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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.
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