Wireless Networks and Protocols MAP-Tele Manuel P. Ricardo - - PowerPoint PPT Presentation

WNP-MPR-Fundaments 1

Wireless Networks and Protocols

MAP-Tele Manuel P. Ricardo

Faculdade de Engenharia da Universidade do Porto

WNP-MPR-Fundaments 2

Topics Scheduled for Today

 Introduction to Wireless Networks and Protocols  Fundamentals of wireless communications

» Transmission » Wireless data links and medium access control » Networking » Mobility concepts and management » Research issues

Physical Network Transport Data link Application Mobility Security Quality of Service

WNP-MPR-Fundaments 3

Wireless Data Link, Wireless Medium Access Control

WNP-MPR-Fundaments 4

 How to model an adaptive wireless data link layer?  How to implement duplex communications in a wireless link?  How to enable multiple access?  What is a random access method?  What is an hidden node? What is an exposed node?  Why is collision avoidance important?  How to avoid the hidden node?  How does the CSMA/CA work?  What is the minimum distance between nodes in CSMA/CA?  What are the services possibly provided by RLC?

WNP-MPR-Fundaments 5

Radio Link

 Radio link affected by propagation environment  Modulation, coding, power

used to overcome avoiding radio adversities

 Service offered by the (wireless) Physical layer

» characterized by data rate (bit/s) and bit error ratio » modern technologies  depends on the radio link operation modes

 Operation mode

» pair (modulation, code), typically » High-Speed Downlink Packet Access (HSDPA/UMTS)  12 modes » IEEE 802.11a  7 modes

Tx Rx

    I N S SNIR

WNP-MPR-Fundaments 6

Radio Link Model – Continuous Time Markov Chain

 Radio link modeled as a Markov Chain  Markov chain state

» Operation mode (modulation, code) » Si  » Characterized by transmit bit rate ri and bit error ratio ei

 Markov chain transition rates

» Process moves only to neighbor states » Estimating the transition rates:

1 2 M-1 … l0 m1 l1 m2 l2 m3 lM-2 mM-1 r0 e0 r1 e1 r2 e2 rM-1 eM-1 Adaptive Transmitter Physical layer

k mk lk  k k+1 n

k+1

n-

k

WNP-MPR-Fundaments 7

Frame Error Ratio, pE

 Adaptive transmission tends to maintain BER constant

by controlling modulation, coding, tx power, …

 Frame Error Ratio

– pe()- bit error ratio of the uncoded system – Gc() - coding gain – Lp – packet length in bits

 If different codes are used for header and information fields

L

BER FER ) 1 ( 1

• 

e

p

WNP-MPR-Fundaments 8

Information Rate (Goodput)

Mean Information rate 



• 



1 M i i i c

r R 

number of bits/symbol Symbol duration



redundant bits introduced by codes



1 2 M-1 … l0 m1 l1 m2 l2 m3 lM-2 mM-1 r0 e0 r1 e1 r2 e2 rM-1 eM-1 Adaptive Transmitter Physical layer

WNP-MPR-Fundaments 9

How to transmit signals in both directions simultaneously?

WNP-MPR-Fundaments 10

Duplex Transmission

 Duplex – transference of data in both directions

Uplink and Downlink channels required

 Two methods for implementing duplexing

» Frequency-Division Duplexing (FDD)

– wireless link split into frequency bands – bands assigned to uplink or downlink directions – peers communicate in both directions using different bands

» Time-Division Duplexing (TDD)

– timeslots assigned to the transmitter of each direction – peers use the same frequency band but at different times

WNP-MPR-Fundaments 11

Duplex Transmission

WNP-MPR-Fundaments 12

How to enable one base station to communicate simultaneously with multiple mobile nodes?

WNP-MPR-Fundaments 13

Multi-Access Schemes

 Multi-access schemes

» Identify radio resources » Assign radio resources to users/terminals using some criteria

 Types of multi-access schemes

» Frequency-Division Multiple Access (FDMA)

resources divided in portions of spectrum (channels)

» Time-Division Multiple Access (TDMA)

resources divided in time slots

» Code-Division Multiple Access (CDMA)

resources divided in orthogonal codes

» Space-Division Multiple Access (SDMA)

resources divided in areas

WNP-MPR-Fundaments 14

FDMA

» Signal space divided along the frequency axis

into non-overlapping channels

» Each user assigned a different frequency channel » The channels often have guard bands » Transmission is continuous over time

channel k channel 2 time code channel 1

WNP-MPR-Fundaments 15

TDMA

» Signal space divided along the time axis

into non-overlapping channels

» Each user assigned a different cyclically-repeating timeslot » Transmission not continuous for any user » Major problem

synchronization among the users in the uplink channels users transmit over channels having different delays uplink transmitters must synchronize

time code … …

WNP-MPR-Fundaments 16

CDMA

 Each user assigned a code to spread his information signal

» Multi-user spread spectrum (Direct Sequence, Frequency Hopping) » The resulting spread signal

– occupy the same bandwidth – transmitted at the same time

 Different bitrates to users

 control length of codes

 Power control required in uplink

» to compensate near-far effect » If not, interference from close user swamps signal from far user

time code channel 1 channel 2 channel k …

WNP-MPR-Fundaments 17

SDMA

 SDMA uses direction (angle) to assign channels to users  Implemented using sectorized antenna arrays

» the 360º angular range divided in N sectors » TDMA or FDMA then required to channelize users

BS

MT-1 MT-2 MT-k

WNP-MPR-Fundaments 18

Combined Multi-Access Techniques

 Current technologies  combinations of multi-access techniques

» GSM: FDMA and then TDMA to assign slots to users

 The cell concept  combined multi-access technique

» SDMA + FDMA

 Cellular planning

f1 f3 f3 f2 f2 f1 f3 f1 f3 f3 f2 f2 f1 f3 f1 f3 f3 f2 a) Group of 3 cells f4 f2 f6 f3 f5 f2 f1 f6 f3 f5 f7 f2 f3 f4 f5 f7 f2 f1 b) Group of 7 cells c) Group of 3 cells, each having 3 sectors f2 f3 f1 f2 f3 f1 f2 f3 f1 f5 f6 f4 f5 f6 f4 f8 f9 f7 f8 f9 f7 f8 f9 f7

WNP-MPR-Fundaments 19

Wireless Medium Access Control

 Medium Access Control (MAC)

assigns radio resources to terminals along the time

 3 type of resource allocation methods

» dedicated assignment

resources assigned in a predetermined, fixed, mode (TDMA)

» random access

terminals contend for the medium (channel)

» demand-based

terminals ask for reservations using dedicated/random access channels

WNP-MPR-Fundaments 20

Hidden, Exposed and Capture Nodes

 Signal strength decays with the transmitter-receiver distance  Carrier sensing depends on the position of the receiver  MAC protocols using carrier sensing  3 type of problematic nodes

» hidden nodes

– C is hidden to A

» exposed nodes

– C is exposed to B

» capture nodes

– D captures A

A C B D

WNP-MPR-Fundaments 21

Hidden, Exposed and Capture Nodes

 Hidden node  C is hidden to A

» A transmits to B; C cannot hear A » If C hears the channel it thinks channel is idle; C starts transmitting »  interferes with data reception at B » In the range of receiver; out of the range of the sender

 Exposed node  C is exposed to B

» B transmits to A; C hears B; C does not transmit; » but C transmission would not interfere with A reception » In the range of the sender; out of the range of the receiver

 Capture  D captures A

» A and D transmit simultaneously to B; but signal strength from D much higher than that from A

A C B D

WNP-MPR-Fundaments 22

MAC Protocols - Aloha, S-Aloha, CSMA

 Aloha  Efficiency of 18 %

if station has a packet to transmit

 transmits the packet  waits confirmation from receiver (ACK)  if confirmation does not arrive in round trip time, the station

computes random backofftime  retransmits packet

 Slotted Aloha  Efficiency of 37 %

stations transmit just at the beginning of each time slot

 Carrier Sense Multiple Access (CSMA)  Efficiency of 54 %

– station listens the carrier before it sends the packet – If medium busy  station defers its transmission

 ACK required for Aloha, S-Aloha and CSMA

WNP-MPR-Fundaments 23

Aloha versus Time Division Multiplexing

WNP-MPR-Fundaments 24

CSMA/CD – Not Used in Wireless

 CDMA/Collision Detection  Efficiency < 80%

– station monitors de medium (carrier sense)

 medium free  transmits the packet  medium busy  waits until medium is free  transmits packet  if, during a round trip time, detects a collision

 station aborts transmission and stresses collision (no ACK packet)

 Problem of CDMA/CD in wireless networks

Collision detection near-end interference makes simultaneous transmission and reception difficult

WNP-MPR-Fundaments 25

How to minimize collision in a wireless shared medium?

WNP-MPR-Fundaments 26

CSMA with Collision Avoidance (CSMA/CA)

S2

DIFS

S3 S1

DATA DIFS S2-bo DIFS S3-bo S3-bo-e S3-bo-r DATA DIFS S3-bo-r DATA

• Packet arrival

DATA

• Transmission of DATA

DIFS

• Time interval DIFS

S2-bo

• Backoff time, station 2
• Elapsed backoff time, station 3

S3-bo-e S3-bo-r

• Remaining backoff time, station 3

WNP-MPR-Fundaments 27

CSMA with Collision Avoidance (CSMA/CA)

 Station with a packet to transmit monitors the channel activity

until an idle period equal to a Distributed Inter-Frame Space (DIFS) has been observed

 If the medium is sensed busy a random backoff interval is

• selected. The backoff time counter is decremented as long as the

channel is sensed idle, stopped when a transmission is detected

• n the channel, and reactivated when the channel is sensed idle

again for more than a DIFS. The station transmits when the backoff time reaches 0

 To avoid channel capture, a station must wait a random backoff

time between two consecutive packet transmissions, even if the medium is sensed idle in the DIFS time

WNP-MPR-Fundaments 28

CSMA/CA – ACK Required

AP

DIFS

S2 S1

SIFS DATA ACK DIFS S2-Backoff SIFS DATA ACK

• Packet arrival

DATA

• Transmission of DATA

DIFS

• Time interval DIFS

WNP-MPR-Fundaments 29

CSMA/CA – ACK Required

 CSMA/CA does not rely on the capability of the stations to detect a collision

by hearing their own transmission

 A positive acknowledgement is transmitted by the destination station to signal

the successful packet transmission

 In order to allow an immediate response, the acknowledgement is transmitted

following the received packet, after a Short Inter-Frame Space (SIFS)

 If the transmitting station does not receive the acknowledge within a specified

ACK timeout, or it detects the transmission of a different packet on the channel, it reschedules the packet transmission according to the previous backoff rules.

 Efficiency of CSMA/CA depends strongly of the number of competing

• stations. An efficiency of 60% is commonly found

WNP-MPR-Fundaments 30

How to enable hidden terminals to sense the carrier?

Hidden node: C is hidden to A

A C B D

WNP-MPR-Fundaments 31

RTS-CTS Mechanism

AP

DIFS

S2 S1

SIFS DATA RTS DIFS S2-bo DATA

• Packet arrival

DATA

• Transmission of DATA

DIFS

• Time interval DIFS

CTS SIFS SIFS ACK

WNP-MPR-Fundaments 32

RTS-CTS Mechanism



For some scenarios where long packets are used or the probability of hidden terminals is not irrelevant, the efficiency of CSMA/CA can be further improved with a Request To Send (RTS) - Clear to Send (CTS) mechanism



The basic concept is that a sender station sends a short RTS message to the receiver

• station. When the receiver gets a RTS from the sender, it polls the sender by sending a

short CTS message. The sender then sends its packet to the receiver. After correctly receiving the packet, the receiver sends a positive acknowledgement (ACK) to the sender



This mechanism is particularly useful to transmit large packets. The listening of the RTS or the CTS messages enable the stations in range respectively of the sender or receiver that a big packet is about to be transmitted. Usually both the RTS and the CTS contain information about the number of slots required to transmit the 4 packets. Using this information the other stations refrain themselves to transmit packets, thus avoiding collisions and increasing the system efficiency.



SIFS are used before the transmission of CTS, Data, and ACK



In optimum conditions the RTS-CTS mechanism may add an efficiency gain of about 15%

WNP-MPR-Fundaments 33

Interference Model – Data and Ack considered

 ti , ri - coordinates of transmitter, receiver of link i  No RTS+CTS considered  If the effect of ACK is also considered

» links i and j may transmit simultaneously if

where,

WNP-MPR-Fundaments 34

Interference Model – Protocol Model

 If D=0, simultaneous transmissions allowed silent links

i i

r t j i dist

• 

) , (

Why?

WNP-MPR-Fundaments 35

Guaranteed Access Control

 Polling

» AP manages stations access to the medium » Channel tested first using a control handshake

WNP-MPR-Fundaments 36

Wireless Radio Link Control

 MAC layer may not always provide acknowledged delivery

e.g., MAC working over dedicated resources (time slot, code)

 Radio Link Control (RLC) sub layer is used in some technologies  Example

» 3 virtual links, represented by 3 RLC instances » RLC uses service provided the MAC sub-layer » Possible functions of this MAC sub-layer

– unacknowledged transfer – selection of appropriate transport format – priority handling between the data flows generated from different RLC instances – multiplexing of information generated by RLC instances into common MAC frames – ciphering of data

WNP-MPR-Fundaments 37

Possible Services Provided by RLC

 Transparent data transfer

» no addition of other information » possible segmentation of the data, forcing transference of short-length packets

 Unacknowledged data transfer

» frames are not acknowledged by the RLC receiver » frame sent by the RLC transmitter has a sequence number » frame arriving with errors at RLC receiver is discarded » upper layer at the receiver knows which frames were discarded » 2 delivery modes at RLC receiver

– Out-of-sequence: frame is delivered to the upper-layer as soon as it is received by the RLC receiver – Duplication avoidance and reordering: frames are delivered by the same order they have been sent and with no duplications

 Acknowledged data transfer

» guarantees error-free and unique delivery » upper layer receiver will get the frames by the correct order » Selective Repeat ARQ is often used » Short frames used, in order to have low FER

WNP-MPR-Fundaments 38

Mobile Networking

Fundaments, IPv6, Mobile IPv6

WNP-MPR-Fundaments 39

 What are the main differences between L2 and L3 networks?  How can a packet switch support mobility?  What is a tunnel? What is a virtual network?  How does IPv6 work?  How does MIPv6 work?  How to optimize an IPv6 route?

WNP-MPR-Fundaments 40

Layered Networking

WNP-MPR-Fundaments 41

Switching - Circuits, Datagram, Virtual Circuits

1 2 4 5 1 2 4 5 1 2 4 5

pak 1 pac 2 pac 3 pak 1 pac 2 pac 3 pak 1 pac 2 pac 3 pak 1 pac 2 pac 3 pak 1 pac 2 pac 3 pak 1 pac 2 pac 3

data

Circuit switching

(e.g. GSM)

Packet switching

(e.g. WLAN)

Virtual circuit switching

(e.g. PDP Context, UMTS) circuit establishment data transference data transference circuit establishment data transference

WNP-MPR-Fundaments 42

Packet Switching

 Technologies: Ethernet, WLAN, 3GPP-LTE, IP  Destination address is used to switch the packet

a

…

input links

…

forwarding table b

1 N

…

N 1

b c a b b c

• utput links

destination address

• utput

link a 1 b N … c 1

WNP-MPR-Fundaments 43

Suppose terminal a moves from port 1 to port 3

What needs to be done, so that terminal a can continue receiving packets?

a

…

input links

…

forwarding table b

1 N

…

N 1

b c a b b c

• utput links

destination address

• utput

link a 1 b N … c 1

WNP-MPR-Fundaments 44

Ethernet Frame

Ethernet

7x 10101010 10101011 Protocolo=IP

WNP-MPR-Fundaments 45

Bridge, Switch

 Interconnects

» 2 LAN technologies (e.g. Ethernet and WLAN) » n segments of the same technology

 Bridge builds forwarding tables automatically  Address learning

» Source Address of received frame is associated to a bridge input port

» station reachable through that port

 Frame forwarding

» When a frame is received, its Destination Address is analysed

– If address is associated to a port  frame forwarded to that port – If not  frame transmitted through all the ports but the input port

MAC

LLC

MAC MAC

RELAY

MAC

LLC

BRIDGE

1 n

switch AP

WNP-MPR-Fundaments 46

Address Learning and Mobility

router 1 8 1 8

switch switch

STA MAC = A 1 8

destination address interface A 1 destination address interface A 1

router

1 8 1 8

switch switch

STA MAC = A 1 8

destination address interface A 8 destination address interface A 8

router 1 8 1 8

switch switch

STA MAC = A 1 8 router 1 8 1 8

switch switch

STA MAC = A 1 8

destination address interface A 8 destination address interface A 8

1 2 3 4

WNP-MPR-Fundaments 47

L2 Networking - Single Tree Required

• Ethernet frame

– No hop-count – Could loop forever – Same for broadcast packet

• Layer 2 network

– Required to have tree topology – Single path between every pair of stations

• Spanning Tree Protocol (STP)

– Running in bridges – Helps building the spanning tree – Blocks ports

L2 Networking - Single Tree Required

WNP-MPR-Fundaments 48

 One bridge/switch simulates multiple LANs / broadcast domains  One LAN may be extended to other bridges

Virtual LANs

S3 S1 S2 va vc S6 S4 S5 vb vc

Preamble

SFD L/T FCS

7 octets

DA=Brdc SA=S3

Pad Data

1 6 6 2 46-1500 4

• ctets

TAG

4

CFI TPID VID=vc

16 3 12

PCP

1

bits

t

WNP-MPR-Fundaments 49

L3 Networking – Packet Formats

Options (variable) Pad (variable) Destination Address Source Address TTL IP identification Protocol IP checksum Flags Fragment offset Length TOS Ver. IHL Data

4 8 16 31

IPv4 IPv6

Destination Address (4 words) Source Address (4 words) Options (variable number) Payload length Hop limit Flow label Ver.

Traf Class

Data

4 8 16 31

Next header

24

WNP-MPR-Fundaments 50

L3 Networking – Router

route table memory CPU forward table forward cache Line Interface MAC memory forward cache Line Interface MAC memory Switch

Third generation

a

… input links …

forwarding table b

1 N

…

N 1

b c a b b c

• utput links

destination address

• utput

link a 1 b N … c 1

WNP-MPR-Fundaments 51

L3 Networking – Multiple Trees

 Every router

» finds the shortest path to the other routers and their attached networks » Calculates its Shortest Path Tree (SPT)

 Routing protocol

» Runs in routers » Helps routers build their SPT » RIP, OSPF, BGP, OLSR, AODV, RPL

Destination Cost NextHop

A 1 A C 1 C D 2 C E 2 A F 2 A G 3 A

B’s routing view

D G A F E B C

WNP-MPR-Fundaments 52

.TCP

 Point to connection between a client and a server; port-to-port  Reliable, flow control  Congestion control

Sender Data (SequenceNum) Acknowledgment + AdvertisedWindow Receiver

WNP-MPR-Fundaments 53

.Multimedia Traffic - Taxonomy

Applications Elastic Intolerant Real time Tolerant Nonadaptive Adaptive Delay adaptive Rate adaptive

(variation of the packet end-to-end delay) (packet loss) (application reaction to packet loss) (type of reaction)

WNP-MPR-Fundaments 54

.RTP+RTCP/UDP

 Multimedia traffic  Application-Level Framing  Data Packets (RTP)

» sequence number » timestamp (app defines “tick”) » transported as UDP packets

 Control Packets (RTCP)

» sent periodically » report loss rate (fraction of packets received since last report) » report measured jitter

WNP-MPR-Fundaments 55

Traditional TCP/IP Communications Stack

T1 IP TCP APP T1 | T2 T2 | T3 IP T3 | T4 IP T5 IP TCP APP

host bridge router router host

T4 | T5

bridge MAC address based switching IP address based switching

Ethernet driver IP TCP

Application Ethernet header IP header TCP header application data Ethernet trailer Ethernet frame IP header TCP header application data IP packet TCP header application data TCP segment application data data

WNP-MPR-Fundaments 56

Tunnel IP-in-IP

T1 IP1 TCP APP T1 | T2 T2 | T3 IP1 T3 | T4 T5 IP2 TCP APP

H1 bridge R1 R2 Server

T4 | T5

bridge

IP2 IP2 IP1

• uter IP header inner IP header

data DA= IP address of R2 (IP1) SA= IP address of H1 (IP1) TTL IP identification IP-in-IP IP checksum flags fragment offset length TOS ver. IHL DA= IP address of Server (IP2) SA= IP address of H1 (IP2) TTL IP identification

• lay. 4 prot.

IP checksum flags fragment offset length TOS ver. IHL TCP/UDP/ ... payload

WNP-MPR-Fundaments 57

.Tunnel PPP over IP (E.g PPTP)

» GRE

– virtual point-to-point link – encapsulates a variety of network layer protocols – routers at remote points – over an IP network

» PPP adequate for

– Authentication – Transporting IP packets

T1 IP1 PPP IP2 T1 | T2 T2 | T3 IP1 T3 | T4 T5 IP2 TCP APP

H1 bridge R1 R2 Server

T4 | T5

bridge

GRE IP2 IP1 TCP APP GRE PPP

WNP-MPR-Fundaments 58

IPv6

WNP-MPR-Fundaments 59

The Need of a New IP

 IPv4

» Small addressing space (232 bits) » Non-continuous usage » Some solutions used to overcome these problems

private networks (NAT), classless networks (CDIR)

 IETF developed new IP version: IPv6

» Same principles of IPv4 » Many improvements » Header re-defined

 IPv6 is essential for mobile communications

Internet of things

WNP-MPR-Fundaments 60

IPv6 – Improvements

» 128 bit addresses (16 octets, 8 shorts ). No classes » Better QoS support (flow label) » Native security functions (peer authentication, data encryption) » Autoconfiguration (Plug-n-play) » Routing » Multicast

WNP-MPR-Fundaments 61

 8 x 16 bit, hexadecimal. Separated by : 47CD : 1234 : 3200 : 0000 : 0000 : 4325 : B792 : 0428  Compressed format: FF01:0:0:0:0:0:0:43  FF01::43  Compatibility with IPv4: 0:0:0:0:0:0:13.1.68.3 or ::13.1.68.3  Loopback address: ::1  Network prefix described by / , same as IPv4 » FEDC:BA98:7600::/40  network prefix = 40 bits

Address Representation

WNP-MPR-Fundaments 62

.Reserved Addresses

Allocation Prefix Fraction of (binary) Address Space

• Unassigned

0000 0000 1/256 Unassigned 0000 0001 1/256 Reserved for NSAP Allocation 0000 001 1/128 Unassigned 0000 01 1/64 Unassigned 0000 1 1/32 Unassigned 0001 1/16 Global Unicast 001 1/8 Unassigned 010 1/8 Unassigned 011 1/8 Unassigned 100 1/8 Unassigned 101 1/8 Unassigned 110 1/8 Unassigned 1110 1/16 Unassigned 1111 0 1/32 Unassigned 1111 10 1/64 Unassigned 1111 110 1/128 Unassigned 1111 1110 0 1/512 Link-Local Unicast Addresses 1111 1110 10 1/1024 Site-Local Unicast Addresses 1111 1110 11 1/1024 Multicast Addresses 1111 1111 1/256

WNP-MPR-Fundaments 63

Addresses – Link-Local, Site-Local, Global Unicast, Anycast

 Link-Local

» Used for communication between hosts in the same LAN /link » Address built from network interface MAC address » Routers do not foward packets having a Link-Local destination address

 Global Unicast

» Global addresses » Address: network prefix + computer identifier » Structured prefixes » Network aggregation; less entries in the router forwarding tables

 Multicast

» Group address; packet received by all the members of the group

 Anycast

» Group address; packet is received by any (only one) member of the group

WNP-MPR-Fundaments 64

Address Formats

Global Unicast address (2000::/3) Link-Local Unicast address (fe80::/10) Anycast address Multicast Address Scope – link, site, global (ff::/8)

001 global rout prefix subnet ID interface ID n bits m bits 128-n-m bits 1111111010 interface ID 10 bits 54 bits 64 bits subnet prefix 00000000000000 n bits 128-n bits 11111111 group ID 8 bits 112 bits flags 4 scope 4

WNP-MPR-Fundaments 65

.Packet Headers - IPv4 and IPv6

Version HLen TOS Length Ident Flags Offset TTL Protocol Checksum SourceAddr DestinationAddr Options (variable) Pad (variable) 4 8 16 19 31 Data Version

Traffic Class

Flow Label Payload Lengtht Next Header Hop Limit SourceAddr (4 words) DestinationAddr (4 words) Options (variable number) 4 8 16 24 31 Data

IPv4 IPv6

WNP-MPR-Fundaments 66

IPv6 Header

 Flow label  identifies packet flow

» QoS, resource reservation » Packets receive same service

 Payload length

» Header not included

 Hop limit = TTL (v4)  Next header

» Identifies next header/extension header

 Options  included as extension headers

Version

Traffic Class

Flow Label Payload Lengtht Next Header Hop Limit SourceAddr (4 words) DestinationAddr (4 words) Options (variable number) 4 8 16 24 31 Data

WNP-MPR-Fundaments 67

Extension Headers

IPv6 Header

Next Header = TCP

TCP header + data Routing Header

Next Header = TCP

TCP header + data IPv6 Header

Next Header = Routing

IPv6 Header

Next Header = Routing

Routing Header

Next Header = Fragment

Fragment Header

Next Header = TCP

Fragment of TCP header + data IPv6 Hop-by-hop TCP Destination Routing Fragment Authenticate. ESP

WNP-MPR-Fundaments 68

.Extension Headers

 Hop-by-hop

» additional information, inspected by every node traversed by the packet » other extension headers inspected only at the destination/pre-defined nodes

 Destination

» information for the destination node

 Routing

» list of nodes to be visited by the packet

 Fragmentation

» made by the source, that must also find MPU

 Authentication

» signature of packet header

 ESP

» data encryption

WNP-MPR-Fundaments 69

.Example of Lab Network

quadro porta banc_3 banc_6 pc3---[HUB]---pc2----+ +----pc2---[HUB]---pc3 2000:0:0:3::/64 | | 2000:0:0:6::/64 | | banc_2 | | banc_5 pc3---[HUB]---pc2--[HUB]-+ +-[HUB]--pc2---[HUB]---pc3 2000:0:0:2::/64 | | | | 2000:0:0:5::/64 | | | | banc_1 | | | | banc_4 pc3---[HUB]---pc2----+ | | +----pc2---[HUB]---pc3 2000:0:0:1::/64 | | 2000:0:0:4::/64 | | 2000:0:0:e::/64| |2000:0:0:d::/64 | | [routerv6] 2000:0:0:1::1 2000:0:0:1::aa 2000:0:0:e::1

WNP-MPR-Fundaments 70

.Configuration examples in Linux

tux13:~# /sbin/ifconfig eth0 inet6 add 2000:0:0:1::1/64 tux13:~# ifconfig eth0 eth0 Link encap:Ethernet HWaddr 00:C0:DF:08:D5:99 inet addr:172.16.1.13 Bcast:172.16.1.255 Mask:255.255.255.0 inet6 addr: 2000:0:0:1::1/64 Scope:Global inet6 addr: fe80::2c0:dfff:fe08:d599/10 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:81403 errors:0 dropped:0 overruns:0 frame:0 TX packets:2429 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 RX bytes:4981344 (4.7 MiB) TX bytes:260692 (254.5 KiB) Interrupt:5 tux13:~# /sbin/route -A inet6 add 2000::/3 gw 2000:0:0:1::aa tux13:~# route -A inet6 Kernel IPv6 routing table Destination NextHop Flags Metric Ref Use Iface ::1/128 :: U 0 0 0 lo 2000:0:0:1::1/128 :: U 0 0 0 lo 2000:0:0:1::/64 :: UA 256 0 0 eth0 2000::/3 2000:0:0:1::aa UG 1 0 0 eth0 fe80::2c0:dfff:fe08:d599/128 :: U 0 0 0 lo fe80::/10 :: UA 256 0 0 eth0 ff00::/8 :: UA 256 0 0 eth0 ::/0 :: UDA 256 0 0 eth0

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.Identifier IEEE EUI-64

Method to create a IEEE EUI-64 identifier from an IEEE 48bit MAC identifier. This is to insert two octets, with hexadecimal values of 0xFF and 0xFE, in the middle of the 48 bit MAC (between the company_id and vendor supplied id). For example, the 48 bit IEEE MAC with global scope: |0 1|1 3|3 4| |0 5|6 1|2 7| +----------------+----------------+----------------+ |cccccc0gcccccccc|ccccccccmmmmmmmm|mmmmmmmmmmmmmmmm| +----------------+----------------+----------------+ 00:C0:DF:08:D5:99 where "c" are the bits of the assigned company_id, "0" is the value of the universal/local bit to indicate global scope, "g" is individual/group bit, and "m" are the bits of the manufacturer-selected extension identifier. The interface identifier would be of the form: |0 1|1 3|3 4|4 6| |0 5|6 1|2 7|8 3| +----------------+----------------+----------------+----------------+ |cccccc1gcccccccc|cccccccc11111111|11111110mmmmmmmm|mmmmmmmmmmmmmmmm| +----------------+----------------+----------------+----------------+ fe80::2c0:dfff:fe08:d599

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Neighbor Discovery (ND) Protocol

 IPv6 node uses ND protocol to

» Find other nodes in the same link /LAN » Find a node MAC address  ND substitutes ARP » Find router(s) in its network » Mantaining information about neighbour nodes

 ND similar to the IPv4 functions

» ARP IPv4 » ICMP Router Discovery » ICMP Redirect

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.ND Messages

» ICMP messages (over IP); using Link Local addresses » Neighbor Solicitation

Sent by a host to obtain MAC address of a neighbour / to verify its presence

» Neighbor Advertisement: Answer to the request » Router Advertisement

Information about the network prefix; periodic or under request Sent by router to IP address Link Local multicast

» Router Solicitation: host solicits from router a Router Advertisment message » Redirect: Used by a router to inform na host about the best route to a destination

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.IPv6 Address Configuration

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.Packet Transmission

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Mobility Management

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 What is the functionality associated to Mobility Management?

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Handoff

 Transference of a call/session to a new cell/service-area  Caused by

» Radio link degradation  terminal movement » Traffic redistribution

T switch

AP

T

AP 1 2 1 2

Terminal Mobility

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Macro-mobility, Micro-mobility



Mobility types

» Macro-mobility: between organizations » Micro-mobility: in the same organization



Handover types

» Vertical handover: between different technologies » Horizontal handover: same technology, same organization

Internet Home Organization 1 Organization 2 Corresponding host Same route Mobile node Mobile node Internet Home Organization 1 Organization 2 Corresponding host Mobile node Mobile node Same route

Macro-mobility Micro-mobility

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Mobility Management

 Mobility management

» Enables network to be aware of the terminal location » Maintains the route/connection to the terminal when it moves

 Mobility management  2 functions

– Location management – Handoff management

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Location Management

 Location registration/update

» Terminal informs network about its current access point; regularly » Network updates terminal location

 New Call/Session/Data delivery

» When a new Call/Session/Data arrives to terminal’s home network

network requested to find the terminal location, either by querying location databases or by paging the terminal

location database

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Handoff Management

 Maintains terminal connection/routes when terminal moves  Initiation: need for handoff identified  New connection/route generation

» Resources found for the handoff connection

– In Network-Controlled Handoff (NCHO)  the network finds the resources – In Mobile-Controlled Handoff (MCHO)  terminal finds resources, network approves

» Routing operations performed

 Data-flow control: delivery of data from old to new paths, maintaining QoS

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Data Flow Transference – Models Commonly Used

I)

1) 2)

II)

1) 2) 3)

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Flow Transference – Multicast model, not commonly used

1) 3) 2)

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 Handled at multiple layers

» Data Link: 3GPP, IEEE networks » Network: Mobile IP, HIP » Transport: Mobile TCP » Application: SIP

 Security and QoS

Affect Mobility Management

– How to avoid new authentication at every new AP? – How to guarantee that radio resources are available at the new AP?

Mobility Management

Physical Network Transport Data link Application Mobility Security Multicast Quality of Service

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How does Skype manage computer mobility?

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Mobile IPv6

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Motivation

How to implement mobility at the IP layer?

RH

MN

HA

IPv6 Internet

RF CN

MN

Home Network Foreign Network

MN - Mobile Node HA – Home Agent CN - Correspondent Node R - Router

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Possible Solutions

 DHCP plus dynamic DNS

» MN in the foreign network » Gets new IP address, uses same name » Current TCP connections will break » Works with existing Internet

 Mobile IPv6

» Mobile Node maintains its original IP address » Mobile Node gets a second IP address » Enables TCP session continuity » Requires mobility aware nodes » IETF RFC 3755

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MN at Home Network

Standard exchange of packets

RH

MN

HA

IPv6 Internet

CN Home Network

CN HA MN

|echo request| | +---------------------->| |echo reply | | |<----------------------+ | | |

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MN visits a Foreign Network (./..)

RH

MN

HA

IPv6 Internet

RF CN

CN HA MN RF MN’

| | | | | | | |MN moves | | | | +---------------------->| | | | |radv | | | | +--------->| | |binding update(CoA) | | | |<-----------------------------------+ | |binding ack | | | | +----------------------------------->| |echo request| | | | + -----------====================================>| | echo reply | | | | |<-----------=====================================+ | | | | |

Tunnel HA  COA

Care-of address COA IP address of HA TTL IP identification IP-in-IP IP checksum flags fragment offset length TOS ver. IHL IP address of MN IP address of CN TTL IP identification

• lay. 4 prot.

IP checksum flags fragment offset length TOS ver. IHL TCP/UDP/ ... payload

CoA

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.MN visits a Foreign Network (../..)

 MN acquires a second IP address (CareOfAddress)

» by DHCP or by listening ICMP Router Advertisement message sent by RF

 MN informs HA about its new address

» MN sends Binding-Update; HA sends Binding-Acknowledge » These are IPv6 messages using a new options mobility header

 HA

» starts behaving as MN » receives traffic sent to MN@home » tunnels this traffic to the CoA of MN

 MN sends traffic to HA, using the tunnel

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MN optimizes the Route to CN (./..)

RH

MN

HA

IPv6 Internet

RF CN

CN HA MN RF MN’

| | | | | |echo request| | | | + -----------====================================>| |echo reply | | | | |<-----------|====================================+ | | | | | |home test init | | | |<-----------|====================================+ |care of test init | | | |<------------------------------------------------+ |care of test| | | | +------------------------------------------------>| |home test | | | | +------------|===================================>| |binding update | | | |<------------------------------------------------+ |binding ack | | | +------------------------------------------------>| |echo request| | | | +------------------------------------------------>| | echo reply | | | | |<------------------------------------------------+ | | | | |

MN

RF

MN

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.MN Optimizes the Route to CN (../..)

 MN detects packet received in tunnel  Optionally, it decides to optimize the route to the CN  MN informs CN about its new address

» MN sends Binding-Update; CN sends Binding-Acknowledge » These are IPv6 messages using a new options mobility header

 Traffic starts to be exchanged directly between MNCN

» MNCN: use of options destination header » CNMN: use of routing options header

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Route Optimization

 IPv6 packets in the CN  MN direction

» 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 (IPv6 destination address = CareOfAddress)  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 DestinationHeader with information about HomeAddress – CN replaces HomeAddress in 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, through I1, I2, I3

As the packet travels from S to I1: Source Address = S Hdr Ext Len = 6 Destination Address = I1 Segments Left = 3 Address[1] = I2 Address[2] = I3 Address[3] = D As the packet travels from I1 to I2: Source Address = S Hdr Ext Len = 6 Destination Address = I2 Segments Left = 2 Address[1] = I1 Address[2] = I3 Address[3] = D As the packet travels from I2 to I3: Source Address = S Hdr Ext Len = 6 Destination Address = I3 Segments Left = 1 Address[1] = I1 Address[2] = I2 Address[3] = D As the packet travels from I3 to D: Source Address = S Hdr Ext Len = 6 Destination Address = D Segments Left = 0 Address[1] = I1 Address[2] = I2 Address[3] = I3

List of visited nodes

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CN HA MN RF MN’

|echo request| | | | +------------------------>| | | |echo reply | | | | |<------------------------+ | | | | |MN moves | | | | +---------------------->| | | | |radv | | | | +--------->| | | binding update | | | |<-----------------------------------+ | |binding ack | | | | +----------------------------------->| |echo request| | | | + -----------====================================>| |echo reply | | | | |<-----------|====================================+ | | | | | |home test init | | | |<-----------|====================================+ |care of test init | | | |<------------------------------------------------+ |care of test| | | | +------------------------------------------------>| |home test | | | | +------------|===================================>| |binding update | | | |<------------------------------------------------+ |binding ack | | | +------------------------------------------------>| |echo request| | | | +------------------------------------------------>| | echo reply | | | | |<------------------------------------------------+ | | | | |