From 6c9fac3bb2fac2e69458ea9f1d66c20b596acf24 Mon Sep 17 00:00:00 2001 From: Othmar Gsenger Date: Thu, 26 Apr 2007 21:29:25 +0000 Subject: must --- internet-draft-satp.html | 99 ++++++++++++++++++++++++++++++++---------------- 1 file changed, 66 insertions(+), 33 deletions(-) (limited to 'internet-draft-satp.html') diff --git a/internet-draft-satp.html b/internet-draft-satp.html index 4113660..5af3075 100644 --- a/internet-draft-satp.html +++ b/internet-draft-satp.html @@ -186,19 +186,25 @@ Copyright © The IETF Trust (2007).

1.  Introduction

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SATP is somehow a mixture of a generic encapsulation protocol like GRE (Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, “Generic Routing Encapsulation (GRE),” March 2000.) [1] and a secure tunneling protocol as IPsec (Kent, S. and R. Atkinson, “Security Architecture for the Internet Protocol,” November 1998.) [2] in tunnel mode. To save some header overhead it uses the encryption technices of SRTP (Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” March 2004.) [3]. It supports peer to peer tunnels, where tunnel endpoints can be any combination of unicast, multicast or anycast hosts, so it defines a Host Anycast Service (Partridge, C., Mendez, T., and W. Milliken, “Host Anycasting Service,” November 1993.) [4] +

SATP is somehow a mixture of a generic encapsulation protocol like GRE (Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, “Generic Routing Encapsulation (GRE),” March 2000.) [3] and a secure tunneling protocol as IPsec (Kent, S. and R. Atkinson, “Security Architecture for the Internet Protocol,” November 1998.) [4] in tunnel mode. To save some header overhead it uses the encryption technices of SRTP (Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” March 2004.) [1]. It supports peer to peer tunnels, where tunnel endpoints can be any combination of unicast, multicast or anycast hosts, so it defines a Host Anycast Service (Partridge, C., Mendez, T., and W. Milliken, “Host Anycasting Service,” November 1993.) [5]


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1.1.  +Notational Conventions

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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 RFC2119 (Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” March 1997.) [2]. +

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2.  Motivation and usage scenarios

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.

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2.1.  Usage scenarions

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2.1.1.  tunneling from unicast hosts over anycast routers to other unicast hosts


@@ -219,7 +225,7 @@ tunneling from unicast hosts over anycast routers to other unicast hosts

In this scenario the payload gets encapsuleted into a SATP packet by a unicast host and gets transmitted to one of the anycast routers. It than gets decapsulated by the router. This router makes a routing descision based on the underlying protocol and transmits a new SATP package to one or more unicast hosts depending on the routing descition.

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2.1.2.  tunneling from unicast hosts to anycast networks


@@ -247,7 +253,7 @@ tunneling from unicast hosts to anycast networks

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2.1.3.  redundant tunnel connection of 2 networks


@@ -270,7 +276,7 @@ redundant tunnel connection of 2 networks

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.

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2.2.  Encapsulation

@@ -316,20 +322,24 @@ Tunneling of IPv6 over IPv4 with RTP payload

When using UDP no flow control or retransmission is done, neither by UDP nor anytun. The encapsulated protocol HAS TO take care of this tasks if needed. UDP however has a checksum of the complete UDP datagram, so a packet gets discarded if there is a biterror in the payload

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2.3.  +
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3.  +Using SATP on top of IP

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3.1.  Fragmentation

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.

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3.  +
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4.  Protocol specification

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3.1.  +
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4.1.  Header format


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3.2.  +
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4.2.  sender ID

The sender ID is a 16bit unsigned integer. It HAS TO be unique for every sender sharing the same anycast address

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3.3.  +
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4.3.  sequence number

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.

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3.4.  +
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4.4.  payload

A packet of the type payload type (e.g. an IP packet).

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3.5.  +
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4.5.  padding (OPTIONAL)

Padding of max 255 octets. None of the pre-defined encryption transforms uses any padding; for 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 padding field is present, than the padding count field MUST be set to the padding lenght.

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3.6.  +
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4.6.  padding count

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.

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3.7.  +
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4.7.  payload type field

The payload type field defines the payload protocol. ETHER TYPE protocol numbers are used. See IANA assigned ethernet numbers . The values 0000-05DC are reserverd and MUST NOT be used. @@ -410,22 +420,45 @@ HEX -

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3.8.  +
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4.8.  Encryption

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Encryption is done in the same way as for SRTP (Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” March 2004.) [3]. This section will only discuss some small changes that HAVE TO be made. +

Encryption is done in the same way as for SRTP (Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” March 2004.) [1]. This section will only discuss some small changes that HAVE TO be made. Please read SRTP RFC3711 section 3-9 (Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” March 2004.) [1] for details. SSRC is replaced by the sender ID +

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5.  +Security Considerations

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As satp uses the same encrytion technics as SRTP (Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” March 2004.) [1], it shares the same security issues. This section will only discuss some small changes. Please read SRTP RFC3711 section 9 (Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” March 2004.) [1] for details.

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5.1.  +Replay protection

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Replay protection is done by a replay list. Every anycast receiver has it's own replay list, which SOULDN'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 reciever. 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. +

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6.  +References

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4. References

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6.1. Normative References

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[1]
[1]Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” RFC 3711, March 2004.
[2]Bradner, S., “Key words for use in RFCs to Indicate Requirement Levels,” BCP 14, RFC 2119, March 1997 (TXT, HTML, XML).
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6.2. Informational References

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[3] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. Traina, “Generic Routing Encapsulation (GRE),” RFC 2784, March 2000.
[2]
[4] Kent, S. and R. Atkinson, “Security Architecture for the Internet Protocol,” RFC 2401, November 1998 (TXT, HTML, XML).
[3]Baugher, M., McGrew, D., Naslund, M., Carrara, E., and K. Norrman, “The Secure Real-time Transport Protocol (SRTP),” RFC 3711, March 2004.
[4]
[5] Partridge, C., Mendez, T., and W. Milliken, “Host Anycasting Service,” RFC 1546, November 1993.
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