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3 Routed Ethernet
Introduction
Features
Routed Ethernet vs.
connection service
Routed Ethernet vs TCP/IP
configuration
E-DOC-CTC-20051017-0167 v1.0
Routed Ethernet, also commonly known as MAC Encapsulated Routing (MER) or
IPoEoA (IP over Ethernet over ATM) relies on standard IP Routing for its forwarding.
The IP packets are wrapped in Ethernet frames before they are sent out on the DSL
line.
SpeedTouch™ operating as
PC configured
DHCP server and
as DHCP client
Internet IP Gateway router
Private DHCP
server
Private IP address
Routed Ethernet has the following features:
Provides Always-On type of connections.
Is auto-configurable if DHCP is enabled on Ethoa interfaces.
Multiple users can simultaneously share a single IP address if NAPT is enabled
on the Ethoa interface or can hide the IP address if NAT is enabled.
Allows the network to be shielded from the Internet via the SpeedTouch™
programmable firewall.
Allows Intranet connections through an IPSec tunnel.
Allows services such as IPQoS, SIP PBX, ISDN backup, IDS.
The Routed Ethernet Packet Service relies on the AAL5/RFC2684 Connection Service
to achieve end-to-end connectivity.
For the SpeedTouch™, this amounts to using the Ethernet over ATM (Ethoa)
Connection Service type. This connection service type implies the encapsulation of
Ethernet frames (often referred to as IEEE802.3, MAC frames or Bridging frames) in
AAL5/ATM.
All SpeedTouch™ products are compliant with RFC2684 "Multi-protocol
Encapsulation over ATM Adaptation Layer 5" and support both the LLC/SNAP and
VC-MUX method for Routed Ethernet V2.0/IEEE802.3 Protocol Data Units (PDUs). By
default the encapsulation method is set to LLC/SNAP.
Two Transmission Control Protocol/Internet Protocol (TCP/IP) scenarios are used for
Routed Ethernet implementations:
The Service Provider requires the use of DHCP for the Routed Ethernet
interface. The SpeedTouch™ embedded DHCP client, configured on top of the
interface will receive its IP configuration from a remote DHCP server, across
the DSL line.
DSLAM
Private IP
address
Connection Service Name: Routed Ethernet
Connection Service Type: ETHoA
Virtual Channel with:
ATM Encapsulation Type: VC-MUX
Chapter 3
Routed Ethernet
BRAS
Internet
17
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