Transcript ECE544Lec10HL09-Mobility

ECE544: Communication Networks-II,
Spring 2009
H. Liu
Lecture 10 (Mobility)
Includes tutorial materials from D. Raychaudhuri, C. Perkins, D. Reininger
Today’s Lecture
• Announcements: Final Exam
• Mobile IP
• Network Security
Announcements
• Final: Monday, May 11, 8:00 PM-11:00 PM,
Location: SEC 210
– OPEN BOOK: Only the textbook, Peterson & Davie,
"Computer Networks: A Systems Approach“ plus 2 pages of
notes are permitted.
– Textbook Chapters 1 – 6, Chapter 8, and Lecture Slides
(Chapters 1 and 2 are not the main focus of this final exam
but are needed as background knowledge)
– Calculator is permitted
• Course Survey: end on Monday, May 4
Review
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Ethernet switching, wireless LAN
MPLS basic, ATM
IP Routing (RIP, OSPF, BGP)
IP Addressing (Subnetting, CIDR, IPV6)
Mobile IP
End-to-End Protocols (UDP, TCP, RTP)
Congestion control and QoS (queuing
disciplines, TCP congestion control,
congestion avoidance, IntServ, DiffServ)
• Network Security
Mobility in Cellular Networks
Cellular Concept of Mobility
• Users have a home system but can
register at visited systems to make and
receive calls – Single Number Service
• Users can roam among systems during
a call and the call is handed-off without
being dropped.
Functional Elements
Home Location Register –
Maintains current customer
Location and service profile
HLR
AC
VLR
Home System
Authentication
Center –
Authenticates users
Visitor Location RegisterMaintains temporary information on
Visiting users.
Visited System
GSM Registration
3) The VLR sends
a registration message
to the HLR.
HLR/AC
VLR
Old VLR
2) VLR queries
previous VLR for user’s
(actually the user’s smart
card) permanent ID.
Visited System
1) Visited system detects handset,
handset transmits temporary ID assigned
by previous system.
Handset
Mobile IP Networks
Name, Address, Routing
• Name: is a location independent
identifier of a host
• Address: indicates where a given host is
located.
• Route: tells how to get to a destination
Mobility Problem: The
Internet Viewpoint
• Internet addresses are assigned in a
topologically significant manner.
– A mobile host must be assigned a new
address when it moves.
• Change host address  connection
breaks.
• Retain host address  routing fails.
• Host address must be preserved
regardless of its location.
Constraints
• Inter-operability with TCP/IP protocol suite.
• Existing networking apps should run
unmodified on mobile hosts.
• System should provide Internet-wide mobility.
• No modification on existing routing
infrastructure should be required.
• Solution should be independent of wireless
hardware technology.
• Solution should have good scaling properties.
IP’s subnet model vs.
Mobility
• Terminals move from one IP subnet to
another, but have the wrong “subnet
prefix” for the destination subnet.
• Solution: two-tier IP addressing
– The mobile keeps its static IP address, but
borrows the service of a “care-of-address”
on whatever IP subnet it happens to be
visiting.
– A “care-of-address”, offered by a mobility
agent, can be shared by visiting mobiles.
Basic Mobile IP
• How does it work?
– Agent discovery: advertisement/solicitation
– MH registration
– Use of Care-of-Address (COA)
– Proxy ARP (Address Resolution Protocol)
– Packet tunneling
– Triangle routing
Key components
Home Address:
MH’s permanent IP address,
network ID of this address identifies
the mobile’s home network.
MH
HA
HN
R1
Home Network:
the network identified
with a mobile node
Home Agent (HA):
a router attached to the MH’s home network
maintains current location information for the MH
is responsible for forwarding packets destined for the
MH when MH is away from home.
R3
Route Optimization
FN
CH
Corresponding Host:
a host or router communicationg
with a mobile node.
R2
Foreign Network:
a network, other than MA’s home
network, that MH is currently
attached to.
Care-of-address:
the IP address of the foreign agent
FN
FA
MH
Mobile Host:
a host capable of changing
its point of attachment to
the Internet
Foreign Agent (FA)
a router in the foreign network that the MH is visiting
provides routing services to the MH while registred
de-tunnels datagram to MH
may serve as default router for outgoing packet from MH
Route Optimization
• Provides a means for nodes to
– cache the bindings of a mobile node
– tunnel their own datagrams directly to the care-ofaddress
– bypass mobile node’s home agent during
datagram delivery
• Allow datagrams sent based on an out-ofdate cached binding, to be forwarded to the
mobile node’s new care-of-address.
Terminology
• Binding cache
– a cache of mobility bindings of mobile nodes
– maintained by CH for use in tunneling datagrams
to those mobile nodes.
• Binding update
– a message indicating a mobile node’s current
mobility binding and its care-of-address.
• Registration lifetime
– the time duration for which a binding is valid.
Route Optimization
• Key features
– Binding cache update
– Smooth handoffs between foreign agents
– New messages
• binding update
• binding request
• binding warning
• binding ack
Binding Cache Creation/Update
• At CH, if no binding cache exists
– datagrams will be routed to MH via basic mobile
IP routing
– home agent should then send a Binding Update
message to the original source node
– CH will then create a binding cache for the MH
• At an FA, if MH has moved to a new FA and
the old FA still receives tunneled datagrams
– old FA send Binding Warning message to
HA to advise the change.
Foreign Agent Smooth Handoff
• As part of registration procedure, the mobile
host may request its new FA to notify its
previous FA on its behalf
– a Previous Foreign Agent Notification extension is included in
the Registration Request message
• The new FA builds a Binding Update message
and transmits it to the mobile node’s previous
FA as part of registration, requesting an ACK
from the previous FA
• Security association between old FA and MH
are used for authentication of the binding
update message.
Mobile IP in IPv6
• Mobile IPv6 shares many features with Mobile
IPv4,
• but:
– Mobility protocol fully integrated into IPv6
– Provides many improvements over Mobile IPv4.
• No Foreign Agent: all care-of-address are collocated
• Intrinsic "Route Optimization" mechanism
• Automatic procedures for acquiring CoA: stateless addr
autoconfig, DHCP (stateful)
Mobile IPv6
• MH uses Binding Update and Binding Ack to inform its HA or a
CH of its new care-of-address
• HA and CH can send Binding Request to MH to request Binding
Update
• Binding Update, Binding Ack, and Binding Request uses IPv6
optional header (Destination Option Header) and can be
piggybacked with data payload
• Use of IPv6 Routing Header option for avoiding triangular
routing
– Destination addr in IPv6 header = MH care-of address
– “type 0” routing header: addr = MH home address
• HA possibly tunnels first few IP packets using IPv6-in-IPv6
encapsulation
– MH sends Binding Update to CH
Mobile IPv4 vs Mobile IPv6
Mobile IPv4
• Advantages:
– a lot of mobile IPv4
implementations are
available on different OS
• Limitations
– too small address space.
– lack of support for
Integrated Route
Optimization
– Control messages not
included inside IPv4 data
packet header
Mobile IPV6
• Advantages
– Address space (128 bit)
– Route optimization
– Optional header structure
to support mobility
– QoS treatment
• Limitations
– IPV6 is not popular yet