665 to pertain to the implementation or use of the technology
 666 described in this document or the extent to which any license
 667 under such rights might or might not be available; nor does it
 668 represent that it has made any independent effort to identify any
 669 such rights.
 670 Information on the procedures with respect to
 671 rights in RFC documents can be found in BCP&nbsp;78 and BCP&nbsp;79.</p>
 672 <p class='copyright'>
 673 Copies of IPR disclosures made to the IETF Secretariat and any
 674 assurances of licenses to be made available,
 675 or the result of an attempt made to obtain a general license or
 676 permission for the use of such proprietary rights by implementers or
 677 users of this specification can be obtained from the IETF on-line IPR
 678 repository at <a href='http://www.ietf.org/ipr'>http://www.ietf.org/ipr</a>.</p>
 679 <p class='copyright'>
 680 The IETF invites any interested party to bring to its attention
 681 any copyrights,
 682 patents or patent applications,
 683 or other
 684 proprietary rights that may cover technology that may be required
 685 to implement this standard.
 686 Please address the information to the IETF at <a href='mailto:ietf-ipr@ietf.org'>ietf-ipr@ietf.org</a>.</p>
 687 </body></html>