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6-4
Cisco AVVID Network Infrastructure Enterprise Quality of Service Design
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Chapter 6 QoS with MPLS in an AVVID-Enabled Network
Overview
Placement of Labels by Mode
As mentioned before, the placement of the label depends on the MPLS mode used.
Figure 6-4
and
Figure 6-5
highlight the application of labels in frame and cell modes for MPLS.
Figure 6-4
Frame-Mode MPLS
Figure 6-5
Cell-Mode MPLS
Labels are inserted between the Layer 2 (frame) header and the Layer 3 (packet) header.
Frame
Header
IP Header
Layer 2
Layer 3
Routing
lookup and label
assignment
Payload
Frame
Header
IP Header
Layer 2
Layer 3
Payload
78353
Label
Layer 2Ѕ
Frame
Header
IP Header
Layer 2
Layer 3
VPI/VCI fields are
used for label
switching
Payload
ATM
Header
ATM Adaptation
Layer 5 (AAL5) Header
Layer 2
Cell 1
Payload
Frame
Header
Layer 2
Layer 3
Payload
Label
Layer 2Ѕ
Label
Layer 2Ѕ
IP Header
Layer 3
IP Header
ATM
Header
Cell 2
Payload
78354