atm in local area networks - it.uc3m.esppacyna/switching/lecture/slides/... · atm in local area...

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(c) Departamento de Ingeneria Telemática, Universidad Carlos III de Madrid

Switching: Switching: ATMATM

ATMATM in Local Area in Local Area NetworksNetworks

JosJoséé FFéélixlix Kukielka Kukielka David LarrabeitiDavid LarrabeitiPiotr PacynaPiotr Pacyna

2(c) Departamento de Ingeneria Telemática, Universidad Carlos III de Madrid

Programme authors and contributors

Teaching material:

David Larrabeiti LópezJosé Félix KukielkaHuw OliverPiotr Pacyna

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Index: ATM1. ATM in Local Area Networks

LAN Emulation (LANE)Multiprotocol Encapsulation over AAL5

2. ATM and InternetworkingClassical IP over ATMNext Hop Resolution Protocol (NHRP)Introduction to Multiprotocol over ATM (MPOA)

3. ATM Traffic Management and Congestion Control

The traffic contract

Reference modelsQuality of Service (QoS)Traffic parametersATM service categories

4. ATM Traffic ControlConnection Admission ControlUsage and network parameter controlTraffic shapingDelay and loss priority controlOther traffic control methods

Congestion recovery


ATM in ATM in Local Area NetworksLocal Area Networks

LAN EmulationLAN Emulation

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Motivation (1)

Currently: Majority of data traffic in private networks sent using Local Area Networks (LANs)

ISO Ethernet / IEEE 802.3Token Ring (IEEE 802.5)

Services available in LANs different from those available in ATM networks, for example:

Connection-less in LAN vs. connection-oriented in ATMBroadcast and Multicast easily to implement on a shared medium as used for LANsLAN MAC addresses based on fabrication number, independent of the network topology

Need interoperability between ATM and LAN!


Motivation (2): LAN Emulation

Objective: Reuse existing applications designed for LANs in an ATM networkDefine a new ATM service: LAN Emulation (LANE)Applications on end systems (work stations, routers, bridges) can connect to ATM networks

Allows for interoperability of applications with both, ATM devices and LAN devices

Corporate Network

Residential network

SME network

ATM network

LANE

LAN CLAN C

LANE

LAN ALAN A

LANE

LAN BLAN B

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LAN Emulation: Need for Interconnection

Different scenarios interconnecting LANs and ATM networks:

LAN/ATM (direct connection)LAN/ATM/LAN (connect two LANs with ATM links)

General solution: RoutersEffective, but introduction of extra processing delay

Further solutions:Transform all end systems to ATM stations cost

Advantage of LAN Emulation:Interoperability between shared medium LANs and ATM networks


Characteristics of LAN Emulation

Connection-less servicesMulticast / broadcast services

Limits overall size of emulated LAN

Example: STM-1 line, 5% broadcast 8 Mbit/sEmulate 10-Mbit/s Ethernet: Capacity almost used...

In reality: Emulate LANs of < 500 – 2000 stations

MAC-layer interface (operating system layer) on ATM stationsEmulation of LANsInterconnection of existing LANs

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Emulated LANs: Service Description

Ethernet/IEEE 802.3

Token Ring/IEEE 802.5

Two types of emulated LANsTwo types of emulated LANs

em. LANA

em. LANB

em. LANZ

ATM network

One or more emulated LANs can coexist in the same ATM network

Being independent from each other

Communicate with each other using routers or bridges


Hardware and Software in LANE

Oper. System

LAN Driver

ATM NICDriver

LANE

Applications

ATM NIC Software

AALATMPHY

NIC: NetworkInterface Card

Computer bus

ComputerCPU andMemory

Computer/Workstation

Oper. System

LAN Driver

LAN NICDriver

Applications

LAN NIC Software

MACPHY

Computer bus

Computer CPU andMemory

Computer/Workstation

LANEAALATMPHY

MAC

PHY

ATMBridge/Router

ATM physical medium Legacy LAN

ATMnetwork

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Architecture of LANE Protocols(Data Path)

Bridge

Applications

TCP/IP

LLC

MAC

Phy. layerPhy. layerPhy. layer

ATM

AAL5MACLayer

LANE

Phy. layer

ATM

Phy. layer

Applications

TCP/IP

LLC

Phy. layer

ATM

AAL5

LANE

ATMnetwork

ATMSwitch LAN

ATM Client LAN Client


LANE: Problems to Handle

For devices connected to the ATM network:How translate ATM addresses to MAC addresses?How adapt a connection-less protocol to a connection-oriented protocol?How to manage multicast and broadcast?

Solution:Client/Server model

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LANE Components

Two different classes: Clients and ServersLANE client (LEC): on a bridge, a terminal, an ATM server,…LANE server:

Can be implemented on separate components or on an ATM switch

Each emulated LAN consists of:One or several clientsA single LAN emulation service with three type of servers:

LAN Emulation Configuration Server (LECS)

LAN Emulation Server (LES)

Broadcast and Unknown Server (BUS)


MACMAC

LANE Components: Example

ATM networkLANE Client(LEC)

MAC MAC MAC

ATM

LANE Client(LEC)

ATM

LANE Server(LES)

BUS

LANE Configuration Server(LECS)

LANSwitch

HubATM

MAC

MAC

LANE Client(LEC)

ATM

LANE Client(LEC)

Router

WWW

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LANE Client (LEC)

Performs data forwarding and address resolutionProvides MAC level emulated Ethernet service Interfaces to higher level softwareImplements LUNI in order to communicate with other components

LEC

VCC’sVCC’s

BUS

LECS

LAN Emulation

LAN Emulation

LES Control distributeControl directMulticast forward Multicast sendData direct

Control distributeControl directMulticast forward Multicast sendData direct

Used by allstations to

determine ATMaddresses ofLES and BUS

Used by allstations to

determine ATMaddresses ofLES and BUS

ATM LAN

ATMWorkstation


LAN Emulation Configuration Server (LECS)

A

B

Assign LEC to em. LAN(by giving the client thethe LES ATM address

LEC obtain info usingconfiguration protocol


Depending on:Depending on:



em. LAN 1

Physical location(ATM address)

em. LAN 2

The identity of aLAN destination

or

LEC

LEC

LECS

LECS

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LAN Emulation Server (LES)

Emulated LAN

LES

Implements control coordination function for emulated LANsRegisters and resolves unicast and multicast MAC addressesRegisters and resolves unicast/multicast route descriptors to ATM addressesOnly one LANE Server for each LEC

LEC

ATM End Systems

ATMHost

ATMWorkstation

s

ATM Bridge


Directly

In-directly

ATMWorkstation

LEC seesa single BUS

LEC seesa single BUS

Broadcast and Unknown Server (BUS)

Main tasks of the BUS:Distribute (broadcast) multi/unicast data from LEC to MAC addressesDeliver initial unicast data when MAC not yet resolvedSupport multicasting/broadcastingRelaying frames to stations with unknown MAC address

LEC BUS

Relaying Frames

Multicast traffic

Unicast data

Multicasting/bcsting

LEC

LEC

LEC

em. LAN

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LANE Connection Types

BUSLEC

LESLEC LECS

LEC

ATM Bridge

LEC

ATM LAN

LEC - LAN Emulation ClientLES - LAN Emulation ServerLECS - LAN Emulation Configuration Server BUS - Broadcast and Unknown Server

1 1

Control direct VCC 1

2 2

2 Multicast send VCC

3

3 Data direct VCC

4

4 Multicast forward VCC

5

5 Control Distribute VCC

ATMWorkstation

LEC

6 Configuration direct VCC

6

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Basic Steps of LANE (LUNI Protocol)

Initialization

Configuration

Joining and Registration

Data Transfer Phase

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Initialization

1. LEC: Getting its appropriate ATM addressRegistration of the address using ILMI

Interim Local Management InterfaceAlternative: Manual pre-configuration

2. LEC: Getting the LECS address:Using the ILMI procedureUsing a well-known SVC (VPI=0, VCI=17) to the LECSUsing a well-known LECS addressManual configuration (in a configuration file on the LEC)

3. LEC: Establishment of a direct connection VCC to the LECS


MAC

Example: Initialization

ATM network

LANE Client(LEC)

ATM

LANE Server(LES)

BUS


Connection with LECS to obtain the LES address1. ILMI procedure with a local switch2. Connecting to a well-known address3. Connecting to a well-known VPI/VCI

ILMILANE Client(LEC)

MAC MAC MAC

LANSwitch

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Configuration

4. If LEC and LECS connected:Utilize a configuration protocol between bothLECS: sends the following information:

ATM address of the LES

ID (textual description) of the LANE in which the LES is

a member

Maximum frame size

Type of the emulated LAN

5. LEC: sends its ATM address & MAC address6. Release of the configuration-direct VCC to the

LECS


Configuration: Example (Client Configuration)

LECS assigns a concrete em. LAN to an LEC ATM address of LES

LECS informs about MAC protocol, MTU,...

MAC

ATM networkLANE Client

(LEC)

MAC MAC MAC

LANE Client(LEC)

ATM

LANE Server(LES)

BUS


LANSwitch

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Joining and Registration: LES

7. LEC: Sets up a direct control VCC to the LES8. LEC: Send a Join_request message to register its

MAC address and ATM address at LES7. Optionally: Could register further MAC addresses for

which is acts as proxy9. LES: Assigns a unique identifier to the LEC

(LECID)10. LES: Adds LEC to the point-to-multipoint control-

distribute VCC11. LES: Adds available information about the LEC to

its table for the address resolution protocol of LANE (LE_ARP). Uses a control direct VCC / control distribute VCC for LE_ARP7. LE_ARP message: contains the ATM address

corresponding to a particular MAC address


Example: Joining with the LES

MAC


(LEC)

MAC MAC MAC

LANE Client(LEC)

ATM

LANE Server(LES)

BUS


LANSwitch

Establishing a control connection to the LESRequest for inclusion into the emulated LAN

• LEC parameters: ATM address, MAC address, MTU, client id, representation id

Response (accept or deny) JOIN REQUEST

JOIN RESPONSE

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Joining and Registration: BUS

12. LEC: Uses the LE_ARP mechanism to get the ATM address of the BUS

Sending an LE_ARP message for the broadcast MAC address (all ones) to the LES LES responds with the ATM address of the BUS

13. LEC: Uses this address to prepare a point-to-point multicast send VCC to the BUS

14. BUS: Adds the LEC to its point-to-multipoint multicast forward VCC

Initialization, configuration, and registration completed.

LEC ready to send data.

Initialization, configuration, and registration completed.

LEC ready to send data.


Example: Registration and Retrieving the BUS ATM Address

MAC


(LEC)

MAC MAC MAC

LANE Client(LEC)

ATM

LANE Server(LES)

BUS


LANSwitch

Register: List of MAC addresses of the traditional LANRequest of the ATM address of the BUS

REGISTER

REQUEST FOR BUS

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Data Transfer

After configuration, initialization, and registration:

Client can already send and receive framesBasic scheme always the same:

Transform MAC frames into ATM cells for transmissionInverse procedure for receiving

Three cases:Unicast MAC frame, known ATM addressUnicast MAC frame, unknown ATM addressMulticast / broadcast MAC frame


LANE Encapsulation (V 1.0)

Bridge PDU (TR or Ethernet)

AAL 5CS

ATM cells

Bridge / Router PDULANEPDU

LANE PDUAAL 5 PDU

Application dataBridgeheader

Token Ring or Ethernet FrameLECID

BridgeTrailer

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Data Transfer Example (Case 1) Unicast MAC frame, known ATM address

Source LEC: verify that destination VC existingNo: create oneYes: send the frame

MAC

ATM network

LANE Client(LEC)

MAC MAC MAC

LANE Client(LEC)

ATM

LANE Server(LES)

BUS



Data Transfer Example (Case 2)

MAC

ATM network

LANE Client(LEC)

MAC MAC MAC

LANE Client(LEC)

ATM

LANE Server(LES)

BUS


Setup of data connection to BUSSend the frame to BUSBUS: forwards to the destinationARP request to LES not to use BUS again later LE_ARP_REQUEST

LE_ARP_RESPONSE

ARP response from LES

Unicast MAC frame, unknown ATM address

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Data Transfer: Unicast

Basic scheme:Send first packets via broadcastSend LE_ARP to get to know ATM addressIf response to LE_ARP:

Store LE_ARP response in a cache (LE_ARP cache)

Send flush packet via broadcastAvoid out-of-order delivery!

Send further packets using unicastIf no answer to LE_ARP (timeout):

Continue broadcast & resend LE_ARPAlternative scheme:

Send LE_ARP first and buffer packets until answer arrivesProblem: Long delay possible before packets are sent


Data Transfer Example (Case 3)

MACMAC

ATM network

LANE Client(LEC)

MAC MAC MAC

ATM

LANE Client(LEC)

ATM

LANE Server(LES)

BUS


HubATM

MAC

MAC

LANE Client(LEC)

ATM

LANE Client(LEC)

Router

WWW

Multicast or broadcast MAC frame

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LANE and Spanning Trees

LANE Protocol supports IEEE spanning tree protocolLECs within switches or LAN bridges exchange bridge packets (BPDU) for the spanning tree protocol using BUS

For each emulated LAN:

Bridge sends BPDUs over the “multicast send” VC to the BUS.BUS: Forwards BPDU to all LECs in the emulated LAN

Each BPDU is seen by all other bridges (as in an Ethernet LAN)If a bridge detects a loop (using the spanning tree protocol):

Disable one of the external ports involved in the loop

First: Turn off LAN ports, then ATM ports (with higher bandwidth)


Implementation (1)Client functions (LEC):

Resides on each LANE station connected to the ATM networkPart of the ATM end station

Represents a set of users identified by their MAC addresses

Server functions (LECS, LES, BUS):Implemented separately or jointlyOn any device with ATM connectivity

LANE Protocol: No specification where the components should be located

However: Vendor prefer to implement server functions in network devices (ATM switches, routers) instead of in terminal equipments or end hosts

Ensure a high reliability and performance

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Implementation: Example

Bridges Routers

Intermediate systemsIntermediate systems

Bridges

Routers

Intermediate systemIntermediate system Work stationHosts

PCs

Terminal stationsTerminal stations

ATM Switch

LANE serviceimplemented

in Router/bridge/switch or dedicated

station

LANE serviceimplemented

in Router/bridge/switch or dedicated

station


Implementation (2)

Communication LEC-LEC and LEC-LES:Using an ATM virtual channel connection (VCC)LEC-LES: Control VCC and Data VCC

Emulated LANs can operate on:Switched virtual circuits (SVCs)Permanent virtual circuits (PVCs)A mixture of SVCs and PVCs

Due to the “flat” (non-hierarchical) architecture of MAC addresses:

Bridges flood the emulated LAN with connectivity information

Reducing the scalability of the approach

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Implementation (3)

Interconnection of emulated LANs:Using routers

Vendors implement LANE protocols on:ATM network interface cardsATM switchesLAN switchesRouters


Optional LANE Capabilities

LE_NARP messages:Send to indicate availability of one particular new MAC address

For example, after startup of a portable computerDistributed to other LECs which update their address cachesImproves convergence for dynamically changing LANs

Intelligent BUSShares knowledge of MAC address reachability with LESThen: Direct forwarding of packets to other LECs possibleMinimizes the complexity of the LEC implementation

Virtual LANsEnable multiple emulated LANs (virtual LANs) over a common ATM network

By controlling the assignments of LES and BUS to the LEC, terminal equipment, bridges and LAN switches

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LANE: Advantages and Disadvantages

Advantages:Enables connectivity between Ethernet / Token Ring and ATMPhysical flexibility

Disadvantages:Limited to bridging (does not scale well)Bridge or router between emulated LANs necessary

Potential performance bottleneckProblem of managing a bridge / routerQoS of ATM hidden to the routing protocols (e.g., IP RSVP & OSPF) (LANE v1.0)


LANE: Updates

LANE 1.0Only multiplexing of VCsNo support for multiple LES or BUS within one emulated LAN

Possible problems: Reliability and bottleneckLANE 2.0

LLC multiplexing to share VCC between different protocolsABR support and other QoS categories of ATMImproved multicast capabilities:

Define filters determining which members of the emulated LAN receive a particular multicast message (no pure broadcast anymore)

Support for MPOA (Multiprotocol over ATM)

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With Buffering of Frames

Packet IP 1

IPA -> IPB

Packet IP 1

IP/ARPIPA, MACA

LECA LES BUS LECB IP/ARPMACB, IPB

ARP(IPA, MACA, IPB, MACB?)MACA -> broadcast

LE_DATA[ARP(IPA, MACA, IPB, MACB?)]

CACHE B<IPA, MACA>


ARP_REPLY(IPA, MACA, IPB, MACB)MACB -> MACA

UNI signaling – establishment of SVC ATMB-ATMA

LE_ARP_REQ[MACB, ATMB, MACA, ATMA?]

LE_ARP_RESP[MACB, ATMB, MACA, ATMA] CACHE B<MACA, ATMA>

CACHE A<MACB, ATMB>

LE_DATA[ARP_REPLY(IPA, MACA, IPB, MACB)]

MACB -> MACAARP_REPLY(IPA, MACA, IPB, MACB)

MACB -> MACA

CACHE A<IPB, MACB>

ETHER[Packet IP 1]

MACA ->MACB

ETHER[Packet IP 1]

MACA ->MACB

LE_DATA[ETHER[Packet IP 1]]MACA ->MACB


Without Buffering (BUS used to send unknown traffic)

Packet IP 1

IPA -> IPB

Packet IP 1

IP/ARPIPA, MACA

LECA LES BUS LECB IP/ARPMACB, IPB


LE_DATA[ARP(IPA, MACA, IPB, MACB?)]

CACHE B<IPA, MACA>



UNI signaling – establishment of SVC ATMB-ATMA

LE_ARP_REQ[MACB, ATMB, MACA, ATMA?]

ETHER[Packet IP 1]

MACA ->MACB

ETHER[Packet IP 1]

MACA ->MACB



CACHE A<IPB, MACB>

LE_DATA[ARP_REPLY(IPA, MACA, IPB, MACB)]

MACB -> MACA

LE_ARP_REQ[MACA, ATMA, MACB, ATMB?]


Packet IP 2ETHER[Packet IP 2]

MACA ->MACB

ETHER[Packet IP 2]

MACA ->MACB

Packet IP 2

IPA -> IPB

CACHE A<MACB, ATMB>

LE_ARP_RESP[MACA, ATMA MACB, ATMB] CACHE B<MACA, ATMA>

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ATM in ATM in Local Area NetworksLocal Area Networks

Multiprotocol Encapsulation Multiprotocol Encapsulation over AAL5over AAL5


Basic Modes of Operation

RFC 2684: defines specific formats for multiprotocolencapsulation over ATM using AAL5. Two transport mechanisms specified:

Protocol encapsulation (or LLC/SNAP encapsulation)

Provides capability to multiplex several protocols over one VCCVC multiplexing:

Each protocol is carried over a separate VCC

ATM network

LLC/SNAP encapsulation (Protocol multiplexing)

VC multiplexing

ATM device

ATM network

ATM device

ATM device

ATM device

Different LANprotocols

Different LANprotocols

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LLC/SNAP Encapsulation

Adds an IEEE 802.2 Logical Link Control (LLC) SubNetwork Attachment Point (SNAP) header to the Protocol Data Unit (PDU) therefore: LLC/SNAP encapsulationLLC/SNAP header: Identifies the PDU type

Enables multiplexing of distinct protocols over a single VC

Advantages:Lower costs (if costs determined per VC)

Disadvantages:Same QoS and bandwidth for all multiplexed protocols in one VCLower efficiency


LLC Encapsulation PDUs(Used in LANE 2.0)

AAL 5TailRFC 2684 PDUAAL 5

PDU

Bridge / RouterPDU

Bridge/RouterHeader

Application Payload

A T M C e l l s

LLC / SNAPHeader

RFC 2684PDU LANE PDU

LANE PDUBridge / Router PDULECID (2

Bytes)

Application Payload BridgeTail

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LLC/SNAP Encapsulation: Header Fields (Non-ISO Protocols)

SNAP

00-80-C2 = Bridge PDU00-00-00 = Routed PDU00-80-C2 = Bridge PDU00-00-00 = Routed PDU

DSAPFE

SSAPFE

Ctrl03

OUI Bridge / Router PDU

00-01 = 802.3 Bridge PDU (CRC included)00-02 = 802.4 Bridge PDU (CRC included)00-03 = 802.5 Bridge PDU (CRC included)00-04 = FDDI Bridge PDU (CRC included)00-07 = 802.3 Bridge PDU (without CRC)00-08 = 802.4 Bridge PDU (without CRC)00-09 = 802.5 Bridge PDU (without CRC)00-0A = FDDI Bridge PDU (without CRC)00-0B = 802.6 Bridge PDU00-0E = 802.1(d) or 802.1(g) STAP Bridge PDU06-00 = XNS Routed PDU08-00 = IP Routed PDU60-03 = DECnet Routed PDU81-37 = IPX Routed PDU

00-01 = 802.3 Bridge PDU (CRC included)00-02 = 802.4 Bridge PDU (CRC included)00-03 = 802.5 Bridge PDU (CRC included)00-04 = FDDI Bridge PDU (CRC included)00-07 = 802.3 Bridge PDU (without CRC)00-08 = 802.4 Bridge PDU (without CRC)00-09 = 802.5 Bridge PDU (without CRC)00-0A = FDDI Bridge PDU (without CRC)00-0B = 802.6 Bridge PDU00-0E = 802.1(d) or 802.1(g) STAP Bridge PDU06-00 = XNS Routed PDU08-00 = IP Routed PDU60-03 = DECnet Routed PDU81-37 = IPX Routed PDU

PID Type

UnnumberedInformation

Frame

UnnumberedInformation

Frame

LLC

FE-FE = ISO Frame

AA-AA = SNAP Header (bridge / router frame)


DSAPFE

SSAPFE

Ctrl03

LLC

LLC/SNAP Encapsulation: Header Fields (Routed ISO Protocols)

LLC Logical Link ControlDSAP Destination SAPSSAP Source SAPSAP Service Access Point


ISO PDU≤ 65.532 octets

Example:Routed ISO PDU

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OUI00 00 00

PID Type08 00

DSAPAA

SSAPAA

Ctrl03

LLC

LLC/SNAP Encapsulation: Header Fields (Routed Non-ISO Protocols)

SNAP Non-ISO PDU ≤ 65.527 octets



SNAP SubNetwork Attachment PointOUI Organizationally Unique IdentifierPID Protocol ID

SNAP SubNetwork Attachment PointOUI Organizationally Unique IdentifierPID Protocol ID

Non-ISO routedPDU (e.g., IP)


LLC/SNAP Encapsulation with Bridges

SNAP

DSAPAA

SSAPAA

Ctrl03

OUI00 80 C2

802.3

PID Type0001/0007

LLC

PAD00 00

MAC destina-tion address

Rest of MACframe

If PID =00 01

FCS LAN

SNAP

DSAPAA

SSAPAA

Ctrl03

OUI00 80 C2

802.6 (MAN)

PID Type00 0B

LLC

Common.PDU

headerMAC destina-tion address

Rest of MACframe

CommonPDU trailer



SNAP SubNetwork Attachment PointOUI Organizationally Unique IdentifierPID Protocol IDFCS Frame Check Sequence (CRC)

SNAP SubNetwork Attachment PointOUI Organizationally Unique IdentifierPID Protocol IDFCS Frame Check Sequence (CRC)

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VC Multiplexing

Only one protocol per virtual channel (VC)In this case: VCs are multiplexed, not the protocols

Used in scenarios where a user can dynamically create and release many ATM VCs economically (e.g., in private ATM networks or ATM SVC networks)Advantages:

Different protocols can get different QoS levels / bandwidthMore efficient (smaller protocol headers)

Disadvantages:Greater number of ATM VCs necessary

Routed protocols: Can make use of all 65.535 octets of an AAL5 PDU

Bridged protocols:Header fields LLC, OUI, PID not necessary. Using the LAN FCS is implicitly defined by the VCC association


Selection of Multiplexing Method

PVCs:Configuration option to be chosen manually

SVCs:Information elements in the signaling protocol between two routers about what multiplexing method to useAlso: signaling whether FCS is included in the PDU or not

Decision which method to use:Also depends on the efficiency of each method

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Efficiency of Multiplexing MethodsEfficiency: Example

Encapsulation of an TCP/IP ACK packet (40 bytes: 20 bytes TCP and 20 bytes IP)

Cell header

TCP/IPACK

TrailerAAL5

5 40 8

VC Multiplexing

Cellheader

LLC/SNAP

TCP/IPACK

Cellheader

PADAAL5

TrailerAAL5

LLC/SNAPEncapsulation

1 ATM cellPayload efficiency: 40+8/48 = 100%

1 ATM cellPayload efficiency: 40+8/48 = 100%

2 ATM cellsPayload efficiency: 48 + 8 / 96 = 58%

2 ATM cellsPayload efficiency: 48 + 8 / 96 = 58%

5 8 40 5 40 8

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