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Vehicular Networking

Malathi VeeraraghavanProfessor

Charles L. Brown Dept. of Electrical & Computer Engineering

University of Virginia

[email protected]

1

[email protected]

Tutorial at IEEE ICC 2011

This work was carried out as part of a sponsored research project from the US DOT FHWA grant no. DTFH61-10-H-00001

Outline

• DSRC

• Standards– IEEE 802.11p, 1609.1-4

– SAEJ2735

• Testbeds and trials

2


• Equipment

• Research literature

• Summary

• Background on IEEE 802.11 and IPv6

Dedicated Short-Range Communication (DSRC)

• Channel allocation

• History

• Use of DSRC• Use of DSRC– Architecture

– Applications

3

US DSRC Channel allocation

CH 172 CH 174 CH 182CH 180CH 178CH 176 CH 184

Critical safety

High power safety

Service channels (SCH)

Service channels (SCH)

Control channel(CCH)

5.85

5.86

5.88

5.89

5.90

5.92

5.91

5.87

• US FCC allocated band: 5.850-5.925 GHz

• 75 MHz band

• Safety margin: 5MHz at lower end

• Critical safety channel: High availability and low latency (HALL)

4

5.85

5.86

5.88

5.89

5.90

5.92

5.91

5.87

Worldwide ITS Spectrum AllocationsWorldwide ITS Spectrum Allocations

5.8 5.9(GHz)

ITU-R5.725 5.875

ISM Band

Frequency

First Second(Additional)DSRC Generation:

5

ISM Band

EUROPE5.795 5.815

0.902 0.928 5.85 5.925North America

JAPAN5.79- 5.81 5.83-5.85

5.77

Talk by S. Oyama, ITS America Annual Meeting, April 2002, http://www.leearmstrong.com/DSRC%20Home/Standards%20Programs/World-

Wide/DSRC%20Standards%20World%20.htm

History

• 1991: US program called Intelligent Vehicle Highway Systems (IVHS)

• 1999: US FCC granted the DSRC band for ITSfor ITS

• 2007: IEEE 802.11p amendment published

• 2006-2007: IEEE working group 1609 releases higher-layer standards

6IEEE paper 2009 by R. Uzcategui and G. Acosta-Marum

Use of DRSC: Architecture

• V2V (Vehicle to Vehicle) and V2I (Vehicle to Infrastructure) communications

• Range up to 1000m

• Data rates from 6-27 Mbps

• Low latency ~50ms

• Security using public key infrastructure (PKI)

7

From Booz Allen Hamilton 2008 Talk at ITSVA conference (Kandarpa)

Architectural components

• RSU (RSE): Roadside Unit (Equipment)

• OBU (OBE): Onboard Unit (Equipment)

• Network Subsystem: – SDN: Service Delivery Node– SDN: Service Delivery Node

– ENOC: Enterprise Network Operations Center

• Backhaul network: RSE to SDN

8

Use of DSRC: Applications

• Safety– NHTSA 2010 report about accidents in 2009:

• 33,800 fatalities & 2.2M injuries

– Direct economic costs of vehicle crashes are $230.6 billion per year (2000 estimate)

• Efficiency/mobility• Efficiency/mobility– Texas Transportation Institute Urban mobility report 2009: “US wasted about $87 billion due to congestion, a 63% increase from the previous decade”

– Signal optimization

– Route guidance systems (avoid congestion)

• Commercial: – Tolling/parking payment, fleet control, park&ride

9

Outline

• DSRC

� Standards– IEEE 802.11p

– IEEE 1609.1-1609.4

– SAE J2735

10

– SAE J2735


• Equipment


• Summary

• Background on IEEE 802.11

WAVE (Wireless Access in Vehicular Environments)

• Standards:– IEEE 802.11p for PHY and MAC

– IEEE 1609 for higher layers

• Why is a new variant 802.11p needed?• Why is a new variant 802.11p needed?– Mobile endpoints – high vehicular speed

– Greater range: 1000 m (vs. 38-46m for 802.11b)

11

IEEE 802.11p

• 802.11p is specified as an amendment to 802.11

• Major differences with 802.11

802.11b 802.11p

Network acquisition Association Fast

Basic Service Set (BSS) Required Can operate without first

12

Basic Service Set (BSS) Required Can operate without firstforming a BSS

Latency Low (for safety applications)

Frequency band 2.4 GHz 5.85-5.925 GHz

Environment Indoor, low-mobility

Outdoor high-mobility

Number of channels 3 channels 7 channels, each 10MHz

Physical layer 20 MHz per channel

10 MHz per channel

Communicating without forming a BSS

• Stations simply transmit and receive on a channel known a priori– e.g. Basic Safety Messages sent in a WAVE Short Message on Control Channel (CCH)

• Timing and Information frame: new • Timing and Information frame: new management frame– allows stations to exchange management information: supported rates, QoS parameters

13

Other changes

• MAC layer: – Since parameters that control MAC operation are sent by access point in a beacon in an 802.11 BSS, for operation without a BSS, use default values set in MIB variables (pre-configuration)values set in MIB variables (pre-configuration)

• Minor changes in information elements

• Interesting: No changes in security section of 802.11 – handled in 1609.2

14

Annex I

15802.11b: maximum EIRP: 36 dBm (4W)

IEEE 1609 WAVE Standards

• 1609.3: network and transport layers

• 1609.4: multi-channel operation

• 1609.2: security services

• 1609.1: resource manager• 1609.1: resource manager

16

WAVE protocol stack

WME: WAVE Management Entity

MIB: Management Information Base

WSMP: WAVE Short Message Protocol17

MLME: MAC Layer Management Entity

PLME: PHY Layer Management Entity

LLC: Logical Link Control

1609.3 outline

• Networking services

• WAVE system operations

• WAVE Management Entity (WME)

• IPv6• IPv6

• WAVE Safety Message Protocol (WSMP)

18

Networking services 1609.3

• Data-plane services– Logical link control (LLC)

– IPv6

– UDP/TCP– UDP/TCP

– Wave Short Message (WSM) Protocol (WSMP)

• Management-plane services

19

WAVE system operations

Operation without a WAVE Basic Services Set (WBSS)

Operation with a WAVE Basic Services Set (WBSS)

Only WAVE short Persistent WBSS Non-persistent

20

Only WAVE short messages sent on the Control Channel (CCH)

Persistent WBSSprovider MAC sends WAVE announcements about WBSS and its applications in every CCH interval

Non-persistent WBSS

with WBSS: WSMs or IP over SCH

1609.3 outline check



�WAVE Management Entity (WME)

• IPv6• IPv6


21

WME: glue that makes it work

• WAVE Management Entity (WME)�WBSS management

�Application registration

�IPv6 configuration�IPv6 configuration

– MIB maintenance

– Channel usage monitoring

– Received Channel Power Indicator (RCPI) monitoring

22

Creation of a WBSS

• A WBSS is initiated at the request of an application

• A WAVE announcement frame is sent on the CCH announcing the new WBSS with its applications

• WAVE announcement frame contains– Wave service advertisement (created by WME)

– Wave service information element (MAC frame body)

• When a WBSS is formed, channel rate and transmission power are specified in the announcement frame

• When there is no WBSS, this information needs to be passed down to the MAC layer in each WSM message

23

Provider and User (roles in a WBSS)

• Any device (OBU or RSU) can be provider or user

• Provider: generates announcements about a WBSS and associated about a WBSS and associated applications

• User: joins a WBSS on receipt of an announcement

24

Creation of a WAVE announcement frame

25

IEEE 1609.3, page 12

WAVE announcement frame (sent on CCH)

Creation of a WAVE announcement frame

System parametersare loaded

26


What the WME constructs

27


WAVE service advertisement

• WAVE service advertisement is constructed by WME

• Application specifies:– Provider Service Context (PSC)

• System parameters:• System parameters:– Channel Info

– WAVE routing advertisement (optional)

• WAVE announcement frame carries information about– Multiple applications, each of which is assigned a Provider Service Identifier (PSID)

– Multiple service channels

28

WAVE service advertisement: PSC

• Provider Service Context– Application priority

– Channel number of the SCH for the WBSS on which this application is being supported

– Optional parameters:– Optional parameters:

o IPv6 address of the device hosting the application

o Service port number (16-bit): like TCP port number

o Provider device addressing (present if IP is being used): indicates if the device sending the WSA is the also the one hosting the application

o MAC address of the device hosting the application if different from the device sending the WSA

29

WAVE service advertisement: Channel info

• Channel Information– SCH channel number

– Adaptable: whether rate is minimum and transmit power level is maximum, or transmit power level is maximum, or whether rate/power are fixed

– Data rate

– Transmit (tx) power level

30

IPv6 configuration

• WAVE routing advertisement (WRA): about infrastructure internetwork connectivity (all mandatory if WRA is present)– Router lifetime: duration for which Default gateway information is valid

– IpPrefix: IPv6 subnet ID

– Prefix Length: subnet mask– Prefix Length: subnet mask

– Default Gateway: IPv6 address of a gateway inside infrastructure that provides connectivity to the Internet

– Default Gateway MAC address

– Separate Gateway MAC: if 0, default gateway is not the device transmitting the WSA

– Primary DNS

– Secondary DNS (optional)

31





� IPv6� IPv6


32

IPv6 usage in WAVE

• OBU calculates its global IPv6 address via stateless configuration– IpPrefix is received in WRA of a WAVE announcement frame rather than in a Router Advertisement message as in stateless autoconfiguration (also DNS and gateway)

• RSU’s IPv6 is configured by a network • RSU’s IPv6 is configured by a network administrator

• If an OBU is a provider of an IP based service, it only uses link-local addresses (Section 6.1 of 1609.3)

• UDP usage expected to be more common than TCP

33





• IPv6• IPv6

�WAVE Safety Message Protocol (WSMP)

34

WSMP

• WAVE Short Message Protocol

• Time-sensitive, high-priority

• Sent directly in MAC/LLC frames

• Provider Service Identifier (PSID) • Provider Service Identifier (PSID) used to determine the application to which WSM should be delivered at the destination

35

Without WBSS operation

• Only Wave Short Message Protocol (WSMP) over the CCH

• There is no opportunity to send a WAVE announcement frame in which information about the channel can be sent

• So the WSM message format carries parameters about the selected channel

• A WAVE Short Message (WSM) can be sent as soon as • A WAVE Short Message (WSM) can be sent as soon as needed – e.g., an emergency brake event

36

WSM Version

Security type

Data Rate

ChannelNumber

Tx PowerLevel

Provider Service ID

WSM length

WSMData

0: unsecured1: signed2: encrypted

WSMPs can be sent on a SCH when operating within a WBSS

WSMP-to-UDP/IP forwarding(user applications)

• Interesting concept (Sections 5.5 and 6.1)– An application can reside off the WAVE device

– When WAVE device receives a WSM with a particular PSID for an application that has pre-registered as being off the device, the WAVE device will encapsulate message payload in UDP/IPv6 packet and forward it to the application

– Application should have registered its IP address and port in – Application should have registered its IP address and port in the UserServiceInfo part of the WME MIB (see Appendix A.1)

• Why is this interesting: – because it allows vehicle OBUs to interconnect with Internet endpoints without itself running IP – new internetworking mechanism – in violation of end-to-end principle

• IEEE 1609 Working Group Public Site

– http://vii.path.berkeley.edu/1609_wave/

– A 2009 presentation calls for removing this feature37



�1609.4: multi-channel operation



38

Multichannel operation 1609.4

• Four services– Channel routing: controls routing of data packets from LLC to appropriate channel

– User priority service: 8 levels of user priority mapped to the four AC classes of 802.11e MAC mapped to the four AC classes of 802.11e MAC access (EDCA) – to be studied in depth later

�Channel coordination service: coordinates channel intervals (channel sync) so that data packets are sent on the correct channels

�MSDU data transfer service: LLC header Ethertype lookup to determine if WSMP or IP and give priority to WSMP

39

Channel coordination service

• Channels vs. intervals– CCH and SCH channels (see DSRC allocation)

– CCH and SCH intervals• Guard intervals between them

• Sync interval: CCH interval + SCh interval• Sync interval: CCH interval + SCh interval

• Precise Pulse Per Second UTC timing provided by GPS used for channel synchronization

40From IEEE 1609.4, Section 6.4

Can an OBU just stay on CCH?

• Yes.

• For devices remaining on CCH during the SCH interval, low-priority frames (user priority 3 or less) may be transmitted at any timeany time

• All devices must monitor CCH during CCH intervals during which all high-priority (user priority 4 and higher) WSMP messages will be sent

41From IEEE 1609.4, Section 6.4

Multichannel operation 1609.4

• Channel coordination management, section 8, states– “A WAVE device will be a member of only one WBSS at a time.”

– Per definition of WAVE device, it could be an RSU or OBU, but if an RSU announces many channels in a WAVE OBU, but if an RSU announces many channels in a WAVE announcement frame isn’t it a member of many WBSS?

• Each RSE operated only one service channel in the Detroit POC (Booz Allen Hamilton Jan 09 report)

42

Single-channel vs. multi-channel devices

• Multi-channel devices are not required to be synchronized to operate on SCH as long as they conform to the requirements of monitoring the CCH during the CCH interval and to ensure transmission of high-priority and to ensure transmission of high-priority CCH messages

43From IEEE 1609.4, Section 8

MSDU Data Transfer

• In data-plane, 1609.4 sits between LLC and MAC, and in control-plane has MLME extension above MLME layer – see WAVE protocol stack

Frames

44

Management frames:WAVE announcement – CCH only

Data frames

WAVE Short Messages (WSM) :CCH and SCH

IP: SCH only




�1609.2: security services


45

Security

• 1609.2: Security services

• European-funded Secure Vehicular Communications (SeVe-Com) project (http://www.sevecom.org)– Good treatment of anonymity– Good treatment of anonymity

• Vehicular Datagram Transport Layer Security (V-DTLS)– Pietrowicz, S.; Hyong Shim; Di Crescenzo, G.; Tao Zhang; “VDTLS - Providing secure communications in vehicle networks,” INFOCOM Workshops 2008, IEEE , vol., no., pp.1-6, 13-18 April 2008

– Used in Detroit Proof of Concept (POC) trials

46

1609.2: Security Services

• Message types– Unsecured

– Signed

– Encrypted

• Algorithms• Algorithms– ECDSA (Elliptic Curve Digital Signature Algorithm)

– Hash algorithms: SHA-224 and SHA-256

– Asymmetric: ECIES (Elliptic Curve Integrated Encryption Scheme) used to transport symmetric key

– Symmetric: AES

47

Specific uses of secured messages

• Secured WSAs carried in WAVE announcement frames– Signed message

– Security Footer carries the signature field, timestamp (avoid replay attacks)timestamp (avoid replay attacks)

– Security Header carries WSIE certificate of signer (and/or certificate chain)

• Support for fragmentation– Some data such as Certificate Revocation Lists (CRLs) or updated root certificates could be too large to fit in a single transmission

48

Specific uses of secured messages

• Secured WSM– Security type field in WSM header

• 0: unsecured; 1: signed; 2: encrypted

– SignedMessage structure:• signer: keying material (certificate, certificate chain) • signer: keying material (certificate, certificate chain) and hash algorithm

• unsigned message

• signature (digital signature itself)

• Security manager:– maintain root certificate store and the Certificate Revocation List (CRL) store

49

Certificate requests

• Applications may send WAVECertificateRequest messages over the air – Uses UDP/IP

• WAVECertificateResponse message sent• WAVECertificateResponse message sent

• Certificate Signing Request (CSR):– request by an entity to a CA to be issued with a certificate

• CSR signing certificate: a certificate used to sign a CSR

50

Security


� European-funded Secure Vehicular Communications (SeVe-Com) project (http://www.sevecom.org)– Good treatment of anonymity– Good treatment of anonymity

• Vehicular Datagram Transport Layer Security (V-DTLS)– Pietrowicz, S.; Hyong Shim; Di Crescenzo, G.; Tao Zhang; “VDTLS - Providing secure communications in vehicle networks,” INFOCOM Workshops 2008, IEEE , vol., no., pp.1-6, 13-18 April 2008


51

Sevecom project(Anonymity)

• Hardware Security Module (HSM) in vehicles and RSUs– all private keys stored in HSM, and all private key operations are executed in HSM

– digital signature generation and decryption of encrypted messagesmessages

– public key operations are executed in OBU

• Pseudonymous authentication (for security and anonymity)– Each OBU has multiple certified public keys (pseudonyms)

– An OBU uses each pseudonym for a short period of time, and then switches to another, not previously used, pseudonym.

52Papadimitratos et. al, IEEE Comm. Mag, Nov. 2008

Sevecom project

• Long-term identity (public-private key pair)

• Short-tem identities (with pseudonyms)

• How to distribute Certificate Revocation Lists (CRLs) to multiple RSUs?

• Secure beaconing: • Secure beaconing: – send “beacon” i.e., BSM, encrypted in the current pseudonym’s private key;

– send along with it the pseudonym certificate with the public key,

– CA signature can be verified in other OBUs, which have preinstalled CA’s public key

• Root CA public keys preloaded in OBUs

53

Sevecom project

• Short-term identity– HSM generates a set of N public key-private key pairs

– Sends N public keys to its CA using its long-term ID to authenticate itself to the CA

– CA returns signed certificates with N pseudonymns

– Each pseudonym has• identifier of the CA, the lifetime of the pseudonym, the public key, and the signature of • identifier of the CA, the lifetime of the pseudonym, the public key, and the signature of

the CA, BUT no information about the identity of the vehicle

– Once a pseudonym is discarded by OBU, cannot go back

– Non-overlapping lifetimes for pseudonyms

– Do pseudonym refills

– Since CA knows relation between pseudonyms and actual identity, authorized parties can obtain this information if required

– For further anonymity, vehicle obtains short-term credentials from foreign CAs when a vehicle enters foreign domain; foreign CA can verify identity with home CA

54

Security


• European-funded Secure Vehicular Communications (SeVe-Com) project (http://www.sevecom.org)– Good treatment of anonymity– Good treatment of anonymity

� Vehicular Datagram Transport Layer Security (V-DTLS)– Pietrowicz, S.; Hyong Shim; Di Crescenzo, G.; Tao Zhang; “VDTLS - Providing secure communications in vehicle networks,” INFOCOM Workshops 2008, IEEE , vol., no., pp.1-6, 13-18 April 2008


55

VDTLS

• Uses the concept of Identity Based Encryption (IBE)– IBE is a public-key encryption system with any arbitrary string, e.g., email address or IP address, used as the recipient’s public key

• Differences with DTLS• Differences with DTLS– DTLS uses certificates and hence privacy cannot be preserved

– Certificate chain exchanges requires over-the-air bandwidth

– Use of certificates requires over-the-air distribution of CRLs (uses bandwidth)

56

VDTLS

• IBE public identities– Service: based on its address information

– Vehicle: based on one of its anonymous certificates• each vehicle is assigned n certificates randomly selected from a pool of N shared certificates called “anonymous certificates” (n: 5 to 20; N: 10K – 30K)(n: 5 to 20; N: 10K – 30K)

• Comparison of messages with DTLS– Retains ClientHello, HelloRequest,ServerHello and Finished

– Redefines ServerKeyExchange and ClientKeyExchange

– Does not use HelloVerifyRequest, Certificate, CertificateRequest, ServerHelloDone, CertificateVerify

57





�1609.1: resource manager�1609.1: resource manager

58

1609.1 Resource Manager

Resource Manager (RM) multiplexes the communications of multiple remote applications, called RMAs, each RMAs, each communicating with multiple OBUs, which run RCPs

59

• RM: Resource Manager

• RMA: RM Application

• RCP: Resource Command Processor

Main purpose

• “RM concept reduces the complexity of the OBUs freeing them from the requirement of executing applications onboard the vehicle”

• RMAs control OBU resources– read/write memory– read/write memory

– user interfaces

– specialized interfaces to other onboard equipment

– optional vehicle security devices

– All resources are mapped into the memory space of the unit

– RM commands and responses defined to allow RMAs to read/write this memory space

60IEEE paper 2009 by R. Uzcategui and G. Acosta-Marum

Outline

• DSRC

� Standards– IEEE 802.11p

– IEEE 1609.1-1609.4

� SAE J2735

61

� SAE J2735


• Equipment


• Summary


Society of Automotive Engineers (SAE)J2735 standard

• Overview

• Example messages and parameters

• Annex A: Priorities

• Annexes B & C: Basic Safety Message • Annexes B & C: Basic Safety Message

• Annex E: Probe Vehicle Data

62

SAE J2735 standardDSRC Message Set Dictionary• Specifies a set of– messages, which contain

– data frames, which contain

– data elements (smallest entities)– data elements (smallest entities)

• Messages can be used on– DSRC

– other wireless technologies

• Annexes are useful

63Nov. 2009 version

Examples of messages

• Ala Carte Message

• Basic Safety Message

• Probe Vehicle Data

• Probe Data Management• Probe Data Management

• Intersection Collision Avoidance

• Traveler Information Message

• Emergency Vehicle Alert

• Signal Request Message

• And 7 others – total of 15 message types

64

Examples of Data frames

• Snapshot: one or more status elements captured and sent in Probe Vehicle Data message– FullPosition Vector (also a data frame)– FullPosition Vector (also a data frame)

– VehicleStatus (also a data frame)

65

FullPositionVector data frame

• Consists of data frames and data elements– Data frames

• DDateTime

• TransmissionandSpeed (transmission state and speed)

• PositionalAccuracy• PositionalAccuracy

– Data elements• Longitude

• Latitude

• Elevation

• Heading

• etc.

66

VehicleStatus data frame(not a complete defn.)

• ExteriorLights, LightbarInUse

• WiperStatus (dataframe)– data elements: WiperStatusFront, WiperStatusRear, WiperRate (front rate and rear rate variables)

• BrakeSystemStatus (data frame)• BrakeSystemStatus (data frame)– BrakeAppliedStatus, AntilockBrakeStatus, StabilityControlStatus, etc.

• SunSensor, RainSensor, AmbientAirTemperature, AmbientAirPressure

• Steering (data frame), AccelerationSet4Way

• VehicleData (VehicleHeight,VehicleType, etc.)

67


• Overview


�Annex A: Priorities

• Annexes B & C: Basic Safety Message • Annexes B & C: Basic Safety Message

• Annex E: Probe Vehicle Data

68

Annex A: Priorities

• J2735 layer: Message priority

• 1609.4: User priority

• 802.11: MAC priority

• Display priority: which message to display on driver’s screen first

• 1609.3: Application priority

69

Message priority(1 to 7)

Urgent

< 10 msec from 10 to 20 msec > 20 msec

Importance

Safety of life 7 5 3

Public safety 6 4 3

Non-priority 2 1 1Non-priority 2 1 1

70

• Safety of life:

• Crash Pending Notification: 7

• Basic safety message: 5

• Public safety:

• Signal Phase and Timing: 6

• Lane Coordination: 4

• Wave Service Annoncement: 3

• Non-priority

• Electronic payments: 2

• Area map: 1

EXAMPLES

1609.4 User priority

• 8 levels to support safety and non-safety applications

• Mapping of J2735 Message priority to 1609.4 User priority (Annex A)– “The main purpose of the message priority is to serve as – “The main purpose of the message priority is to serve as input to the protocol at the next lower layer in a transmitting device. If the lower layer supports prioritization, it might use message priority in determining how to treat a given message.”

– “In particular, the similarity between the message priority scale (1 to 7) and the IEEE 1609 User priority scale (0 to 7) does not imply that a simple mapping is appropriate.”

71

From Annex A of J2735

1609.4 User Priority Access Category

7 Highest AC3

6

5 AC2

44

3 AC1

0

2 AC0

1

72

0 is higher than 2 and 1 due to historical IEEE development evolution as a way to add a new “lowest priority”

User priority to transmission access categories

• MAC layer does this mapping

• Internal contention contention first won by an AC, and then external contention

73From IEEE 1609.4

MAC: Enhanced Distributed Channel Access (EDCA)

• Arbitration inter-frame space (AIFS): The minimum time interval between the wireless medium becoming idle and the start of frame transmission

• Contention Window (CW): Random number • Contention Window (CW): Random number of time slots to wait

• Transmit Opportunity (TXOP): Maximum duration in msec; If 0, it permits only one MSDU.

74

Medium Access

• If free: wait for AIFS and send

• If busy: wait for AIFS and then CW75

MAC transmission priorities

• AC_VI: video

• AC_VO: voice

• AC_BE: best effort

• AC_BK: background

76From Stibor et. al (2007) paper

• Random number of slots where slot time is 8µs

• TXOP = 0 for all cases

• Actual parameter set more general for CW

Actual standardFrom IEEE 1609.4

77

In 802.11 Association Response message, EDCA Parameter Set for use on this BSS is passed from AP to station


• Overview


• Annex A: Priorities

�Annexes B & C: Basic Safety Message �Annexes B & C: Basic Safety Message

�Annex E: Probe Vehicle Data

78

Annexes B and CBasic Safety Message (BSM)

• No WBSS formed

• Broadcasts – not unicast – no ACKs

• Frequent: every 100ms

• Support multiple applications• Support multiple applications– message content based on needs of applications many of which need same vehicle data

• BSM sent in WSMP (WAVE short message protocol)

• Sent on CCH: since no WBSS, only WSMPs can be sent on CCH

79

Annex E: Probe Data messages

• Probe data collected by vehicles at periodic intervals: 42 types of data!

• All collected snapshots are uploaded to RSU from OBU when vehicle is in range

• WBSS used• WBSS used

• SCH used

• WSMP or UDP/IP

• Single-attempt unicast

• RSU announces Provider Service Identifier

80

Three types of snaphots

• Periodic– 4 seconds if speed is 20 mph (urban)

– 20 seconds if speed is 60 mph (rural)

• Event triggered• Event triggered– certain vehicle status elements change

• Starts and stops– when a vehicle starts or stops moving

81

Annex E: Prob Message Management

• Controls the production of snapshots by time or distance

• Modifies thresholds for triggered snapshotssnapshots

• Modifies thresholds for start/stop snapshots

• Can be applied just to a random sample of vehicles

82

Outline

• DSRC

• Standards– IEEE 802.11p

– IEEE 1609.1-1609.4

– SAE J2735

83

– SAE J2735

� Testbeds and trials

• Equipment


• Summary


US Testbeds

• Vehicle Infrastructure Integration (VII) Proof of Concept (POC) Test– MI VII testbed (Detroit POC)

– NY VII testbed– NY VII testbed

– CA VII testbed

• SafeTrip-21 (started 2008)

• Europe and Japan testbed listing

[IntelliDrive, Connected Vehicle]

84References provided in literature survey document

VII Project Overview• VIIC members

– BMW, Daimler, Chrysler, Ford, Honda, Nissan, GM, VW, Toyota

– Develop VII technologies to implementation readiness, validation through Proof of Concept (POC)

85

(POC)• Infrastructure side is supported by Booz Allen Hamilton subcontracted by the US DOT– Install RSEs in Detroit Test Environment– Setup and support VII network operations– Develop VII network services for testing during the POC

Kapsch (Moring) 2008 talk

Documents (2009)

• Final Reports: VII Proof-of-Concept – Executive Summary

– Results and Findings

– Technical Description

• From VIIC and Booz Allen Hamilton

• VIIC:• VIIC:– http://ntl.bts.gov/lib/31000/31000/31079/14443.pdf– http://ntl.bts.gov/lib/31000/31100/31135/14477_files/14477.pdf

– http://ntl.bts.gov/lib/31000/31100/31136/14458_files/14458.pdf

• BHA– http://ntl.bts.gov/lib/31000/31000/31078/14481.pdf

– http://ntl.bts.gov/lib/31000/31300/31334/14488.pdf

86

POC Development Test Environment (DTE)• 55 Road-Side Equipment (RSE) Sites

(11 freeway, 44 arterial)• Over 45 Square Miles Covered

• 75 Center-Line Miles of Roadway

• 27 vehicles equipped with OBEs

Booz Allen Hamilton (Kandarpa) 2008 Talk & Kapsch (Moring) 2008 talk

Detroit Backhaul Communications

• A communication link between the Detroit SDN and each RSE will be installed in Detroit – termed Backhaul Communications

• Different Backhaul Communications Technologies Used:– WiMax: 19 sites (6 Mbps)

Michigan DTE - SDN

Node 2Used:– WiMax: 19 sites (6 Mbps)– Wireline: 20 sites (T1)– 3G: 16 sites (850 kbps)

• Data streams from all RSEs will be aggregated at the SDN

• Network Users will interface with the SDN through an Access Gateway (providing the necessary security protection)

AT&T managed services (aggregation

layer)

AT&T Wireline Service

WiMAX Service

ANode 1

Sprint

EV-DO rev A Service

G. Krueger, MI DOT 2007 talkand Jan. 09 BAH report

POC Application Name LeadTraveler Information

Booz Allen

Signal Timing Optimization

Ramp Metering

Weather Information

Applications used for POC testing

Corridor Management: Planning Assistance

Corridor Management: Load Balancing

In-Vehicle Signage

VIIC

Off-Board Navigation

Make Payment for Parking

Make Payment for Toll

Vehicle Situation Indication (Heartbeat)

Traffic Signal Indication (SPAT/GID)

From Booz Allen Hamilton 2008 Talk

Services deployed

• Advisory Message Distribution Service (AMDS): Enables “Network Users” to send SAE J2735 compliant advisory messages to vehicles.

• Probe Data Service (PDS): Enables the distribution of SAE J2735 compliant Probe Data from RSE to “Network User” subscribers. The RSE to OBE Interface is secured using Vehicular Datagram Transaction Level Security (V-DTLS)subscribers. The RSE to OBE Interface is secured using Vehicular Datagram Transaction Level Security (V-DTLS)

• Information Lookup Service (ILS): Enables Network Users to look up RSE IP, Location, Status, etc., information.

• Communication Service (Comms): Enables data communications between vehicles and Network Servers

• Positioning Service (POS): receives data from external sources (small-scale High-Accuracy Differential GPS) and delivers it via the RSEs to OBEs that can then use the data to improve the accuracy of their GPS position estimates.

90

Data from three sets of trials

• On the Michigan testbed, three sets of trials were conducted– POC trials (2008)

– NCAR trials (2009)

– NCAR trials (2010)– NCAR trials (2010)

• Data available to researchers:– https://datacapture.noblis.org/content/michigan-testbed-imt-prototype-data-environment-available

• Our analysis appears in a paper in IEEE IWCMC 2011

91

OBE architecture

92

OBE description

• EuroTech DuraCOR processing unit– Ruggedized off-the-shelf platform

– Intel 400 MHz processor, 256 MB RAM, 2 GB disk

– Ports• eight serial ports, two controller area network (CAN) interfaces, four USB ports, 10/100 Ethernet ports, VGA, audio, and four USB ports, 10/100 Ethernet ports, VGA, audio, and keyboard/mouse interfaces.

– GPS device internal to processing unit

• External GPS receiver to improve position accuracy

• Two Mini-PCI expansion ports: DSRC card (Atheros chipset) and security accelerator

• OS: Wind River Linux

93

OBE Software

94

Open Services Gateway Initiative (OSGi) framework

• Communications manager: application and message managers (interface with applications), and transport channel (interface with WAVE/DSRC radio)

• Positioning service: uses both the external and internal GPS receivers, interfacing with a GPS daemon (in Linux O/S)

• Human Machine Interface (HMI) manager: visual and audible • Human Machine Interface (HMI) manager: visual and audible messages to the driver, and supports prioritization of display messages

• Security services: certificate management, 1609.2 mechanisms for signing and/or encrypting messages

• Vehicle interface service: offers applications a socket interface (with a new protocol family PF CAN for Controller-Area Network bus) to obtain data collected by in-vehicle sensors.

95

RSE software

96

RSE hardware: KapschRSE, SDN, ENOC Software: Booz Allen Hamilton

RSE software

• Proxy manager: provides a simple management service to control the various proxy applications resident in the RSE from the ENOC

• Radio handler: communications management • Radio handler: communications management for the various proxy applications resident in the RSE

• DSRC Radio Stack: hybrid hardware/software implementation of 1609/802.11p protocols

97

RSE software

• Security: VPN client for communications with SDN + 1609.2 security libraries and the certificate manager + a local IP-based encryption/decryption capability to protect probe data over the airprotect probe data over the air

• HMM: monitors the health, provides for fault diagnosis, and provides an SNMP agent to update various MIBs associated with performance and fault isolation monitoring.

98

Results and findings

• Primary goals mostly met: – Validate Standards

– Provide Core Services

– Support Applications

– Demonstrate Security and Privacy

99

– Demonstrate Security and Privacy

From Booz Allen Hamilton Executive Summary


• DSRC radio:– DSRC range: I2V: 1100m and V2I: 400m

– Communication quality was reduced by an “unbalanced link” situation whereby the OBE would commence transmission of data after coming into the range of an RSE, but at a distance too far for the RSE to receive the OBE’s data (VDTLS handshake resolved this in POC)

– Overlapping range of multiple RSEs: highlighted an issue involving

100

– Overlapping range of multiple RSEs: highlighted an issue involving prioritization and service selection

• Probe Data Service:– Initial PDS tests involving vehicles equipped with OBEs showed probe data loss rates greater than 60 percent. Implementation of VDTLS greatly improved the probe data loss rates by requiring the OBE and RSE to set up a VDTLS connection before transmitting probe data.

• Communications Service:– Management of network communications resources for multiple simultaneous applications is more complex than expected.

From Booz Allen Hamilton Executive Summary


• Positioning service:– Currently, commercially feasible positioning technologies in vehicles do not support lane-level accuracy, which is required for some applications. Commercial products from two different vendors were used in the testing, and neither one met the lane‐level accuracy requirement.neither one met the lane‐level accuracy requirement.

• Security and privacy:– By provisioning “anonymous certificates,” the VII POC certificate authority enabled anonymity and privacy for vehicle‐to‐vehicle communication.

– Demonstrated the successful interoperability of the 1609.3 (network) and 1609.2 (security) protocols for providing POC security services using WAVE.

101From Booz Allen Hamilton Executive Summary

Two other findings

• V‐DTLS allows only one vehicle to send probe data to an RSE at a time– No MAC-layer collisions between probe data messages

• Java used in POC implementation is not ‐

• Java used in POC implementation is not suitable for sending/receiving low‐latency messages such as SignalPhaseAndTiming/Geographic Information (SPAT/GID) message and heartbeat, as it has too much overhead.

102From Booz Allen Hamilton Executive Summary

Recommendations

• Communications:– 1609.3 needs to include measures of signal quality and reliability: avoids problems of a user joining a service that is too distant to be used reliably

– Need arbitration between multiple services available from multiple providers (when within range of multiple from multiple providers (when within range of multiple RSEs)

– Applications should be able to decline services, suppress service notifications, to query available services, and vote to arbitrate between competing services

– CSMA window size should take into account CCH/SCH time interval synchronization

– Message priority needs to be re-thought

103From VIIC Results and Findings

Recommendations

• Positioning:– Need system requirements for position accuracy reported by user devices (specific method should be left unprescribed)

• Security:– Need more threat analysis

– Two secure communications protocols (V‐HIP and V‐DTLS) developed for the POC, and optimized for use with the WAVE/DSRC 1609

‐ ‐

for the POC, and optimized for use with the WAVE/DSRC 1609 protocols, need to be further developed with the end goal of submission to the appropriate standards bodies

• Probe Data Service:– Rules to maintain user-privacy very complex

– Not clear if collecting this volume of data is necessary or useful

– PDM needs more thought: multiple directives from different requesters

• Heartbeat service: – Timing anomalies (CPU usage, parallel threads)

– Need timeliness requirements to prevent erroneous information

104From VIIC Results and Findings

VII Calif. Test Bed Infrastructure

•Access to 60 miles of Right-of-Way– Three, parallel, 20-mile long North/South routes: US 101; SR 82 (El Camino Real); and I-280

•14 Road Side Equipment (RSE) sites are installed and operating, with approved FCC licenses– Mix of freeway / intersection locations

•26 more RSE sites have been selected and surveyed•26 more RSE sites have been selected and surveyed– Installation of RSEs will continue through 2008

•Backhaul: wired (T1 lines) and wireless (3G cellular; WiMAX, Municipal WiFi) – Communications technology choice is site dependent

•Back End Data Servers– “Service Delivery Node” located at the 511 TIC in Oakland– IP-based; additional servers can be located anywhere

From Susan Dickey’s 2008 talk

Connected Traveler($12.4M project, started Apr. 08)

106Bart Cima, IBI group, 2008 talk

EU and Japan testbeds

• European projects:– E-Safety: CVIS, SAFESPOT and COOPERS; http://www.ibtta.org/files/PDFs/Toulminet_Gwenaelle.pdf

– More projects listed in Car-to-Car Consortium web site: http://www.car-to-car.org/index.php?id=6&L=0

• Japan projects:• Japan projects:– AHS, Advanced Safety Vehicle (ASV), Driving Safety Support Systems (DSSS)

– Smartway project, http://www.nilim.go.jp/japanese/its/3paper/pdf/060131trb.pdf

107

Outline

• DSRC


– IEEE 1609.1-1609.4

– SAE J2735

108

– SAE J2735


� Equipment


• Summary


DSRC Product Vendors

• Kapsch – used in US VII testbeds

• Savari – used in CA SafeTrip-21 and Arizona E-VII

• DSRC Consortium: Raytheon, Sirit, Transcore, Mark IV

• Arada• Arada

• TechnoCom and Card Access

• Econlite, Q-Free, IRD, EFKON

• Oki Electric

• Others: Shenzhen Genvict, Sumitomo, Toshiba, Motorola

109http://www.researchandmarkets.com/reports/669645

Kapsch TrafficCom

• Products– Multiband Configurable Networking Unit (MCNU) R1551 – RSU

– eWAVE (Embedded WAVE) module: to create OBUs

– Incident detection system with video analysis

– Smart traffic sensor: highly-compact, intelligent video sensor for automatic detection and analysis for traffic safety for automatic detection and analysis for traffic safety applications

– Telematics platform: modular software system for implementing secondary telematics applications on basis of the Kapsch toll system

– WAVE starter kit: sophisticated hardware and software platform for application testing

• http://www.kapsch.net/US/EN/KTC/Pages/default.aspx

• Kapsch group has other products in GSM, access, etc.

110

Kapsch RSUMultiband Configurable Networking Unit

• Implements IEEE 802.11p and 1609.2-.4, SAE J2735

• Installed on traffic poles, street signs and highways

• Two high-speed Ethernet ports and two wireless interfaces

• Built-in GPS receiver• Built-in GPS receiver

• Linux host – for application development

• Several radio bands supported (2.4-5.925 GHz range)

• IPv4 and IPv6 routing

• FTP and web servers

• Used in VII Proof-of-Concept testbeds

111

Kapsch applications

• Electronic Toll Collection

• E-Commerce

• Vehicle Safety/Crash Avoidance

• Emergency & Transit Vehicle• Emergency & Transit Vehicle

• Signal Preemption

• Traffic and Traveler Information

• Commercial Vehicle & Fleet Management

• Automotive OEM/Telematics

112

Savari MobiWAVETM OBU &StreetWAVETM RSU

• Linux systems

• DSRC/WiFi/3G radios, Ethernet & Bluetooth

• GPS receiver

• IEEE 802.11p, 1609.3 & .4

• Interoperable with Kapsch MCNU and Denso • Interoperable with Kapsch MCNU and Denso WSU, and Econolite, Siemens traffic controllers

• Touch-panel display

• Web based management

• SDK for application development

• Savari: supplier for the USDOT's California SafeTrip-21 and Arizona’s E-VII

113

Applications identified in Savari’s web site

• Mobility– Intelligent ramp metering

– Intelligent signal control

– Traffic congestion data collection

– Traffic signal priority for emergency and transit vehicles

– Crash data, amber alert dissemination– Crash data, amber alert dissemination

– Parking spot locator

• Safety– Traffic signal violation warning

– Curve over-speed warning

– Left turn assistant

– Stop sign movement assistance

– Approaching emergency vehicle warning

– Pedestrian crossing warning

114

Savari applications contd.

• Electronic Payment– Toll collection, Open road tolling, Gas payment

– Drive through payment, Parking lot payment

• Outdoor Networks– Public WiFi network connectivity

– Public safety first responder networks– Public safety first responder networks

– Transportation system monitoring

– Telemetry

– Mobile security and surveillance

115

DSRC consortium

• Raytheon, Sirit, Transcore, Mark IV

• Raytheon HTMS (www.raytheon.com/htms)– Highway Transportation Management Systems (HTMS)

– Electronic toll systems

• Sirit:• Sirit:– focussed on Automatic Vehicle Identification, Parking & Access Control, Asset Management and Supply Chain Systems

• Transcore:– RFID and vehicle tracking

– ITS system integration services

116

Arada Systems

• LocoMate™ - OBU and RSU

• Atheros’ MiniPCI AR5414 based WLAN chipset on the AR7100 platform (Atheros' wireless network processors)

• US DSRC• US DSRC

• 802.11p, 1609.3/.4

• Channel switch time <= 3ms

• http://www.aradasystems.com

117

Technocom and Card Access

• March 27, 2007 alliance formed

• Card Access: hardware for WAVE/DSRC

• TechnoCom: software solutions for WAVE/DSRC WAVE/DSRC

• http://www.technocom-wireless.com

118

Econolite

• Autoscope video detection system

• ASC/3 traffic controller: signal priority demonstration by combining with DSRCwith DSRC

• Data collection and management service

• http://www.econolite.com/

119

Q-Free

• Q-Free – products and solutions for– Road user charging and traffic surveillance

– Applications• electronic toll collection for road financing, congestion charging

• truck-tolling, law enforcement and parking/access control

• Technologies• Technologies– DSRC (tag)

– Automatic Number Plate Recognition (ANPR), also called Automatic License Plate Recognition (ALPR)

– GNSS (Global Navigation Satellite System)

• http://www.q-free.com

120

International Road Dynamics (IRD)

• Traffic data collection systems

• Sensors: in-road, on-road, non-intrusive

• Toll Treadle Systems • Toll Treadle Systems

• Vehicle Weighers

• Traffic control safety

http://www.irdinc.com/products

121

Efkon Business Units

• ITS payment systems

• Radio communications for critical applications (public safety)

• Plaza based toll turn key systems

• Satellite applications

• T,TT - Transport, Traffic Telematics– Toll and ETC Systems

– Operations

– Traffic Telematics (ISO-CALM products and high level SAT solutions)

– Traffic Law Enforcement Systems (Red light and speed violations, WIM)

– AFC-Automated Fee Collection System

– Parking and Access

– Traffic Management

• Services: tolling contract in Ireland

• Products: OBUs

122

Oki Electric

• Oki DSRC technology

• Management System of Parking Lot by Monthly Contract

• Management System of Employee Parking Lot

• Management System of Exclusive Parking Lot for the Physically Disabled

• Pay Parking Lot System for Stores• Pay Parking Lot System for Stores

• Gate System

• Self Service Gas Station Payment System

• CRM System

• http://www.oki.com/jp/SSC/ITS/eng/dsrc_prkidxe.html

123

Outline

• DSRC


– IEEE 1609.1-1609.4

– SAE J2735

124

– SAE J2735


• Equipment

� Research literature

• Summary


Research literature surveyed

• Tutorial papers [4]

• Simulation platforms and tools [7]

• Simulation studies – mostly 802.11p [10]

• Experimental studies [2]

• Testbeds/trials [7]• Testbeds/trials [7]

• Vehicular Ad Hoc Network (VANET) routing [13]

• Transport protocols [3]

• MAC protocols [5]

• Security [2]

Total: 53

125

Summary

• DSRC

• IEEE 802.11p, 1609.1-4

• SAEJ2735

• Equipment• Equipment

• Testbeds & Trials


• Background on 802.11

126

Background on IEEE 802.11

• Wireless LANs

• Popularly called Wifi

Version Frequency Rate Physical-layer

127

layer

802.11b 2.4GHz 11Mbps FH and DS

802.11g 2.4GHz 54Mbps OFDM

802.11a 5 GHz 54Mbps OFDM

OFDM: Orthogonal Frequence Division MultiplexingFH: Frequency HoppingDS: Direct Sequence (spread spectrum)

Distributed Coordination Function (DCF) – basic mode

• This mode of 802.11 is a random access MAC• When a node needs to send data, it senses the medium. If idle, wait for a period of DIFS and if the medium is still idle after DIFS, send immediately.

• If when the medium is sensed it is busy; then

128

• If when the medium is sensed it is busy; then– wait for medium to be idle for a DIFS (DCF IFS) period – then decrement backoff timer until

• medium becomes busy again; freeze timer, OR• timer reaches 0; transmit frame

– if two stations have their timers reach 0; collision will occur; for every retransmission attempt, increase the contention window (CW), idle period after a DIFS, exponentially; 2i –1 starting with CWmine.g., 7, 15, 31.

DCF mode transmissionwithout RTS/CTS

source

destination

DIFSData

AckSIFS

CW

129

otherNAV

Defer access

DIFSCW

Random backoff time

Network Allocation Vector (NAV):The source computes time to transmit the frame as it knows the size and transmission rate. This value is placed in the “Duration field” of the 802.11 MAC header. Other stations use this value to set the NAV value, during which time they defer access of the me.RTS/CTS: Request to send/Clear to send

DCF MAC

130

• Send immediately (after DIFS) if medium is idle• If medium was busy when sensed, wait a CW after it becomes idle (because many stations may be waiting when medium is busy; if they all send the instant the medium becomes idle, chances of collision are high)

802.11b DS

• Takes a 1Mbps data signal and converts it into a 11 Mbps signal

• 11 channels in the 2.4Ghz band (5Mhz spacing)

• Channels separated by center frequencies at least 30Mhz apart can operate without interference

131

30Mhz apart can operate without interference

• If total bandwidth is only 83.5 Mhz, only three 802.11 LANs using DS can have overlapping cells

• FCC only allocates between 2412 and 2462

Ad-hoc vs. infrastructure based

• Ad-hoc– No fixed network infrastructure needed– A wireless endpoint sends and all nodes within range can pick up signal

– Each packet carries destination and source address

132

– Each packet carries destination and source address

– How do you know addresses of nodes in your region?

• Infrastructure mode– Access point receives and relay packets

Infrastructure based architecture

Distribution System (DS)

Access points (AP)

133

• Independent BSS (IBSS): has no access point– adhoc mode; only wireless stations

• Infrastructure BSS defined by stations sending Associations to register with an access point

Basic Service

Set (BSS)

802.11 MAC frame format

Framecontrol

Duration/ID

Address1

Address2

Address3

Address4

Seq.control

Frame body FCS

40-2312666 6 222bytes

MAC header

134

Protocolversion

Type Sub-type ToDS

FromDS

MoreFrag

MoreData

Retry PwrMgmt

WEP Order

22bits 4 1 1 1 1 1 1 1 1

WEP: Wired Equivalent Privacy - encryption scheme FCS: Frame Check Sequence (for error detection, like CRC)

Field explanations

• Type/sub-type field indicates the type of message– Management:

• Association/Authentication/Beacon

– Control

135

– Control• RTS, CTS, CF-end, ACK

– Data• Data only, or Data + CF-ACK, or Data + CF-Poll or Data + CF-Poll + CF-ACK

CF: Contention Free mode: the access point polls one station after another

Field explanations

• To DS and From DSTo DS From DS Message

0 0 station-to-station frames in an IBSS;

all management/control frames

0 1 From AP to station

136

1 0 From station to AP

1 1 From one AP to another on DS

• More Frag: 802.11 supports fragmentation of data• More Data: In polling mode, station indicates it has more data to

send when replying to CF-POLL• RETRY is 1 if frame is a retransmission; WEP (Wired Equivalent

Privacy)• Power Mgmt is 1 if in Power Save Mode; Order = 1 for strictly

ordered service

Field explanations

• Duration/ID: Duration in DCF mode (used in NAV)/ID is used in PCF mode

• Address fields

To DS From DS Address 1 Address 2 Address 3 Address 4

0 0 DA SA BSSID N/A

137

0 0 DA SA BSSID N/A

0 1 DA BSSID SA N/A

1 0 BSSID SA DA N/A

1 1 RA TA DA SA

RA: Receiver Address TA: Transmitter AddressDA: Destination Address SA: Source AddressBSSID: MAC address of AP in an infrastructure BSS

Field explanations

Sequencenumber

Fragmentnumber

4 bits 12 bits

DurationFramecontrol

2 2

RA FCS

6 4 bytes

Sequence control field ACK frame

138

• Sequence control– Sequence number remains the same for all retransmissions of a data unit

– Sequence numbers of all fragments of a data unit are the same– Fragmentation Threshold determines size of fragments– Maximum size of MAC frame payload is 2312 bytes– Not included in ACK frame

• Broadcast and multicast frames are not ACK’ed

Features of 802.11 MAC protocol

• Supports MAC functionality (address fields)

• Error detection (FCS)

• Error correction (sequence numbers & ACK)

• Fragmentation (More Frag)

139

• Fragmentation (More Frag)

• Flow control: stop-and-wait

Registration

• Why should an endpoint register with the access point:– allows the access point to decide whether or not to send a frame on its wireless link based on the destination MAC address in the frame header

140

destination MAC address in the frame header

• Association, reassociation and disassociation

IPv6 background

• RFC 4291: IPv6 Addressing Architecture– Three types of unicast addresses

• Global

• Site local

• Link local• Link local

• RFC 4862: IPv6 Stateless Address Autoconfiguration

• RFC 4861: Neighbor Discovery for IP version 6 (IPv6)– Router advertisement format

141

Global-use IPv6 (unicast) address formatn bits m bits 128-n-m bits

Interface IDsubnet IDglobal routing prefix

Interface ID: a1:67:89:ff:fe:9f:ae:b4

MAC address: a1:67:89:9f:ae:b4

insert two octets 0xff and 0xfe

• Global address– significant difference from IPv4

– interface addresses are derived from a global routing prefix/subnet ID (effectively an identifier for a “network”) and Ethernet MAC address

142

MAC address: a1:67:89:9f:ae:b4

Stateless autoconfiguration

• Prefixes are obtained from Router Advertisements– which are sent on all-nodes multicast address

– Prefix information option field contains prefix information information

• Nodes receiving router adv. use their own interface MAC address with the received prefix to create their global IPv6 address

• Use Neighbor solicitation messages to detect duplicate addresses

143

Local-use (unicast) address formats

10 bits 54 bits 64 bits

10 bits 54 bits 64 bits

Interface ID01111111010Link-localaddress

Site-local

• Link-local: when no routers are present

• Site-local: for addressing inside a site without a global prefix

144

Interface IDsubnet ID1111111011Site-localaddress