Transcript Next Generation Networks `96

Methods of ATM Internetworking
What is LAN Emulation?

Lan Emulation provides for:
–
–
–
–
all existing LAN applications to run over ATM
the use of ATM as a backbone to interconnect existing
“legacy” LANs
the interconnection of ATM-attached servers/workstations
to each other and to those on “legacy” LANs
multiple Emulated LANs which are logically separate, to
use the same physical ATM network
Ethernet
Token Ring
ATM
Network
Ethernet
Token Ring
Physical and Emulated LANs
Scenario 1

An ATM network interconnecting multiple Ethernet
segments and ATM-attached end-systems
–
–
–
Ethernet to Ethernet
Ethernet to ATM
ATM to ATM
Ethernet
Bridge
Ethernet
Bridge
ATM
Network
ATM-attached
stations
Scenario 2

An ATM network interconnecting multiple Token-Ring
rings and ATM-attached end-systems
–
–
–
Token Ring to Token Ring
Token Ring to ATM
ATM to ATM
Ring
Ring
Bridge
Bridge
ATM
Network
ATM-attached
stations
LAN Emulation Protocol Stack
ATM Host
ATM Switch
ATM-LAN Bridge
LAN Host
Existing
Applications
Existing
Applications
IP
IP
NDIS/ODI Driver I/f
Bridging
LAN
Emulation
MAC
AAL5
AAL5
LAN Emulation
AAL5
ATM
Physical Layer
NDIS/ODI Driver I/f
ATM
Physical Physical
ATM
Physical Physical
MAC
Physical Layer
Emulated LAN Types

An Emulated LAN provides the functionality of a
single LAN segment:
–
–

an Ethernet/802.3 segment, or
a Token-Ring/802.5 ring
An Emulated LAN does not emulate all the
segment-specific details of the emulated type,
e.g.:
–
–
No collisions
No tokens, no beacon frames
LANE Architecture
LAN Emulation UNI
LAN Emulation Service
LAN Emulation Client:
ATM Workstation
LAN Emulation UNI
Initialization
Address Registration
Address Resolution
Data Forwarding
Legacy
LAN
LAN Emulation Client:
ATM Bridge
ATM workstation: One LANE Client for each emulated LAN
LE Service Components

LE Configuration Server
–

LE Server
–

Provides configuration information, address of
LE Server
Implements Address Registration/ Resolution
functions
Broadcast/Unknown Server
–
Performs all broadcasting and multicasting
and unknown unicast distribution
LE Service Components
LANE Control Connections
LE Configuration
Server
Control Direct VCC
LE Server
LAN Emulation Client
Control Distribute
VCC
Other LE Clients
Broadcast/Unknown
Server (BUS)
LANE Data Connections
LE Configuration
Server
Multicast Send VCC
LE Server
Multicast Forward
VCC
LAN Emulation Client
Data
Direct
VCCs
Broadcast/Unknown
Server (BUS)
Other
LE Clients
LUNI Protocol Overview





Initialization
Configuration
Joining
Registration and BUS
Initialization
Data Movement
Initialization





Must determine the ATM address of the LECS
Use SNMP ILMI to get address from a table in the
switch and place call to that address
Use well-known ATM address
If that fails, use the VPI/VCI 0/17 PVC as the
connection to the LECS
If LECS is not available, try the LES
Configuration

LE Client provides the LECS with:
–
–
–

ATM address
MAC address
LAN types and frame sizes requested
LECS Returns:
–
–
LES address
LAN type and frame size to use
Joining




Create Control Direct bi-directional VCC
Transmit Join Request (ATM address, LAN info,
proxy indication, optional MAC address)
Possibly accept Control Distribute VCC before Join
Response is received
May time out or fail
Registration and BUS Initialization




Register any MAC addresses
Resolve 0xffffffffffff MAC address to get ATM
address of BUS
Create bi-directional Multicast Send VCC to BUS
Accept bi-directional Multicast Forward VCC from
BUS
Data Movement





When a data frame is available for
transmission, check internal cache
If unknown, ask the LES
While waiting for response, may transmit
frame(s) via BUS
Establish direct connection when response is
received
Connections are timed out on inactivity
LAN Applications

The advantage of LAN Emulation is that
–

The disadvantage of LAN Emulation is (also) that
–


the use of ATM is hidden from the applications
All existing applications can use LAN-Emulation
New applications, in order to use the power to ATM:
–
–

the use of ATM is hidden from the applications
need to be cognizant of ATM, and thus
need to use an ATM-aware API (e.g., Classical IP)
Both types of applications can co-exist, side by side
Interoperability



A logical “subnet” is either an Emulated LAN or an
ATM-aware subnet
Logical subnets are interconnected via routers
The driver for the ATM-adapter card needs to support
the relevant type of logical subnet.
“ATM-aware”
subnet
Emulated
LAN
Router or ATM
Server
“ATM-aware”
subnet
Emulated
LAN
LAN Emulation Version 2.0

LUNI 2.0
–
–
–
–
–

Compatible with LUNI 1.0
Optional to multiplex ELANs on same VCC
Improved QoS support
Additional support for Multicast
Persistent Data Direct VCCs stay up across server
failures
LNNI 2.0
–
–
–
–
Multivendor LE service component interoperability
Up to 20 LES/BUS pairs; up to 2000 LE Clients
Standardized server failover
Selective Multicast Server to offload multicasts from
BUS
Summary



All existing LAN applications can run on an
Emulated LAN
LAN Emulation allows ATM to be used as a
backbone to interconnect “legacy” LANs and
ATM-attached hosts
To exploit the power of ATM, new
applications need to use ATM-specific API’s,
rather than LAN-Emulation