Cisco 10000 - Manual (Page 39)

1-7
Cisco 10000 Series Router Software Configuration Guide
OL-2226-23
Chapter 1 Broadband Aggregation and Leased-Line Overview
Broadband Architecture Models
L2TP Access Concentrator Architecture
Figure 1-7 shows an L2TP access concentrator (LAC) model.
Figure 1-7 LAC Topology
In the figure, wholesale providers tunnel subscriber PPP sessions to the retail provider. PPP in
L2TP sessions are encapsulated in IP packets and forwarded over any IP transport network.
Routed Bridge Encapsulation Architectures
Figure 1-8 shows a routed bridge encapsulation (RBE) model.
CPE
PPP in L2TP sessions,
encapsulated in IP
Retail
providers
LNS
provider 1
76266
Wholesale
provider
LAC
Access network
(ATM or Ethernet)
IP transport
network
Subscribers
LNS
provider n
LNS
provider 2
PPPoA PPPoE
over ATM PPPoE
natively on
Ethernet/802.1q
Typically 1
tunnel per LAC
per retail provider