The MPLS-OPS Archive

[vola ray <vola_ray@yahoo.com>]

hill,
Let me Clarify some things to follow more............
There are two types of Routers: Edge (LER/PE), Core (P)
DSCP bits may be needed in the Edge Routers, but they are not Important
for the Core Routers. Core Routers perform QoS based on the Exp bits 
embedded in the MPLS labels. I will provide some info here.....
Mostly all QoS treatment on MPLS are handled via ASIC (HW) or
Commercial Network Processor chips, while the LSP Signaling is handled
via SW.

             EdgeRouter
      Receive Direction from End User Devices:
Here you receive IP packets from End User Devices and insert Labels,
provided you have established the LSP via the Core (P) Routers. So based
on the FEC you insert the Corresponding Label and txmit it to the Core
Router. But before txmit you have to perform QoS treatment on the IP
packet, also when you receive the Packet from End User you perform similar
QoS treatment. Now if the DSCP bits are set on the TOS field that tells
what treatment it needs. But it needs to be validated as per the configured
service and interfaces. It is also Important to note that one IP adress
from the End User may have One or More Labels based on the Service Label
Agreements and Configurations of the IP Services. In such cases those types
of IP packets will come with same IP address but different DSCP (I hope so!!)
bits.
       Receive Direction from the Core Router:
Here you receive the IP packet with MPLS label and perform QoS treatment,
strip the Label and pass it to the End User Devices. And based on the Label
embedded Exp bits you know what QoS treatment is necessary. 
             CoreRouter
      Receive Direction from Edge Router:
You receive the IP packet with Label and perform Label Switching. Based on
the Exp bits in the label you perform the QoS treatment. DSCP bits may not
be Important.
      Receive Direction from other Core Router:
Just perform Label Switching. QoS treatment is based on the Exp bits, again DSCP
bits may not be Important.
Hope this may help you,
vola
-----------------------------------------------------------------------
Geoff 

It may be worth mentioning here that in MPLS we have the option 
to completely ignore the TOS bits in the IP packet and write our own
COS into the EXP field of the MPLS shim header 
this can be done either by trusting the settings from the customer or by
filtering 
on TCP/UDP port number to define the traffic type before assigning a class
and writing the EXP 

MPLS traffic is prioritised through the network by the EXP field so if you
neglect to configure 
a copy into or fresh write of the exp field I am not sure what the default
behaviour is 

Can any one answer that question for me 
Hill 


-----Original Message-----
From: mpls-ops-request@mplsrc.com [mailto:mpls-ops-request@mplsrc.com]On
Behalf Of mpls-ops@mplsrc.com
Sent: 26 April 2001 08:18
To: Geoff Bennett; Hass, Barry; Marinzulich, Matias; 'Ashwin
Moranganti'; 'MP LS'; MPLS@UU.NET; mpls-ops@mplsrc.com
Subject: RE: MPLS Trafficdriven


geoff,
As U mentioned.....
"But the problem is how do you recognise the appropriate
 traffic types."
Well we can solve this Problem:
In the Ingress Router the ASIC device is already Configured
to handle respective Packet types based on Profiles/Policies.
End user can set the DSCP field in the transmitted IP packet 
to the Ingress Router. Now after receiving the IP Packet, 
Router checks the IP address and the DSCP field then validates 
via looking into the Port number and other stuff. By the way
ASIC must be configured with such stuff to process such Traffic.
Hence if somebody is sending email but prtending this is a VoIP
packet it can be easily detected and either packet can be dropped
or DSCP field changed accordingly. This is completely a configuration
issue as to how to set up the ASIC for what type of traffic.
SNMP or CLI can be used to configure such things.
Hope, this helps........
vola

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