MAP-Tele Manuel P. Ricardo -...
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WNP-MPR-mip-mesh 1 Wireless Networks and Protocols MAP-Tele Manuel P. Ricardo Faculdade de Engenharia da Universidade do Porto
Transcript of MAP-Tele Manuel P. Ricardo -...
WNP-MPR-mip-mesh 1
Wireless Networks and Protocols
MAP-Tele
Manuel P. Ricardo
Faculdade de Engenharia da Universidade do Porto
WNP-MPR-mip-mesh 2
Topics Scheduled for Today
…
♦ Convergence and interoperability of wireless systems: bringing all together» 4G wireless networks
» 3GPP approach» 3GPP approach
» Mobile IPv6 approach– Basics on Mobile IP
– 3GPP plans for adopting Mobile IPv6
– Media Independent handover
» Wireless mesh– Basics on ad-hoc networks
– The IEEE 802.11 mesh networks
» Research issues
…
WNP-MPR-mip-mesh 3
Basics on Mobile IP
♦ How to move between IP networks while maintaining a connection active?
♦ What are the differences between MIPv4 and MIPv6?♦ What are the differences between MIPv4 and MIPv6?
♦ How is routes optimization in MIPv6
♦ How does the Dual Stack MIPv6 work?
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Mobile IPv4Mobile IPv4
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Motivation
♦ IP datagram forwarding is based on IP destination address
♦ IP network address �� physical network
♦ Changing network � changing IP address
♦ How to implement mobility at the IP layer?
♦ Possible solution» Register new IP address near the DNS server
» Problems– DNS registration takes time
– TCP connections will break
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Mobile IPv4 - Terminology
♦ MN, Mobile Node
♦ HA, Home Agentregisters MN location
♦ FA, Foreign Agent♦ FA, Foreign Agentagent in the visited network
♦ COA, Care-of AddressMN’s IP address in the visited network
♦ CN, Correspondent Nodehost which communicates with the MN
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Example
router
HA
MN
mobile end-systemInternet
router
routerend-system
FA
home network
foreign network
(physical home networkfor the MN)
(current physical network for the MN)
CN
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Data transference to MN
HA
MN2
Internet
sender
FA
home network
foreignnetwork
receiver
1
3
1. Sender sends to the IP address of MN,HA intercepts packet
2. HA tunnels packet to COA (FA) by encapsulation
3. FA forwards the packet to the MN
CN
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Data transference from MN
HA
MN1
Internet
receiver
FA
home network
foreignnetwork
sender
1. Sender sends to the IP addressof the receiver as usual,FA works as default router
CN
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Mobility phases
routerHA
routerFA
Internet
homenetwork
MN
foreignnetwork
COA
CN
routerHA
routerFA
Internet
router
1.
2.
3.home
networkMN
foreignnetwork
4.
CN router
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MN – Agents communication
♦ MN identifies the network » Mobility agents send regularly messages to their networks
ICMP Router Advertisement messages
» MN listens messages; determines the network– Its home network, or
– A visited network � MN obtains new address – the CoA– A visited network � MN obtains new address – the CoA
♦ In the visited network, after obtaining CoA, MN» MN sends COA to HA (via FA) � new locationregistered at the HA
» At the home network– HA assumes the MN home IP address
– Packets destined to the MN IP home address
are intercepted by HA and tunnelled to the MN (CoA address)
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ICMP Router Advertisment –Mobility Extensiom
preference level 1router address 1
#addressestype
addr. size lifetimechecksum
0 7 8 15 16 312423code
preference level 2router address 2
R – registration requiredB – FA busyH – agent is HAF – agent is FA
COA 1COA 2
type sequence numberlength
preference level 2
. . .
registration lifetime
. . .
R B H F M G r reserved
F – agent is FAM – minimal encaspulation acceptedG – GRE encapsulation acceptedr – not usedT – FA supports reverse tunneling
Message sent by mobility agents (HA and FA)
T
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To think about
♦ Can we remove the Foreign Agent from MIPv4? What are the consequences of it?
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MN registration in the Home Agent
MN HAMN FA HA
t
t
• Co-located address• Tunnel will end at the MN• Address obtained by DHCP, for instance
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Registration messages
Type –registration request, registration replyS – Maintain old bindingB –broadcast messages shall be forwardedD – co-located addressM – minimal encapsulation acceptedG – GRE encapsulation acceptedr – not used
port UDP 434
r – not usedT – FA supports reverse tunnelingx - ignored
home agenthome address
type lifetime0 7 8 15 16 312423
identification
COA
extensions . . .
S B DMG r T x
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Tunnels
original IP header original data
new datanew IP header
outer header inner header original data
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IP in IP (mandatory)
Care-of address COAIP address of HA
TTLIP identification
IP-in-IP IP checksumflags fragment offset
lengthTOSver. IHL
IP identification flags fragment offsetlengthTOSver. IHL
IP address of MNIP address of CN
TTLIP identification
lay. 4 prot. IP checksumflags fragment offset
TCP/UDP/ ... payload
Tunnel HA � COA
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To think about
♦ What is NAT (Network Address Translation)?
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NAT – Network Address Translation
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To think about
♦ Does MIPv4 work when MN has a private CoA address?
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Mobile IPv6Mobile IPv6
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Mobile IPv6 – working principles
♦ Differences to MIPv4» No ForeignAgent
» Registration signalling (HomeAddress �� CareOfAddress )
– Sent as an IPv6 extension header � Mobility Header
– Bindingrelations (HomeAddress �� CareOfAddress ) also in the CNs
♦ Binding messages» BindingUpdate
– MN informs HA/CN of its CareOfAddress
» BindingAcknowledgement– Received by MN. Confirms BindingUpdate
» BindingRefreshRequest– Sent by HA/CN. Requests MN to refresh binding
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Binding
♦ MN moves to a visited network– MN auto-configures new address � COA
– COAnetwork prefix == prefix of the visited network
– MN asks for registration of COA in HA
MN sends IPv6 packet with BindingUpdate(extension header)
– HA registers MN and replies with BindingAcknowledgment– HA registers MN and replies with BindingAcknowledgment
♦ Tunnel MN - HA– HA, in home networks� Intercepts packet to MN� Sends packet to COA; by tunnel
– MN� Sends packet in tunnel to HA
WNP-MPR-mip-mesh 24
CoA autoconfiguration, in the visited network
♦ MN » Listens RouterAdvertismentmessages
– In mobility routers � up to 50 msg/s
– Obtains network prefix
» Builds address in the visited network, the CareOfAddress
♦ DHCPv6 may be used by MN to obtain CoA
Routing Prefix MAC address
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Route optimization
♦ When MN receives a tunnelled packet» it sends BindingUpdateto CN
♦ HomeAddress �� CareOfAddress binding– also at the CN
♦ Packets exchanged directly between MN e CN
WNP-MPR-mip-mesh 26
Route optimization
♦ IPv6 packets in direction CN � MN» CN
– Before sending a packet to MN, reads its Bindings cache
– Is there is no entry � packet sent as usual
– If there is an entry� Sends packet to CareOfAddress (destination address = CareOfAddress)
Includes in the packet a RoutingHeader having 2 hops � Includes in the packet a RoutingHeader having 2 hops
(list of addresses to be visited)
– 1º hop � CareOfAddress; 2º hop � MN HomeAddress
» MN – Receives packet in CareOfAddress
– Forwards packet to itself (MN home address)
♦ IPv6 packets in the MN � CN direction– Source address = CareOfAddress
– Inclusion of DestinationHeaderwith information on HomeAddress
– CN replaces HomeAddressin the packet source address
so that the socket structure may contain the correct information � HomeAddress
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Routing Header –Packet sent from S to D, passing by I1, I2, I3As the packet travels from S to I1:
Source Address = S Hdr Ext Len = 6Destination Address = I1 Segments Left = 3
Address[1] = I2Address[2] = I3Address[3] = D
As the packet travels from I1 to I2:
Source Address = S Hdr Ext Len = 6Destination Address = I2 Segments Left = 2Destination Address = I2 Segments Left = 2
Address[1] = I1Address[2] = I3Address[3] = D
As the packet travels from I2 to I3:
Source Address = S Hdr Ext Len = 6Destination Address = I3 Segments Left = 1
Address[1] = I1Address[2] = I2Address[3] = D
As the packet travels from I3 to D:
Source Address = S Hdr Ext Len = 6Destination Address = D Segments Left = 0
Address[1] = I1Address[2] = I2Address[3] = I3
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cn ha mn router novo mn| | no' moves | || | +------------------------------>|| | | |radv || | | +-------------->|| | binding update | || |<--------------------------------------------+| |binding ack | | || +-------------------------------------------->||echo request| | | |+ -----------=============================================>|| echo reply | | | ||<-----------==============================================+|home test init | | |
pin
g
|<-----------==============================================+| care of test init | | ||<---------------------------------------------------------+|care of test| | | |+--------------------------------------------------------->||home test | | | |+------------=============================================>|| binding update | | ||<---------------------------------------------------------+| binding ack | | |+--------------------------------------------------------->||echo request| | | |+--------------------------------------------------------->|| echo reply | | | ||<---------------------------------------------------------+| | | | |
pin
g
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Dual Stack Mobile IPv6Dual Stack Mobile IPv6
(DSMIPv6)
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DSMIPv6
DS-HA
♦ Extends MIPv6 to allow » registration of IPv4 addresses
» transport of both IPv4 and IPv6 packets in the tunnel to MN-HA
» MN to roam over IPv6 and IPv4 (public and private) networks
♦ Assumes» MN and HA are both IPv4 and IPv6-enabled
» Uses only MIPv6 signalling
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DSMIPv6 – Mobility Management
Visited network supports IPv6» MN sends regular MIPv6 BindingUpdate
» MN registers IPv6 CoA to HA
» HA creates two binding cache entries,
both pointing to MN-CoA-IPv6both pointing to MN-CoA-IPv6– MN-home-address-IPv6 �� MN-CoA-IPv6
– MN-home-address-IPv4 �� MN-CoA-IPv6
» HA tunnels traffic to MN-CoA-IPv6
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DSMIPv6 – Mobility Management
Visited network supports IPv4 only -public addresses» MN tunnels MIPv6 BindingUpdatemessage to the HA IPv4 address
» HA creates two binding caches entries,
both pointing to the MN-CoA-IPv4both pointing to the MN-CoA-IPv4– MN-home-address-IPv6 �� MN-CoA-IPv4
– MN-home-address-IPv4 �� MN-CoA-IPv4
» All the packets addressed to MN-home-addresses (IPv4 or IPv6)
are encapsulated in an IPv4 tunnel HAv4��MN-CoA-IPv4
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DSMIPv6 – Mobility Management
Visited network supports IPv4 only -private addresses» HA listens in an UDP port, over a public IPv4 address
» MN tunnels MIPv6 BindingUpdatemessage to HA IPv4/port addresses
» HA creates two binding caches entries,
both pointing to the public-MN-CoA-IPv4/port (recall NAT)both pointing to the public-MN-CoA-IPv4/port (recall NAT)– MN-home-address-IPv6 �� public-MN-CoA-IPv4/port
– MN-home-address-IPv4 �� public-MN-CoA-IPv4/port
» At the HA, the packets addressed to MN home addresses (IPv4 or IPv6)– are first encapsulated in UDP packet (port to port),
– then encapsulated in an IPv4 tunnel ending at the public-MN-CoA-IPv4
(recall the NAT functionality)IPv4/IPv6
UDP
IPv4
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To think about
♦ Is the IPv4/IPv6 packet received in (linux) user or kernel space?
IPv4/IPv6
♦ How can the contents of this packet be delivered to, for instance, the Web-browser running on top of TCP/IPv4?
UDP
IPv4
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DSMIPv6 – Route Optimization
♦ Visited network supports IPv6 � similar to MIPv6
♦ Visited network supports IPv4 onlynot possible; communication always through the Home Agent
♦ Not possible for traffic addressed to the Mobile Node's IPv4 home address
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3GPP plans for adopting Mobile IP
♦ What MIP based solutions are currently being studied in 3GPP?
♦ How are these solutions expected to work?
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Mobility between 3GPP-WLAN Interworking and 3GPP Systems
♦ Plans for Release 8
♦ Requirements» Smooth migration from legacy network with minimal impacts on dual
mode UEs, I-WLAN and 3GPP systems
» Architecture, functions and procedures shall be re-used» Architecture, functions and procedures shall be re-used
» Both IPv4 and IPv6 addresses shall be supported
» Service continuity between 3GPP PS network and I-WLAN with IP address preservation
♦ Possible solution based on DSMIPv6» 3GPP TS 23.327, TS 23.827
♦ Conclusions based on the SAE report may lead to other solutions» See 3GPP TR 23.882
WNP-MPR-mip-mesh 38
WLANAccessNetwork
PDG/AR
3GPP AAAServer HSS
WAG
WwWu
Wn Wp
Wx
H3H2
Home Mobility Service Architecture
Home Agent function at home PLMN
UE
GERAN/UTRAN SGSN
HAExternal
PDNHGi
Iu_ps/Gb
Uu/Um
H1
GGSN/AR
Gn
H3
WNP-MPR-mip-mesh 39
WLANAccess Network
PDG/AR
WAGWn Wp The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have Wx
Wd*
HSS3GPP AAA
server3GPP AAA
proxy
Visited Mobility Service Architecture
Home Agent function outside the hPLMN
UE
Access Network
GERAN/UTRAN SGSN
HA
AR
ExternalPDN
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been corrupted. RHGi
Iu_ps/Gb
The image cannot be displayed. Your computer may not have enough memory to open the image, or the image may have been corrupted. Restart your computer, and then open the file again. If the red x still appears, you may have to delete the image and then insert it again.Uu/Um
H3
H1
H2
GGSN/AR
H3
HPLMNVPLMN
Gn
WNP-MPR-mip-mesh 40
H1 PDN Attach
UE HA 3GPP AAA Server
1. HA discovery
2. IKEv2 Security Association establishment& IPv6 HoA allocation 2. Auth. & Authorization
3GPP AAA Proxy
& IPv6 HoA allocation 2. Auth. & Authorization
3. Binding Update
4. Binding Acknowledgement
WNP-MPR-mip-mesh 41
H1 PDN Attach
1. UE discovers the Home Agent (e.g using the DNS service)
2. A security association is established between UE and HA » to secure the DS-MIPv6
» HA communicates with AAA infrastructure to complete authentication
» HA assigns IPv6 home address/prefix to UE » HA assigns IPv6 home address/prefix to UE
» If HA@ vPLMN– interaction HA@vPLMN �� AAA/HSS@hPLMN involves AAA-Proxy@vPLMN
3. UE sends BindingUpdate» UE may request an IPv4 home address from the HA
4. HA replies with BindingAck» HA may assign IPv4 home address to UE
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To think about
♦ Why does HA “assign home addresses”? What about the IP addresses gathered by the UE through the GPRS-attach and IWLAN -attach?IWLAN -attach?
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Handover from IWLAN to 3GPP access
1. UE discovers the GPRS,and decides to transfer sessions to GPRS
2. UE starts GPRS attach procedure, which includes » GGSN selection, IP address assignment to the UE (CoA)» GTP tunnel establishment between UE and GGSN
3. UE sends BindingUpdatemessage to HA 4. HA sends BindingAckto UE
WNP-MPR-mip-mesh 44
Handover from 3GPP access to IWLAN access
1. UE discovers the IWLAN,and decides to transfer sessions to IWLAN
2. UE establishes an IPsec tunnel with PDG,and gets new IP address (CoA)
3. UE sends BindingUpdatevia IWLAN4. DSMIPv6 tunnel established between UE and HA; UE can exchange data through IWLANUE GGSN HAPDG6. UE Discovers 3GPP IWLAN access and initiates HO
UE GGSN HAPDG1. UE Discovers 3GPP IWLAN access and initiates HO3. H1 PDN Attach or BU/BA8. DSMIPv6 Tunnel
8. DSMIPv6 Tunnel2. IPsec tunnel establishmentIPsec Tunnel DSMIPv6 tunnel
WNP-MPR-mip-mesh 45
UE Initiated Detach
1. UE sends BindingUpdateto HA with Binding-Lifetime = 0
2. HA sends the BindingAckto UE
3. UE tears down security association between UE and HA
4. The HA communicates with AAA infrastructure to tear down the H2 session
3GPP AAA 3GPP AAA UE HA 3GPP AAA Server
3. IKEv2 Security Association tear down
4. H2 session termination
1. Binding Update
2. Binding Acknowledgement
3GPP AAA Proxy
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IEEE 802.21
♦ What other efforts are being developed to help macro mobility?
♦ How does the 802.21 work?
WNP-MPR-mip-mesh 47
Problem Characterization
♦ Increasing number of interfaces on devices » mostly radio interfaces
♦ Device has difficulties in finding its best connection» connection at L2, but not at the network layer
» connect to the wrong of many APs available » connect to the wrong of many APs available based on signal strength criteria alone
♦ Many (vertical) handover mechanisms available
♦ Unified mechanism for handover decisions would help
� new standard, IEEE 802.21» common across, at least, 802 media
» based on L2 Triggers to make Mobile IP like protocols to work fast
» based on media independentinformation
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The Use Case
802.3802.11802.16
Internet
DeskUndocked & walking around
Headed out of the building
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Handover Initiation
Handover Preparation
Handover Execution
Scope of 802.21
Genesis for 802.21
Search New Link
Network DiscoveryNetwork Selection
Handover Negotiation
Setup New Link
Layer 2 ConnectivityIP Connectivity
Transfer Connection
Handover SignalingContext TransferPacket Reception
IEEE 802.21 helps with Handover Initiation, Network Selection and Interface Activation
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The role of IEEE 802.21
IEEE802.11r
802.16e
3GPP/2VCC I-WLAN
SAE-LTEIEEE
802.21 Horizontal Handovers
IP Mobility & Handover Signaling
Inter-working & Handover Signaling
802.21
IETF
MIPFMIP
SIP
HIPNETLMM
DNA MIPSHOP
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Link Layer TriggersState Change
PredictiveNetwork Initiated Network Information
Applications (VoIP/RTP)
Connection Management
Mobility Management Protocols
Handover Management
Handover Policy
ET
F
802.21 - Key Services
Network Initiated Network InformationAvailable NetworksNeighbor MapsNetwork ServicesHandover Commands
Client InitiatedNetwork Initiated
Vertical Handovers
802.21 MIH Function
Protocol and Device Hardware
WLAN Cellular WMAN
L2 Triggers and Events
Information Service
Mobility Management Protocols
Smart Triggers
Information Service
Handover Messages
Handover Messages IE
EE
802
.21
IET
WNP-MPR-mip-mesh 52
Link Up
Link Going Down
Link Down
Connected
Disconnected
L2 Triggers and Events
♦ State Change Events » Link Up
» Link Down
» Link Parameters Change
♦ Predictive Events
WLAN
WWAN
Link Up Link Down
Link Up Link Switch
Make before Break
Time
♦ Predictive Events » Link Going Down
♦ Network Initiated Events » Load Balancing
» Operator Preferences
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No Event Type Event Name Description
1 State Change Link Up L2 Connection established
2 State Change Link Down L2 Connection is broken
3 Predictive Link Going Down L2 connection breakdown imminent
4 State Change Link Detected New L2 link has been found
5 State Change Link Parameters Change Change in specific link parameters has crossed pre-
Link Layer Events
5 State Change Link Parameters Change Change in specific link parameters has crossed pre-specified thresholds (link Speed, Quality metrics)
6 Administrative Link Event Rollback Event rollback
7 Link Transmission Link SDU Transmit Status Improve handover performance through local feedback as opposed to waiting for end-to-end notifications
8 Link Synchronous Link Handover Imminent L2 intra-technology handover imminent (subnet change). Notify Handover information without change in link state.
9 Link Synchronous Link Handover Complete Notify handover state
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802.21 Information
Server
WLAN
WWAN
Global Network Map
•List of Available Networks
Media Independent Information Service
WMAN
WWAN
Network Type SSID/ Cell ID
BSSID Operator Security NW Channel QoS Physical Layer Data Rate
GSM 13989 N/A AT&T NA NA 1900 N/A N/A 9.6 kbps
Network Type SSID/ Cell ID
BSSID Operator Security NW Channel QoS Physical Layer Data Rate
GSM 13989 N/A AT&T NA NA 1900 N/A N/A 9.6 kbps
802.11b Intel 00:00:… Intel .11i EAP-PEAP 6 .11e OFDM 11 Mbps
Network Type SSID/ Cell ID
BSSID Operator Security EAP Type Channel QoS Physical Layer Data Rate
GSM 13989 N/A Oper-1 NA NA 1900 N/A N/A 9.6 Kbps
802.11n Enterprise 00:00:… Oper-2 .11i EAP-PEAP 6 .11e OFDM 100 Mbps
802.16e NA NA Oper-3 PKM EAP-PEAP 11 Yes OFDM 40 Mbps
•List of Available Networks- 802.11/16/22, GSM, UMTS
•Link Layer Information- Neighbor Maps
•Higher Layer Services- ISP, MMS, ….
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Information Element Description Comments
List of networks available List all network types that are available given client location
E.g., 802.11, 802.16, GSM, GPRS/EDGE, UMTS networks
Location of PoA Geographical Location, Civic address, PoA ID
E.g. GML format for LBS or network management purpose
Operator ID Name of the network provider E.g. Could be equivalent to Network ID.
Roaming Partners List of direct roaming agreements E.g. in form of NAIs or MCC+MNC
Information Elements
Roaming Partners List of direct roaming agreements E.g. in form of NAIs or MCC+MNC
Cost Indication of costs for service/network usage
E.g, Free/Not free or (flat rate, hourly, day or weekly rate)
Security Link layer security supported Cipher Suites and Authentication Methods, Technology specific, e.g. WEP in 802.11, 802.11i, PKM in 802.16, etc.
Quality of Service Link QoS parameters 802 wide representation, application friendly
PoA Capabilities Emergency Services, IMS Services, etc. Higher Layer Services
Vendor Specific IEs Vendor/Operator specific information Custom information
WNP-MPR-mip-mesh 56
Handover
• Types of Handover Based on Control Model• Terminal Controlled
• Terminal Initiated, Network Assisted
• Network Initiated and Network Controlled
• Handover Commands for Network Initiated Handovers• Handover Commands for Network Initiated HandoversNo Command
NameMIHF <> MIHF Description
1 MIH Handover Initiate
Client <> Network Initiates handovers and sends a list of suggested networks and suggested PoA (AP/BS).
2 MIH Handover Prepare
Network <> Network This command is sent by MIHF on old network to MIHF on suggested new network . This allows the client to query for resources on new network and also allows to prepare the new network for handover
3 MIH Handover Commit
Client <> Network In this case the client commits to do the handover based on selected choices for network and PoA.
4 MIH Handover Complete
Client <> Network
Network <> Network
This is a notification from new network PoA to old network PoA that handover has been completed, new PoA has been established and any pending packets may now be forwarded to the new PoA.
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No New Mobility Protocols
Does Not handle Handover Execution
No Redesign of
MIH Amendments for 802.11
New items in scope of 802.21
No Redesign of Existing PHY/MAC
WNP-MPR-mip-mesh 58
No New Mobility Protocols
Does Not handle Handover Execution
MIH Amendments for 802.16
New SAPs in scope of 802.21
L2.5
No Redesign of Existing PHY/MAC
WNP-MPR-mip-mesh 59
Basics on ad-hoc networks
♦ What is an ad-hoc network?
♦ What are the differences between and ad-hoc wireless network and a wired network?
♦ What are the characteristics of the most important ad-hoc routing protocols?
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♦ Auto-configurable networks
♦ Having wireless links
♦ Mobile nodes � dynamic topology
♦ Isolated networks or interconnected to Internet
Ad-Hoc Networks (Layer 3)
♦ Nodes forward traffic
♦ Routing protocols
A B C
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IETF MANET - Mobile Ad-hoc Networking
Mobile
MobileRouter
Manet
FixedNetwork
MobileDevices
Mobile IP, DHCP
Router End system
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Route calculation in wired networks
♦ Distance vector» Messages exchanged periodically with neighbours
» Message indicates reachable nodes and their distance
» Algorithm takes long time to converge
» Eg. RIP 61
A» Eg. RIP
♦ Link state» Router informs periodically the other routers about its links state
» Every router gets information from all other routers
» Lots of traffic
» Eg. OSPF
4
32
1
9
1
1D
FE
B
C
WNP-MPR-mip-mesh 63
Route calculation in Ad-Hoc Netoworks-Characteristics
N1
N4
N2
N5
N3
N1
N4
N2
N5
N3
Ad-hoc network» Dynamic topology
– Depends on node mobility
» Interference– Radio communications
» Asymmetric links– Received powers and attenuation unequal in the two directions
good linkweak link
time = t1 time = t2
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Routing in Ad-hoc Networks
♦ Conventional routing protocols – Built for wired networks � whose topology varies slowly
– Assume symmetric links
♦ In Ad-hoc networks» Dynamic topology �information required to be refreshed more frequently» Dynamic topology �information required to be refreshed more frequently
– energy consumption
– radio resources for with signaling information
» Wireless node may have scarce resources (bandwidth, energy) …
♦ New routing strategies / protocols for ad-hoc networks– 2 type : reactive e pro-active
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To think about
♦ How can we avoid a large signaling overhead (number of routing messages) in ad-hoc networks
WNP-MPR-mip-mesh 66
AODV – A needs to send packet to B
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AODV – A sends RouteRequest
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AODV – B replies with RouteReply
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AODV - Characteristics
» Decision to request a route
» Broadcast of Route-request
» Intermediate nodes get routes to node A
» Route-reply sent in unicast by same path» Route-reply sent in unicast by same path
» Intermediate nodes get also route to node B
» Routes haveTime-to-live, in every node
» Needs symmetric graph
WNP-MPR-mip-mesh 70
Pro-active routing protocols
♦ Routes built using continuous control traffic
♦ Routes are maintained
♦ Advantages, disadvantages » Constant control traffic» Constant control traffic
» Routes always available
♦ Example – OLSR (RFC 3626)» OLSR - Optimized Link-State Routing protocol
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OLSR – Main functions
♦ Detection of links to neighbour nodes
♦ Optimized forwarding / flooding (MultiPoint Relaying)
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OLSR – Detecting links to neighbour nodes
♦ Using HELLO messages
♦ All nodes transmit periodically HELLO messages
♦ HELLO messages group neighbour by their state
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OLSR – MultiPoint Relaying (MPR)
♦ MultiPoint Relaying (MPR)» Special nodes in the network
» Used to– Limit number of nodes retransmiting packets
– Reduce number duplicated retransmissions
♦ Each node selects its MPRs, which must» Be at 1 hop distance
» Have symmetric links
♦ MPR set selected by a node» Must be minimum
» Must enable communication with every 2-hop-away nodes
♦ Node is MPR if it has been selected by other node
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OLSR – Link State
♦ In wired networks, OSPF» Every node floods the network
» With information about its links state
♦ OLSR does the same, using 2 optimizations♦ OLSR does the same, using 2 optimizations» Only nodes associated to MPR are declared in link state message
� Reduced message length
» Only the MPR nodes send link state messages
� Smaller number of nodes sending messages
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OLSR – Link state, example
♦ Messages which declare the links state» “Topology Control Messages”
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The IEEE 802.11 mesh networks
♦ How will the 802.11s Mesh Network work?
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Note: This set of slides reflects the view of a 802.11s draftstandard.
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IEEE 802.11s - Main Characteristics
♦ Network topology and discovery
♦ Inter-working
♦ Path Selection and Forwarding
♦ MAC Enhancements
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Elements of a WLAN Mesh Network
• MP - Mesh Point– establishes links with
neighbor MPs
• MAP - Mesh AP
Bridgeor Router
Mesh Portal
MP
• MAP - Mesh AP– MP + AP
• MPP - Mesh Portal
• STA – 802.11 station– standard 802.11 STA
MAP
MAP
STA
STA
MP
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L2 Mesh Network - Emulates 802 LAN Segment
59
7
6
4
3
802 LAN
Broadcast LAN• Unicast delivery• Broadcast delivery• Multicast delivery
11
1312
710
2
Support for connecting an 802.11s mesh to an 802.1D bridged LAN• Broadcast LAN (transparent forwarding)• Learning bridge• Support for bridge-to-bridge communications: Mesh Portal participates in STP
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To think about
♦ Suppose A sends a frame to B (MAC layer). What MAC addresses are required for the frame transmitted between the two Ethernet switches?
♦ And what MAC addresses are required for the frame transmitted between the two MAPs? Why are the 2 cases different?between the two MAPs? Why are the 2 cases different?
ethernetswitch
ethernetswitchA B
MAP MAPA B))) ))) )))
I)
II)
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Mesh Data Frames
♦ Data frames » based on 802.11 frames - 4 MAC address format» extended with: 802.11e QoS header, and new Mesh Control header field
FrameControl
DurAddr
1Addr
2Addr
3Seq
ControlAddr
4QoS
ControlMesh
ControlBody FCS
2 2 6 6 6 2 6 2 3 4
♦ Mesh Control Field» TTL – eliminates possibility of infinite loops (recall these are mesh networks!)» Mesh E2E Seq
MAC Header
Mesh E2ESeq
Mesh Control
MeshTTL
0 7 8 23
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Topology Formation
♦ Mesh Point discovers candidate neighbors » based on beacons, which contain mesh information
– WLAN Mesh capabilities
– Mesh ID
♦ Membership in a WLAN Mesh Network » determined by (secure) association with neighbors
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Mesh Association
57
63
MeshID: mesh-AMesh Profile: (link state, …)
1. MP X discoversMesh mesh-Awith profile (link state, …)
2. MP X associates/ authenticateswith neighbors in the mesh, since it can support the Profile 8
7
12
4
X
Capabilities:Path Selection: distance vector, link state
3. MP X begins participating in link state path selectionand data forwarding protocol
One active protocol in one mesh
but alternative protocols in different meshes
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Interworking - Packet Forwarding
11
59
710
6
4
3
1312
102
Destination inside or outside
the Mesh?
Portalforwards
the message
Use pathto the
destination
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Hybrid Wireless Mesh Protocol (HWMP)
Combines
» on-demand route discovery– based on AODV– based on AODV
» proactive routing to a mesh portal – distance vector routing treebuilt and maintained rooted at the Portal
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HWMP Example 1: No Root, Destination Inside the Mesh
• Communication: MP4 � MP9
• MP4 – checks its forwarding table for an
entry to MP9 5
62
1
X
entry to MP9
– If no entry exists, MP4 sends a broadcast RREQ to discover the best path to MP9
• MP9 replies with unicast RREP
• Data communication begins
59
710
4
3
8
On-demand path
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HWMP Example 3: No Root, Destination Outside the Mesh
♦ Communication: MP4 � X
♦ MP4 » first checks its forwarding table for an entry to X
» If no entry exists, MP4 sends a broadcast RREQ to discover the best path to X 5
62
1
X
to discover the best path to X
» When no RREP received, MP4 assumes X is outside the mesh and sends messages destined to X to Mesh Portals
♦ Mesh Portal that knows X may respond with a unicast RREP
59
710
4
3
8
On-demand path
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HWMP Example 2: Root, Destination Inside the Mesh
♦ Communication: MP 4 � MP 9
♦ MPs learn Root MP1 through Root Announcementmessages
5
62
1
XRoot
♦ MP 4 checks its forwarding table for an entry to MP9
♦ If no entry exists, MP4 forwards message on the proactive path to Root MP1
♦ When MP1 receives the message, it forwards on the proactive path to MP9
♦ MP9, receiving the message, may issue a RREQ back to MP 4 to establish a path that is more efficient than the path via Root MP1
59
710
4
3
8
Proactive pathOn-demand path
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HWMP Example 4: Root, Destination Outside the Mesh
♦ Communication: MP4 � X
♦ MPs learn Root MP1 through Root Announcementmessages
5
62
1
XRoot
♦ If MP4 has no entry for X in its forwarding table, MP 4 may forward the message on the proactive path toward the Root MP1
♦ When MP1 receives the message, if it does not have an active forwarding entry to X it may assume the destination is outside the mesh
♦ Mesh Portal MP1 forwards messages to other LAN segments
59
710
4
3
8
Proactive path
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Radio Aware OLSR (RA-OLSR)
♦ OLSR may be used in alternative to AODV
♦ RA-OLSR proactively maintains link-state for routing
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MAC Enhancements for Mesh
♦ Intra-mesh Congestion Control
♦ Common Channel Framework (Optional)
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Need for Congestion Control
♦ Mesh characteristics» Heterogeneous link capacities along the path of a flow
» Traffic aggregation: Multi-hop flows sharing intermediate links
♦ Issues with the 802.11 MAC for mesh» Nodes blindly transmit as many packets as possible, regardless of how » Nodes blindly transmit as many packets as possible, regardless of how
many reach the destination
» Results in throughput degradation and performance inefficiency
2
1
7
6
3
High capacity linkLow capacity linkFlow
4
5
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Intra-Mesh Congestion Control Mechanisms
♦ Local congestion monitoring (informative)» Each node actively monitors local channel utilization
» If congestion detected, notifies previous-hop neighbors and/or the neighborhood
♦ Congestion control signaling» Congestion Control Request (unicast)
» Congestion Control Response (unicast)
» Neighborhood Congestion Announcement (broadcast)
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Common Channel
♦ Common channel» Unified Channel on which MPs jointly operate
» Using RTX, the transmitter suggests a destination channel» Receiver accepts/declines the suggested channel using CTX
» The transmitter and receiver switch to the destination channel
» Data is transmitted
MP1
MP2
MP3
MP4
» Data is transmitted» Then they switch back
RTXCommonChannel
DataChannel n
DataChannel m
CTX
SIFS
CTX
SIFS
RTX
≥ DIFS
DIFS
DATA
SwitchingDelay
ACK
SIFS CTX
SIFS
RTX
≥ DIFS
SwitchingDelay
DATA
SwitchingDelay DIFS
ACK
SIFS
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Control Frames
♦ Request to Switch (RTX) Frame
FrameControl
Duration/ID
RA TADestination
Channel Info.FCS
2 2 6 6 2 4
♦ Clear to Switch (CTX) Frame
FrameControl
Duration/ID
RADestination
Channel Info.FCS
2 2 6 2 4
