Hi Bryan, Cos is set for layer 2 devices like switches. You can only set DSCP & Precedence on layer 3 devices like routers. so if you to do marking of packets at the layer 2 ingress you would go with cos and at layer 3 devices you can map them to dscp.
Regards Sushil Menon On Thu, Aug 20, 2009 at 12:31 AM, Bryan Bartik <[email protected]> wrote: > Edward, not every organization or network will treat DSCP values the same. > That is why you can have a DSCP-DSCP translation table the domain border. > CoS is layer 2, DSCP is layer 3. > > On Wed, Aug 19, 2009 at 12:41 PM, Bodnar, Edward <[email protected] > > wrote: > >> So this brings me back to when to use CoS or when to use DSCP. Do I >> have to use both? Can I use one over the other and when would I use DSCP vs >> CoS. >> >> >> >> *From:* prakash patel [mailto:[email protected]] >> *Sent:* Wednesday, August 19, 2009 2:38 PM >> >> *To:* Bodnar, Edward; [email protected] >> *Subject:* RE: [OSL | CCIE_RS] QOS question >> >> >> >> Everything is about changing the default. >> >> Yes in some cases , you do like to bypass the mapping of COS-DSCP..and >> trust DSCP. >> >> In some case you like to change the DSCP if device is marking with DSCP >> >> In some cases you changed it based on COS if device is not marking DSCP. >> >> >> >> >> >> ------------------------------ >> >> From: [email protected] >> To: [email protected]; [email protected] >> Date: Wed, 19 Aug 2009 13:32:45 -0500 >> Subject: RE: [OSL | CCIE_RS] QOS question >> >> I would think you would still need to do a DSCP to CoS mapping then back >> to DSCP. I am looking at some configuration and then seem to just pass the >> DSCP mapping right through the switches. >> >> >> >> *From:* prakash patel [mailto:[email protected]] >> *Sent:* Wednesday, August 19, 2009 2:28 PM >> *To:* Bodnar, Edward; [email protected] >> *Subject:* RE: [OSL | CCIE_RS] QOS question >> >> >> >> FOr internal schduling /queing >> >> >> >> ------------------------------ >> >> From: [email protected] >> To: [email protected]; [email protected] >> Date: Wed, 19 Aug 2009 13:15:57 -0500 >> Subject: RE: [OSL | CCIE_RS] QOS question >> >> So any time I pass from a layer 2 device to a layer 3 device I need to >> translate the CoS to DSCP. And any time I go from a layer 3 device to layer >> 2 device I need to translate DSCP to CoS? If this is true then why do that >> have DSCP to DSCP translations in switches ? >> >> >> >> *From:* prakash patel [mailto:[email protected]] >> *Sent:* Wednesday, August 19, 2009 2:09 PM >> *To:* Bodnar, Edward; [email protected] >> *Subject:* RE: [OSL | CCIE_RS] QOS question >> >> >> >> Layer 2 devices connection ...USE COS >> >> LAYER 3 devices use DSCP. >> >> >> >> >> >> >> >> ------------------------------ >> >> From: [email protected] >> To: [email protected] >> Date: Wed, 19 Aug 2009 13:01:01 -0500 >> Subject: [OSL | CCIE_RS] QOS question >> >> When would I use CoS over DSCP or DSCP over CoS. >> >> >> ------------------------------ >> >> With Windows Live, you can organize, edit, and share your photos. Click >> here. <http://www.windowslive.com/Desktop/PhotoGallery> >> >> >> ------------------------------ >> >> Get back to school stuff for them and cashback for you. Try BingT >> now.<http://www.bing.com/cashback?form=MSHYCB&publ=WLHMTAG&crea=TEXT_MSHYCB_BackToSchool_Cashback_BTSCashback_1x1> >> >> >> ------------------------------ >> >> Get back to school stuff for them and cashback for you. Try BingT >> now.<http://www.bing.com/cashback?form=MSHYCB&publ=WLHMTAG&crea=TEXT_MSHYCB_BackToSchool_Cashback_BTSCashback_1x1> >> >> _______________________________________________ >> For more information regarding industry leading CCIE Lab training, please >> visit www.ipexpert.com >> >> > > > -- > Bryan Bartik > CCIE #23707 (R&S), CCNP > Sr. Support Engineer - IPexpert, Inc. > URL: http://www.IPexpert.com > > _______________________________________________ > For more information regarding industry leading CCIE Lab training, please > visit www.ipexpert.com > >
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