From: Petr Lapukhov (petr@internetworkexpert.com)
Date: Fri Sep 19 2008 - 14:38:45 ART
Igor,
Those are actually "different" ECN technologies. The first one
("random-detect ECN") works with TCP and WRED. Instead of randomly dropping
packets, scheduler sets ECN bits in IP header ToS byte, signaling
ECN-capable endpoints to respond to network congestion. This feature works
specifically with TCP and congesting management based on WRED.
The last two have to deal with Frame-Relay ECN signaling. Those are used in
Frame-Relay switching code and apply to switched PVCs crossing a particular
DCE interface.
The command "frame-relay congestion-management threshold ecn {bc|be}
<THRESHOLD%>" instructs router to monitor interface output queue. If the
queue depth grows above the configured "ECN Be" threshold percentage, then
the router sets BECN/FECN bits in all input/output Frame-Relay packets
marked with DE bit. However, if the queue depth climbs above "ECN Bc"
threshold, then the router adds ECN bits to ALL packets (either DE and
non-DE marked). Note that this feature is "interface-wide" and affects all
PVCs.
You may also enable ECN thresholding on PVC shaping queue, by applying the
command "frame-relay congestion threshold ecn" under a "map-class
frame-relay" for a specific PVC. This feature monitor the specific PVC
software queue, not the shared interface queue. The procedure makes ECN
marking "PVC specific" and aware of "per-VC" congestion state.
In addition to ECN signaling thresholds in Frame-Relay networks, you may
also configure "DE-bit" threshold that specifies the level of queue depth
where router starts dropping DE-marked packets.
All the above mentioned features are part of Frame-Relay adaptive congestion
management. Generally speaking, those are SP related, and you dont have to
deal with them in the R&S lab.
HTH
Further Reading:
http://www.cisco.com/en/US/docs/ios/wan/configuration/guide/wan_cfg_frm_rly_ps6350_TSD_Products_Configuration_Guide_Chapter.html#wp1055798
-- Petr Lapukhov, CCIE #16379 (R&S/Security/SP/Voice) petr@internetworkexpert.comInternetwork Expert, Inc. http://www.InternetworkExpert.com Toll Free: 877-224-8987 Outside US: 775-826-4344
2008/9/18 Igor M. <imanassypov@rogers.com>
> Hi gang, > > Anyone knows if there is a significant difference between following fr > congestion management tools? > > 1. under policy-map 'random-detect ecn' > 2. under pvc 'frame-relay congestion-management threshold ecn 75' > 3. under fr map-class 'frame-relay congestion threshold ecn 75' > > From what I understand, 2 & 3 would be legacy and 1 comes from MQC. But > functionally-wise - are they same or different? > > Thanks > > ---------------------- > > I.M., M.Eng. P.Eng. > > Network Architect > > CI Investments > > ---------------------- > > > Blogs and organic groups at http://www.ccie.net > > _______________________________________________________________________ > Subscription information may be found at: > http://www.groupstudy.com/list/CCIELab.html
Blogs and organic groups at http://www.ccie.net
This archive was generated by hypermail 2.1.4 : Sat Oct 04 2008 - 09:26:18 ART