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"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"> </td></tr>
148 <tr><td class=
"header">Expires: July
4,
2008</td><td class=
"header"> </td></tr>
149 </table></td></tr></table>
150 <h1><br />secure anycast tunneling protocol (SATP)
<br />draft-gsenger-secure-anycast-tunneling-protocol-
01</h1>
152 <h3>Status of this Memo
</h3>
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
6 of BCP
79.
</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
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
“work in progress.
”</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>
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>
176 This Internet-Draft will expire on July
4,
2008.
</p>
178 <h3>Copyright Notice
</h3>
180 Copyright
© The Internet Society (
2008).
</p>
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.,
“IP Encapsulation within IP,
” October
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,
“Generic Routing Encapsulation (GRE),
” March
2000.
</span><span>)
</span></a> [
4]. It supports both anycast receivers and senders.
186 </p><a name=
"toc"></a><br /><hr />
187 <h3>Table of Contents
</h3>
189 <a href=
"#anchor1">1.
</a>
191 <a href=
"#anchor2">1.1.
</a>
192 Notational Conventions
<br />
193 <a href=
"#anchor3">2.
</a>
194 Motivation and usage scenarios
<br />
195 <a href=
"#anchor4">2.1.
</a>
196 Usage scenarions
<br />
197 <a href=
"#anchor5">2.1.1.
</a>
198 Tunneling from unicast hosts over anycast routers to other unicast hosts
<br />
199 <a href=
"#anchor6">2.1.2.
</a>
200 Tunneling from unicast hosts to anycast networks
<br />
201 <a href=
"#anchor7">2.1.3.
</a>
202 Redundant tunnel connection of
2 networks
<br />
203 <a href=
"#anchor8">2.2.
</a>
205 <a href=
"#anchor9">3.
</a>
206 Using SATP on top of IP
<br />
207 <a href=
"#anchor10">3.1.
</a>
209 <a href=
"#anchor11">3.2.
</a>
211 <a href=
"#anchor12">4.
</a>
212 Protocol specification
<br />
213 <a href=
"#anchor13">4.1.
</a>
215 <a href=
"#anchor14">4.2.
</a>
216 sequence number
<br />
217 <a href=
"#anchor15">4.3.
</a>
219 <a href=
"#anchor16">4.4.
</a>
221 <a href=
"#anchor17">4.5.
</a>
222 payload type field
<br />
223 <a href=
"#anchor18">4.6.
</a>
225 <a href=
"#anchor19">4.7.
</a>
226 padding (OPTIONAL)
<br />
227 <a href=
"#anchor20">4.8.
</a>
228 padding count (OPTIONAL)
<br />
229 <a href=
"#anchor21">4.9.
</a>
231 <a href=
"#anchor22">4.10.
</a>
232 authentication tag (RECOMMENDED)
<br />
233 <a href=
"#anchor23">4.11.
</a>
235 <a href=
"#anchor24">5.
</a>
236 Security Considerations
<br />
237 <a href=
"#anchor25">5.1.
</a>
238 Replay protection
<br />
239 <a href=
"#anchor26">6.
</a>
240 IANA Considerations
<br />
241 <a href=
"#rfc.references1">7.
</a>
243 <a href=
"#rfc.references1">7.1.
</a>
244 Normative References
<br />
245 <a href=
"#rfc.references2">7.2.
</a>
246 Informational References
<br />
247 <a href=
"#rfc.authors">§</a>
248 Author's Address
<br />
249 <a href=
"#rfc.copyright">§</a>
250 Intellectual Property and Copyright Statements
<br />
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"> TOC
</a></td></tr></table>
256 <a name=
"rfc.section.1"></a><h3>1.
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,
“Generic Routing Encapsulation (GRE),
” March
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,
“Security Architecture for the Internet Protocol,
” November
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,
“Host Anycasting Service,
” November
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,
“The Secure Real-time Transport Protocol (SRTP),
” March
2004.
</span><span>)
</span></a> [
1].
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"> TOC
</a></td></tr></table>
265 <a name=
"rfc.section.1.1"></a><h3>1.1.
266 Notational Conventions
</h3>
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.,
“Key words for use in RFCs to Indicate Requirement Levels,
” March
1997.
</span><span>)
</span></a> [
2].
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"> TOC
</a></td></tr></table>
272 <a name=
"rfc.section.2"></a><h3>2.
273 Motivation and usage scenarios
</h3>
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.
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"> TOC
</a></td></tr></table>
279 <a name=
"rfc.section.2.1"></a><h3>2.1.
280 Usage scenarions
</h3>
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"> TOC
</a></td></tr></table>
284 <a name=
"rfc.section.2.1.1"></a><h3>2.1.1.
285 Tunneling from unicast hosts over anycast routers to other unicast hosts
</h3>
286 <br /><hr class=
"insert" />
287 <a name=
"tunnel_mode"></a>
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 -----------
293 unicast ------+---------- router ------------+------ unicast
295 --------- router -----------
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> Figure
1 </b></font><br /></td></tr></table><hr class=
"insert" />
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.
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"> TOC
</a></td></tr></table>
306 <a name=
"rfc.section.2.1.2"></a><h3>2.1.2.
307 Tunneling from unicast hosts to anycast networks
</h3>
308 <br /><hr class=
"insert" />
309 <a name=
"open_tunnel_mode"></a>
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
317 unicast -------+----------Router --+--- DNS Server
321 -------Router -+---- DNS Server
325 unicast | encrypted | anycast | plaintext
326 tunnel | communication | tunnel | anycast
327 endpoint | using SATP | endpoint | services
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> Figure
2 </b></font><br /></td></tr></table><hr class=
"insert" />
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.
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"> TOC
</a></td></tr></table>
335 <a name=
"rfc.section.2.1.3"></a><h3>2.1.3.
336 Redundant tunnel connection of
2 networks
</h3>
337 <br /><hr class=
"insert" />
338 <a name=
"connect_networks"></a>
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
344 Network - Router ------------x Network
346 Router ----------- ---------------Router
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|
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> Figure
3 </b></font><br /></td></tr></table><hr class=
"insert" />
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.
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"> TOC
</a></td></tr></table>
359 <a name=
"rfc.section.2.2"></a><h3>2.2.
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.
364 </p><br /><hr class=
"insert" />
365 <a name=
"transport_udp"></a>
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 +------+-----+-------------------------------+
375 Tunneling of Ethernet over UDP/IPv6
377 +------+-----+---------------------------+
378 | | | +------+-----+-----+ |
379 | IPv4 | UDP | SATP | IPv6 | UDP | RTP | |
380 | | | +------+-----+-----+ |
381 +------+-----+---------------------------+
383 Tunneling of IPv6 over UDP/IPv4 with RTP payload
385 +------+-------------------------------+
386 | | +----------------+-----+ |
387 | IPv6 | SATP | Ethernet
802.3 | ... | |
388 | | +----------------+-----+ |
389 +------+-------------------------------+
391 Tunneling of Ethernet over IPv6
393 +------+---------------------------+
394 | | +------+-----+-----+ |
395 | IPv4 | SATP | IPv6 | UDP | RTP | |
396 | | +------+-----+-----+ |
397 +------+---------------------------+
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> Figure
4 </b></font><br /></td></tr></table><hr class=
"insert" />
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"> TOC
</a></td></tr></table>
404 <a name=
"rfc.section.3"></a><h3>3.
405 Using SATP on top of IP
</h3>
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"> TOC
</a></td></tr></table>
409 <a name=
"rfc.section.3.1"></a><h3>3.1.
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.
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.
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"> TOC
</a></td></tr></table>
420 <a name=
"rfc.section.3.2"></a><h3>3.2.
423 <p>ICMP messages MUST be relayed according to
<a class='info' href='#RFC2003'
>rfc2003 section
4<span> (
</span><span class='info'
>Perkins, C.,
“IP Encapsulation within IP,
” October
1996.
</span><span>)
</span></a> [
3]. This is needed for path MTU detection.
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"> TOC
</a></td></tr></table>
427 <a name=
"rfc.section.4"></a><h3>4.
428 Protocol specification
</h3>
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"> TOC
</a></td></tr></table>
432 <a name=
"rfc.section.4.1"></a><h3>4.1.
434 <br /><hr class=
"insert" />
435 <a name=
"prot_header_table"></a>
438 </p><div style='display: table; width:
0; margin-left:
3em; margin-right: auto'
><pre>
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 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
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> Figure
5 </b></font><br /></td></tr></table><hr class=
"insert" />
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"> TOC
</a></td></tr></table>
464 <a name=
"rfc.section.4.2"></a><h3>4.2.
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.
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"> TOC
</a></td></tr></table>
471 <a name=
"rfc.section.4.3"></a><h3>4.3.
474 <p>The sender ID is a
16 bit unsigned integer. It HAS TO be unique for every sender sharing the same anycast address
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"> TOC
</a></td></tr></table>
478 <a name=
"rfc.section.4.4"></a><h3>4.4.
481 <p>The MUX (multiplex) field is a
16 bit unsigned integer. It is used to destinguish multible tunnel connections.
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"> TOC
</a></td></tr></table>
485 <a name=
"rfc.section.4.5"></a><h3>4.5.
486 payload type field
</h3>
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>
492 <p>Some examples for protocol types
493 </p><div style='display: table; width:
0; margin-left:
3em; margin-right: auto'
><pre>
498 0800 Internet IP (IPv4)
499 6558 transparent ethernet bridging
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> Figure
6 </b></font><br /></td></tr></table><hr class=
"insert" />
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"> TOC
</a></td></tr></table>
507 <a name=
"rfc.section.4.6"></a><h3>4.6.
510 <p>A packet of the type payload type (e.g. an IP packet).
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"> TOC
</a></td></tr></table>
514 <a name=
"rfc.section.4.7"></a><h3>4.7.
515 padding (OPTIONAL)
</h3>
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.
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"> TOC
</a></td></tr></table>
523 <a name=
"rfc.section.4.8"></a><h3>4.8.
524 padding count (OPTIONAL)
</h3>
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.
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"> TOC
</a></td></tr></table>
530 <a name=
"rfc.section.4.9"></a><h3>4.9.
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,
“The Secure Real-time Transport Protocol (SRTP),
” March
2004.
</span><span>)
</span></a> [
1] for details
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"> TOC
</a></td></tr></table>
537 <a name=
"rfc.section.4.10"></a><h3>4.10.
538 authentication tag (RECOMMENDED)
</h3>
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.
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"> TOC
</a></td></tr></table>
544 <a name=
"rfc.section.4.11"></a><h3>4.11.
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,
“The Secure Real-time Transport Protocol (SRTP),
” March
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,
“The Secure Real-time Transport Protocol (SRTP),
” March
2004.
</span><span>)
</span></a> [
1] for details.
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>
553 <p>Difference between SRTP and SATP
554 </p><div style='display: table; width:
0; margin-left:
3em; margin-right: auto'
><pre>
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
561 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
562 | SRTP ROC least significant | SRTP SEQ |
563 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
572 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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> Figure
7 </b></font><br /></td></tr></table><hr class=
"insert" />
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"> TOC
</a></td></tr></table>
579 <a name=
"rfc.section.5"></a><h3>5.
580 Security Considerations
</h3>
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,
“The Secure Real-time Transport Protocol (SRTP),
” March
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,
“The Secure Real-time Transport Protocol (SRTP),
” March
2004.
</span><span>)
</span></a> [
1] for details.
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"> TOC
</a></td></tr></table>
586 <a name=
"rfc.section.5.1"></a><h3>5.1.
587 Replay protection
</h3>
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.
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"> TOC
</a></td></tr></table>
593 <a name=
"rfc.section.6"></a><h3>6.
594 IANA Considerations
</h3>
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.
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"> TOC
</a></td></tr></table>
600 <a name=
"rfc.section.7"></a><h3>7.
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"> TOC
</a></td></tr></table>
605 <h3>7.1.
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,
“<a href=
"ftp://ftp.isi.edu/in-notes/rfc3711.txt">The Secure Real-time Transport Protocol (SRTP)
</a>,
” RFC
3711, March
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>,
“<a href=
"ftp://ftp.isi.edu/in-notes/rfc2119.txt">Key words for use in RFCs to Indicate Requirement Levels
</a>,
” BCP
14, RFC
2119, March
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>,
“<a href=
"ftp://ftp.isi.edu/in-notes/rfc2003.txt">IP Encapsulation within IP
</a>,
” RFC
2003, October
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>
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"> TOC
</a></td></tr></table>
617 <h3>7.2.
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>,
“<a href=
"ftp://ftp.isi.edu/in-notes/rfc2784.txt">Generic Routing Encapsulation (GRE)
</a>,
” RFC
2784, March
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>,
“<a href=
"ftp://ftp.isi.edu/in-notes/rfc2401.txt">Security Architecture for the Internet Protocol
</a>,
” RFC
2401, November
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>,
“<a href=
"ftp://ftp.isi.edu/in-notes/rfc1546.txt">Host Anycasting Service
</a>,
” RFC
1546, November
1993.
</td></tr>
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"> TOC
</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"> </td>
632 <td class=
"author-text">Othmar Gsenger
</td></tr>
633 <tr><td class=
"author-text"> </td>
634 <td class=
"author-text">Puerstingerstr
32</td></tr>
635 <tr><td class=
"author-text"> </td>
636 <td class=
"author-text">Saalfelden
5760</td></tr>
637 <tr><td class=
"author-text"> </td>
638 <td class=
"author-text">AT
</td></tr>
639 <tr><td class=
"author" align=
"right">Phone:
</td>
640 <td class=
"author-text"></td></tr>
641 <tr><td class=
"author" align=
"right">Email:
</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:
</td>
644 <td class=
"author-text"><a href=
"http://www.gsenger.com/satp/">http://www.gsenger.com/satp/
</a></td></tr>
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"> TOC
</a></td></tr></table>
648 <h3>Full Copyright Statement
</h3>
649 <p class='copyright'
>
650 Copyright
© The Internet Society (
2008).
</p>
651 <p class='copyright'
>
652 This document is subject to the rights,
653 licenses and restrictions contained in BCP
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
“AS IS
” 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
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
675 Information on the procedures with respect to
676 rights in RFC documents can be found in BCP
78 and BCP
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
687 patents or patent applications,
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>