WIRELESS WIRELESS PROTOCOLSPROTOCOLS

The ISO OSI Reference The ISO OSI Reference ModelModel

• A NetworkA Network is a complex piece of hardware and is a complex piece of hardware and Software. Software.

• Therefore, Therefore, International Standard International Standard OrganizationOrganization ( (ISOISO)) adopted a layered adopted a layered approach for networks. approach for networks.

• The network is broken into The network is broken into sevenseven layers, each layers, each of them has well-defined function such that of them has well-defined function such that each layer offers a service to the higher layer. each layer offers a service to the higher layer.

• The model is called The model is called ISO OSI (Open Systems ISO OSI (Open Systems Interconnect) Reference ModelInterconnect) Reference Model..

• IEEE defined a four layers model for LANIEEE defined a four layers model for LAN

The OSI Reference Model The OSI Reference Model LayersLayers

Application

Data Link

Presentation

Network

Physical

Session

Transport

Physical Medium

Application

Data Link

Presentation

Network

Physical

Session

Transport

Host A Host B

IEEE 802 Model LayersIEEE 802 Model Layers

Protocol Definision Protocol Definision

• Protocol:Protocol: is a set of rules and conventions is a set of rules and conventions used by the layer to communicate with similar used by the layer to communicate with similar peer layer in another (remote) system. peer layer in another (remote) system.

• Peer:Peer: The similar layer on a different The similar layer on a different machine.machine.– The peer processes communicate with each other The peer processes communicate with each other

using a using a protocolprotocol. .

• A set of layers and protocols is called a A set of layers and protocols is called a network architecture.network architecture.

Key Features of a ProtocolKey Features of a Protocol

• SyntaxSyntax– Concerns the format of the data blocksConcerns the format of the data blocks

• SemanticsSemantics– Includes control information for coordination and Includes control information for coordination and

error handlingerror handling

• TimingTiming– Includes speed matching and sequencingIncludes speed matching and sequencing

Agents Involved in Protocol Agents Involved in Protocol CommunicationCommunication

• ApplicationsApplications– Exchange data between computers (e.g., electronic Exchange data between computers (e.g., electronic

mail)mail)

• ComputersComputers– Connected to networksConnected to networks

• NetworksNetworks– Transfers data from one computer to anotherTransfers data from one computer to another

Protocol ArchitectureProtocol Architecture

• Functions of physical layer:Functions of physical layer:– Encoding/decoding of signalsEncoding/decoding of signals– Preamble generation/removal (for synchronization)Preamble generation/removal (for synchronization)– Bit transmission/receptionBit transmission/reception– Includes specification of the transmission mediumIncludes specification of the transmission medium

Protocol ArchitectureProtocol Architecture

• Functions of medium access control (MAC) Sub Functions of medium access control (MAC) Sub layer:layer:– On transmission, assemble data into a frame with address On transmission, assemble data into a frame with address

and error detection fieldsand error detection fields

– On reception, disassemble frame and perform address On reception, disassemble frame and perform address recognition and error detectionrecognition and error detection

– Govern access to the LAN transmission mediumGovern access to the LAN transmission medium

• Functions of logical link control (LLC) Sub Layer:Functions of logical link control (LLC) Sub Layer:– Provide an interface to higher layers and perform flow and Provide an interface to higher layers and perform flow and

error controlerror control

Separation of LLC and MACSeparation of LLC and MAC

• The logic required to manage access to a The logic required to manage access to a shared-access medium not found in traditional shared-access medium not found in traditional layer 2 data link controllayer 2 data link control

• For the same LLC, several MAC options may For the same LLC, several MAC options may be providedbe provided

MAC Frame FormatMAC Frame Format

• MAC controlMAC control– Contains Mac protocol informationContains Mac protocol information

• Destination MAC addressDestination MAC address– Destination physical attachment pointDestination physical attachment point

• Source MAC addressSource MAC address– Source physical attachment pointSource physical attachment point

• CRCCRC– Cyclic redundancy checkCyclic redundancy check

Logical Link ControlLogical Link Control

• Characteristics of LLC not shared by other Characteristics of LLC not shared by other control protocols:control protocols:– Must support multiaccess, shared-medium nature Must support multiaccess, shared-medium nature

of the linkof the link– Relieved of some details of link access by MAC Relieved of some details of link access by MAC

layerlayer

LLC ServicesLLC Services

• Unacknowledged connectionless serviceUnacknowledged connectionless service– No flow- and error-control mechanismsNo flow- and error-control mechanisms– Data delivery not guaranteedData delivery not guaranteed

• Connection-mode serviceConnection-mode service– Logical connection set up between two usersLogical connection set up between two users– Flow- and error-control providedFlow- and error-control provided

• Acknowledged connectionless serviceAcknowledged connectionless service– Cross between previous twoCross between previous two– Datagrams acknowledgedDatagrams acknowledged– No prior logical setupNo prior logical setup

Differences between LLC and Differences between LLC and HDLCHDLC

• LLC uses asynchronous balanced mode of LLC uses asynchronous balanced mode of operation of HDLC (type 2 operation)operation of HDLC (type 2 operation)

• LLC supports unacknowledged connectionless LLC supports unacknowledged connectionless service (type 1 operation) service (type 1 operation)

• LLC supports acknowledged connectionless LLC supports acknowledged connectionless service (type 3 operation)service (type 3 operation)

• LLC permits multiplexing by the use of LLC LLC permits multiplexing by the use of LLC service access points (LSAPs)service access points (LSAPs)

IEEE 802.11 ServicesIEEE 802.11 Services

Mobile IP UsesMobile IP Uses

• Enable computers to maintain Internet connectivity Enable computers to maintain Internet connectivity while moving from one Internet attachment point to while moving from one Internet attachment point to anotheranother

• Mobile – user's point of attachment changes Mobile – user's point of attachment changes dynamically and all connections are automatically dynamically and all connections are automatically maintained despite the changemaintained despite the change

• Nomadic - user's Internet connection is terminated Nomadic - user's Internet connection is terminated each time the user moves and a new connection is each time the user moves and a new connection is initiated when the user dials back ininitiated when the user dials back in– New, temporary IP address is assignedNew, temporary IP address is assigned

Operation of Mobile IPOperation of Mobile IP

• Mobil node is assigned to a particular network – Mobil node is assigned to a particular network – home networkhome network

• IP address on home network is static – home addressIP address on home network is static – home address• Mobile node can move to another network – foreign Mobile node can move to another network – foreign

networknetwork• Mobile node registers with network node on foreign Mobile node registers with network node on foreign

network – foreign agentnetwork – foreign agent• Mobile node gives care-of address to agent on home Mobile node gives care-of address to agent on home

network – home agentnetwork – home agent

Capabilities of Mobile IPCapabilities of Mobile IP

• Discovery – mobile node uses discovery Discovery – mobile node uses discovery procedure to identify prospective home and procedure to identify prospective home and foreign agentsforeign agents

• Registration – mobile node uses an Registration – mobile node uses an authenticated registration procedure to inform authenticated registration procedure to inform home agent of its care-of addresshome agent of its care-of address

• Tunneling – used to forward IP datagrams Tunneling – used to forward IP datagrams from a home address to a care-of addressfrom a home address to a care-of address

DiscoveryDiscovery

• Mobile node is responsible for ongoing discovery Mobile node is responsible for ongoing discovery processprocess– Must determine if it is attached to its home network or a Must determine if it is attached to its home network or a

foreign networkforeign network

• Transition from home network to foreign network can Transition from home network to foreign network can occur at any time without notification to the network occur at any time without notification to the network layerlayer

• Mobile node listens for agent advertisement messagesMobile node listens for agent advertisement messages– Compares network portion of the router's IP address with Compares network portion of the router's IP address with

the network portion of home addressthe network portion of home address

Move DetectionMove Detection

• Mobile node may move from one network to another Mobile node may move from one network to another due to some handoff mechanism without IP level due to some handoff mechanism without IP level being awarebeing aware– Agent discovery process is intended to enable the agent to Agent discovery process is intended to enable the agent to

detect such a movedetect such a move

• Algorithms to detect move:Algorithms to detect move:– Use of lifetime field – mobile node uses lifetime field as a Use of lifetime field – mobile node uses lifetime field as a

timer for agent advertisementstimer for agent advertisements– Use of network prefix – mobile node checks if any newly Use of network prefix – mobile node checks if any newly

received agent advertisement messages are on the same received agent advertisement messages are on the same network as the node's current care-of addressnetwork as the node's current care-of address

Co-Located AddressesCo-Located Addresses

• If mobile node moves to a network that has no If mobile node moves to a network that has no foreign agents, or all foreign agents are busy, it can foreign agents, or all foreign agents are busy, it can act as its own foreign agentact as its own foreign agent

• Mobile agent uses co-located care-of addressMobile agent uses co-located care-of address– IP address obtained by mobile node associated with mobile IP address obtained by mobile node associated with mobile

node's current network interfacenode's current network interface

• Means to acquire co-located address:Means to acquire co-located address:– Temporary IP address through an Internet service, such as Temporary IP address through an Internet service, such as

DHCPDHCP– May be owned by the mobile node as a long-term address May be owned by the mobile node as a long-term address

for use while visiting a given foreign networkfor use while visiting a given foreign network

Registration ProcessRegistration Process

• Mobile node sends registration request to Mobile node sends registration request to foreign agent requesting forwarding serviceforeign agent requesting forwarding service

• Foreign agent relays request to home agentForeign agent relays request to home agent

• Home agent accepts or denies request and Home agent accepts or denies request and sends registration reply to foreign agentsends registration reply to foreign agent

• Foreign agent relays reply to mobile nodeForeign agent relays reply to mobile node

Wireless Application Protocol Wireless Application Protocol (WAP)(WAP)

• Open standard providing mobile users of wireless Open standard providing mobile users of wireless terminals access to telephony and information terminals access to telephony and information servicesservices– Wireless terminals include wireless phones, pagers and Wireless terminals include wireless phones, pagers and

personal digital assistants (PDAs)personal digital assistants (PDAs)– Designed to work with all wireless network technologies Designed to work with all wireless network technologies

such as GSM, CDMA, and TDMAsuch as GSM, CDMA, and TDMA– Based on existing Internet standards such as IP, XML, Based on existing Internet standards such as IP, XML,

HTML, and HTTPHTML, and HTTP– Includes security facilitiesIncludes security facilities

WAP Protocol StackWAP Protocol Stack

WAP Programming ModelWAP Programming Model

Wireless Datagram Protocol Wireless Datagram Protocol (WDP)(WDP)

• Used to adapt higher-layer WAP protocol to the Used to adapt higher-layer WAP protocol to the communication mechanism used between mobile communication mechanism used between mobile node and WAP gatewaynode and WAP gateway

• WDP hides details of the various bearer networks WDP hides details of the various bearer networks from the other layers of WAPfrom the other layers of WAP

• Adaptation may include:Adaptation may include:– Partitioning data into segments of appropriate size for the Partitioning data into segments of appropriate size for the

bearerbearer

– Interfacing with the bearer networkInterfacing with the bearer network

Wireless Control Message Wireless Control Message Protocol (WCMP)Protocol (WCMP)

• Performs the same support function for WDP as Performs the same support function for WDP as ICMP does for IPICMP does for IP

• Used in environments that don’t provide IP bearer Used in environments that don’t provide IP bearer and don’t lend themselves to the use of ICMPand don’t lend themselves to the use of ICMP

• Used by wireless nodes and WAP gateways to report Used by wireless nodes and WAP gateways to report errors encountered in processing WDP datagramserrors encountered in processing WDP datagrams

• Can also be used for informational and diagnostic Can also be used for informational and diagnostic purposespurposes