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T-110.5110 Computer Networks II Mobility Issues 6.10.2008. Prof. Sasu Tarkoma. Contents. Overview Mobile IP NEMO Transport layer solutions i3 SIP mobility. Mobility. What happens when network endpoints start to move? What happens when networks move? Problem for on-going conversations - PowerPoint PPT Presentation
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T-110.5110 Computer Networks IIT-110.5110 Computer Networks II
Mobility IssuesMobility Issues
6.10.20086.10.2008
Prof. Sasu Tarkoma
ContentsContents
•Overview
•Mobile IP
•NEMO
•Transport layer solutions
• i3
•SIP mobility
MobilityMobility
•What happens when network endpoints start to move?
•What happens when networks move?
•Problem for on-going conversations– X no longer associated with address– Solution: X informs new address
•Problem for future conversations– Where is X? what is the address?– Solution: X makes contact address available
•In practice not so easy. Security is needed!
Mobility
Micro Macro Global
Intra-subnet
Intra-domain Inter-domain
Cellular IP (1998)
TMIP (2001)
Hierarchical MIP (1996)
Hawaii (1999)
Dynamic Mobility Agent (2000)
HMIPv6 (2001)
MIP (1996)
MIPv6 (2001)
Time (evolutionary path)
Classifying Mobility ProtocolsClassifying Mobility Protocols
Routing vs. mobilityRouting vs. mobility
• Topology data aggregation is necessary
– Cannot track all hosts in the world
– IP addresses determined by topology
• Network gives the routing prefix
• Mobile hosts must change their IP addresses
– Causes sockets / connections to break
• How to communicate address changes?
• Two approaches:
– Let routing handle it not scalable
• Done by ad hoc routing protocols
– Let end-systems handle it protocol is needed
• Goal of a mobility protocol
– Transport and applications do not see address changes
– Mobility transparency
Networks: MobilityNetworks: Mobility
R
Public Switched Data Network
RouterRouter
R R R R
Backbone LAN
Router Router
MAN
NAT
AP
GPRS/UMTSAccess network NAT
BS BS
MH
MH
Ad hoc
MH
RendezvousRendezvous
•How to find the moving end-point?
– Tackling double jump
• What if both hosts move at the same time?
• Requires a rendezvous point
•Mobility management is needed!
– Initial rendezvous
– Can be based on directories
– Requires fast updates to directories
• Does not work well for DNS
Security issuesSecurity issues
•Address stealing
– Alice and Bob communicate
– Mallory tells Alice
• Bob is now at C
•Address flooding
– Mallory downloads from Alice, Bob, etc.
– Mallory tells everybody
• I have moved to C
Mobile IPMobile IP
•Two versions
– IPv4 (optional)
– integrated into IPv6 (with IPSec security)
•Home Agent (HA)
– Home address
– Initial reachability
– Triangular routing / reverse tunneling
•Route optimization
– Tunnels to bypass HA
– HA as a rendezvous point
Mobility Example:Mobile IP Mobility Example:Mobile IP Triangular RoutingTriangular Routing
Home agent
Correspondenthost
Foreign agent
Mobile host
Home link Foreign link
Ingress filtering causes problems for IPv4 (home address as source), IPv6 uses CoA
so not a problem . Solutions:(reverse tunnelling) or
route optimization
Foreign agent left out of MIPv6. No special
support needed withIPv6 autoconfigurationDELAY!
Care-of-Address (CoA)
Reverse TunnellingReverse Tunnelling
Home agent
Correspondenthost
Router
Mobile host
Home link Foreign link
DELAY!
Care-of-Address (CoA)
Firewalls and ingress filtering no longer a
problemDouble triangular routing leads to overhead and increases congestion
Firewalls and ingress filtering no longer a
problemDouble triangular routing leads to overhead and increases congestion
Mobility Example:Mobile IPv6 Mobility Example:Mobile IPv6 Route OptimizationRoute Optimization
Home agent
Correspondenthost
Router
Mobile host
Home link Foreign link
MH sends a binding update to CHwhen it receives a tunnelled packet.
CH sends packets using routing header
First, a Return Routability test to CH. CH sends home test and CoA test packets. When MH receives both,
It sends the BU with the Kbm key.
Secure tunnel (ESP)
MIPv6MIPv6
• MIP6 utilizes IPv6 header options for signalling between the HA and CN.
• The important changes are a new extension header (mobility header)
for the creation and management of binding, a new routing header
type to allow packets to be routed directly from CN to a MN CoA (home
address in ext), and a new destination type (MN to CN, home address
again)
• MIP6 uses the new IPv6 autoconfiguration mechanism to determine the
CoA, and thus does not need a FA.
• Using autoconfiguration, the MN receives Router Advertisements that
contain the routing prefixes of the visited network. This prefix
information is then combined with the interface ID (MAC address) of the
MN to obtain the CoA.
• MIP6 also supports the dynamic discovery of the HA or HAs.
Extension HeadersExtension Headers
Mobility Header
Upper Layer headers
DataMH
CN to MN MN to CN
MN, HA, and CN for Binding
MH Type in Mobility Header: Binding Update, Binding Ack, Binding Err, Binding refresh
Source: Chittaranjan Hota, Computer Networks II lecture 22.10.2007
MIPv6 Operation: Mobile on a Foreign networkMIPv6 Operation: Mobile on a Foreign network
1
Stateless address Auto configuration
(Acquiring COA)
2 Foreign Network
4
3
Duplicate address detection, Proxy neighbor discovery, and Binding cache update
5 Update Binding Update List
Bidirectional tunnel
Source: Chittaranjan Hota, Computer Networks II lecture 22.10.2007
MIPv6: Dynamic Home Agent DiscoveryMIPv6: Dynamic Home Agent Discovery
12
Home Agents List Preference ValueHome Agent 2 6Home Agent 1 2
Home Agents List Preference ValueHome Agent 2 6Home Agent 1 2
1 Dynamic Home Agent Address Discovery request to anycast address
2 DHAAD reply with addresses of home agents with their preferences
Mobile Node
1
2
Source: Chittaranjan Hota, Computer Networks II lecture 22.10.2007
Source: Microsoft, Understanding Mobile IPv6
Security in Mobile IPSecurity in Mobile IP
• MIPv6 RFC 3775/3776– Protection of Binding Updates HA, CNs– IPsec extension headers or the binding authorization data
option– Binding management key, Kbm, which is established through
return routability procedure– Protection of mobile prefix discovery– Protection of the mechanisms that MIPv6 uses for
transporting data
• Protecting binding updates– Must be secured through IPsec– ESP is used for updates and acks
• Shoulds: init messages, prefix discovery
Return RoutabilityReturn Routability
Mobile Node Correspondent Node Home Agent
HOTI (HOme address Test Init)
COTI (Care-Of address Test Init )
HOTI
COT (Care-Of Test )
HOT (HOme Test)
HOT
BU
ACK BU
MN
CN
HA4
12
3
Can see HOT but not COT
Claim to own home address
Use current address as CoA.
Offpath attack using refresh
Sends COTI and HOTI to CN, construct Kbm claim
ownership of CoAsend binding updates, break
comms. with CN.Offpath attack
Both HOTI and HOT are encrypted. Malicious node may be able to forward traffic to neighbor if
has a valid HA
MiTM attacks. Cannot construct
Kbm.
Offpath attacksOffpath attacks
•DoS attacks: memory/processing capability exhaustion. Connection termination.
•Reflection attacks. Victim’s IP address is spoofed, receiver will respond, causing messages sent to the victim
– Ingress filtering can help
•MiTM attacks. Attacker compromises routers on-path. Route injection.
MIP specific attacksMIP specific attacks
•Prevent connections between CN and MN by picking a home address and RR
•Attacker can move to another location and refresh binding, continue deny service to MN while offpath
•Solutions
– When location changes, MN runs RR (malicious node fails this if offpath)
– Public keys and certificates, IKE
– Cryptographically generated address (CGA)
CGA and MIPCGA and MIP
•Each node has a key-pair
•Produce h(PK, data) 64 bits that can be used as the interface identifier
•Put this into IPv6 address host part
cryptographically generated address
•MN can prove it owns such an address by providing a signature inside a message
•CGA can be used to prove that a noede owns a particular addres, but not that a node is currently located at this address
RR is needed
Hierarchical Mobile IPHierarchical Mobile IP
•HMIPv6 is specified in RFC 4140
•Introduces local Mobility Anchor Points (MAP) that are essentially Home Agents
•MAPs can be located at any level in a hierarchical network of routers, including the access routers.
•The aim of the HMIPv6 is to minimize the signaling latency and reduce the number of required signaling messages.
•As long as the MN stays inside one MAP domain it only needs to update its location with the MAP.
•The localized mobility management can also be completely handled on the network side without MN's involvement at the IP mobility protocol level.
NEMONEMO
•It is also possible for a whole subnetwork to roam from one part of the Internet to another.
•Network Mobility (NEMO) is specified in RFC 3963
•The technical solution of NEMO is based on MIP6. NEMO allows subnetworks to change their location in a network.
•This is realized using a mobile router that manages the mobile network. The mobile router updates its HA regarding the CoA of the mobile router.
•A NEMO compliant HA can act also as a MIP6 HA. The basic solution creates a bi-directional tunnel between the mobile router and the HA, which effectively keeps the mobile network reachable.
•Hosts behind the mobile router do not need to be aware of mobility in any way.
Hierarchical Mobile IP (HMIP)Hierarchical Mobile IP (HMIP)
InternetLocalizing Registrations
HA
FA1
FA2FA3
FA4
FA5FA6
MH@FA1
MH@FA2
MH@FA4
MH@VL
Lineage <FA4, FA2, FA1>
<FA5 FA2, FA1>
<FA6, FA3, FA1>
MH@FA5
Common ancestor = FA2 (nearest)
Common ancestor = FA1 (nearest)
MH@FA3
MH@FA6
MH@VL
Source: Chittaranjan Hota, Computer Networks II lecture 22.10.2007
Multi-layer OperationMulti-layer Operation
•Mobility and multi-homing can be realized on different layers
– Network
• Mobile IP, HMIP, NEMO
– Between network and transport
• Host Identity Protocol (HIP)
– Transport (SCTP)• TCP extensions, SCTP (TrASH)
– Application
• SIP, Wireless CORBA, overlays
• Re-establish TCP-sessions after movement
TCP Solutions to MobilityTCP Solutions to Mobility
•When MN initiates a connection, it tells the CN it’s new IP address through SYN
•CN uses DNS lookup to locate a MN
•TCP Migrate option is used to migrate to a new connection
•(s_ip, s_port, d_ip, d_port) to (s_ip, s_port, d_ip’,d_port’)
•Segmented TCP, Indirect TCP (I-TCP)
•SCTP multihoming can be used as well
CN MN CN
MN after movement (Migrate SYN, Migrate SYN/ACK, ACK)
Source: Chittaranjan Hota, Computer Networks II lecture 22.10.2007
SIP MobilitySIP Mobility•Session mobility allows a user to maintain and manage a
media session across devices
•Terminal mobility allows a device to move between IP subnets while continuing to be reachable for incoming requests and maintaining sessions across subnet changes
•Personal mobility allows the addressing of a single user
•Located at different terminals by using the same logical address
•Service mobility allows users to maintain access to services while moving or changing devices and network service providers
•SIP implements these using URLs, proxies, and redirect servers. The home domain keeps track of users and devices. Message forking
Host Identity ProtocolHost Identity Protocol
•New cryptographic namespace
•Connection endpoints mapped to 128 bit host identity tags (hashes of public keys)
•Mapping at HIP layer
•4-phase Base Exchange with cryptographic puzzle for DoS prevention
•IPSec for network-level security
Identity/Locator splitIdentity/Locator split
Process
Transport
ID Layer
IP Layer
Link Layer
identifier
locator
Application-layer mobilityApplication-layer mobility
•Many application-layer protocols are, in principle, similar to Mobile IP
•Moving entity may differ
– Instead of host we have object, session, entity, or interests
•For example:
– Object mobility
• Wireless CORBA
– Session mobility
• SIP
– Interest mobility
• Content-based routing
– Generic mobility
• i3 overlay, service composition
Internet Indirection Infrastructure (i3) Internet Indirection Infrastructure (i3)
• An Overlay infrastructure.
• Every packet is associated with an identifier.
• Receiver receives using identifier
A Trigger
(Natural Support for Mobility)
Movement with a different address
[Source: http://i3.cs.berkeley.edu/]
i3: How it Works?i3: How it Works?
(A Receiver R inserts a trigger into i3)
(A Sender S sends a packet with same identifier 37, that is delivered to R)
CHORD ensures O (log N ) no. of intermediate hops to reach at the destination
[http://i3.cs.berkeley.edu/]
Mobile Web ServerMobile Web Server
Gateway
BrowserWebserver
Operator
Firewall
2.5/3G
InternetDNS
12
3
By courtesy of Johan WikmanPresented in EuroOSCON 2006
Indirection PointsIndirection Points
•Mobility may be characterized by indirection points
– Mobile IP
• Single fixed indirection point
– Location / Identity split
• Single indirection point
– SIP
• Single fixed indirection point (home domain) (other are possible)
– Content-based routing
• Many indirection points
Lessons to learnLessons to learn
•Hierarchical routing likely to stay
– Addresses carry topological information
– Efficient and well established
•Applications face changing connectivity
– QoS varies
– periods of non-connectivity
•Identifiers and locators likely to split
•Mobility management is needed
•Probably changes in directory services
– Overlays have been proposed
SummarySummary
•Topology based routing is necessary
•Mobility causes address changes
•Address changes must be signalled end-to-end
– Alternative: use triangular routing as in Mobile IP
•Mobility management needed
– Initial rendezvous: maybe a directory service
– Double jump problem: rendezvous needed
•Many engineering trade-offs