From: Scott F. Robohn (sfr@xxxxxxxx)
Date: Mon Jun 21 1999 - 23:31:18 GMT-3
Ben,
First, don't sweat it. There's not a whole lot you can do
with ATM in the context I'm hearing. It'll be new, but
do-able.
BTW, Bruce (Caslow) is also working ATM into the current
version of the class he's teaching.
The best place to start is CCO. You can also check out
http://academy.fore.com for a good generic LANE tutorial.
Some more comments below...
> Ben Rife wrote:
> 1. What hardware constitutes a client to client connection
> via ATM, in other words, what's in the middle?
I'll answer this as a LANE question. LANE is a
client-server architecture that emulates the broadcast
functionality built-in with ethernet and token ring over
ATM. ATM is connection-oriented (you pass no user data
until a connection is formed), so you have to create
services to emulate that broadcast function. You
essentially 'fake out' the IP (or IPX or AppleTalk or...)
clients into thinking there's a broadcast mechanism at work
- and there is, it just needs to be turned on.
LANE consists of the following components:
(1) LANE Clients (LECs) that are placed where 'ATM stops',
so they're on the edge of the ATM network. LECs use the
services defined below. A LEC can go on:
a. a router interface so that other LECs can talk to the
router LEC and route out of an ELAN (this interface gets a
Layer 3 address)
b. a LANE module so that multiple legacy (e.g., ethernet)
ports can talk to other LECs on the ATM network (this
interface does _not_ get an L3 address; the hosts handing
off the ethernet ports have them)
c. an LS1010 ASP for management purposes (gets an L3
address).
(2) The LAN Emulation Server (LES) (one of three services)
performs two primary functions: to keep track of the LECs
joined to the ELAN and to perform MAC-NSAP address
resolution (LE-ARP processing). A LEC can go on:
a. a router interface
b. a LANE module
c. an LS1010 ASP
Sensing a trend yet?
(3) The Broadcast and Unknown Server (BUS) that handles the
forwarding of LANE frames to destination addresses that
haven't been resolved yet. When you create a LES ('lane
server-bus ethernet name BEN-ELAN'), you automatically
create a BUS. The BUS can go wherever the LES can.
The LES and BUS are never bound to an L3 address. For a
given ELAN, there is at least one active LES and one active
BUS, which we typically refer to as the LES/BUS since
they're almost _always_ configured together. You can put a
LEC and a LES/BUS for an ELAN on a single subinterface, or
you can put them on different subinterfaces. We generally
use subinterfaces for LANE entities.
(4) The LAN Emulation Configuration Server (LECS - note the
potential acronym confusion) is like 'directory services'
for LANE. You call 411 (a well-known address) and ask for a
phone number, and then you call that number. Similarly, a
LEC calls the LECS asking for the NSAP address of an ELAN it
wants to join; the LECS (if it knows that ELAN name) returns
the NSAP address of the LES to the requesting LEC, so the
LEC can then call the LES directly.
An LECS goes on a major interface instead of a subinterface
(on the A2/0/0 on an LS1010 or A13/0/0 of the C5500 with
ASP), implying you only can have one LECS per device. You
only need one LECS for an ATM network with MANY ELANs.
So, your ATM network could look like the following:
- one LECS that has NSAP addresses for the LES/BUS's of many
ELANs
- one active LES/BUS per ELAN
- many LECs that join a given ELAN
> 2. With respect to the lab, I assume we will have to
> configure some of these devices, for Lane. What does a
> Lane config look like? Where do you configure the LES,
> LECS, and BUS? Can these be done on one router/switch?
>
> 3. What configuration needs to be done on a switch versus
> a router?
1. Create an LECS somewhere - router, LANE mod, or LS1010
2. Create a LES/BUS for an ELAN - router, LANE mod, or
LS1010
3. Create LECs to join the ELAN - and give them L3 addresses
> 4. What's the difference between a Lightstream (LS1010)
> and a Cat5k ?
LS1010: An ATM switch - ATM interfaces, cell backplane, no
ethernet (except for out-of-band management)
Cat5: Primarily an ethernet switch, but it can have a LANE
module that connects to the ethernet backplane and converts
frame traffic into ATM cells that then go to an ATM switch.
The 5500 can have a frame backplane and a cell backplane
(really an embedded LS1010) in the same chassis.
> 5. What if any, is the connection between ELAN's and
> VLAN's ? How do you configure a router to route between
> ELAN's and where is the router placed/connected to?
The LANE Module bridges this gap (no pun intended). You
associate a VLAN with a LEC on the LANE module:
int a0.10 multi
lane client ether <vlan-number> <elan-name>
To route between ELANs, you have different subinterfaces
with different LECs and different IP subnets.
This has been quite LANE-oriented. PVCs could come into
play as well.
I gotta hit the sack. Perhaps some others can add...
Regards,
Scott
ps - Paul: I'd be happy to contribute some time to a FAQ on
this.
-- >>Scott F. Robohn, CCNP/ATM, FLCI/FLCE...sfr@ccci.com<< >>Chesapeake Computer Consultants, Inc...703-623-3752<<
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