RFC Errata
RFC 4944, "Transmission of IPv6 Packets over IEEE 802.15.4 Networks", September 2007
Note: This RFC has been updated by RFC 6282, RFC 6775, RFC 8025, RFC 8066, RFC 8931
Source of RFC: 6lowpan (int)See Also: RFC 4944 w/ inline errata
Errata ID: 4359
Status: Verified
Type: Technical
Publication Format(s) : TEXT
Reported By: Gabriel Montenegro
Date Reported: 2015-05-07
Verifier Name: Brian Haberman
Date Verified: 2015-09-14
Section 5.1 says:
ESC: Specifies that the following header is a single 8-bit field for the Dispatch value. It allows support for Dispatch values larger than 127.
It should say:
ESC: Specifies that the following header is a single 8-bit field for the Dispatch value. It allows support for Dispatch values larger than 63.
Notes:
The (non-ESCaped) Dispatch value is a 6-bit selector. However, it used to be a 7-bit selector, which has a value at most 127. When the field became a 6-bit selector, this maximum became 63, but the referring text was never updated.
For historical reference, see an early version from IETF 67 proposing the Dispatch value within the Dispatch header as a 7-bit field:
http://6lowpan.tzi.org/FrontPage?action=AttachFile&do=view&target=tentative-draft2-ietf-6lowpan-format-07.txt
The dispatch type is defined by a zero-bit as the first bit. The
dispatch type and header is shown here:
1 2 3
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|0| Dispatch | type-specific header
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Dispatch 7-bit selector. Identifies the type of header
immediately following the Dispatch type.
The relevant slides also show this (slide 8): http://6lowpan.tzi.org/FrontPage?action=AttachFile&do=view&target=6lowpan-header-proposal-2.ppt