21-7
Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 21 Configuring L2VPN Interworking
Ethernet/VLAN to ATM AAL5 Interworking
Figure 21-1
Protocol Stack for ATM AAL5 to Ethernet Local Switching Bridged
Interworking—With VLAN Header
In Cisco IOS Release 12.2(33)SB, the Ethernet/VLAN to ATM AAL5 AToM has the following
restrictions:
•
The following translations are only supported and other translations are dropped:
–
Ethernet without LAN FCS (AAAA030080C200070000)
–
Spanning tree (AAAA030080C2000E)
•
ATM encapsulation type supported for bridged interworking is aal5snap. However, ATM
encapsulation types supported for routed interworking are aal5snap and mux.
•
The existing QoS functionality for ATM is supported, including setting the ATM CLP bit.
•
Only ATM AAL5 VC mode is supported. ATM VP and port mode are not supported.
•
SVCs are not supported.
•
Individual AAL5 ATM cells are assembled into frames before being sent across the pseudowire.
•
Non-AAL5 traffic, (such as OAM cells) is punted to be processed at RP level. A VC that has been
configured with OAM cell emulation on the ATM PE router (using the
oam-ac emulation-enable
CLI command) can send end-to-end F5 loopback cells at configured intervals toward the CE router.
•
When the pseudowire is down, an F5 end-to-end segment AIS/RDI (Alarm indication signal/Remote
defect indication) is sent from the PE router to the CE router.
•
If the Ethernet frame arriving from Ethernet CE includes a 802.1Q header (VLAN header), due to
the type of endpoint attachment (Ethernet port mode), the VLAN header stays in the frame across
the pseudowire (
Figure 21-2
).
270308
ATM
CE
Eth
CE
ATM
Ethernet
PE
ATM Header
MAC Header
DA
SA
MAC Header
DA
SA
Ethertype 81-00
VLAN Tag
Type/Length
Ethertype 81-00
VLAN Tag
Type/Length
Remainder of
MAC Frame
Remainder of
MAC Frame
CPCS - UU CPI
Length
CRC
LAN FCS
LLC
(AA-AA)
LLC(03) OUI (00)
OUI
(80-C2)
PID
(00-07)
PAD
(00-00)