Passing variables on redirect

I have a question regarding to redirect function which happens outside of asterisk:
user_a_call->asterisk_x->media_server (redirect)->asterisk_x->user_b_call

The call log is something like this:

-- Called SIP/LSIP/+3xxxxx
-- SIP/LSIP-00000001 is ringing
-- SIP/LSIP-00000001 redirecting info has changed, passing it to SIP/MSIP-00000000
-- SIP/LSIP-00000001 is ringing

== Using SIP RTP TOS bits 184
== Using SIP RTP CoS mark 5

The question is: How can i pass some variables from the first chain to the redirected one?
When I run the “Dumping Info For Channel” (after redirect) i can not see any variable which were in the previous chain.

You probably don’t have enough _s.

[quote]Multiple Inheritance
If the name is prefixed by “" (two underbar characters) in the channel, then the variable is inherited and the "” will remain intact in the new channel. Therefore any channels then created by the new channel will also receive the variable with “[/quote]”, continuing the inheritance indefinitely. … nheritance