7. LAN EMULATION (LANE)

Goal: How can existing Ethernet and Token Ring be integrated with ATM?

Need: All LAN-based network applications assume that LAN is capable of • Delivery of packets to individual destinations according to a

unique MAC address, without the necessity for any kind of connection set-up to that address.

• Delivery of broadcast packets to all stations on the LAN or a specified group of stations, by means of a special kind of MAC destination address indicating broadcast or multicast.

1

ATM World

• Not offering these services.• ATM delivers data on VCCs which need to be set up between source and destination

ATM (Connection-Oriented) LANs (Connectionless)

• LAN EMULATION:

Masks the complexities of ATM connection set-up from applications that expect connectionless data delivery.

PHYSICAL and EMULATED LANs

ATM Network

ATM Network

Physical LAN Emulated LAN

ATMSwitch

ATMSwitch

ATMSwitch

ATMWorkstation

ATM PC

Token Ring

BridgeBridge

Ethernet

Ethernet

LAN Emulation Services• Configuration• Address Resolution• Broadcast

PROTOCOL LAYERSATM Host with LANE

NICLAN Host

* Purpose: Fooling the application software into believing that is talking toa standard network adapter driver.

IPX: NetWare Internetworking Protocol

(Network Driver Interface Specification

or

Open Data Link

Interface) *

Existing Application Software

IP IPX NDIS ODI

LAN Emulation

AAL 5

ATM

PHY PHY PHY

ATM ATM

PHY PHY

ATM

MAC

LANE

AAL 5

802.1DBridging

PHY

MAC

IP IPXNDIS ODI

Existing Application Software

Layer 2 LAN Switch

ATM Switch

ATM SWITCH

Bridge

LANE COMPONENTS

An Emulated LAN consists of multiple LAN Emulation Clients (LECs) and LAN Emulation Services.

From Single Emulated LAN perspective:

Legacy LAN

Legacy LAN

LAN Emulation Server

Broadcast and Unknown Server

LAN Emulation Configuration Server

LEC

LEC

LES

BUS

LECS

LEC

LUNI

LUNI

LUNI

Bridge

Bridge

LANE SERVICES

LUNI: LAN Emulation User to Network Interface

LANE PROTOCOL INTERFACES

ATM Network

ATM Network

ATM Host

Layer 2 Switch

Router

LECS

BUS

LES

LES

1

n

BUS1

n

LANE Clients LANE ServersNote: The Phase 1 LANE spec only specifies the LUNI interface

UNI

LUNILNNI

LNNI

LEC: (LAN EMULATION CLIENTS) (e.g., ATM Host, Layer 2 Switch, Router)

* Any end-station or bridge that implements LAN Emulation.

* A process that resides in end-station or a bridge providing entry point to ELAN.

* Entity in an end-system that performs DATA FORWARDING, ADDRESS

RESOLUTION, and other control functions for a single end-system within a

single ELAN.

* LEC also provides a standard LAN interface to any higher layer entity that interfaces to the LEC.

* An ATM NIC or LAN switch interface to an ELAN supports a single LEC for each ELAN to which they are connected.

* An end-system that connects to multiple ELANs (maybe over the same UNI) will have one LEC per ELAN.

LEC: (Ctd)

* Each LEC is identified by a unique ATM address and is associated with one or more MAC addresses reachable through that ATM address.

* In case of ATM NIC LEC maybe associated with only a single MAC address.

* In case of LAN Switch LEC is associated with all the MAC addresses reachable through the ports of that LAN switch which are assigned to a particular ELAN.

* In the latter case set of addresses may change, i.e., MAC nodes come up and down. PROXY concept can be used!!

* Ethernet-to-Token Ring Interconnection: Two Different ELANs which must be interconnected through an ATM switch which acts as a client on each ELAN.

LES * Implements the control function for a particular ELAN.

* Each LES is identified by a unique ATM address. * Registering and resolving MAC addresses into

ATM addresses;

* It also responds to LEC queries. * Each emulated LAN has ONLY one LES.

* Belonging to a particular ELAN means to have a control relationship with that ELAN’s particular

LES. * LES acts as a CLEARING HOUSE for ADDRESS RESOLUTION.

Bottomline: LES provides ADDRESS RESOLUTION MECHANISM for resolving MAC Addresses. Also registration of an LEC, Forwarding Address Resolution Requests, Managing LEC Address Registration Information.

BUS * is a MULTICAST SERVER. * Used to flood unknown destination

address traffic and forward multicast and broadcast traffic to clients within a particular ELAN.

* Each LEC is associated with only a single BUS per ELAN,

but there may be multiple BUSs within a particular ELAN.

* BUS to which a LEC connects is identified by a unique ATM

address. * In the LES, this is associated with the broadcast

(“all ones”) and this mapping is normally configured into

the LES.

LECS

* Assigns individual LECs to different (particular) ELANs.

* It does this by providing each LEC with the ATM address of the LES for the emulated LAN assigned to

it.

* There is logically one LECS per network and this serves all ELANs within that domain.

REMARK: * System Architecture allows these components to be

distributed among multiple physical devices. * These components are connected to each other by

multiple Virtual Channels (VCs).

LOCATION of LAN EMULATION COMPONENTS

LAN Emulation Client

LAN Emulation Client

LAN Emulation Client

LAN Emulation Server

Broadcast/Unknown Server

LANE Configuration Server

LAN Emulation Client

LAN Emulation Client

Token Ring

ATM Concentrator

ATM Switch

Token RingSwitch

TR Hub

Full DuplexToken Ring

Ethernet Hub

Router

ATM End Stations

LOCATION OF LANE COMPONENTS

LEC

• In any PC or workstations directly connected to ATM network. Reside in devices such as Bridges, LAN Switches, Routers…

• As a software (on an ATM card!) Operates underneath a standard LAN Driver interface,

ODI (Novell Open Data Link Interface) or NDIS (Microsoft Network Data Link Interface

Specification)

• LEC is the integral part of driver software for ATM adapter card.

LES, BUS, LECS processes need to reside on hosts that are easily accessed by all LECs.Located on the same host or different hosts.

In Actual World:On any workstation attached to the ATM network(dedicated PC or WS)e.g., implemented as Netware Loadable Modules (NLMs) and run on an existing or dedicated Netware server.AlternativeLES, BUS, LECS can be on a processor integrated with an ATM switch. 10

• Each LEC is an entity within an ATM end system, acting on its own behalf and on the behalf of traditional LAN users identified by MAC addresses.• LEC is a software process running on any ATM connected LAN switch, router, PC, or workstation.

LAN (LEC)Emulation Clients

LES-1

LES-N

LAN (LEC)Emulation Servers

ATM

ATM

ATM

LECSLUNI

13

ATM Host

Layer 2 Switch

Router

ATM NETWORK

BUS-1

BUS-NLNNI

LNNI

Configuration Direct VCC. This is a bidirectional point-to-point VCC that is established between the LEC and the LECS as part of the LECS Connect phase. It is used by the LEC to obtain configuration information such as the ATM address of the LES.

Control Direct VCC. This is a bidirectional point-to-point VCC that is established between the LEC and the LES for the purpose of sending control information. Set up by each LEC when joined the ELAN.

LANE CONTROL CONNECTIONS

CONTROL TRAFFIC: Control VCCs carrying control messages between a LEC & either the LECS or the LES.

LANEClient LECS

Configuration

Direct VCC

LANEClient

LES Control

Direct VCC

Control Distribute VCC. This is a unidirectional VCC set up from the LES back to the LEC. This is either point-to-point (LES LANE Client (LEC)) or typically point-to-multipoint (LES many clients (LECs)).

LANE CONTROL CONNECTIONS

LANEClient

Control

Distribute VCC

LANEClient

LES

Control

Distribute VCC

LANE Control Connections (Overview)

ControlDistribute

VCC

ControlDirectVCC

ControlDirectVCC

ConfigurationDirect

VCC

ConfigurationDirectVCC

LANE Server(LES)

LANE Client(LEC)

LANE ConfigurationServer (LECS)

LAN Switch

ATM Host

LANE Client(LEC)

Data VCCs connect the LECs to each other and to the BUS. They carry encapsulated Ethernet or Token Ring frames.

LANE DATA CONNECTIONSDATA TRAFFIC:

Data Direct VCC:

This is a bidirectional point-to-point VCC that is established between two LECs that want to exchange data. Two LECs will use the same data direct VCC to carry all packets between them => to save bandwidth & set up overheads!

LANEClient

LANEClient

Data Direct VCC LANEClient

LANEClient

Remark:

LANE supports existing LANs which do not support QoS; => Data Direct Connections will typically be UBR or ABR connections.

LANE DATA CONNECTIONS (Ctd)

Multicast Send VCC:This is a bidirectional point-to-point VCC set up by the LECs to the BUS.

LANEClient

LANEClient

Multicast Send VCCBUSBUS

This VCC is used for sending multicast data frames to the BUS, as well as initial unicast data frames whose ATM address is not known to the source LEC.

A LEC may receive data frames over this VCC.

MULTICAST FORWARD VCC

• This is a unidirectional VCC set up to the LEC from the BUS. • This is typically a point-to-multipoint connection with each

LEC as a leaf.

*This VCC is used for forwarding multicast data frames to LECs.

LANE CLIENT

(LEC)

BUSMulticast Forward VCC

LANE DATA CONNECTIONS (Overview)

LANE Client (LEC)

ATM Host LAN Switch

Broadcast and Unknown Server (BUS)

LANE Client (LEC)Data Direct

VCC

Multicast Send VCC

Multicast Send VCC

Multicast Forward VCC

LANE FUNCTIONS• INITIALIZATION. LEC obtains the ATM address of the LES and establishes connections with the LES and BUS; Joining or Leaving a given ELAN. (Connect Phase, Configuration Phase, Join Phase, BUS Connect Phase)

• REGISTRATION. LEC registers its MAC address(es) with the LES. (in case of Token Ring, a list of source route descriptors that LEC represents for source route bridging)

LANE FUNCTIONS

• ADDRESS RESOLUTION. Enables a source LEC to obtain the ATM address of the destination LEC for the purpose of establishing a Data Direct VCC.

• DATA TRANSFER.

Determine which VCC to send data on and then encapsulate

in AAL5 frames.

I. INITIALIZATION

1.Connection Phase (LEC connection to LECS)2.Configuration Phase3.Join Phase4.BUS Connect Phase

I. INITIALIZATION

1. Connection Phase (LEC to LECS)

Upon initialization (such as power-up), the LEC must first obtain its own ATM address (through Address Registration) from LECS:

To do this, LEC must first find the LOCATION (ATM address) of the LECS. THREE METHODS:

Use SNMP ILMI commands from the adjacent switch and obtain the LECS ATM address OR

Use the well-known ATM address of the LECS assigned by the ATM Forum OR

Use the well-known PVC (VPI = 0; VCI = 17) to connect to the LECS.

2. Configuration Phase

After finding the location of the LECS, the LEC will establish the “Configuration Direct VCC” to the LECS.

Figure shows the “CONTROL FRAMES” that flow between the LEC and LECS, OVER the “Configuration Direct VCC” and some important operational variables that are carried.

LEC LECSLE_CONFIGURE_REQUEST

(Configuration Direct VCC)

LEC LECSLE_CONFIGURE_RESPONSE

(Configuration Direct VCC)

Information: C1 : LEC ATM ADDRESS

Information: C2 : LAN Type (Ethernet or Token Ring) C3 : Max. Frame Size C5 : ELAN Name C9 : Target ATM Address of the LES

3. Join Phase

LEC establishes a “Control Direct VCC” to the LES and attempts to join as a member of the ELAN.

LEC LESLE_JOIN_REQUEST

(Control Direct VCC)

Information: C1 : LEC ATM Address C2 : LAN Type C3 : Max. Frame Size C4 : Proxy LEC (any other MAC address it is

proxying (Optional!!!) C5 : ELAN Name C6 : Local Unicast MAC Address (Optional)

The unique MAC address associated with the LEC. This enables the LEC to register this address and its associated ATM address, C1 variable with the LES.

LEC LESLE_JOIN_RESPONSE

CONTROL DISTRIBUTE VCC

Information: C2: LAN Type C3: Max Frame Size

C5: ELAN Name C14: LECID (unique LEC Identifier, assigned by LES for

every LEC that joins the ELAN.)

During JOIN process, LES issues to the LEC a 2-byte identity code (LECID)

that is unique for this LEC.This value will be used as LAN Emulation header to be appended to all Ethernet or Token Ring frames before they are segmented into cells.

REMARK: The LEC will exchange information with the LES so that the LES can

maintain a table of details of all LECs currently active on the ELAN.

REMARK: LES has the option of responding to the LEC on Control Direct

connection, or via a unidirectional point-to-multipoint Control Distribute connection to all LECs.

REMARK:

Connecting to the LES and Joining the Emulated LAN

LAN Emulation

Client (LEC)

LAN Emulation

Server (LES)

1LEC sets up Control Direct VCC 2LEC sends

LE_JOIN_REQUEST

3LES optionally sets up Control Distribute VCC 4LES sends

LE_JOIN_RESPONSE

ToOther LECs

14

4. BUS (Broadcast and Unknown Server) CONNECT PHASE (How to Handle Broadcast and Multicast?)

When LEC registers with LES; LEC locates the BUS by sending an LE_ARP_REQUEST to the LES, in order to find the ATM address that corresponds to the broadcast MAC address (hex: F^{12}).

LES responds to this LE_ARP request with the ATM address of the BUS.

LEC uses this to establish a “MULTICAST SEND VCC” to the BUS.

BUS sets up a return path to the LEC, then automatically adds the LEC to an existing point-to-multipoint “MULTICAST FORWARD VCC” or BUS may establish a point-to-point VCC to the LEC.

Once the BUS connect phase is complete, then LEC can send broadcast and multicast frames to BUS.

BUS sends then broadcast and multicast frames to all LECs that are registered with it (including the sender LEC) USING THE MULTICAST FORWARD VCC.

Once the BUS Connect Phase is complete, LEC is initialized and data transfer can begin.

LANEClient

LECS LES BUS

Configuration Direct VCC

Control Direct VCC

Control Distribute VCC

Multicast Send VCC

Multicast Forward VCC

Control and Data VCCs Established During the Initialization Phase

II. ADRESS REGISTRATION

Each LEC must register the additional MAC addresses it represents with the LES that were not registered during the JOIN phase. LES builds a table of ATM Address-MAC address pairs that it uses to respond to Address Resolution requests made later by another LEC.

Information: C1: LEC ATM addressC6: Local Unicast MAC

address C8: Route Descriptor (If

SRB) C14: LECID

LEC LESLE_REGISTER_REQUESTCONTROL DIRECT VCC

LEC LESLE_REGISTER RESPONSE

“CONTROL DIRECT VCC” or“CONTROL DISTRIBUTE VCC”

Information:

STATUS C14 : LECID

LEC LES“CONTROL DIRECT VCC”

LE_UNREGISTER_REQUEST

Information: C1 : LEC ATM ADDRESS C6 : LOCAL UNICAST MAC ADDRESS C8 : Route Descriptor (If SRB) C14 : LECID

LEC LESLE_UNREGISTER RESPONSE

“CONTROL DIRECT VCC” or“CONTROL DISTRIBUTE VCC”

Information : STATUS C14 : LECID

III. ADDRESS RESOLUTION(requires LES and a protocol LE_ARP (LAN Emulation Resolution Protocol_ for communicating with LES)

26

51 Ethernet-ATMBridge

ATM

Learned MAC

Addresseson Ethernet

Port

5126

Resolved MACAddresses

on ATM Port

MAC MapAddress to VCI73 688 369 6

14 8

69

73Ethernet-ATM

Bridge

14

88

VCI=6

VCI=3

VCI=8

3Emulated MAC Address

ADRESS RESOLUTION PROCESS

LAN Application

ATM Network

Look up VCCto match this DA

Remove LE Headerand assemble frame

Add 2Byte LE Headerand Segment Frame

Resolve address and set up VCC

Send Data

Destination AddressSource Address; Data

Receive Data

Destination AddressSource Address; Data

DA-VCCMapping Table

Call Setup

DestinationAddress

Call Connect

VCI

Send Data

VCIData

Receive Data

VCIData

MatchFound?

No Yes

Address Resolution (Ctd)•Used by source LEC to associate a destination MAC

address with the matching ATM address.•Purpose: Provide to the source LEC the ATM address

of the destination LEC.•The destination LEC could be a workstation or a

bridge (transparent or source-routing) which is providing a proxy LEC function for the legacy MAC devices behind it.*

•When the source LEC has a frame to transmit to a destination MAC address and it does not already have a Data Direct VCC open nor does it have an entry in its own MAC-to-ATM address cache (C16 variable), it sends an LE_ARP_REQUEST over the Control Direct VCC to the LES.

* (LEC needs to know the ATM address of another LEC that it knows the MAC address for, it sends a request to LES using LE-ARP).

Address Resolution (Ctd)•PROXY: If LEC is a transparent bridge it represents

hundreds of MAC addresses. This list may change over time.

•Stations in Ethernet come and go. This type of LEC is not permitted to register its MAC addresses with LES.

•Too much overhead to maintain tables.

• Instead LEC registers as a “PROXY” and LES must forward all LE_ARP requests to it through “Control Direct VCCs” so that it can respond directly to the LEC that is requesting.

Address Resolution (Ctd.)• How the LES behaves depends on whether the

MAC destination address is registered with the LES.

• The LES can respond to the address resolution

request in the following manner:

• If the LE_ARP_REQUEST contains the broadcast

MAC address (all ones) as the destination MAC

address, then the LES will respond with the ATM

address of the BUS in the LE_ARP_RESPONSE. This is performed during the BUS connect phase

of the LEC initialization process.

Address Resolution (Ctd.)•If the destination MAC address is known to the LES

(registered), then the LES will return the destination ATM address to the source LEC in an LE_ARP_RESPONSE.

•This control frame is sent over the Control Direct VCC or Control Distribute VCC.

•Forwarding it over the latter will enable other LECs to

update their LE_ARP caches (C16) but will incur some network and LEC processing overhead.

•If the destination MAC address is unknown to the LES, then the LES will forward the LE_ARP_REQUEST to other LECs over the Control Direct VCC or Control Distribute VCC.

This will typically be the case if the destination MAC address belongs to a workstation attached to a legacy LAN on the other side of the bridge.

EXAMPLE (REGISTERED ADDRESS SOLUTION)

LANE Client #1 wants to send a frame to another LEC (not shown) that has registered its MAC address with the LES. It will then send an LE_ARP_REQUEST over the Control Direct VCC to the LES. The LES will respond with an LE_ARP_RESPONSE, which contains the ATM address of the destination LEC. The source LEC installs the new MAC-to-ATM address mapping in its own LE_ARP cache (C16) and then sets up a Data Direct VCC to the destination LEC.

LANEClient LES

LE_ARP_REQUEST (LECID, Source MAC Address,Source ATM Address, Destination MAC Address, …)

Control Direct VCC

Control Distribute VCC or Control Direct VCC

LE_ARP_RESPONSE (LECID, Source MAC Address,Source ATM Address, Destination MAC Address, Destination

ATM Address, …)

Address Resolution for Unregistered MAC Address

• Only LECs that are directly attached to the ATM network are allowed to register their own MAC

addresses. • Devices such as ATM LAN bridges are allowed to register only their own MAC addresses, or if they are token-ring source-route bridges, then their route descriptors.

• For example, an Ethernet-to-ATM transparent bridge will not register with the LES any of the MAC addresses of Ethernet-attached workstations that it has learned about.

• Instead, it will respond to LE_ARP_REQUESTS that have been forwarded to it from the server with its own ATM address, the MAC address of the actual Ethernet-attached workstation, and a flag indicating that the MAC address is “remote” from the LEC that responded.

Address Resolution for Unregistered MAC Address

• If LEC fails to resolve a MAC address by means of LE_ARP_REQUEST, it may forward the frame to BUS using the “Multicast Send VCC”.

• BUS will treat this frame as if it were a broadcast or multicast, and will forward it to all registered LECs.

• If these LECs are transparent bridges, their bridging logic dictates that such frames should be forwarded on all attached LAN segments.

• When the target station replies, the bridge on that segment will learn of its whereabouts, and the next time a LEC attempts an address resolution to this MAC address, the bridge will be able to respond.

•

Example Unregistered Address Solution

LANE Client1

LESLANE Client2

LE_ARP_REQUEST(LECID, Source MAC Address, Source ATM address, Destination MAC Address, …)

Control Direct VCC

LE_ARP_REQUEST

Control Distribute VCC

LE_ARP_REQUEST

LE_ARP_RESPONSE(LECID, Source MAC Address, Source ATM Address, Destination MAC Address, Destination ATM Address, Remote Address Flag, …)

Control Direct VCC

LE_ARP_RESPONSELE_ARP_RESPONSE

Control Distribute VCC

• LANE Client #1 wishes to transmit a frame to a destination MAC Address that is unregistered.• It is in fact an Ethernet workstation that is attached to LANE Client #2. • LANE Client #2 is actually an Ethernet-to-ATM bridge. • So after LANE Client #1 sends the first frame to the BUS which will in turn forward it out its Multicast Forward VCC to all LECs on the ELAN, it sends an LE_ARP_REQUEST to the LES. • Because it is unregistered the LES forwards the request on its Control Distribute VCC to all LECs on the ELAN.• LANE Client #2 receives the request, checks its own MAC address cache (it is a transparent learning bridge) and determines that it contains a match for the destination MAC-address value in the request. • LANE Client #2 then issues an LE_ARP_RESPONSE that contains the destination MAC address (C27), its own ATM address, and sets a flag to indicate that the address is remote.• The response is forwarded back to LANE Client #1 who caches the information and now can set up a Data Direct VCC.

Address Resolution Control Frames

LEC LESLE_ARP_REQUEST

“Control Direct VCC”

Information:

Source MAC Address

Source ATM Address

Destination MAC Address

C14 LECID

LEC LESLE_ARP_RESPONSE

“Control Direct VCC” or

“Control Distribute VCC”

Information: Source MAC Address Source ATM Address Destination MAC Address Destination ATM Address Remote Flag C14 LECID

!!!!!

LEC LESLE_NARP_REQUEST

“Control Direct VCC”

Information:

MAC Address that is no longer valid

Source ATM Address

Destination ATM Address (previously representing the invalid MAC Address)

C14: LECID

Remark: Used when LEC (typically a proxy LEC) wishes to invalidate an existing MAC-to-ATM address mapping.

LEC LESLE_TOPOLOGY_REQUEST

“CONTROL DIRECT VCC”

or “Forwarded by LES over Control Distribute VCC”

• Information: Topology Change Flag

C14 LECID

• Remark:Sent out by either LEC or LES to inform other members of the ELAN that a change in the network topology is under way.

The Address Resolution Process

1LEC sends LE_ARP_REQUESTfor target_mac_addressCONTROL DIRECT VCC

Target

LAN Emulation

Server(LES)

(Clearing house for

address requests)

2LES forwards LE_ARP_REQUEST to all other LECs that it knows about.

4LES forwards LE_ARP_RESPONSE to LEC 5

Source LEC sets up Data Direct VCC to target LECDATA DIRECT VCC

3Target LEC sends LE_ARP_RESPONSE to LES

LAN Emulation

Client (LEC)

LAN Emulation

Client (LEC)

Source

11

Data frames can flow between a source LEC and a destination in one of two ways:

• Data Direct VCC

• Multicast Send VCC to the BUS and then back out over the Multicast Forward VCC.

• If a source LEC has already established a Data Direct VCC to a destination LEC, then all unicast frames will flow over that connection.

• If the source LEC does not have a Data Direct VCC established, then it may forward the frames up to the BUS via the Multicast Send VCC.

• The BUS in turn will forward the frames back out its Multicast Forward VCC to the destination LEC or may use the Multicast Send VCC.

IV. DATA TRANSFER

•It is up to the BUS implementation to decide which one to use, but both cannot be used at the same time.

•In this mode LAN Emulation does indeed provide a connectionless service because the source LEC can begin transmitting without having to first set up a Data Direct VCC.

•All multicast and broadcast frames are forwarded to the BUS over the Multicast Send VCC.

•Again the BUS can use either the Multicast Send VCC or Multicast Forward VCC to propagate the multicast or broadcast frames to the members of the ELAN.

•In this operation, it is possible for a sending LEC to receive a copy of its own broadcast frame.

DATA TRANSFER (Ctd)

• However, the sending LEC inspects the LECID that is contained in each frame.

• Those frames that contain a LECID that matches that of the sending LEC are filtered out.

• It may be possible for two paths to exist between a source and destination LEC pair: one through the BUS and one through a Data Direct VCC.

• This could introduce a situation where frames are delivered out of order, i.e., first frame gets delayed in the BUS and second frame arrives sooner by Data Direct VCC. (LEC was set up when the address is resolved).

• To address this situation, a mechanism called the LAN Emulation Flush Protocol was developed. (Eliminates the “OUT OF ORDER”)

Data Transfer (Cntd)

FLUSH PROTOCOL

Client A

BUS

Client B

FLUSHFLUSH

DIRECT VCC

• Clients can send unicast packets via BUS while trying to resolve the address Out of Order arrivals.

• When the “Direct VCC” is set up, clients send a “FLUSH MESSAGE” to destination. Destination returns it to source.

• Source can then send packets on “Direct VCC”

• If a source LEC detects that it is receiving frames over both a Data Direct VCC and a Multicast Forward VCC, it will send an LE_FLUSH_REQUEST over one of the paths to ensure that all frames on the path have reached their destination.

• The source LEC will not send any frames over the path it sent the flush request until it receives a flush response with a matching transaction ID.

• The LEC receiving the flush request will return a response.

Data Transfer (Cntd)

REMARK:

• Each Data Direct connection is aged. If no packets are sent between LECs for 20 minutes, SVC cleared normally.

• Of course, a new connection can be established later if it is necessary.

Data Transfer (Cntd)

LAN EMULATION FLUSH CONTROL FRAMES

LECLE-FLUSH-REQUEST

“DATA DIRECT VCC” or“MULTICAST SEND VCC”

Information: Transaction ID Destination MAC Address Destination ATM Address

Information: Transaction ID Destination MAC Address Destination ATM Address

LECLE-FLUSH-RESPONSE

“CONTROL DIRECT VCC”for forwarding to LEC

LES

LAN EMULATION SIGNALING

LAN CLIENT 1

LAN CLIENT 1

LAN CLIENT 2

LAN CLIENT 2

SWITCHSWITCH SWITCHSWITCH

SETUP SETUP SETUP

CONNECT CONNECTCONNECT

READY_IND

READY_QUERY

READY_IND

Excluding the READY_IND and READY_QUERY messages which are specific to Data Direct VCC establishment, the flows for setup and teardown are similar to those for point-to-point and point-to-multipoint SVCs. In this example the source LEC that wishes to initiate a Data Direct VCC, LANE Client #1 will generate a SETUP message. The information elements contained in this message include AAL parameters (AAL5), traffic descriptors (forward/backward PCR), broadband bearer capability (BCOB-X), QoS class (0 for best-effort), and a broadband low-layer information (BLLI) which indicates the type of LANE connection that is being established (e.g., Data Direct VCC, Control Direct VCC). Once LANE Client #1, receives a CONNECT message it is ready to start sending data. However, Client #1 must first send a READY_IND message as soon as it is ready to receive frames on the newly established VCC. At that point, it will consider call establishment to be complete. If for some reason the READY_IND message is lost, the destination LEC, LANE Client #2 will wait a period of time and then send a READY_QUERY message to LANE Client #1.

• Allows multiple LESs

• LAN Emulation Network-to-Network Interface (LNNI) (Specifies interfaces for communication between the LES entities)

LAN EMULATION (VERSION 2.0)

LECSLESBUS

LECSLESBUS

LOGICAL ELAN

PHYSICALELAN 1

PHYSICAL ELAN 2

LNNI

• Server cache synchronization protocol

• Changes to LAN Emulation;

User-to-Network Interface (LUNI):

* Quality of Service (8 global classes)

* Enhanced support for PVC

* LLC Multiplexing

* Support for ABR

* Enhanced multicast support (Multicast trees (VCs)) (Different from broadcast trees)

LANE v2.0

• LANE encompasses a complex set of protocols.

• Software Implementation of LANE servers takes about 50K lines of C code and a LEC implementation is about 20K lines.

• Debugging these codes is a large task!!

FINAL REMARKS