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Versions: 00 01 02 draft-mattsson-lwig-security-protocol-comparison

Network Working Group                                        J. Mattsson
Internet-Draft                                               Ericsson AB
Intended status: Informational                         November 11, 2017
Expires: May 15, 2018


            Message Size Overhead of CoAP Security Protocols
                draft-mattsson-core-security-overhead-02

Abstract

   This document analyzes and compares per-packet message size overheads
   when using different security protocols to secure CoAP.  The analyzed
   security protocols are DTLS 1.2, DTLS 1.3, TLS 1.2, TLS 1.3, and
   OSCORE.  DTLS and TLS are analyzed with and without compression.
   DTLS are analyzed with two different alternatives for header
   compression as well as with and without Connection ID.

Status of This Memo

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   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on May 15, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of




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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Overhead of Security Protocols  . . . . . . . . . . . . . . .   3
     2.1.  DTLS  . . . . . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.1.  DTLS 1.2  . . . . . . . . . . . . . . . . . . . . . .   3
       2.1.2.  DTLS 1.2 with 6LoWPAN-GHC . . . . . . . . . . . . . .   3
       2.1.3.  DTLS 1.2 with raza-6lo-compressed-dtls  . . . . . . .   4
       2.1.4.  DTLS 1.3  . . . . . . . . . . . . . . . . . . . . . .   5
       2.1.5.  DTLS 1.3 with 6LoWPAN-GHC . . . . . . . . . . . . . .   5
       2.1.6.  DTLS 1.3 with raza-6lo-compressed-dtls  . . . . . . .   6
     2.2.  DTLS with Connection ID . . . . . . . . . . . . . . . . .   7
       2.2.1.  DTLS 1.2 with Connection ID . . . . . . . . . . . . .   7
       2.2.2.  DTLS 1.2 with Connection ID and 6LoWPAN-GHC . . . . .   7
       2.2.3.  DTLS 1.3 with Connection ID . . . . . . . . . . . . .   8
       2.2.4.  DTLS 1.3 with Connection ID and 6LoWPAN-GHC . . . . .   9
     2.3.  TLS . . . . . . . . . . . . . . . . . . . . . . . . . . .  10
       2.3.1.  TLS 1.2 . . . . . . . . . . . . . . . . . . . . . . .  10
       2.3.2.  TLS 1.2 with 6LoWPAN-GHC  . . . . . . . . . . . . . .  10
       2.3.3.  TLS 1.3 . . . . . . . . . . . . . . . . . . . . . . .  11
       2.3.4.  TLS 1.3 with 6LoWPAN-GHC  . . . . . . . . . . . . . .  11
     2.4.  OSCORE  . . . . . . . . . . . . . . . . . . . . . . . . .  12
   3.  Overhead with Different Parameters  . . . . . . . . . . . . .  14
   4.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .  15
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .  16
   6.  Informative References  . . . . . . . . . . . . . . . . . . .  16
   Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  18
   Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .  18

1.  Introduction

   This document analyzes and compares per-packet message size overheads
   when using different security protocols to secure CoAP over UPD
   [RFC7252] and TCP [I-D.ietf-core-coap-tcp-tls].  The analyzed
   security protocols are DTLS 1.2 [RFC6347], DTLS 1.3
   [I-D.rescorla-tls-dtls13], TLS 1.2 [RFC5246], TLS 1.3
   [I-D.ietf-tls-tls13], and OSCORE [I-D.ietf-core-object-security].
   The DTLS and TLS record layers are analyzed with and without
   compression.  DTLS are analyzed with two different alternatives
   ([RFC7400] and [raza-6lo-compressed-dtls]) for header compression as
   well as with and without Connection ID
   [I-D.rescorla-tls-dtls-connection-id].






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2.  Overhead of Security Protocols

   To enable comparison, all the overhead calculations in this section
   use AES-CCM with a tag length of 8 bytes, a plaintext of 6 bytes, and
   the sequence number '05'.  This follows the example in [RFC7400],
   Figure 16.

2.1.  DTLS

2.1.1.  DTLS 1.2

   This section analyzes the overhead of DTLS 1.2 [RFC6347].  The nonce
   follow the strict profiling given in [RFC7925].  This example is
   taken directly from [RFC7400], Figure 16. .

   DTLS 1.2 Record Layer (35 bytes, 29 bytes overhead):
   17 fe fd 00 01 00 00 00 00 00 05 00 16 00 01 00
   00 00 00 00 05 ae a0 15 56 67 92 4d ff 8a 24 e4
   cb 35 b9

   Content type:
   17
   Version:
   fe fd
   Epoch:
   00 01
   Sequence number:
   00 00 00 00 00 05
   Length:
   00 16
   Nonce:
   00 01 00 00 00 00 00 05
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   DTLS 1.2 gives 29 bytes overhead.

2.1.2.  DTLS 1.2 with 6LoWPAN-GHC

   This section analyzes the overhead of DTLS 1.2 [RFC6347] when
   compressed with [RFC7400].  The compression was done with
   [OlegHahm-ghc].

   Note that the compressed overhead is dependent on the parameters
   epoch, sequence number, and length.  The following is only an
   example.



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   Note that the sequence number '01' used in [RFC7400], Figure 15 gives
   an exceptionally small overhead that is not representative.

   Note that this header compression is not available when DTLS is
   exchanged over transports that do not use 6LoWPAN together with
   6LoWPAN-GHC.

   Compressed DTLS 1.2 Record Layer (22 bytes, 16 bytes overhead):
   b0 c3 03 05 00 16 f2 0e ae a0 15 56 67 92 4d ff
   8a 24 e4 cb 35 b9

   Compressed DTLS 1.2 Record Layer Header and Nonce:
   b0 c3 03 05 00 16 f2 0e
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   When compressed with 6LoWPAN-GHC, DTLS 1.2 with the above parameters
   (epoch, sequence number, length) gives 16 bytes overhead.

2.1.3.  DTLS 1.2 with raza-6lo-compressed-dtls

   This section analyzes the overhead of DTLS 1.2 [RFC6347] when
   compressed with [raza-6lo-compressed-dtls].

   Note that the compressed overhead is dependent on the parameters
   epoch and sequence number.  The following is only an example.

   Note that this header compression is not available when DTLS is
   exchanged over transports that do not use 6LoWPAN together with raza-
   6lo-compressed-dtls.

   Compressed DTLS 1.2 Record Layer (19 bytes, 13 bytes overhead):
   90 17 01 00 05 ae a0 15 56 67 92 4d ff 8a 24 e4
   cb 35 b9

   NHC
   90
   Compressed DTLS 1.2 Record Layer Header and Nonce:
   17 01 00 05
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   When compressed with raza-6lo-compressed-dtls, DTLS 1.2 with the
   above parameters (epoch, sequence number) gives 13 bytes overhead.



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2.1.4.  DTLS 1.3

   This section analyzes the overhead of DTLS 1.3
   [I-D.rescorla-tls-dtls13].  The only change compared to DTLS 1.2 is
   that the DTLS 1.3 record layer does not have an explicit nonce.

   DTLS 1.3 Record Layer (27 bytes, 21 bytes overhead):
   17 fe fd 00 01 00 00 00 00 00 05 00 0e ae a0 15
   56 67 92 4d ff 8a 24 e4 cb 35 b9

   Content type:
   17
   Version:
   fe fd
   Epoch:
   00 01
   Sequence number:
   00 00 00 00 00 05
   Length:
   00 0e
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   DTLS 1.3 gives 21 bytes overhead.

2.1.5.  DTLS 1.3 with 6LoWPAN-GHC

   This section analyzes the overhead of DTLS 1.3
   [I-D.rescorla-tls-dtls13] when compressed with [RFC7400]
   [OlegHahm-ghc].

   Note that the overhead is dependent on the parameters epoch, sequence
   number, and length.  The following is only an example.

   Note that this header compression is not available when DTLS is
   exchanged over transports that do not use 6LoWPAN together with
   6LoWPAN-GHC.












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   Compressed DTLS 1.3 Record Layer (20 bytes, 14 bytes overhead):
   b0 c3 11 05 00 0e ae a0 15 56 67 92 4d ff 8a 24
   e4 cb 35 b9

   Compressed DTLS 1.3 Record Layer Header and Nonce:
   b0 c3 11 05 00 0e
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   When compressed with 6LoWPAN-GHC, DTLS 1.3 with the above parameters
   (epoch, sequence number, length) gives 14 bytes overhead.

2.1.6.  DTLS 1.3 with raza-6lo-compressed-dtls

   This section analyzes the overhead of DTLS 1.3
   [I-D.rescorla-tls-dtls13] when compressed with
   [raza-6lo-compressed-dtls].

   Note that the compressed overhead is dependent on the parameters
   epoch and sequence number.  The following is only an example.

   Note that this header compression is not available when DTLS is
   exchanged over transports that do not use 6LoWPAN together with raza-
   6lo-compressed-dtls.

   Compressed DTLS 1.3 Record Layer (19 bytes, 13 bytes overhead):
   90 17 01 00 05 ae a0 15 56 67 92 4d ff 8a 24 e4
   cb 35 b9

   NHC
   90
   Compressed DTLS 1.3 Record Layer Header and Nonce:
   17 01 00 05
   c3 03 05 00 16 f2 0e
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   When compressed with raza-6lo-compressed-dtls, DTLS 1.3 with the
   above parameters (epoch, sequence number) gives 13 bytes overhead.








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2.2.  DTLS with Connection ID

   This section analyzes the overhead of DTLS with Connection ID
   [I-D.rescorla-tls-dtls-connection-id].  The overhead calculations in
   this section uses Connection ID = '42'.  DTLS with a Connection ID =
   '' (the empty string) is equal to DTLS without Connection ID.

2.2.1.  DTLS 1.2 with Connection ID

   This section analyzes the overhead of DTLS 1.2 [RFC6347] with
   Connection ID [I-D.rescorla-tls-dtls-connection-id].

   Note that the overhead is dependent on the parameter Connection ID.
   The following is only an example.

   DTLS 1.2 Record Layer (35 bytes, 29 bytes overhead):
   17 fe fd 00 01 00 00 00 00 00 05 42 00 16 00 01
   00 00 00 00 00 05 ae a0 15 56 67 92 4d ff 8a 24
   e4 cb 35 b9

   Content type:
   17
   Version:
   fe fd
   Epoch:
   00 01
   Sequence number:
   00 00 00 00 00 05
   Connection ID:
   42
   Length:
   00 16
   Nonce:
   00 01 00 00 00 00 00 05
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   DTLS 1.2 with Connection ID gives 30 bytes overhead.

2.2.2.  DTLS 1.2 with Connection ID and 6LoWPAN-GHC

   This section analyzes the overhead of DTLS 1.2 [RFC6347] with
   Connection ID [I-D.rescorla-tls-dtls-connection-id] when compressed
   with [RFC7400] [OlegHahm-ghc].





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   Note that the compressed overhead is dependent on the parameters
   epoch, sequence number, Connection ID, and length.  The following is
   only an example.

   Note that the sequence number '01' used in [RFC7400], Figure 15 gives
   an exceptionally small overhead that is not representative.

   Note that this header compression is not available when DTLS is
   exchanged over transports that do not use 6LoWPAN together with
   6LoWPAN-GHC.

   Compressed DTLS 1.2 Record Layer (23 bytes, 17 bytes overhead):
   b0 c3 04 05 42 00 16 f2 0e ae a0 15 56 67 92 4d
   ff 8a 24 e4 cb 35 b9

   Compressed DTLS 1.2 Record Layer Header and Nonce:
   b0 c3 04 05 42 00 16 f2 0e
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   When compressed with 6LoWPAN-GHC, DTLS 1.2 with the above parameters
   (epoch, sequence number, Connection ID, length) gives 17 bytes
   overhead.

2.2.3.  DTLS 1.3 with Connection ID

   This section analyzes the overhead of DTLS 1.3
   [I-D.rescorla-tls-dtls13] with Connection ID
   [I-D.rescorla-tls-dtls-connection-id].

   Note that the overhead is dependent on the parameter Connection ID.
   The following is only an example.

















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   DTLS 1.3 Record Layer (28 bytes, 22 bytes overhead):
   17 fe fd 00 01 00 00 00 00 00 05 42 00 0e ae a0
   15 56 67 92 4d ff 8a 24 e4 cb 35 b9

   Content type:
   17
   Version:
   fe fd
   Epoch:
   00 01
   Sequence number:
   00 00 00 00 00 05
   Connection ID:
   42
   Length:
   00 0e
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   DTLS 1.3 gives 22 bytes overhead.

2.2.4.  DTLS 1.3 with Connection ID and 6LoWPAN-GHC

   This section analyzes the overhead of DTLS 1.3
   [I-D.rescorla-tls-dtls13] with Connection ID
   [I-D.rescorla-tls-dtls-connection-id] when compressed with [RFC7400]
   [OlegHahm-ghc].

   Note that the overhead is dependent on the parameters epoch, sequence
   number, Connection ID, and length.  The following is only an example.

   Note that this header compression is not available when DTLS is
   exchanged over transports that do not use 6LoWPAN together with
   6LoWPAN-GHC.

   Compressed DTLS 1.3 Record Layer (21 bytes, 15 bytes overhead):
   b0 c3 12 05 42 00 0e ae a0 15 56 67 92 4d ff 8a
   24 e4 cb 35 b9

   Compressed DTLS 1.3 Record Layer Header and Nonce:
   b0 c3 12 05 42 00 0e
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9




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   When compressed with 6LoWPAN-GHC, DTLS 1.3 with the above parameters
   (epoch, sequence number, Connection ID, length) gives 15 bytes
   overhead.

2.3.  TLS

2.3.1.  TLS 1.2

   This section analyzes the overhead of TLS 1.2 [RFC5246].  The changes
   compared to DTLS 1.2 is that the TLS 1.2 record layer does not have
   epoch and sequence number, and that the version is different.

   TLS 1.2 Record Layer (27 bytes, 21 bytes overhead):
   17 03 03 00 16 00 00 00 00 00 00 00 05 ae a0 15
   56 67 92 4d ff 8a 24 e4 cb 35 b9

   Content type:
   17
   Version:
   03 03
   Length:
   00 16
   Nonce:
   00 00 00 00 00 00 00 05
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   TLS 1.2 gives 21 bytes overhead.

2.3.2.  TLS 1.2 with 6LoWPAN-GHC

   This section analyzes the overhead of TLS 1.2 [RFC5246] when
   compressed with [RFC7400] [OlegHahm-ghc].

   Note that the overhead is dependent on the parameters epoch, sequence
   number, and length.  The following is only an example.

   Note that this header compression is not available when TLS is
   exchanged over transports that do not use 6LoWPAN together with
   6LoWPAN-GHC.









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   Compressed TLS 1.2 Record Layer (23 bytes, 17 bytes overhead):
   05 17 03 03 00 16 85 0f 05 ae a0 15 56 67 92 4d
   ff 8a 24 e4 cb 35 b9

   Compressed TLS 1.2 Record Layer Header and Nonce:
   05 17 03 03 00 16 85 0f 05
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   When compressed with 6LoWPAN-GHC, TLS 1.2 with the above parameters
   (epoch, sequence number, length) gives 17 bytes overhead.

2.3.3.  TLS 1.3

   This section analyzes the overhead of TLS 1.3 [I-D.ietf-tls-tls13].
   The change compared to TLS 1.2 is that the TLS 1.3 record layer uses
   a different version.

   TLS 1.3 Record Layer (27 bytes, 21 bytes overhead):
   17 03 01 00 16 00 00 00 00 00 00 00 05 ae a0 15
   56 67 92 4d ff 8a 24 e4 cb 35 b9

   Content type:
   17
   Version:
   03 01
   Length:
   00 16
   Nonce:
   00 00 00 00 00 00 00 05
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   TLS 1.3 gives 21 bytes overhead.

2.3.4.  TLS 1.3 with 6LoWPAN-GHC

   This section analyzes the overhead of TLS 1.3 [I-D.ietf-tls-tls13]
   when compressed with [RFC7400] [OlegHahm-ghc].

   Note that the overhead is dependent on the parameters epoch, sequence
   number, and length.  The following is only an example.





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   Note that this header compression is not available when TLS is
   exchanged over transports that do not use 6LoWPAN together with
   6LoWPAN-GHC.

   Compressed TLS 1.3 Record Layer (23 bytes, 17 bytes overhead):
   02 17 03 c3 01 16 85 0f 05 ae a0 15 56 67 92 4d
   ff 8a 24 e4 cb 35 b9

   Compressed TLS 1.3 Record Layer Header and Nonce:
   02 17 03 c3 01 16 85 0f 05
   Ciphertext:
   ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   When compressed with 6LoWPAN-GHC, TLS 1.3 with the above parameters
   (epoch, sequence number, length) gives 17 bytes overhead.

2.4.  OSCORE

   This section analyzes the overhead of OSCORE
   [I-D.ietf-core-object-security].

   Note that the overhead is dependent on the included CoAP Option
   numbers as well as the length of the OSCORE parameters Sender ID and
   sequence number.

   Note that Sender ID = '' (empty string) can only be used by one
   client per server.

   The examples below assume that the original messages does not have
   payload (note that this does not affect the overhead).

   The below calculation Option Delta = '9', Sender ID = '' (empty
   string), and Sequence Number = '05', and is only an example.
















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   OSCORE Request (19 bytes, 13 bytes overhead):
   92 09 05
   ff ec ae a0 15 56 67 92 4d ff 8a 24 e4 cb 35 b9

   CoAP Option Delta and Length
   92
   Option Value (flag byte and sequence number):
   09 05
   Payload Marker
   ff
   Ciphertext (including encrypted code):
   ec ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   The below calculation Option Delta = '9', Sender ID = '42', and
   Sequence Number = '05', and is only an example.

   OSCORE Request (20 bytes, 14 bytes overhead):
   93 09 05 42
   ff ec ae a0 15 56 67 92 4d ff 8a 24 e4 cb 35 b9

   CoAP Option Delta and Length
   93
   Option Value (flag byte, sequence number, and Sender ID):
   09 05 42
   Payload Marker
   ff
   Ciphertext (including encrypted code):
   ec ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   The below calculation uses Option Delta = '9' and is only an example.

















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   OSCORE Response (17 bytes, 11 bytes overhead):
   90
   ff ec ae a0 15 56 67 92 4d ff 8a 24 e4 cb 35 b9

   CoAP Delta and Option Length:
   90
   Option Value
   -
   Payload Marker
   ff
   Ciphertext (including encrypted code):
   ec ae a0 15 56 67 92
   ICV:
   4d ff 8a 24 e4 cb 35 b9

   OSCORE with the above parameters gives 13-14 bytes overhead for
   requests and 11 bytes overhead for responses.

   Unlike DTLS and TLS, OSCORE has much smaller overhead for responses
   than requests.

3.  Overhead with Different Parameters

   The DTLS overhead is dependent on the parameter Connection ID.  The
   following overheads apply for all Connection IDs with the same
   length.

   The compression overhead (GHC) is dependent on the parameters epoch,
   sequence number, Connection ID, and length.  The following overheads
   should be representative for sequence numbers and Connection IDs with
   the same length.

   The compression overhead (raza-6lo-compressed-dtls) is dependent on
   the length of the parameters epoch and sequence number.  The
   following overheads apply for all sequence numbers with the same
   length.

   The OSCORE overhead is dependent on the included CoAP Option numbers
   as well as the length of the OSCORE parameters Sender ID and sequence
   number.  The following overheads apply for all sequence numbers and
   Sender IDs with the same length.










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       Sequence Number                '05'       '1005'     '100005'
       -------------------------------------------------------------
       DTLS 1.2                        29          29          29
       DTLS 1.3                        21          21          21
       TLS  1.2                        21          21          21
       TLS  1.3                        21          21          21
       -------------------------------------------------------------
       DTLS 1.2 (Raza)                 13          13          14
       DTLS 1.3 (Raza)                 13          13          14
       -------------------------------------------------------------
       DTLS 1.2 (GHC)                  16          16          17
       DTLS 1.3 (GHC)                  14          14          15
       TLS  1.2 (GHC)                  17          18          19
       TLS  1.3 (GHC)                  17          18          19
       -------------------------------------------------------------
       OSCORE Request                  13          14          15
       OSCORE Response                 11          11          11

            Figure 1: Overhead as a function of sequence number
                        (Connection/Sender ID = '')

       Connection/Sender ID            ''         '42'       '4002'
       -------------------------------------------------------------
       DTLS 1.2                        29          30          31
       DTLS 1.3                        21          22          23
       -------------------------------------------------------------
       DTLS 1.2 (GHC)                  16          17          18
       DTLS 1.3 (GHC)                  14          15          16
       -------------------------------------------------------------
       OSCORE Request                  13          14          15
       OSCORE Response                 11          11          11

         Figure 2: Overhead as a function of Connection/Sender ID
                            (Sequence Number = '05')

4.  Summary

   DTLS 1.2 has quite a large overhead as it uses an explicit sequence
   number and an explicit nonce.  DTLS 1.3, TLS 1.2, and TLS 1.3 have
   significantly less (but not small) overhead.

   Both DTLS compression methods provides very good compression. raza-
   6lo-compressed-dtls achieves slightly better compression but requires
   state.  GHC is stateless but provides slightly worse compression.  As
   DTLS 1.3 uses the same version number as DTLS 1.2, both GHC and raza-
   6lo-compressed-dtls works well also for DTLS 1.3.





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   The Generic Header Compression (6LoWPAN-GHC) can in addition to DTLS
   1.2 handle DTLS 1.3, DTLS with Connection ID, TLS 1.2, and TLS 1.3.
   The Generic Header Compression (6LoWPAN-GHC) works very well for
   Connection ID and the overhead seems to increase exactly with the
   length of the Connection ID (which is optimal).  The compression of
   TLS is not as good as the compression of DTLS (as the static
   dictionary is more or less a DTLS record layer).  Similar compression
   levels as for DTLS could be achieved also for TLS, but this would
   require different static dictionaries for each version of TLS (as TLS
   1.2 and TLS 1.3 uses different version numbers).  GHC works as good
   for DTLS 1.3 as for DTLS 1.2 as the version number is the same.

   raza-6lo-compressed-dtls is not able to handle DTLS with Connection
   ID or TLS, all extensions requires an updated mechanism.

   The header compression is not available when (D)TLS is exchanged over
   transports that do not use 6LoWPAN together with 6LoWPAN-GHC or raza-
   6lo-compressed-dtls.

   OSCORE has much lower overhead than DTLS and TLS.  The overhead of
   OSCORE is smaller than DTLS over 6LoWPAN with compression, and this
   small overhead is achieved even on deployments without 6LoWPAN or
   6LoWPAN without DTLS compression.  OSCORE is lightweight because it
   makes use of some excellent features in CoAP, CBOR, and COSE.

5.  Security Considerations

   This document is purely informational.

6.  Informative References

   [I-D.ietf-core-coap-tcp-tls]
              Bormann, C., Lemay, S., Tschofenig, H., Hartke, K.,
              Silverajan, B., and B. Raymor, "CoAP (Constrained
              Application Protocol) over TCP, TLS, and WebSockets",
              draft-ietf-core-coap-tcp-tls-10 (work in progress),
              October 2017.

   [I-D.ietf-core-object-security]
              Selander, G., Mattsson, J., Palombini, F., and L. Seitz,
              "Object Security for Constrained RESTful Environments
              (OSCORE)", draft-ietf-core-object-security-06 (work in
              progress), October 2017.

   [I-D.ietf-tls-tls13]
              Rescorla, E., "The Transport Layer Security (TLS) Protocol
              Version 1.3", draft-ietf-tls-tls13-21 (work in progress),
              July 2017.



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   [I-D.rescorla-tls-dtls-connection-id]
              Rescorla, E. and H. Tschofenig, "The Datagram Transport
              Layer Security (DTLS) Connection Identifier", draft-
              rescorla-tls-dtls-connection-id-01 (work in progress),
              October 2017.

   [I-D.rescorla-tls-dtls13]
              Rescorla, E., Tschofenig, H., and N. Modadugu, "The
              Datagram Transport Layer Security (DTLS) Protocol Version
              1.3", draft-rescorla-tls-dtls13-01 (work in progress),
              March 2017.

   [OlegHahm-ghc]
              Hahm, O., "Generic Header Compression", July 2016,
              <https://github.com/OlegHahm/ghc>.

   [raza-6lo-compressed-dtls]
              Raza, S., Shafagh, H., and O. Dupont, "Compression of
              Record and Handshake Headers for Constrained
              Environments", March 2017,
              <http://shahidraza.info/draft-raza-6lo-compressed.txt>.

   [RFC5246]  Dierks, T. and E. Rescorla, "The Transport Layer Security
              (TLS) Protocol Version 1.2", RFC 5246,
              DOI 10.17487/RFC5246, August 2008,
              <https://www.rfc-editor.org/info/rfc5246>.

   [RFC6347]  Rescorla, E. and N. Modadugu, "Datagram Transport Layer
              Security Version 1.2", RFC 6347, DOI 10.17487/RFC6347,
              January 2012, <https://www.rfc-editor.org/info/rfc6347>.

   [RFC7252]  Shelby, Z., Hartke, K., and C. Bormann, "The Constrained
              Application Protocol (CoAP)", RFC 7252,
              DOI 10.17487/RFC7252, June 2014,
              <https://www.rfc-editor.org/info/rfc7252>.

   [RFC7400]  Bormann, C., "6LoWPAN-GHC: Generic Header Compression for
              IPv6 over Low-Power Wireless Personal Area Networks
              (6LoWPANs)", RFC 7400, DOI 10.17487/RFC7400, November
              2014, <https://www.rfc-editor.org/info/rfc7400>.

   [RFC7925]  Tschofenig, H., Ed. and T. Fossati, "Transport Layer
              Security (TLS) / Datagram Transport Layer Security (DTLS)
              Profiles for the Internet of Things", RFC 7925,
              DOI 10.17487/RFC7925, July 2016,
              <https://www.rfc-editor.org/info/rfc7925>.





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Acknowledgments

   The authors want to thank Ari Keraenen, Francesca Palombini, and
   Goeran Selander for reviewing previous versions of the draft.

   All 6LoWPAN-GHC compression was done with [OlegHahm-ghc].

Author's Address

   John Mattsson
   Ericsson AB
   Faeroegatan 6
   Kista  SE-164 80 Stockholm
   Sweden

   Email: john.mattsson@ericsson.com



































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