From: Bob Nelson (nelsnjr@cox.net)
Date: Tue May 17 2005 - 22:38:02 GMT-3
All:
I have searched the archives on this site and still do not have a good
handle on this issue. Can someone clarify this?
What I have researched:
1. TCP and LLC2 encapsulation have local acknowledgement and reliable
transport
2. FST and Direct do not have either local acknowledgement or reliable
transport.
Sources: Solie - CCIE Practical Studies Vol 1 page 898 - Cisco
DLSw+ Design and Implementation Guide - pages 12-14
Statements in documentation that confuse me:
Cisco IOS Bridging and IBM Networking Guide page BC-291 (under the
Direct configuration heading)
dlsw remote-peer 0 frame-relay interface serial 0/1 pass-thru
"Specifying the pass-thru option configures the router so that the
traffic will not be locally acknowledged
(DLSw+ normally locally acknowledges traffic to keep traffic on the
WAN to a minimum)"
Question 1 - Why do we need the pass-thru option here since by default
Direct encapsulation does not
perform local acknowledgement. (see #2 above)
Cisco DLSw+ Design and Implementation Guide - pages 12-14 (Advanced
Configuration Section)
dlsw remote-peer 0 frame-relay interface serial 01 33 pass-thru
int s1
frame-relay map dlsw 33
"In this example, data-link connection identifier (DLCI) 33 on
serial interface 1 will be used to transport DLSw+ traffic.
Specifying pass-thru implies that the traffic is not locally
acknowledged. Leaving pass-thru off will cause the
traffic to be locally acknowledged, which means it is transported in
LLC2 to ensure reliable delivery."
Question 2 - Again, why specify pass-thru when Direct encapsulation does
not do local acknowledgment anyway?
Additionally, how can leaving pass-through off magically make this
configuration transport packets using LLC2
without changing the frame-relay map statement from dlsw to frame-relay
map llc2 33?
A CCIE bootcamp student manual
dlsw remote-peer 0 frame-relay interface 0/1 201 pass-thru
"The pass-thru option can be added to other remote-peer methods as
well.
This will prevent the local acknowledgements and keepalives from
going across the WAN"
Question 3 - My understanding of the pass-thru is that this will not perform
local acknowledgement and
will pass both the acknowledgements and keepalives end-to-end. Is this what
pass-thru actually does or
does it prevent local acknowledgements? Additionally, why do we need this
if according to Cisco, Direct
encapsulation does not support local acknowledgements and keepalives are
end-to-end.
Thanks,
Bob
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