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Ethernet/VLAN to ATM AAL5 Interworking
Figure 21-4
ATM CE
The advantage of this architecture is that the Ethernet PE (connected to the Ethernet segment) operates
similarly to Ethernet like-to-like services.
On the PE with Interworking function, in the direction from the ATM segment to MPLS cloud, the
bridged encapsulation (ATM/SNAP header) is discarded and the Ethernet frame is encapsulated with the
labels required to go through the pseudowire using the VC type 5 (Ethernet)
In the opposite direction, after the label disposition from the MPLS cloud, Ethernet frames are
encapsulated over AAL5 using bridged encapsulation.
Figure 21-5
has an encapsulation type of aal5snap.
Figure 21-5
ATM
CE
ATM AAL5 to Ethernet VLAN 802.1Q AToM—Bridged Interworking
This interworking type provides interoperability between ATM attachment VC and Ethernet VLAN
attachment VC connected to different PE routers. Bridged encapsulation is used, corresponding to the
Bridged (Ethernet) Interworking mechanism.
Cisco 10000 Series Router Software Configuration Guide
21-10
Network Topology for ATM to Ethernet AToM Bridged Interworking
VPI/VCI
ATM Link
PE with
interworking
function
shows the protocol stack for ATM to Ethernet AToM Bridged Interworking. The ATM side
Protocol Stack for ATM to Ethernet AToM Bridged Interworking—Without VLAN
Header
ATM
ATM
PE
ATM Header
LLC
(AA-AA)
LLC(03) OUI (00)
OUI
(80-C2)
PID
(00-07)
PAD
(00-00)
MAC Header
DA
SA
Type/Length
Remainder of
Remainder of
MAC Frame
MAC Frame
CPCS - UU CPI
Length
CRC
Pseudowire using EoMPLS
Tunnel LSP
P Router
P Router
MPLS Network
MPLS Emulated VC of
Tunnel Label
VC Label
Control Word
MAC Header
DA
SA
Type/Length
Chapter 21
Configuring L2VPN Interworking
Ethernet
Ethernet Link
PE
(Figure
21-5).
Ethernet
Eth
PE
Tunnel Label
VC Label
Control Word
MAC Header
MAC Header
DA
DA
SA
SA
Type/Length
Type/Length
Remainder of
Remainder of
MAC Frame
MAC Frame
LAN FCS
Ethernet
CE
Eth
CE
OL-2226-23
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