From: Chris Larson (clarson52@comcast.net)
Date: Wed Dec 10 2003 - 10:28:18 GMT-3
DSCP is also usefull to provide deifferentiation within classes. For
instance if you were to follow Cisco's relative priority model of
application classification they recommend something like:
Gold
Silver
Best-Effort
Less then best effort
With 3 to 4 apps maximum within the each of the classes (at least the
premium classes should only have 3 or 4 max) and TOS only having 8 values
(0 - 7) each class would only have 1 or 2 ToS values as a differentiator.
With DSCP, the Gold class could have 3 or 4 apps in it and each app would
have a precedence within the class allowing them to be weighted within the
class. Same with silver, best effort and kazza...I mean less then best
effort.
Especially less then best effort. We don't want to assign all less then best
effort traffic a ToS of 0. We do not want to treat Kazza or limewire and our
backups the same. We want backups and kazza to both be less then best effort
but our backups will probably be at the top within the less then best effort
class with all the other stuff having a value less then the backups within
that class.
----- Original Message -----
From: "Michael Snyder" <msnyder@revolutioncomputer.com>
To: <ccielab@groupstudy.com>
Cc: <swm@emanon.com>
Sent: Wednesday, December 10, 2003 2:38 AM
Subject: Set Router Telnet Traffic to DSCP EF
> One of the first things that came up after I learned the relationship
> between (Precedence TOS) and DSCP, was Scott Morris asking me what I
> would use it for. After thinking about it, I came up with a lab
> requirement that has a real world use!
>
> Requirement - Router originated telnet traffic should have a dscp of EF.
>
> Kicker - Do this without using any interface commands.
>
> Solution -
>
> R7
>
> ip local policy route-map setdscp
> !
> access-list 100 permit tcp any any eq telnet
>
> route-map setdscp permit 10
> description EF bit pattern 101 110 = P5 T12
> match ip address 100
> set ip precedence critical
> set ip tos 12
>
> Proof of Working Solution
>
> R8 (with dscp acl I have posted at end of email.)
>
> interface Serial0
> ip address 150.50.101.2 255.255.255.252
> ip access-group 110 in
> ip router isis
> encapsulation ppp
> no peer neighbor-route
> no fair-queue
> service-module 56k clock source internal
>
>
> R8#clear access-list counters
>
> R8#show access-lists
> Extended IP access list 110
> permit ip any any dscp default
> permit ip any any dscp 1
> permit ip any any dscp 2
> permit ip any any dscp 3
> permit ip any any dscp 4
> permit ip any any dscp 5
> permit ip any any dscp 6
> permit ip any any dscp 7
> permit ip any any dscp cs1
> permit ip any any dscp 9
> permit ip any any dscp af11
> permit ip any any dscp 11
> permit ip any any dscp af12
> permit ip any any dscp 13
> permit ip any any dscp af13
> permit ip any any dscp 15
> permit ip any any dscp cs2
> permit ip any any dscp 17
> permit ip any any dscp af21
> permit ip any any dscp 19
> permit ip any any dscp af22
> permit ip any any dscp 21
> permit ip any any dscp af23
> permit ip any any dscp 23
> permit ip any any dscp cs3
> permit ip any any dscp 25
> permit ip any any dscp af31
> permit ip any any dscp 27
> permit ip any any dscp af32
> permit ip any any dscp 29
> permit ip any any dscp af33
> permit ip any any dscp 31
> permit ip any any dscp cs4
> permit ip any any dscp 33
> permit ip any any dscp af41
> permit ip any any dscp 35
> permit ip any any dscp af42
> permit ip any any dscp 37
> permit ip any any dscp af43
> permit ip any any dscp 39
> permit ip any any dscp cs5
> permit ip any any dscp 41
> permit ip any any dscp 42
> permit ip any any dscp 43
> permit ip any any dscp 44
> permit ip any any dscp 45
> permit ip any any dscp ef (42 matches)
> permit ip any any dscp 47
> permit ip any any dscp cs6
> permit ip any any dscp 49
> permit ip any any dscp 50
> permit ip any any dscp 51
> permit ip any any dscp 52
> permit ip any any dscp 53
> permit ip any any dscp 54
> permit ip any any dscp 55
> permit ip any any dscp cs7
> permit ip any any dscp 57
> permit ip any any dscp 58
> permit ip any any dscp 59
> permit ip any any dscp 60
> permit ip any any dscp 61
> permit ip any any dscp 62
> permit ip any any dscp 63
> R8#
>
>
> So using a route-map with the ip local policy, we can set any dcsp for
> router traffic as we wish. VPN, Voice, Rip, Ping all comes to mind.
> Not sure all those protocols have DSCP bits, but if they do, we can set
> them.
>
> What is the relation ship between DSCP and Precedence-TOS?
>
> Well, dscp is a 6 bit value, to covert it we need to pad it with a
> leading zero and ending zero to the value. I'll do it step by step.
>
> 1) ef expedited forwarding bit pattern 101110
>
> Prepend and append a zero to bring it to eight bits.
>
> 2) 0101 1100
>
> Now read the first four bits in hex, that's the Precedence.
> Read the second four bits in hex, that is the TOS.
>
> 3) 0x5= decimal 5, 0xC= decimal 12
>
> Now just plug them into the route-map
>
> R7(config)#route-map setdscp permit 10
> R7(config-route-map)#set ip pr
> R7(config-route-map)#set ip precedence 5
> R7(config-route-map)#set ip tos 12
> R7(config-route-map)#
>
> Show run
> route-map setdscp permit 10
> set ip precedence critical
> set ip tos 12
>
>
>
> That's it. It's a very simple relationship; if you can read hex. If
> you can't read hex, I've posted the basic table at the end of this
> email. Anybody that tells you that you can't set dscp in a route-map is
> mistaken. It can be done, and there's some places where's it's the only
> choice (such as in `ip local policy`).
>
> BTW, thanks Scott for pointing me in the right direction.
>
>
>
> From: Scott Morris [mailto:swm@emanon.com]
> Sent: Sunday, November 16, 2003 1:59 PM
> To: 'Michael Snyder'; ccielab@groupstudy.com
> Subject: RE: routemap to set dcsp
>
> Ok, that would likely to something there, but why not just set ip dscp?
> You can't do this in a route-map, but in the policy-map you could do
> that.
>
> But otherwise, yet... 101 and 1100 would suffice to set the appropriate
> bits.
>
> For others wondering where the heck that all came from, RFC 1349 breaks
> things down a little differently for the 8-bit ToS field where the first
> three bits are still IP Precedence, then the next four bits are called
> tos bits and the last bit is called MBZ (Must Be Zero). Who ever said
> engineers didn't have a sense of humor? :)
>
> As for viewing them, not really... Other than setting up an access-list
> that permits things with a dscp value of EF and looking at the number of
> matches.
>
> Scott Morris, CCIE4 (R&S/ISP-Dial/Security/Service Provider) #4713,
> CISSP, JNCIS, et al. IPExpert CCIE Program Manager IPExpert Sr.
> Technical Instructor swm@emanon.com/smorris@ipexpert.net
> http://www.ipexpert.net
>
>
>
> access-list 110 permit ip any any dscp default
> access-list 110 permit ip any any dscp 1
> access-list 110 permit ip any any dscp 2
> access-list 110 permit ip any any dscp 3
> access-list 110 permit ip any any dscp 4
> access-list 110 permit ip any any dscp 5
> access-list 110 permit ip any any dscp 6
> access-list 110 permit ip any any dscp 7
> access-list 110 permit ip any any dscp cs1
> access-list 110 permit ip any any dscp 9
> access-list 110 permit ip any any dscp af11
> access-list 110 permit ip any any dscp 11
> access-list 110 permit ip any any dscp af12
> access-list 110 permit ip any any dscp 13
> access-list 110 permit ip any any dscp af13
> access-list 110 permit ip any any dscp 15
> access-list 110 permit ip any any dscp cs2
> access-list 110 permit ip any any dscp 17
> access-list 110 permit ip any any dscp af21
> access-list 110 permit ip any any dscp 19
> access-list 110 permit ip any any dscp af22
> access-list 110 permit ip any any dscp 21
> access-list 110 permit ip any any dscp af23
> access-list 110 permit ip any any dscp 23
> access-list 110 permit ip any any dscp cs3
> access-list 110 permit ip any any dscp 25
> access-list 110 permit ip any any dscp af31
> access-list 110 permit ip any any dscp 27
> access-list 110 permit ip any any dscp af32
> access-list 110 permit ip any any dscp 29
> access-list 110 permit ip any any dscp af33
> access-list 110 permit ip any any dscp 31
> access-list 110 permit ip any any dscp cs4
> access-list 110 permit ip any any dscp 33
> access-list 110 permit ip any any dscp af41
> access-list 110 permit ip any any dscp 35
> access-list 110 permit ip any any dscp af42
> access-list 110 permit ip any any dscp 37
> access-list 110 permit ip any any dscp af43
> access-list 110 permit ip any any dscp 39
> access-list 110 permit ip any any dscp cs5
> access-list 110 permit ip any any dscp 41
> access-list 110 permit ip any any dscp 42
> access-list 110 permit ip any any dscp 43
> access-list 110 permit ip any any dscp 44
> access-list 110 permit ip any any dscp 45
> access-list 110 permit ip any any dscp ef
> access-list 110 permit ip any any dscp 47
> access-list 110 permit ip any any dscp cs6
> access-list 110 permit ip any any dscp 49
> access-list 110 permit ip any any dscp 50
> access-list 110 permit ip any any dscp 51
> access-list 110 permit ip any any dscp 52
> access-list 110 permit ip any any dscp 53
> access-list 110 permit ip any any dscp 54
> access-list 110 permit ip any any dscp 55
> access-list 110 permit ip any any dscp cs7
> access-list 110 permit ip any any dscp 57
> access-list 110 permit ip any any dscp 58
> access-list 110 permit ip any any dscp 59
> access-list 110 permit ip any any dscp 60
> access-list 110 permit ip any any dscp 61
> access-list 110 permit ip any any dscp 62
> access-list 110 permit ip any any dscp 63
>
>
>
> af11 assured forwarding (af11) bit pattern 001 010 = P1 T4
> af12 assured forwarding (af12) bit pattern 001 100 = P1 T8
> af13 assured forwarding (af13) bit pattern 001 110 = P1 T12
>
> af21 assured forwarding (af21) bit pattern 010 010 = P2 T4
> af22 assured forwarding (af22) bit pattern 010 100 = P2 T8
> af23 assured forwarding (af23) bit pattern 010 110 = P2 T12
>
> af31 assured forwarding (af31) bit pattern 011 010 = P3 T4
> af32 assured forwarding (af32) bit pattern 011 100 = P3 T8
> af33 assured forwarding (af33) bit pattern 011 110 = P3 T12
>
> af41 assured forwarding (af41) bit pattern 100 010 = P4 T4
> af42 assured forwarding (af42) bit pattern 100 100 = P4 T8
> af43 assured forwarding (af43) bit pattern 100 110 = P4 T12
>
> cs1 class selector codepoint 1 (precedence 1) 001 = P1 T0
> cs2 class selector codepoint 2 (precedence 2) 010 = P2 T0
> cs3 class selector codepoint 3 (precedence 3) 011 = P3 T0
> cs4 class selector codepoint 4 (precedence 4) 100 = P4 T0
> cs5 class selector codepoint 5 (precedence 5) 101 = P5 T0
> cs6 class selector codepoint 6 (precedence 6) 110 = P6 T0
> cs7 class selector codepoint 7 (precedence 7) 111 = P7 T0
>
> ef expedited forwarding bit pattern 101 110 = P 5 T 12
>
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