RFC 5357, "A Two-Way Active Measurement Protocol (TWAMP)", October 2008

Note: This RFC has been updated by RFC 5618, RFC 5938, RFC 6038, RFC 7717, RFC 7750, RFC 8545

Errata ID: 1594
Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT
Reported By: Alfred Hoenes
Date Reported: 2008-11-05
Held for Document Update by: Lars Eggert

Section 3.8,1st para says:

                                vvvvvvvvvvvvvvvvv
                                                        [...].  The
|  message is terminated with a single block HMAC to complete the Stop-
   Sessions command.  [...]

It should say:

<<  either:  >>

                                                        [...].  The
|  message is terminated with a single-block HMAC to complete the Stop-
   Sessions command.  [...]

<<  or:  >>

                                       vvvvvvvvvv
                                                        [...].  The
|  message is terminated with a single HMAC block to complete the Stop-
   Sessions command.  [...]

Notes:

In any way this is problematic because the term "block" has not been
introduced into the RFC text. (That's also a problem for 4.2.1!)

Even in the restricted context of SHA (FIPS PUB 180-2/3) and HMAC
(FIPS PUB 197), the term "block" does not uniquely identify a
specific number of octets.
For SHA-1, SHA-224, and SHA-256, the block size is 512 bits,
for SHA-384 and SHA-512 it is 1024 bits.

But OWAMP uses a truncated version of HMAC-SHA-1 with a 128-bit MAC,
(officially denoted as HMAC-SHA-1-128), and apparently that is carried
over to TWAMP without mention in the RFCs.

It remains unclear from the text what precisely was intended to say.


Hint: Errata Note entered on request of the responsible AD before
resolution with the authors.

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