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

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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">January 2008</td></tr>
 147 <tr><td class="header">Intended status: Informational</td><td class="header">&nbsp;</td></tr>
 148 <tr><td class="header">Expires: July 4, 2008</td><td class="header">&nbsp;</td></tr>
 149 </table></td></tr></table>
 150 <h1><br />secure anycast tunneling protocol (SATP)<br />draft-gsenger-secure-anycast-tunneling-protocol-01</h1>
 151
 152 <h3>Status of this Memo</h3>
 153 <p>
 154 By submitting this Internet-Draft,
 155 each author represents that any applicable patent or other IPR claims of which
 156 he or she is aware have been or will be disclosed,
 157 and any of which he or she becomes aware will be disclosed,
 158 in accordance with Section&nbsp;6 of BCP&nbsp;79.</p>
 159 <p>
 160 Internet-Drafts are working documents of the Internet Engineering
 161 Task Force (IETF), its areas, and its working groups.
 162 Note that other groups may also distribute working documents as
 163 Internet-Drafts.</p>
 164 <p>
 165 Internet-Drafts are draft documents valid for a maximum of six months
 166 and may be updated, replaced, or obsoleted by other documents at any time.
 167 It is inappropriate to use Internet-Drafts as reference material or to cite
 168 them other than as &ldquo;work in progress.&rdquo;</p>
 169 <p>
 170 The list of current Internet-Drafts can be accessed at
 171 <a href='http://www.ietf.org/ietf/1id-abstracts.txt'>http://www.ietf.org/ietf/1id-abstracts.txt</a>.</p>
 172 <p>
 173 The list of Internet-Draft Shadow Directories can be accessed at
 174 <a href='http://www.ietf.org/shadow.html'>http://www.ietf.org/shadow.html</a>.</p>
 175 <p>
 176 This Internet-Draft will expire on July 4, 2008.</p>
 177
 178 <h3>Copyright Notice</h3>
 179 <p>
 180 Copyright &copy; The Internet Society (2008).</p>
 181
 182 <h3>Abstract</h3>
 183
 184 <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.
 185
 186 </p><a name="toc"></a><br /><hr />
 187 <h3>Table of Contents</h3>
 188 <p class="toc">
 189 <a href="#anchor1">1.</a>&nbsp;
 190 Introduction<br />
 191 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor2">1.1.</a>&nbsp;
 192 Notational Conventions<br />
 193 <a href="#anchor3">2.</a>&nbsp;
 194 Motivation and usage scenarios<br />
 195 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor4">2.1.</a>&nbsp;
 196 Usage scenarions<br />
 197 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor5">2.1.1.</a>&nbsp;
 198 Tunneling from unicast hosts over anycast routers to other unicast hosts<br />
 199 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor6">2.1.2.</a>&nbsp;
 200 Tunneling from unicast hosts to anycast networks<br />
 201 &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor7">2.1.3.</a>&nbsp;
 202 Redundant tunnel connection of 2 networks<br />
 203 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor8">2.2.</a>&nbsp;
 204 Encapsulation<br />
 205 <a href="#anchor9">3.</a>&nbsp;
 206 Using SATP on top of IP<br />
 207 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor10">3.1.</a>&nbsp;
 208 Fragmentation<br />
 209 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor11">3.2.</a>&nbsp;
 210 ICMP messages<br />
 211 <a href="#anchor12">4.</a>&nbsp;
 212 Protocol specification<br />
 213 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor13">4.1.</a>&nbsp;
 214 Header format<br />
 215 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor14">4.2.</a>&nbsp;
 216 sequence number<br />
 217 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor15">4.3.</a>&nbsp;
 218 sender ID<br />
 219 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor16">4.4.</a>&nbsp;
 220 MUX<br />
 221 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor17">4.5.</a>&nbsp;
 222 payload type field<br />
 223 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor18">4.6.</a>&nbsp;
 224 payload<br />
 225 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor19">4.7.</a>&nbsp;
 226 padding (OPTIONAL)<br />
 227 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor20">4.8.</a>&nbsp;
 228 padding count (OPTIONAL)<br />
 229 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor21">4.9.</a>&nbsp;
 230 MKI (OPTIONAL)<br />
 231 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor22">4.10.</a>&nbsp;
 232 authentication tag (RECOMMENDED)<br />
 233 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor23">4.11.</a>&nbsp;
 234 Encryption<br />
 235 <a href="#anchor24">5.</a>&nbsp;
 236 Security Considerations<br />
 237 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#anchor25">5.1.</a>&nbsp;
 238 Replay protection<br />
 239 <a href="#anchor26">6.</a>&nbsp;
 240 IANA Considerations<br />
 241 <a href="#rfc.references1">7.</a>&nbsp;
 242 References<br />
 243 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#rfc.references1">7.1.</a>&nbsp;
 244 Normative References<br />
 245 &nbsp;&nbsp;&nbsp;&nbsp;<a href="#rfc.references2">7.2.</a>&nbsp;
 246 Informational References<br />
 247 <a href="#rfc.authors">&#167;</a>&nbsp;
 248 Author's Address<br />
 249 <a href="#rfc.copyright">&#167;</a>&nbsp;
 250 Intellectual Property and Copyright Statements<br />
 251 </p>
 252 <br clear="all" />
 253
 254 <a name="anchor1"></a><br /><hr />
 255 <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>
 256 <a name="rfc.section.1"></a><h3>1.&nbsp;
 257 Introduction</h3>
 258
 259 <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.
 260                                 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].
 261
 262 </p>
 263 <a name="anchor2"></a><br /><hr />
 264 <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>
 265 <a name="rfc.section.1.1"></a><h3>1.1.&nbsp;
 266 Notational Conventions</h3>
 267
 268 <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].
 269 </p>
 270 <a name="anchor3"></a><br /><hr />
 271 <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>
 272 <a name="rfc.section.2"></a><h3>2.&nbsp;
 273 Motivation and usage scenarios</h3>
 274
 275 <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.
 276 </p>
 277 <a name="anchor4"></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"></a><h3>2.1.&nbsp;
 280 Usage scenarions</h3>
 281
 282 <a name="anchor5"></a><br /><hr />
 283 <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>
 284 <a name="rfc.section.2.1.1"></a><h3>2.1.1.&nbsp;
 285 Tunneling from unicast hosts over anycast routers to other unicast hosts</h3>
 286 <br /><hr class="insert" />
 287 <a name="tunnel_mode"></a>
 288
 289 <p>An example of SATP used to tunnel in a unicast client - anycast server model
 290 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 291                     --------- router -----------
 292                    /                            \
 293     unicast ------+---------- router ------------+------ unicast
 294     host           \                            /        host
 295                     --------- router -----------
 296
 297   unicast  | encrypted     |  anycast  | encrypted     |  unicast
 298   tunnel   | communication |  tunnel   | communication |  tunnel
 299   endpoint | using SATP    |  endpoint | using SATP    |  endpoint
 300 </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" />
 301
 302 <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 decision.
 303 </p>
 304 <a name="anchor6"></a><br /><hr />
 305 <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>
 306 <a name="rfc.section.2.1.2"></a><h3>2.1.2.&nbsp;
 307 Tunneling from unicast hosts to anycast networks</h3>
 308 <br /><hr class="insert" />
 309 <a name="open_tunnel_mode"></a>
 310
 311 <p>An example of SATP used to encrypt data between a unicast host and anycast networks
 312 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 313                        -------Router -+---- DNS Server
 314                       /                \
 315                      /                  --- 6to4 Router
 316                     /
 317     unicast -------+----------Router --+--- DNS Server
 318     host            \                   \
 319                      \                   --- 6to4 Router
 320                       \
 321                        -------Router -+---- DNS Server
 322                                        \
 323                                         --- 6to4 Router
 324
 325   unicast  | encrypted     |  anycast  | plaintext
 326   tunnel   | communication |  tunnel   | anycast
 327   endpoint | using SATP    |  endpoint | services
 328
 329 </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" />
 330
 331 <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.
 332 </p>
 333 <a name="anchor7"></a><br /><hr />
 334 <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>
 335 <a name="rfc.section.2.1.3"></a><h3>2.1.3.&nbsp;
 336 Redundant tunnel connection of 2 networks</h3>
 337 <br /><hr class="insert" />
 338 <a name="connect_networks"></a>
 339
 340 <p>An example of SATP used to connect 2 networks
 341 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 342               Router -----------   ---------------Router
 343             /                   \ /                     \
 344     Network - Router ------------x                       Network
 345        A    \                   / \                     /   B
 346               Router -----------   ---------------Router
 347
 348             | packets       |  packets  |  packets      |
 349  plaintext  | get           |  take a   |  get          | plaintext
 350  packets    | de/encrypted  |  random   |  de/encrypted | packets
 351             |de/encapsulated|   path    |de/encapsulated|
 352
 353 </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" />
 354
 355 <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.
 356 </p>
 357 <a name="anchor8"></a><br /><hr />
 358 <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>
 359 <a name="rfc.section.2.2"></a><h3>2.2.&nbsp;
 360 Encapsulation</h3>
 361
 362 <p>SATP does not depend on which lower layer protocols is used, but this section gives an example of how packets could look like.
 363
 364 </p><br /><hr class="insert" />
 365 <a name="transport_udp"></a>
 366
 367 <p>Examples of SATP used with different lower layer and payload protocols
 368 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 369     +------+-----+-------------------------------+
 370     |      |     |      +----------------+-----+ |
 371     | IPv6 | UDP | SATP | Ethernet 802.3 | ... | |
 372     |      |     |      +----------------+-----+ |
 373     +------+-----+-------------------------------+
 374
 375 Tunneling of Ethernet over UDP/IPv6
 376
 377     +------+-----+---------------------------+
 378     |      |     |      +------+-----+-----+ |
 379     | IPv4 | UDP | SATP | IPv6 | UDP | RTP | |
 380     |      |     |      +------+-----+-----+ |
 381     +------+-----+---------------------------+
 382
 383 Tunneling of IPv6 over UDP/IPv4 with RTP payload
 384
 385     +------+-------------------------------+
 386     |      |      +----------------+-----+ |
 387     | IPv6 | SATP | Ethernet 802.3 | ... | |
 388     |      |      +----------------+-----+ |
 389     +------+-------------------------------+
 390
 391 Tunneling of Ethernet over IPv6
 392
 393     +------+---------------------------+
 394     |      |      +------+-----+-----+ |
 395     | IPv4 | SATP | IPv6 | UDP | RTP | |
 396     |      |      +------+-----+-----+ |
 397     +------+---------------------------+
 398
 399 Tunneling of IPv6 over IPv4 with RTP payload
 400 </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" />
 401
 402 <a name="anchor9"></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"></a><h3>3.&nbsp;
 405 Using SATP on top of IP</h3>
 406
 407 <a name="anchor10"></a><br /><hr />
 408 <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>
 409 <a name="rfc.section.3.1"></a><h3>3.1.&nbsp;
 410 Fragmentation</h3>
 411
 412 <p>
 413            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.
 414
 415 </p>
 416 <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.
 417 </p>
 418 <a name="anchor11"></a><br /><hr />
 419 <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>
 420 <a name="rfc.section.3.2"></a><h3>3.2.&nbsp;
 421 ICMP messages</h3>
 422
 423 <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.
 424 </p>
 425 <a name="anchor12"></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"></a><h3>4.&nbsp;
 428 Protocol specification</h3>
 429
 430 <a name="anchor13"></a><br /><hr />
 431 <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>
 432 <a name="rfc.section.4.1"></a><h3>4.1.&nbsp;
 433 Header format</h3>
 434 <br /><hr class="insert" />
 435 <a name="prot_header_table"></a>
 436
 437 <p>Protocol Format
 438 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 439       0                   1                   2                   3
 440       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
 441      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 442      |                         sequence number                       | |
 443      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 444      |           sender ID           |              MUX              | |
 445    +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+ |
 446    | |         payload type          |                               | |
 447    | +-------------------------------+                               | |
 448    | |              ....        payload        ...                   | |
 449    | |                               +-------------------------------+ |
 450    | |                               | padding (OPT) | pad count(OPT)| |
 451    +#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+#+-+
 452    | ~                          MKI (OPTIONAL)                       ~ |
 453    | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 454    | :                 authentication tag (RECOMMENDED)              : |
 455    | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
 456    |                                                                   |
 457    +- Encrypted Portion                       Authenticated Portion ---+
 458 </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" />
 459
 460 <p>
 461 </p>
 462 <a name="anchor14"></a><br /><hr />
 463 <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>
 464 <a name="rfc.section.4.2"></a><h3>4.2.&nbsp;
 465 sequence number</h3>
 466
 467 <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.
 468 </p>
 469 <a name="anchor15"></a><br /><hr />
 470 <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>
 471 <a name="rfc.section.4.3"></a><h3>4.3.&nbsp;
 472 sender ID</h3>
 473
 474 <p>The sender ID is a 16 bit unsigned integer. It HAS TO be unique for every sender sharing the same anycast address
 475 </p>
 476 <a name="anchor16"></a><br /><hr />
 477 <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>
 478 <a name="rfc.section.4.4"></a><h3>4.4.&nbsp;
 479 MUX</h3>
 480
 481 <p>The MUX (multiplex) field is a 16 bit unsigned integer. It is used to destinguish multible tunnel connections.
 482 </p>
 483 <a name="anchor17"></a><br /><hr />
 484 <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>
 485 <a name="rfc.section.4.5"></a><h3>4.5.&nbsp;
 486 payload type field</h3>
 487
 488 <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.
 489         <br /><hr class="insert" />
 490 <a name="prot_type_table"></a>
 491
 492 <p>Some examples for protocol types
 493 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 494 HEX
 495 0000 Reserved
 496 .... Reserved
 497 05DC Reserved
 498 0800 Internet IP (IPv4)
 499 6558 transparent ethernet bridging
 500 86DD IPv6
 501 </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" />
 502
 503
 504
 505 <a name="anchor18"></a><br /><hr />
 506 <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>
 507 <a name="rfc.section.4.6"></a><h3>4.6.&nbsp;
 508 payload</h3>
 509
 510 <p>A packet of the type payload type (e.g. an IP packet).
 511 </p>
 512 <a name="anchor19"></a><br /><hr />
 513 <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>
 514 <a name="rfc.section.4.7"></a><h3>4.7.&nbsp;
 515 padding (OPTIONAL)</h3>
 516
 517 <p>Padding of max 255 octets.
 518 None of the pre-defined encryption transforms uses any padding; for
 519    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 length.
 520 </p>
 521 <a name="anchor20"></a><br /><hr />
 522 <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>
 523 <a name="rfc.section.4.8"></a><h3>4.8.&nbsp;
 524 padding count (OPTIONAL)</h3>
 525
 526 <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.
 527 </p>
 528 <a name="anchor21"></a><br /><hr />
 529 <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>
 530 <a name="rfc.section.4.9"></a><h3>4.9.&nbsp;
 531 MKI (OPTIONAL)</h3>
 532
 533 <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
 534 </p>
 535 <a name="anchor22"></a><br /><hr />
 536 <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>
 537 <a name="rfc.section.4.10"></a><h3>4.10.&nbsp;
 538 authentication tag (RECOMMENDED)</h3>
 539
 540 <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.
 541 </p>
 542 <a name="anchor23"></a><br /><hr />
 543 <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>
 544 <a name="rfc.section.4.11"></a><h3>4.11.&nbsp;
 545 Encryption</h3>
 546
 547 <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.
 548 </p>
 549 <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.
 550 </p><br /><hr class="insert" />
 551 <a name="srtp_vs_satp"></a>
 552
 553 <p>Difference between SRTP and SATP
 554 </p><div style='display: table; width: 0; margin-left: 3em; margin-right: auto'><pre>
 555       0                   1                   2                   3
 556       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
 557      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 558      |                     SATP    sequence number                   |
 559      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 560                                      =
 561      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 562      |  SRTP ROC least significant   |           SRTP SEQ            |
 563      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 564
 565
 566       0                   1                   2                   3
 567       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
 568      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 569      |           SATP  MUX           |       SATP sender ID          |
 570      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 571                                      =
 572      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 573      |                           SRTP SSRC                           |
 574      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
 575 </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" />
 576
 577 <a name="anchor24"></a><br /><hr />
 578 <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>
 579 <a name="rfc.section.5"></a><h3>5.&nbsp;
 580 Security Considerations</h3>
 581
 582 <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.
 583 </p>
 584 <a name="anchor25"></a><br /><hr />
 585 <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>
 586 <a name="rfc.section.5.1"></a><h3>5.1.&nbsp;
 587 Replay protection</h3>
 588
 589 <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.
 590 </p>
 591 <a name="anchor26"></a><br /><hr />
 592 <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>
 593 <a name="rfc.section.6"></a><h3>6.&nbsp;
 594 IANA Considerations</h3>
 595
 596 <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.
 597 </p>
 598 <a name="rfc.references"></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 <a name="rfc.section.7"></a><h3>7.&nbsp;
 601 References</h3>
 602
 603 <a name="rfc.references1"></a><br /><hr />
 604 <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>
 605 <h3>7.1.&nbsp;Normative References</h3>
 606 <table width="99%" border="0">
 607 <tr><td class="author-text" valign="top"><a name="RFC3711">[1]</a></td>
 608 <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>
 609 <tr><td class="author-text" valign="top"><a name="RFC2119">[2]</a></td>
 610 <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>
 611 <tr><td class="author-text" valign="top"><a name="RFC2003">[3]</a></td>
 612 <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>
 613 </table>
 614
 615 <a name="rfc.references2"></a><br /><hr />
 616 <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>
 617 <h3>7.2.&nbsp;Informational References</h3>
 618 <table width="99%" border="0">
 619 <tr><td class="author-text" valign="top"><a name="RFC2784">[4]</a></td>
 620 <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>
 621 <tr><td class="author-text" valign="top"><a name="RFC2401">[5]</a></td>
 622 <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>
 623 <tr><td class="author-text" valign="top"><a name="RFC1546">[6]</a></td>
 624 <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>
 625 </table>
 626
 627 <a name="rfc.authors"></a><br /><hr />
 628 <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>
 629 <h3>Author's Address</h3>
 630 <table width="99%" border="0" cellpadding="0" cellspacing="0">
 631 <tr><td class="author-text">&nbsp;</td>
 632 <td class="author-text">Othmar Gsenger</td></tr>
 633 <tr><td class="author-text">&nbsp;</td>
 634 <td class="author-text">Puerstingerstr 32</td></tr>
 635 <tr><td class="author-text">&nbsp;</td>
 636 <td class="author-text">Saalfelden  5760</td></tr>
 637 <tr><td class="author-text">&nbsp;</td>
 638 <td class="author-text">AT</td></tr>
 639 <tr><td class="author" align="right">Phone:&nbsp;</td>
 640 <td class="author-text"></td></tr>
 641 <tr><td class="author" align="right">Email:&nbsp;</td>
 642 <td class="author-text"><a href="mailto:satp@gsenger.com">satp@gsenger.com</a></td></tr>
 643 <tr><td class="author" align="right">URI:&nbsp;</td>
 644 <td class="author-text"><a href="http://www.gsenger.com/satp/">http://www.gsenger.com/satp/</a></td></tr>
 645 </table>
 646 <a name="rfc.copyright"></a><br /><hr />
 647 <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>
 648 <h3>Full Copyright Statement</h3>
 649 <p class='copyright'>
 650 Copyright &copy; The Internet Society (2008).</p>
 651 <p class='copyright'>
 652 This document is subject to the rights,
 653 licenses and restrictions contained in BCP&nbsp;78,
 654 and except as set forth therein,
 655 the authors retain all their rights.</p>
 656 <p class='copyright'>
 657 This document and the information contained herein are provided
 658 on an &ldquo;AS IS&rdquo; basis and THE CONTRIBUTOR,
 659 THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY),
 660 THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM
 661 ALL WARRANTIES,
 662 EXPRESS OR IMPLIED,
 663 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 664 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 665 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.</p>
 666 <h3>Intellectual Property</h3>
 667 <p class='copyright'>
 668 The IETF takes no position regarding the validity or scope of any
 669 Intellectual Property Rights or other rights that might be claimed
 670 to pertain to the implementation or use of the technology
 671 described in this document or the extent to which any license
 672 under such rights might or might not be available; nor does it
 673 represent that it has made any independent effort to identify any
 674 such rights.
 675 Information on the procedures with respect to
 676 rights in RFC documents can be found in BCP&nbsp;78 and BCP&nbsp;79.</p>
 677 <p class='copyright'>
 678 Copies of IPR disclosures made to the IETF Secretariat and any
 679 assurances of licenses to be made available,
 680 or the result of an attempt made to obtain a general license or
 681 permission for the use of such proprietary rights by implementers or
 682 users of this specification can be obtained from the IETF on-line IPR
 683 repository at <a href='http://www.ietf.org/ipr'>http://www.ietf.org/ipr</a>.</p>
 684 <p class='copyright'>
 685 The IETF invites any interested party to bring to its attention
 686 any copyrights,
 687 patents or patent applications,
 688 or other
 689 proprietary rights that may cover technology that may be required
 690 to implement this standard.
 691 Please address the information to the IETF at <a href='mailto:ietf-ipr@ietf.org'>ietf-ipr@ietf.org</a>.</p>
 692 <h3>Acknowledgment</h3>
 693 <p class='copyright'>
 694 Funding for the RFC Editor function is provided by
 695 the IETF Administrative Support Activity (IASA).</p>
 696 </body></html>