Network Layer Location Management Mobile IP

1
Network Layer Location Management Mobile IP

• Y. Richard Yang
• 2/17/2009

2
Recap Wireless Link Layer

• The basic services of the link layer
• framing, link reliability, etc
• link access
• interference, hidden terminal
• quality of service (and fairness) control

3
Distributed Sharing of Unlicensed Spectrum

• Utilization of allocated spectrum is sow
• Federal Communications Committee (FCC) is
  increasing unlicensed spectrum allocation
• Industry, Science, and Medicine (ISM)
• Unlicensed Personal Communication Service (UPCS)
  1910-1930 MHz and 2390-2400 MHz (30 Mhz)
• National Information Infrastructure (NII) Band
  350 Mhz
• 59-64 Ghz Millermeter Wave band
• Cross-protocol spectrum sharing is difficult

4
One Proposal for UPCS Spectrum Etiquette

• Upper bound on energy level official
• A station must Listen Before Talk (LBT)
  official
• be quite for a monitoring time M after the
  previous energy level stops
• Penalty for using a channel non-official
• if a station holds a channel for a duration H,
  the station cannot transmit for P(H) amount of
  time as a penalty

Question what property do you want P(H) to hold?
5
How to Design P(H)?

• Assume an arrived bit of a user is transmitted
  immediately if the user is having the channel
  otherwise the bit has to wait until the next
  interval
• What is the average delay

M
H
P(H)
H
6
Discussion

• Spectrum sharing is largely still an open field
• There are several proposals and evaluations,
  e.g.,
• http//dx.doi.org/10.1023/A1019129906297
• http//ccr.sigcomm.org/online/?qnode/385
• A potential term project topic

7
Recap Wireless Link Layer

• The basic services of the link layer
• link access
• interference, hidden terminal
• quality of service (and fairness) control
• framing, link reliability, etc
• Guided by network layer
• transmit to which neighbor at what quality

8
Network Layer Services

• Transport packets from source to dest
• Network layer protocol in every host, router
• Basic functions
• Control plane
• compute routing from sources to destinations
• Data plane forwarding
• move packets from input interface to appropriate
  output interface(s)

9
Network Layer API

• API (provided to upper layer)
• transmit( info, src, dest, )
• A key decision in network layer design is how to
  represent destinations?
• we refer to how applications specify destinations
  as the addressing scheme
• the supported addressing scheme(s) can have
  profound impacts on usability, flexibility, and
  scalability

10
Discussion How to Specify a Destination?
11
Two Basic Approaches for Identifying Destinations

• Locators
• encode locations on network topology
• Identifiers (ID)
• independent of network topology

12
Addressing Scheme Sensornet Example

• Destination message to a sensor (e.g., who
  detected fire)
• ltID Dgt
• ltLat37.3169 Long-121.8740gt
• lttemperature highestgt

13
Addressing Scheme Telephone

• Very first scheme connection by operators to
  business
• ID or locator?
• The telephone numbering scheme
• invented in 1888 by Almon Strowger, an
  undertaker No longer will my competitor steal
  all my business just because his wife is a BELL
  operator.

14
Telephone Addressing Scheme

• E.164 Maximum 15 digits
• Hierarchical addressing scheme country code
  national destination code (optional) subscriber
  number)
• e.g., 1-203-432-6400
• Why hierarchical addressing scheme?
• 203-432 uniquely determines the switch upon which
  the telephone is attached to
• Issues of such a scheme?

15
Addressing Scheme Internet

• How to specify the destination which is the color
  printer on the 4th floor of AKW
• Internet domain name lw4c.cs.yale.edu
• Internet protocol (IP) address 128.36.231.8
• building AKW floor4 entity printer
  quality color

16
Addressing Scheme IP
223.1.1.1

• IP address 32-bit identifier for an interface
• An IP address is associated with an interface
  /sbin/ifconfig -a

223.1.2.9
223.1.1.4
223.1.1.3
223.1.3.2 11011111 00000001 00000011 00000010
223
1
2
3
17
IP Addressing
223.1.1.2
223.1.1.1
223.1.1.4

• Hierarchical scheme
• network part (high order bits)
• host part (low order bits)
• Whats a network? (from IP address perspective)
• device interfaces with same network part of IP
  address
• link layer can reach each other

223.1.1.3
223.1.7.0
223.1.9.2
223.1.9.1
223.1.7.1
223.1.8.1
223.1.8.0
223.1.2.6
223.1.3.27
223.1.2.1
223.1.2.2
223.1.3.2
223.1.3.1
18
Why Hierarchy?
223.1.1.2
223.1.1.1
223.1.1.4

• The hierarchy is important for the scalability of
  Internet routing
• The routing system handles only the number of
  networks
• 275,280 networks on Jan. 3 2009
• 625 mil hosts in Jan. 2009)

223.1.1.3
223.1.7.0
223.1.9.2
223.1.9.1
223.1.7.1
223.1.8.1
223.1.8.0
223.1.2.6
223.1.3.27
223.1.2.1
223.1.2.2
223.1.3.2
223.1.3.1
http//ftp.isc.org/www/survey/reports/current/
19
Routing in IP/Telephone Networks

• Represent network as a graph
• Determine a pathto each destination on the
  graph
• Q what does a nodein the graph represent?

20
Key Problems

• Location management
• due to user mobility (roaming), hierarchical
  routing (address aggregation) may cause user
  devices to be not attached to their
  networks/switches
• need forwarding/location management
• Dynamic routing
• due to node mobility/wireless connectivity, link
  connectivity/quality can be highly dynamic
• need to design routing protocols that are
  effective in handling dynamic topologies
• Broadcast wireless
• there can be interference among links and paths
  (need good link performance metrics or scheduling)

21
Outline

• Admin.
• Network addressing schemes
• Location management in cellular networks

22
Routing in Cellular Networks

• Cellular networks face the location management
  problem
• a phone may be out of its home switch
• How GSM handles out-of-switch phones
• a global home location register (HLR) database
  for each carrier
• each base transceiver station (BTS) has a visitor
  location register (VLR)

23
MS (mobile station) BSC (base station
controller) BTS (base transceiver station) MSC
(mobile switching center) GMSC (gateway MSC)
GSM
fixed network
Network Switching Subsystem and
OperationSubsystem
HLR
GMSC
MSC
MSC
BSC
MS
BSC
MS
BTS
Radio Subsystem
VLR
MS
MS
MS
MS
BTS
BTS
VLR
VLR
VLR
BTS
BTS
VLR
24
Two Primitives for Cellular Location Management

• Mobile station reports to the network of the
  cell it is in
• called update
• uses the uplink channel
• Network queries different cells to locate a
  mobile station
• called paging
• uses the downlink channel

25
Performance of the Two Primitives

• A city with 3M users
• During busy hour (11 am - noon)
• Assume each paging message is 100 bits
• Update only
• update messages 25.84 millions
• Q why so many update messages?
• Paging only
• paging traffic 1433 calls/sec
• Q bw? arrival rate?

26
Location Management Through Location Areas (LA)

• A hybrid of paging and update
• Used in the current cellularnetworks such as GSM
• Partitions the cells into location areas (LA)
• e.g., around 10 cells in diameter in current
  systems
• Each cell (BTS) periodicallyannounces its LA id
• If a mobile station arrives at a new location
  area, it updates the base station about its
  presence
• When locating a MS, the network pages the cells
  in an LA

27
How to Decide the LAs A Simple Model

• Assume the cells are given
• Cell i has on average Ni users in it during one
  unit time each user receives c calls per unit
  time
• There are Nij users move from cell i to cell j in
  a unit of time

28
How to Decide the LAs A Simple Scenario

• Separate LAs for cells 1 and 2
• update cost N12 N21
• paging cost c (N1 N2)
• Merge cells 1 and 2 into a single LA
• update cost 0
• paging cost 2 c (N1 N2)
• When to merge and when to separate?

29
Discussions

• The LA design should consider
• call pattern when (how often) does a mobile
  station receive a call?
• mobility model how does a mobile station move?
• How to further improve the performance of
  location management?

30
Dynamic/Distributed Location Management Schemes

• In dynamic/distributed location management
  schemes, each user makes independent decision
  about when to update

31
Dynamic/Distributed Location Management Schemes

• Timer based
• A MS sends an update after some given time T
• Movement based
• A MS sends an update after it has visited N
  different cells
• Distance based
• A MS sends an update after it has moved away for
  D distance (need ability to measure distance)
• Profile based
• A MS predicts its mobility model and updates the
  network when necessary

32
Timer-based Location Management

• A MS sends an update after some given timer T
• The network pages the MS upon a call request at
  all cells which the MS can potentially arrive
  during T
• cells reachable from last update cell, e.g.,
  within distance vmax T, where vmax is the
  maximum speed
• Question how to determine T?

33
Timer-based Location Management

• Assume time between call arrivals is Tcall
• Cell radius is dcell
• Total bandwidth cost

34
Summary Location Management

• Two primitives of location management in cellular
  networks
• update (a proactive approach)
• paging (a reactive approach)
• The location area (LA) approach
• a hybrid approach
• Distributed approaches
• timer based
• movement based
• distance based
• profile based

35
Mobile IP
36
Mobile IP Architecture

• Assume the current Internet addressing and
  routing architecture
• Design extensions to handle out of network
  devices

37
Mobile IP Terminology

• Mobile Node (MN)
• the node under consideration
• Home Agent (HA)
• a stationary network node (e.g., a router) at the
  home network
• Foreign Agent (FA)
• a network node (e.g. a router) in the foreign
  network
• Care-of Address (COA)
• the address in the foreign network
• Correspondent Node (CN)
• communication partner

38
Illustration
HA
Internet
router
home network
(physical home network for the MN)
FA
foreign network
router
(current physical network for the MN)
39
Mobile IP Operations

• Basic idea of Mobile IP
• a MN acquires a COA in a foreign network from a
  foreign agent
• registers to the home agent
• all messages sent to its home address is
  forwarded by its home agent to its COA

40
Discovering the Agents and Care-of Address

• Mobile IP discovery process
• (home or foreign) agent broadcasts advertisements
  at regular intervals
• announce the network
• list one or more available care-of addresses
• mobile node takes a care-of address
• mobile node can also send solicitation to start
  the process

41
Registering the Care-of Address

• Mobile node sends an update (called) registration
  request) to its home agent with the care-of
  address information
• Home agent approves/disapproves the request
• Home agent adds the necessary information to its
  routing table
• Home agent sends a registration reply back to the
  mobile node

42
Registration Operations in Mobile IP

• MH Mobile Host HA Home Agent
• FA Foreign Agent

43
Data Transfer from the Mobile Node
HA
1
MN
Internet
home network
sender
FA
foreignnetwork
1. Sender sends to the IP address of the
receiver as usual, FA works as default router
CN
receiver
44
Data Transfer to the Mobile Node
HA
2
MN
Internet
home network
receiver
3
foreign network
FA
1. Sender sends to the IP address of MN, HA
intercepts packet 2. HA tunnels packet to COA,
here FA, by encapsulation 3. FA forwards the
packet to the MN
1
CN
sender
45
Tunneling Operations in Mobile IP
Correspondent Node X
46
Discussion

• Any problems of the Mobile IP approach?

47
Triangular Routing

• Triangular Routing
• CN sends all packets via HA to MN
• higher latency and network load
• Solution
• CN learns the current location of MN
• direct tunneling to this location
• HA or MN informs a CN about the location of MN
• Problem of the solution
• big security problems !

48
Handoff

• Change of FA (COA)
• packets on-the-fly during the change can be lost
• Solution
• new FA informs old FA to avoid packet loss, old
  FA buffers and then forwards remaining packets to
  new FA
• this information also enables the old FA to
  release resources for the MN

49
Summary Mobile IP

• An out-of-network mobile node (MN) registers its
  current reachable address (COA) with its home
  agent
• Home agent forwards packets to the MN
• Several optimization techniques to improve
  efficiency and reduce packet losses during
  mobility

50
Preview How to Routing?
51
Backup Slides
52
Change of Foreign Agent
CN
HA
FAold
FAnew
MN
Data
Data
Data
Update
ACK
Data
Data
MN changeslocation
Registration
Update
ACK
Data
Data
Data
Warning
Request
Update
ACK
Data
Data
t
53
Micro Mobility

• A very typical scenario of Mobile IP is that a MN
  visits a company or university
• the MN may change foreign networks multiple times
  in the foreign network, generating much control
  traffic

54
Handoff Aware Wireless Access Internet
Infrastructure (HAWAII)

• Operation
• MN obtains co-located COAand registers with HA
• Handover MN keeps COA,new BS answers Reg.
  Requestand updates routers
• MN views BS as foreign agent

1
2
3
4
BS
3