After talking to Scott, I've pulled together a list of things that can
be improved by using base64:
Revising how we generate Call-Ids and related matters.
The application can supply to CallId a hostport string. If this is
not supplied, Call-Ids will be generated in a format that is similar
to the current format, but 5 characters shorter:
s-XXXXXXXXXXX-NNN
where XXXXXXXXXXX is the base64 representation (in a suitable alphabet
-- see below) of a 64-bit (actually, 66-bit) crypto-random number, and
NNN is a decimal counter. (The application can provide a string to
replace "s".)
If the application provides a hostport string, the format is:
[EMAIL PROTECTED]
where XXXXXX is the base64 representation of a 32-bit (actually,
36-bit) crypto-random number, and NNN is a decimal counter.
Tags generated by CallId::getNewTag will be 6 base64 characters rather
than 8 hex characters.
Via branch-id counter parts will be 3 base64 characters rather than 4
hex characters, and the signed-branch and loopdetectkey will be 22
base64 characters rather than 32 hex characters.
This will require enhancing the NetBase64Codec class to generate
and decode base64 encodings in non-standard alphabets.
In regard to the encoding alphabet:
base64 requires 3 characters other than the letters and digits. The
standard characters are '+', '/', and '='. BranchId uses two
separator characters, '-' and '~', although they can be located by
counting characters, so the same character can be used for both.
RouteState signatures will be 22 base64 characters, rather than 32 hex
characters. RouteState uses 4 separator characters, '!', '.', '~',
and '*'.
BranchIds and RouteStates must/should (respectively) be 'token'
character strings. Call-Ids can contain 'word' characters, which
includes all the 'token' characters. Unfortunately, tokens may not
contain '/', but RouteState currently can generate them.
The available token characters are:
- already used to separate subfields
. RouteState delimiter
! RouteState delimiter
% used for %-escaping
* RouteState delimiter
_ to be used to replace '/' in base64
+ can be interpreted as space in URIs
` replaces '=' in base64
' replaces '+' in base64
~ RouteState delimiter
Can loopdetectionkey be reduced to, say, 32 bits, rather than the full
128 bits?
Comments?
Dale
_______________________________________________
sipx-dev mailing list
[email protected]
List Archive: http://list.sipfoundry.org/archive/sipx-dev
Unsubscribe: http://list.sipfoundry.org/mailman/listinfo/sipx-dev
