Page 1 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Wireless Networks III: advanced conceptsHans-Peter Schwefel, Joao Figueiras, and Tatiana K. Madsen
http://www.kom.auc.dk/~hps
• Mm1 IP Mobility Support (HPS)
• Mm2 IP-based Multimedia Subsystem (hps)
• Mm3 tbd (maybe wireless applications and cross-layer aspects??)
• Mm4 Localisation & location-based services (jf)
• Mm5 Advanced ad-hoc networking (tkm)
Note: Slide-set contains more material than covered in the lecture!
Page 2 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Extended layered communication model• Ultimate goal of (wireless)
service provisioning: user satisfaction
• Focus in this course: network aspects, i.e. Layers 2-5
Functionalities, that are difficult to assign to single layers:
• Mobility support• Quality of service support• Security (authentication, etc.)• Dependability/Resilience... More later in this session/course[see also WNII]
L3: Network Layer: IP
L2: MAC/LLC
L4: Transport: TCP, UDP, RTP/UDP
Application
(L5) Session Control, e.g. SIP
Middleware
User Interface
User
L1: PHYS
User Environment
Netw
ork QoS
Application Q
oS
User perceived Q
oS
Page 3 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Content 1. Background • Mobility & Handover Types
2. Link-Layer Hand-over• Example: WLAN 802.11
3. Network Layer Mobility Support: MIP• Motivation, Principles, Messages• Performance Enhancements: HMIP• MIPv6
4. Higher-Layer Mobility Support• Transport Layer Mobility, e.g. mobile SCTP• Host Identity Protocol, HIP
5. Additional Hand-over aspects• Multi-homing & flow mobility
• Reminder: Mobility in GPRS/UMTS
• TCP in hand-over situations
6. Summary & Outlook
Appendix: Experimental Measurements
Goal: Make students familiar with • underlying problems• solution approaches • Overview on key technologiesrequired to support mobility in IP-
based networks
Page 4 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Background II: Mobility types
Assumption in this lecture: Infrastructure networks (only first hop wireless)
Different Levels of Mobility:• Pico (e.g. within same radio cell)• Micro (e.g. within same subnet)• Macro (e.g. across subnets but within same administrative domain)• Global (e.g. across different administrative domains)
D Internet
GPRS
NetworkCellular access(GPRS)
RouterSwitchWLAN AP
WLAN AP
WLAN AP
WLAN AP
Router
Router
Router
Router
’Alternative’ classification:
• vertical mobility: changing access technology
Mobile Host
Page 5 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Background III: Handover & more mobility typesHand-over classification:• Mobile initiated or network-initiated• Backward or forward• mobile controlled or network controlled• Mobile-assisted or network assisted or unassisted• Proactive or reactive• Make-before-break or break-before make• Soft or hard• fast (without ‚noticable‘ delay)• smooth (no loss of data) • seamless = fast + smooth
More mobility types ...• Host Mobility • User Mobility • Application Mobility• Network Mobility
... and related identifiers• IP address, hostname (DNS)• User-name (e.g. SIP URL)• ---• address prefix / subnetmask
Page 6 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Content 1. Background • Mobility & Handover Types
2. Link-Layer Hand-over• Example: WLAN 802.11
3. Network Layer Mobility Support: MIP• Motivation, Principles, Messages• Performance Enhancements: HMIP• MIPv6
4. Higher-Layer Mobility Support• Transport Layer Mobility, e.g. mobile SCTP• Host Identity Protocol, HIP
5. Hand-over extensions• Multi-homing & flow mobility
• Reminder: Mobility in GPRS/UMTS
• TCP in hand-over situations
6. Summary & Outlook
Appendix: Experimental Measurements
Page 7 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Link-Layer Hand-over: Measurements 802.11b
Scenario• Hard Handover in 802.11b• Both APs use same SSID • HO initiated by pulling cable
from AP1 (’Istanbul’)
Source: Master Thesis, Rui Martins
Page 8 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Measurements II: Hard Hand-over
Page 9 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Measurements III: Soft Hand-over Scenario
Page 10 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Measurements IV: Soft Handover Results
Page 11 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Content 1. Background • Mobility & Handover Types
2. Link-Layer Hand-over• Example: WLAN 802.11
3. Network Layer Mobility Support: MIP• Motivation, Principles, Messages• Performance Enhancements: HMIP• MIPv6
4. Higher-Layer Mobility Support• Transport Layer Mobility, e.g. mobile SCTP• Host Identity Protocol, HIP
5. Hand-over extensions• Multi-homing & flow mobility
• Reminder: Mobility in GPRS/UMTS
• TCP in hand-over situations
6. Summary & Outlook
Appendix: Experimental Measurements
Revision (for some of you...)
Page 12 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Problem: IP address identifies host as well as topological locationReason: IP Routing:
– Routes selected based on IP destination address– network prefix (e.g. 129.13.42) determines physical subnet– change of physical subnet change of IP address to have a topological correct address
• Solution? Host-based routing: Specific routes to each host– Handover change of all routing table entries in each (!) router– Scalability & performance problem
• Solution? Obtain new IP-address at hand-over– Problem: how to identify host after handover? DNS update performance/scalability problem– Higher protocol layers (TCP/UDP/application) need to ‘handle’ changing IP address
Development of mobile IP
Mobile IP Motivation: Host mobility & Routing
Subnet A
Subnet BIP networkMobile Node
Page 13 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Mobile IP: Requirements (RFC 3344)• Transparency
– mobile end-systems keep their IP address– point of attachment to the fixed network can be changed– continuation of communication after handover possible (transparent to
transport layer in mobile node as well as to correspondent node)• Compatibility
– support of the same layer 2 protocols as IP– no changes to correspondent nodes and routers required
• Security– authentication of all registration messages
• Efficiency and scalability– only small data volume for additional messages to/from the mobile node
(connection typically via a low bandwidth radio link)– world-wide support of a large number of mobile nodes (via the whole Internet)
Page 14 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Mobile IP: Principles & Terminology
Underlying Approach: separate host identifier and location identifier maintain multiple IP addresses for mobile host
Terminology:• Mobile Node (MN) with fixed IP address IP1 (home address)• Home Network: subnet that contains IP1 • Home Agent (HA): node in home network, responsible for packet forwarding to MN• Visited Network: new subnet after roaming / handover• Care-of Address (CoA): temporary IP address within visited network• Foreign Agent (FA): node in visited network, responsible for packet forwarding to CoA
Home network
Visited network
IP networkMobile Node
Home Address IP1
HA
FA Home Address IP1
Care of Address: CoA1Correspondent Node
Page 15 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Home Network
Mobile IP: Tunneling &Triangle Routing
CN sends packets to the MN using its Home Address IP1 HA tunnels them to FA, using CoA1; FA forwards them to MNMN sends packets back to the CN using IP2 (without any tunneling)Home Agent needs to contain mapping of care-of address to home address (location register)
Mobile NodeIP1, CoA1
Home Agent Subnet
Correspondent Node (CN)IP2
Visited Network
FA
←IP1
CoA1→
IP2 →
Source: Mobile IPv4 illustrated
Page 16 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Mobile IP: TunnelingDefault encapsulation:
• IP-within-IP (RFC2003)
Other Approaches:
• Minimal encapsulation (RFC2004)
• Generic Routing Encapsulation (GRE) (RFC1702)
IP-within-IP encapsulation
Page 17 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Tunneling: IP in IP Encapsulation• IP-in-IP-encapsulation (support in MIP mandatory, RFC 2003)
– tunnel between HA and COA
Care-of address COAIP address of HA
TTLIP identification
IP-in-IP IP checksumflags fragment offset
lengthDS (TOS)ver. IHL
IP address of MNIP address of CN
TTLIP identification
lay. 4 prot. IP checksumflags fragment offset
lengthDS (TOS)ver. IHL
TCP/UDP/ ... payload
• Drawback of tunneling– Possibly long routes between CN and MN (many hops)– Increase of data volume increase (additional 20 bytes IP header)
possibly fragmentation
Page 18 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Tunneling: Minimal Encapsulation• Minimal encapsulation (optional)
– avoids repetition of identical fields (e.g.TTL, IHL, version, DS/TOS)
– only applicable for un-fragmented packets (no space left for fragment identification)
care-of address COAIP address of HA
TTLIP identification
min. encap. IP checksumflags fragment offset
lengthDS (TOS)ver. IHL
IP address of MNoriginal sender IP address (if S=1)
Slay. 4 protoc. IP checksum
TCP/UDP/ ... payload
reserved
Page 19 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Mobile IP: Agent Discovery & Registration
• Mobile Node finds out about FA through Agent Advertisements– FAs broadcast Advertisements in periodic intervals– Advertisements can be triggered by an Agent Solicitation from the MN
• Care of Address of the MN is determined, either– Dynamically, e.g. using Dynamic Host Configuration Protocol (DHCP)– Or: use IP address of FA as CoA
• MN registers at FA and HA: Registration Request & Reply– MN signals COA to the HA via the FA– HA acknowledges via FA to MN
• Registration with old FA simply expires (limited life-time, soft-state)
FAHA MN
[Agent Solicitation] (opt.)Agent Advertisement
Registration Request
Registration Reply Time
Obtain c/o address
Page 20 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
type = 16R: registration requiredB: busy, no more registrationsH: home agentF: foreign agentM: minimal encapsulationG: GRE encapsulationr: =0, ignored (former Van Jacobson compression)T: FA supports reverse tunnelingreserved: =0, ignored
MIP messages:Agent advertisement
preference level 1router address 1
#addressestype
addr. size lifetimechecksum
COA 1COA 2
type = 16 sequence numberlength
0 7 8 15 16 312423code
preference level 2router address 2
. . .
registration lifetime
. . .
R B H F M G r reservedT
Procedure:
• HA and FA periodically broadcast advertisement messages into their subnets
• MN listens to these messages and detects, if it is in the home or a (new?) foreign network
• when new foreign network: MN reads a COA from the advertisement (opt.)
ICMP Router Discovery extension:
Page 21 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
MIP messages: registration request & reply
home agenthome address
type = 1 lifetime0 7 8 15 16 312423
T x
identification
COA
extensions . . .
S B D MG rS: simultaneous bindingsB: broadcast datagramsD: decapsulation by MNM mininal encapsulationG: GRE encapsulationr: =0, ignoredT: reverse tunneling requestedx: =0, ignored
Registration Request (via UDP)
home agenthome address
type = 3 lifetime0 7 8 15 16 31
code
identification
extensions . . .
Registration Reply (UDP)
Example codes:registration successful• 0 registration accepted• 1 registration accepted, but simultaneous mobility bindings unsupportedregistration denied by FA•65 administratively prohibited•66 insufficient resources•67 mobile node failed authentication
•68 home agent failed authentication•69 requested Lifetime too longregistration denied by HA•129 administratively prohibited•131 mobile node failed authentication•133 registration Identification mismatch•135 too many simultaneous mobility bindings
Page 22 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
MIP: Care-of addressesMN obtains local care-of address either• from FA Advertisement (see before)• Or via Dynamic Host Configuration Protocol (DHCP)
– supplies systems with all necessary information, such as IP address, DNS server address, domain name, subnet mask, default router etc.
– Client/Server-Model: client sends request via L2 broadcast
time
server(not selected)
client server(selected)
initialization
collection of replies
selection of configuration
initialization completed
confirmation ofconfiguration
determine the configurationDHCPDISCOVER
DHCPOFFER
DHCPREQUEST(reject)
DHCPACK
DHCPDISCOVER
DHCPOFFER
DHCPREQUEST(options)
determine the configuration
Page 23 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Hierarchical Approaches• Optimization for:
• long registration delay• inefficient routing paths• Frequent re-registration at HA (even though
mostly ‘local’ mobility
• Example (Hierarchical Mobile IPv4):– Hierarchy of Foreign Agents – Every FA re-tunnels the packets to the next
FA until it reaches the MN
– When a handoff occurs, the MN sends a regional registration request to the lowest level FA
– FAs can also re-direct up-stream packets, if the destination (home-address) is registered within their domain
Similar Approach using ‘local Home Agents’ (called Mobility Anchor Points) in HMIPv6draft-ietf-mobileip-hmipv6-08.txt (June2003)
Page 24 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Hybrid Approaches: Cellular IP• Solutions to the local management of micro-mobility events • Mobile IP is used for global mobility• A gateway (GW) acts as foreign agent for each domain (all MNs use GW address as c/o)
• Within the domain: host-based routing• routing cache entries using soft-state• routing cache updated by upstream packets• separate paging cache for in-active nodesrouters within domain have to be CIP aware
• Similar approach: Hand-off Aware Wireless Access Internet Infrastructure (HAWAII)
CIP Gateway
Internet
BS
MN1
data/controlpackets
from MN 1
Mobile IP
BSBS
MN2
packets fromMN2 to MN 1
Page 25 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Hand-over prediction using localization
• Different methods to obtain device positions•Triangulation (signal strength, time of arrival), e.g. GPS•Database Correlation
• Hand-over optimization• predict future location based on estimated past trajectory• use prediction to start hand-over procedure in advance
•Problems• Accuracy of localization
•Adequate filtering techniques (see example)•Include knowledge of building geometry•Include knowledge of mobility patterns
• Timeliness of location information•E.g., Bluetooth localization with several AP 4-10 seconds
Page 26 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
MIP Security Aspects I: Basics (optional)• General security requirements (Security Architecture for the Internet Protocol, RFC
1825)– Authentication
the origin of the data can be determined– Integrity
messages cannot be modified by a third party– Confidentiality
only authorized partners (e.g. sender & receiver) can read the data– Non-Repudiation
sender cannot deny sending of data– Prevention of Traffic Analysis
creation of traffic and user profiles should not be possible– Replay Protection
replay of earlier messages by an attacker can be detected• Additionally: Availability (Prevent Denial of Service Attacks)
Page 27 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
• Security Association (SA) for registrations– extended authentication of registration
registration reply
registration requestregistration request
MIP security aspects II: Security associations(optional)
MH FA HAregistration reply
MH-HA authenticationMH-FA authentication FA-HA authentication
– SA contains the following parameters– Destination IP address– Cryptographic method for encryption/authentication– Encryption/authentication key– Lifetime of key– Specific parameters depending on cryptographic method
Page 28 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Registration Request
MIP security aspects III: Registration (optional)Registration Reply
Identification Reg. Request
1 0 1 0 1 1 0 1 1 1 0 1 1 0 1 1Identification Reg. Reply
1 0 1 0 1 1 0 1 1 1 0 1 1 0 1 1
1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1Identification Reg. Reply Identification next Reg. Request
64
Identification field: protection against replay attacks
• time stamps: 32 bit time-stamp + 32 bit random number
• Nonces: 32bit random number (MH) + 32 bit random number (HA)
Page 29 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
MIP security aspects IV: Authentication extension (optional)
• Part of Registration Messages: MN <->HA, MN<->Fa, FA<->HA
•Computation of Autenticator: cryptographic keyed Hash function (e.g. HMAC-MD5 Algorithm) covering
•UDP payload•All earlier extensions•Type, length and SPI of authentication extension
Using the shared, secret key
• SPI (security parameter index) - determines algorithm, mode, and key
Page 30 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
MIP security aspects V: Firewall traversalIngress Filtering
Problem: MN sends packets to CN with source address = Home Address (and not c/o address)
Firewalls at domain boundaries suspect IP –Spoofing discard packets
Solution: Reverse Tunneling HACH
MH
Firewall
Page 31 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
IP Version 6 (IPv6)IPv6• Basic Header 40 Bytes• 128-bit Network Addresses• Flow label (QoS)• No fragmentation in the network• ‘Built-in’ Security• Neighbor Discovery• Extension Headers:
Routing, Fragmentation, Authentication, Encryption
IPv4• Basic Header 20 Bytes• 32-bit Network Addresses• Type of Service field• Router may fragment packets• IPsec as an enhancement• ARP (Address Resolution Protocol)• Options
Version Priority Flow LabelPayload Length Type of Next Hdr. Hop Limit
Source Address
Destination Address
Offset0812162024283236
4
40
0 1 2 3
Next Header
Page 32 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
IPv6 in mobile settings• Large number of IP addresses (each device needs at
least two addresses!)• Stateless autoconfiguration (can replace DHCP)• Route Optimisation via binding updates to CN
– Return Routability Procedure• Validate ownership of addresses• Exchange Authentication Information
– Binding update with check of authentication info– Soft-state approach: automatic expiry
• IPv6 Extension Header: Mobility Header (Next Header Value=135)
– Binding Refresh Request (MH Type=0)– Home Test Init (1), Care-of Test Init (2)– Home Test (3), Care-of Test (4)– Binding Update (5), BU ACK (6), BU Error (7)
Page 33 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Content 1. Background • Mobility & Handover Types
2. Link-Layer Hand-over• Example: WLAN 802.11
3. Network Layer Mobility Support: MIP• Motivation, Principles, Messages• Performance Enhancements: HMIP• MIPv6
4. Higher-Layer Mobility Support• Transport Layer Mobility, e.g. mobile SCTP• Host Identity Protocol, HIP
5. Hand-over extensions• Multi-homing & flow mobility
• Reminder: Mobility in GPRS/UMTS
• TCP in hand-over situations
6. Summary & Outlook
Appendix: Experimental Measurements
Page 34 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Transport Layer ProtocolsGoal: data transfer between application (processes) in end-systems
• support of multiplexing/de-multiplexing e.g. socket API
data stream/connection identified by:two IP addresses, protocol number, two port numbers
Page 35 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Overview: Transport Protocols
• User Datagram Protocol UDP (RFC 768)– Connectionless– Unreliable– No flow/congestion control
• Transmission Control Protocol TCP (RFC 793, 1122, 1323, 2018, 2581)– Connection-oriented (full duplex)– Reliable, in-order byte-stream delivery– Flow/congestion control
• Stream Control Transport Protocol SCTP (see later)• Real-Time Transport Protocol RTP
– Uses UDP– Provides: Time-stamps, sequence numbers– Supports: codecs, codec translation, mixing of multi-media streams
Page 36 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Streaming Control Transmission Protocol (SCTP)
• Defined in RFC2960 (see also RFC 3257, 3286)• Purpose initially: Signalling Transport• Features
– Reliable, full-duplex unicast transport (performs retransmissions)– TCP-friendly flow control (+ many other features of TCP)– Multi-streaming, in sequence delivery within streams
Avoid head of line blocking (performance issue)– Multi-homing: hosts with multiple IP addresses, path monitoring (heart-beat mechanism),
transparent failover to secondary paths• Useful for provisioning of network reliability
Host A Host BIPa1
IPa2 IPb2
IPb1
Separate Networks
SCTP Association
Page 37 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Transport Layer Handover in SCTP
1. MN communicates with CN via established SCTP association (From IP1 to IP CN)
2. When MN comes in Range of AP B• MN obtains new IP address IP2• MN adds IP2 to the existing SCTP association
Address configuration Change (ASCONF) Chunk
3. When connection should be transferred to new AP B• MN sets primary address to IP2• MN deletes old IP1 from SCTP association (ASCONF
chunk)
IP1
IP 2
Correspondent Node
AP A
AP B
Page 38 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
SCTP Mobility support: Discussion• SCTP Handover transparent for network
– No additional network infrastructure needed– Possible use-case: switch to peer-to-peer mode without network support
• avoids tunneling and tri-angular routing
• Endpoints need to support SCTP (with dynamic control of IP addresses)• Signalling to every correspondent node necessary (for every established SCTP
association) for high number of parallel connections, large signalling volume over air interface
• Dynamic Naming Service for connection set-up from CN required (to establish the initial SCTP association)– Dynamic DNS– Other location mechanisms (e.g. based on SIP URLs)
• Only usable for traffic without real-time requirements (due to SCTP flow/congestion control)– but similar approaches, e.g. for RTP, possible
• Simultaneous Handover (Mobile Node and Correspondent Node) can lead to loss of connection
Page 39 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Host Identity Protocol (HIP)• IETF drafts, see http://www.ietf.org/html.charters/hip-charter.html• Underlying ideas for mobility support
– Separate host identifier (HI, ‘name’) and locator (‘IP address’)– Dynamic name service or rendezvous server for pre-session mobility– Update of mapping of host identifier locator at handovers– Mechanism works between transport
and network layer• In combination with security
– Host Identity Name space based on public keys
– Hash of HI 128bit Host Identity Tag attached to packets
– 4-packet basic exchange (cookies, Diffie-Hellman Key Exchange)
Source: Semester Project, Roost/Toft/Haraldson
Page 40 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Host Identity / Host identifier
• Host Identity in HIP is a public asymmetric key pair.– RSA– DSA– Possible others
• Host Identifier (HI) is the public key which is used to refer the Host Identity.– Statically globally unique.– Used for host authentication.– Variable length (Depending on cryptographic algorithm).
• Host Identity Tag (HIT)– is a fixed length (128 or 64 bit) representation of a Host Identifier– Can be used as IPv6 address– Goal: low collision probability
Page 41 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
HIP Base exchange
• Beginning of a HIP connection• Consists of a 4-way handshake.• Involves :
– Host authentication– IPsec encryption key exchange
(Diffie-Hellman)– DoS prevention via first handshake
• After Base exchange: only ‘normal’ IPsec packets
• Mobility support via ‘re-direction of Ipsec associations’
Page 42 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Content 1. Background • Mobility & Handover Types
2. Link-Layer Hand-over• Example: WLAN 802.11
3. Network Layer Mobility Support: MIP• Motivation, Principles, Messages• Performance Enhancements: HMIP• MIPv6
4. Higher-Layer Mobility Support• Transport Layer Mobility, e.g. mobile SCTP• Host Identity Protocol, HIP
5. Hand-over extensions• Multi-homing & flow mobility
• Reminder: Mobility in GPRS/UMTS
• TCP in hand-over situations
6. Summary & Outlook
Appendix: Experimental Measurements
Page 43 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Multi-homing and flow mobility• Multi-homing: Host supports multiple interfaces with potentially different
IP addresses – E.g. for redundancy purposes (e.g. SCTP)– Simultaneous, multiple wireless access techniques
• Goal: redirect different data-streams via ‚appropriate‘ interfaces– only one home address (as host identificator)– multiple c/o addresses (one per interface)
Flow Mobility, e.g. extension of mobile IP (IETF draft):
• HA contains mapping [home address, flow identifier]
c/o address• Flows identified by (ranges of)
• Source IP addresses (CNs)• Protocol type (TCP, UDP, etc.)• Port Numbers, DSCPs, etc.
UMTS
Access NW
WLAN
Access NW
IP1 (UMTS)
IP2 (WLAN)
IP Transport(Multimedia) Application
Server
Flow 1Flow 2
Page 44 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Reminder: Mobility in GPRS/UMTS
G G SNSG SN
D HC P
R ADIU S
IM S D o m ain
H SS
H L R/AuC
RNC
Node B
Node B
N etw ork Services
SS7, G r
SS 7, G c
G RX Netw o rk
D N SG n-SEC
DN S G n-PRI
G n N etw ork
D N S E xt
B G
G i N etw ork
D M Z
D NSExt
E -m ail
HT T Pproxy
D N S NS
D N S IM S
P-C S C F
I/S -C S CF
MN O 1`s B ackbone
AS N etw o rk
M essages
FT P
V ideo
DN SAS
C orp. Network
VPN -G W Y
AS
B G
IDS
ID S
M N O 1`s N etw ork
B G
1 2 3 4 5 6 7 8 9 * 0 # U E1
BG
In ternetAS
M N O 3
UE3
M N O 2
UE2
IMS
Roaming Support: • UE attaches with SGSN in visited network• PDP context is set-up to GGSN in home network (via Gp interface, GRX network)
Page 45 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Transport of IP packets
ApplicationServerGGSNTerminal SGSNUTRAN
GTP-UGTP-U
User IP (v4 or v6)
Radio Bearer
IP tackets are tunnelled through the UMTS/GPRS network(GTP – GPRS tunneling protocol)
L1
RLC
PDCP
MAC
IPv4 or v6
Application
L1
RLC
PDCP
MAC
ATM
UDP/IPv4 or v6
GTP-U
AAL5
Relay
L1
UDP/IPv4 or v6
L2
GTP-U
IPv4 or v6
Iu-PSUu Gn Gi
ATM
UDP/IPv4 or v6
GTP-U
AAL5
L1
UDP/IPv4 or v6
GTP-U
L2
Relay
L1
L2
IPv4 or v6
[Source: 3GPP]
Page 46 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
TCP-mechanisms in wireless settings
• TCP assumes congestion when packets are dropped– possibly wrong in wireless networks: here we often have packet loss due to
transmission errors– furthermore, mobility itself can cause packet loss (handover losses)
or temporary connection disruptions (timeouts or even broken TCPconnections)
performance of an unchanged TCP degrades severely– however, TCP cannot be changed fundamentally due to the large base of
installation in the fixed network, TCP for mobility has to remain compatible– the basic TCP mechanisms are needed to for congestion control in the wired
network parts
Page 47 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
TCP Performance Degradation
At right end of graph: About 30% packets lost due to wireless link but approx. 95% TCP throughput reduction!!
Example using Bursty Loss Model:• While current state i: packets
corrupted with probability εi
• After each packet: state transition with probability pik
Average Packet Loss Probability:
Page 48 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
TCP over WLAN 802.11b
0
100000
200000
300000
400000
500000
600000
700000
800000
00:00 00:02 00:04 00:06 00:08 00:10 00:12
Th
rou
gh
pu
t (B
yte
s/se
c)
Time
Influence of Distance and Obstacles in Wireless LAN (Downstream)
Direct Line of Sight ConectionLine of Sight 5mOut-of-Sight 5m
Out-of_sight 20m
• Strongly reduced throughput in scenario with poor channel conditions
• No TCP retransmissions observedWLAN link-layer retransmissions (together with rate adaptation) effective in these scenarios
Source: Master Thesis, D. Dungs
Page 49 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
TCP over Bluetooth• Long-term throughput
smaller than achieved maximum in some measurements
• No TCP level retransmissions
Source: Master Thesis, D. Dungs
Page 50 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
TCP over Bluetooth: detailed analysis
0
20000
40000
60000
80000
100000
120000
140000
160000
00:00 00:05 00:10 00:15 00:20 00:25 00:30 00:35
Thr
ough
put (
byte
/s)
Time
UDP Throughput over time (Downstream)
Instantaneous ThroughputInstantaneous Averaged Throughput
Transmission Throughput
• Additional performance metric: throughput average over 10 packets
• Throughput drop-down by approx. 33% after ca. 15 sec. in that experiment
• Possible explanation– BT Packet scheduler / link
symmetry– [interference]
Source: Master Thesis, D. Dungs
Page 51 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Measurement Setup: MIP Handover (Topology I)
Tokyo Delft
Legend:
Aalborg
Fixed Host
Mobile Host
Router
Mobile Node
Toronto
Foreign Agent 210.10.3.254
Switch
WLAN Access Point
8 MBit/s 8 MBit/s
100 MBit/s100 MBit/s
100 MBit/s
Shanghai
100 MBit/sForeign Agent 110.10.1.254
Frankfurt
Server
10.10.2.254Shanghai
10.10.3.X10.10.1.XDownstreamTCP data & UDP probing
Home Agent
• WLAN APs configured with different SSIDs
• HO triggered by change of SSID in mobile node
Page 52 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
MIP hand-over delays• Long HO delays due to
DHCP configuration (standard Windows XP)
• Also realistic in some future scenarios
– Vertical hand-overs– Interface
reconfigurations at Handover (SDR)
• TCP timeout mechanism can in worst case approximately double hand-over delays
Source: Master Thesis, D. Dungs
Page 53 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
TCP Proxy
Mobile Node
Foreign Agent 2
100 MBit/s100 MBit/s
100 MBit/s100 MBit/s
Foreign Agent 1
TCP Proxy Home Agent
Correspondent Node (Server)
Linux Router
100 MBit/s
100 MBit/s
Access Point 1 Access Point 2
Proxy location: Home Agent subnet
• Receives MIP messages and TCP fragments via policy-based routing at HA and Linux Router
• Reverse Tunneling activated – TCP Proxy also processes
upstream ACK packets
Proxy Functionality:• Split-connection approach (TCP
RENO)• After disconnection
– CN is frozen by Zero Window Advertisment
• Upon successful MIP registration:– TCP data transfer is
immediately resumed (when MIP response sent)
• [Additional performance enhancing features]
– not HO related not activated here!
Page 54 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
TCP: Improvements using Proxy
Page 55 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Content 1. Background • Mobility & Handover Types
2. Link-Layer Hand-over• Example: WLAN 802.11
3. Network Layer Mobility Support: MIP• Motivation, Principles, Messages• Performance Enhancements: HMIP• MIPv6
4. Higher-Layer Mobility Support• Transport Layer Mobility, e.g. mobile SCTP• Host Identity Protocol, HIP
5. Hand-over extensions• Multi-homing & flow mobility
• TCP in hand-over situations6. Summary & Outlook
Appendix: Experimental Measurements
Page 56 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
PAN
CAN
BBT
BT
BT
BT
You
Br
VD
aT
VD
aT
YouYouMe
aT
B aTBr
BRo/Br
aT
B aTBr
BThird Party
Ro/Br
aT
Br : BridgeRo : Router
Network Architectures beyond cellular networks
Personal Area Networks (PANs)• Devices attached to or in vicinity of person
group mobility models• Wireless communication
• Between devices within PAN• To infrastructure networks• Between two PANs
Wireless multi-hop communication
Impact of wireless multi-hop• Mutual interference• MAC protocol deficiencies• Need for modified routing (ad-hoc domain)• For PANs: Group Mobility!
[see http:/www.ist-magnet.org]
Page 57 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Outlook: Future wireless networksServices andapplications
IP based core network
IMT-2000UMTS
WLANtype
cellularGSM
short rangeconnectivity
WirelinexDSL
otherentities
DABDVB
New radiointerface
Properties of future networks (‘4G’):• Heterogeneous access
technologies – 802.11, Bluetooth, cellular, etc.
• IP-based core network– Mobility support on IP layer
(complemented by higher-layer methods)• Mobile IP one major candidate
• wireless multi-hop connections• Personalization (Personal Area Networks,
Personal Networks)• Reconfigurability (Software Defined Radio)• Context Sensitivity
Page 58 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
References
• C. Perkins: ’Mobile IP: Design Principles and Practices.’ Addison-Wesley, 1998. • IETF Working groups (see also for RFCs and drafts):
– Mobile IP: http://www.ietf.org/html.charters/mobileip-charter.html– IPsec: http://www.ietf.org/html.charters/ipsec-charter.html– IPv6: http://www.ietf.org/html.charters/ipv6-charter.html– Others: nemo, mip4, dhcp, seamoby
• J. Schiller: ’Mobile Communications’. Addison-Wesley, 2000.• A. Festag, ‘Mobile Internet II, Overview of current mobility approaches’ (lecture material).
TU Berlin, 2002.• Seok Joo Koh, ‘mSCTP: Use of SCTP for IP Mobility Support’, Presentation, IT Forum,
Korea, 2003• H. Schulzrinne, E. Wedlund, ‘Application-Layer Mobility Using SIP’. Mobile Computing and
Communications Review, Vol. 1, No. 2
Page 59 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Acknowledgements
• Lecture notes: Mobile Communciations, Jochen Schiller, www.jochenschiller.de
• Student work (TU Munich, AAU)– Stefan Rank (Master Thesis)– Rui Martins (Master Thesis)– Thorbjørn H. Jørgensen and Lars B. Pedersen (Semester project)– Lars Roost, Per Toft, Gustav Haraldson (Semester project)– Dennis Dungs (Master Thesis)
• Lecture notes: Wireless communication protocols (R. Prasad, TKM)
Page 60 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Exercises
1. Hand-over optimization via location information: Assume an infrastructure WLAN network with multiple subnets and MIPv4 for mobility support. The network infrastructure itself now provides another component, called ’location server’, that can upon request provide geographic coordinates as well as estimation of movement vectors of mobile devices.– Develop an approach to shorten the MIP hand-over delays using hand-over prediction. Show a
message flow for your improved solution (if necessary, feel free to introduce additional entities in your network, or additional functionalities on the Mobile Node)
2. Vertical hand-over between heterogeneous access networks: – Discuss the steps that are necessary to perform a mid-session hand-over from a WLAN hotspot
network to a UMTS access network (hint: MM1 from last semester).– Discuss how mobile IP can be used to support such a hand-over. Where would the home-agent
need to be placed? What possible problems can arise? Consider the structure of the headers at the GGSN in this setting (and be reminded of TFTs, see MM1 last semester)?
Page 61 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Additional Material
Page 62 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Performance Analysis of Hand-over Mechanisms:
Experimental Analysis
Based on semester project by Thorbjørn H. Jørgensen and Lars B. Pedersen,
Aalborg University, Spring 2004
Page 63 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Content1. Scenarios and Mobility
Support Schemes• Migrating IP address• Mobile IPv4• (Mobile) SCTP
2. Measurement Methodology• Approach• Parameter definitions
4. Results and Discussion• Migrating IP address• Mobile IPv4• Mobile SCTP• Comparison of schemes
Page 64 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Migrating IP address (I): setup
• Hand-over only within same subnet• Transparent to transport layer• Hand-over script based on Linux standard bash script commands
10.10.3.169
BT
WLAN
10.10.1.58
BTWLAN
UDP Packet StreamerPacket monitorHandover script
Subnet 10.10.1.X Subnet 10.10.3.X
Page 65 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Migrating IP address (II): Gratuitous ARP
10.10.1.42(00-E0-2D-59-4A-7C)
10.10.1.80(00-E0-2D-59-3D-7B)
ARP cache (Layer 2)IP address MAC address
10.10.1.80 00-E0-2D-59-3D-7B
ARP cache (Layer 2)IP address MAC address
10.10.1.80 00-E0-2D-59-3D-7B
ARP cache (Layer 2)IP address MAC address10.10.1.1 00-E0-2D-39-54-9C
10.10.1.42 00-E0-2D-59-4A-7A
10.10.1.1(00-E0-2D-39-54-9C)
10.10.1.42 00-E0-2D-59-4A-7A10.10.1.1 00-E0-2D-39-54-9C
Gratuitous ARP RequestProtocol Type Request
Sender Protocol Address 10.10.1.42
Target Protocol Address 10.10.1.42
Sender Hardware Address 00-E0-2D-59-4A-7C
Page 66 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
MIP: setup
UDP Packet streamer
10.10.3.169BT
WLANMobile NodeHADDR: 10.10.1.80
BTWLAN
Subnet 10.10.1.X Subnet 10.10.3.X
HA10.10.1.254
FA10.10.3.254
WLAN
• HUT Dynamic MIP–FA or MN decapsulation
• Mobile Node–Handover scripts for forcing handover
Page 67 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
SCTP: setup
SCTPPacket streamer
10.10.3.169BT
WLAN
Mobile Node
BTWLAN
Subnet 10.10.1.X Subnet 10.10.3.XWLAN
• SCTPlib (from sctp.de)– Partial support for Mobile extension– no dynamic modification of IP addresses of association in current implementation
• Mobile node–Handover script for forcing handover
Page 68 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Measurement Methodology: Packet streamers
SCTP Packet Streamer:• Client/Server application
–Maintain association• Reliable transport protocol
–Flow control mechanisms !
INIT
INIT ACK
COOKIE ECHO
COOKIE ACK
STREAM PACKET
STREAM PACKET
STREAM PACKET
STREAM PACKET
ASCONF
ASCONF ACK
STREAM PACKET
STREAM PACKET
STREAM PACKET
STREAM PACKET
SHUTDOWN
SHUTDOWN ACK
Client Server
Association created
Association initiated
Handover initiated
Shutdown initiated
• Handover determined from packet stream– With deterministic inter packet time– UDP and SCTP packet streamer
• Packet stream captured on mobile node (Ethereal)
Page 69 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Definition of handover delay
1: 10
0Ha
ndov
er in
itiat
ed
Last
pac
ket o
n NI
C 1
Firs
t pac
ket o
n N
IC 2
Hand
over
end
ed
[s]
Han
dove
r sta
rted
Handover delay(Soft handover )
Total handover delay(Hard handover )
1:11: 21: 31 :41:51: 61: 71: 81 :9
1: 111:121:1 31: 161: 141 :151: 161:1 71: 181: 191: 211:20
2:2 82: 291: 222 :302: 312:3 22: 332: 342: 352:362:3 72: 382: 392 :40
Page 70 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Migrating IP address: Results• Precision
–Inter-packet time 5ms•Results (w. 95% conf. interv.)
–Bluetooth WLAN•18.8ms±3.2 (Soft)•31.5ms±2.8 (Hard)
–WLAN Bluetooth•25.9ms±3.2 (Soft)•60.4ms±2.1 (Hard)
Page 71 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
MIP: handover delay distribution
Home BT Foreign WLAN, MN decapsulation
• problems with packet forwarding FA MN cause long delays in many measurements
Page 72 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
SCTP: handover delay distribution
• BT WLAN in different subnets• Problem with long total handover delay (>3s), but not for WLAN BT handover
– possibly due to ‘inter-working’ problems between SCTP library and WLAN device driver
Page 73 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Page 74 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Page 75 Hans Peter SchwefelWireless Networks III, Fall 2006: MM1, IP Mobility Support
Reference
• Lars B. Pedersen, Thorbjørn H. Jørgensen: ’Experimental Analysis of Mobility Support Schemes for vertical Handover’, Project Report, 6th semester communication networks, Aalborg University, June 2004.
For additional experimental investigations:• Lars J. Roost, Per N. Toft, Gustav Haraldson: ’The Host Identity Protocol – An
experimental evaluation’, Project Report, 6th semester communication networks, Aalborg University, June 2005.