Configuring Mpls And Eompls Qos; Understanding Mpls Qos - Cisco Catalyst 3750 Software Configuration Manual

Configuring MPLS and EoMPLS QoS

The tagged packet is received on the CE port that is configured for per-port EoMPLS tunneling. The PE1
switch examines the packet headers and looks at the tables stored in the switch to determine what to do
with the packet. Because the port is configured for per-port EoMPLS tunneling, the switch does not
remove any VLAN tags that are in the packet, but assigns the packet to an internal VLAN. Only the
customer port and the ES port are configured with that internal VLAN, which makes the PE1 ES port
the only possible destination for the packet.
The ES port encapsulates the packet header with the tunnel label and the VC label and forwards the
packet to the next hop, in this case Router A, for it to be sent across the MPLS network.
The router receives the packet and forwards it over the MPLS network to the remote PE2 switch. PE2
removes the MPLS encapsulation and sends the packet out of the port associated with the VC label.
Customer Switch B removes the final VLAN tag and forwards the packet to the remote host B.
VLAN-based EoMPLS packet flow is basically the same as port-based EoMPLS, except that the
customer VLAN is used instead of an internal VLAN. The PE1 switch looks up the customer VLAN ID
to determine that the packet is forwarded to the ES port, where the packets is again examined and
encapsulated with the tunnel label and VC label based on the EoMPLS for that VLAN.
Configuring MPLS and EoMPLS QoS
Quality of service (QoS) in MPLS and EoMPLS enables network administrators to provide differentiated
types of service across an MPLS network. Each packet can receive the particular kind of service
specified by the packet QoS. To preserve QoS IP precedence bits, you must globally disable QoS.
After you enable QoS, you can preserve Differentiated Services Code Point (DSCP) or IP precedence
bits by using a trusted configuration at the interface level. For more information, see the
Ingress Classification by Using Port Trust States" section on page
are automatically overwritten by the value of the preserved bits. For example, if you preserve the DSCP
bits, the IP precedence and CoS bits are overwritten with the value of the DSCP bits. You can also set
MPLS and EoMPLS QoS priority by using 3 experimental bits in the MPLS label to determine the
priority of packets.
The switch supports only DSCP and IP precedence classification for MPLS and EoMPLS.
Note
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Understanding MPLS QoS

Service in an MPLS network can be specified in different ways, for example, by using the IP precedence
bit settings in IP packets. When you send IP packets from one site to another, the IP precedence field
(the first 3 bits of the DSCP field in the header of an IP packet) specifies the QoS. Based on the IP
precedence marking, the packet is given the desired treatment such as latency or bandwidth. If the
network is an MPLS network, the IP precedence bits are copied into the MPLS EXP field at the edge of
the network.
Catalyst 3750 Metro Switch Software Configuration Guide
30-18
Understanding MPLS QoS, page 30-18
Enabling MPLS and EoMPLS QoS, page 30-20
Chapter 30 Configuring MPLS and EoMPLS
"Configuring
26-42. However, the unpreserved bits
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