1 kommunikatsiooniteenuste arendus irt0080 loeng 6 avo ots telekommunikatsiooni õppetool, ttÜ...
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Kommunikatsiooniteenuste arendusIRT0080Loeng 6
Avo Otstelekommunikatsiooni õppetool,
TTÜ raadio- ja sidetehnika [email protected]
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Access
Multi-service User Terminal
Common Core
Network
Basic Access Network
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Architectural Layout
Multi-service User Terminal (MUT)
Basic Access Network cells
Com
mon
Cor
e
Net
wor
k P
lane
Internet
IP backbone
Managed IP Network
Servic
e Net
work
Plane
RANs
B
asic A
ccess
Netw
ork
Plane
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Typical Broadband IP Model
L2TP Tunnel
Access PoP
ISP
ISP
INTERNET
Carrier IP core
Access PoP
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BAS
Broadband ‘Direct’
Access PoP
ASP
ASP
INTERNET
Access PoP
Carrier IP core
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Link Layer Mobility
• Handover is taken care of by the involved BSs (and BSS) of the RAN
• Applicable only to the same RAN
• Within IP sub-network
• Transparent to the network layer– Care-of-Address is retained
– No registration activity involved
• BAN signaling not necessary
BS
BS
BS
BS
BS
BS
BS
BSS
IP Subnet: 160.243.x.x
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Micro and Macro Mobility in IP
BS
BS
BS
BS
BS
BS
BS
BSS
BS
BS
BS
BS
BS
BS
BS
BSS
BS
BS
BS
BS
BS
BS
BS
BSS
BS
BS
BS
BS
BS
BS
BS
BSS
IP Subnet: 160.241.x.x
IP Subnet: 160.242.x.x IP Subnet:
160.243.x.x
IP Subnet: 160.244.x.x
IP C
ore
RA
N
Roo
t CC
N/In
tern
et
Macro Domain/Region
Micro Domain
Subnets
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Heterogeneous Wireless Networks
Internet
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IP Protocol StackApplication
Telnet, FTP, RPC,SIP, SAP, SDP, RTP/RTCP, RTSP
HTTP, SMTP, etc.
TCP and UDP
IP/ICMP, Routing Protocols, Mobile IP, IP Multicast/IGMP, etc.
Ethernet, ATM, 802.11, HIPERLAN, UMTS, Bluetooth, etc.
Presentation
Session
Transport
Network
Link
Physical
User Space
Device Drivers and Hardware
Operating System
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IP Mobility
• No true IP mobility is available
• L2TP provides limited IP mobility within the boundaries of the specific access network
• Only MobileIP technology can provide true IP mobility to end users
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IP Mobility – the Problem• Internet Protocol routes packets to their
destination according to IP addresses
• IP addresses are associated with a fixed network location
• TCP Protocol uses IP addresses and port number to identify a session
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IP Mobility ProblemMobile Computer at Home Link:
Internet
Link C204.71.200.xxx
Link A129.187.109.xxx
Link B129.187.222.xxx
129.187.109.40
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IP Mobility ProblemMobile Computer to Foreign Link:
Internet
Link C204.71.200.xxx
Link A129.187.109.xxx
Link B129.187.222.xxx
129.187.109.40
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IP Mobility ProblemMobile Computer at Foreign Link:
Internet
Link C204.71.200.xxx
Link A129.187.109.xxx
Link B129.187.222.xxx
129.187.109.40
Different SubnetNumber
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IP Mobility ProblemMobile Computer at Foreign Link:
Internet
Link C204.71.200.xxx
Link A129.187.109.xxx
Link B129.187.222.xxx
129.187.109.40
Different SubnetNumber
?
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IP Mobility –Mobile IP
• One IP address for identifying a mobile node. The original & permanent IP adress at home link: Home Address
• One IP address for locating a mobile node. A temporary IP address at current (foreign) link: Care-of Address
• Transparency for higher layers (including applications)
Home Address Home Address
IP Home Address Home AddressCare-of Address Care-of
Address
Dual Adressing
Transparency
A Node that can move from Access Point to Access Point being always reachable for other nodes by hisHome Address.
a Router at the Home Network where the Mobile Nodecan register its Care of Address.
Static IP Address of the mobile Host in his Home Network(e.g. used to identify TCP connections)
Temporary IP Address that identifies the Mobile Nodein a visited Network (CoA)
The Router in the Foreign Network, that provides CoA
Terminology in Mobile IP
Mobile Node
Home Agent
Home Address
Care-of Address
Foreign Agent
The node which is connected to the Mobile NodeCorrespondent Node
for visiting Mobile Nodes
Requirements for Mobility in Internet
Mobility • Increasing number of users asks for Mobility Support in Internet
Transparency • Mobility shall be transparent to all Protocol Layers above IP
Routing • Mobility shall be compatible to all Routing Protocols and shall optimize routes
Easy to use • Mobility shall be as easy to handle as with Mobile Phones in GSM
Security • Mobility shall not decrease security in Internet
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Mobile IP – Basic Mechanisms• Discovery of the Care–of Address (CoA)
using Router Advertisements
• Registering the Care–of Address
• Tunneling to the Care–of Address
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Mobile IP Scenario
Internet
R
R
R
Home LinkLink A
Link B
Link CHome Agent
Foreign Agent Mobile Node
Node C
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Mobile Node registers at its Home Agent
Internet
R
R
R
Link B
Link CHome Agent
Foreign Agent Mobile Node
Host C Mobile Node sends Binding Update Home Agent confirms with Binding Acknowledgement
1
2
12
Home LinkLink A
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Tunneling
DecapsulationEncapsulation
SourceDestination
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Internet
Home Agent
R
R
R
Mobile Node moves
Home NetworkNetwork A
Network B
Network C
R RouterCorrespondent
Node
Mobile Node
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Mobile Node sends Binding Update
Home Agent confirms with Binding Acknowledgement
Mobile Node registers at its Home Agent
Internet
Home Agent
Mobile Node
R
R
RNetwork B
Network C
Network A
CorrespondentNode
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Internet
Correspondent Node C initiates connection and sends packets to the Home Address of the Mobile Node
Home Agent intercepts packets and tunnels themto the Mobile Node
Mobile Node sends answer directly to Host C
Home Agent
R
Mobile Node
R
R
Triangular Routing during Initial Phase
Network B
Network C
Network A
CorrespondentNode C
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Internet
Mobile Node sends Binding Update to Correspondent Node C
Now Correspondent Node can address the CoA of the Mobile Node directly
Home Agent
R Mobile Node
R
R
Normal Operation by Route Optimization
Network B
Network C
Network A
CorrespondentNode
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Internet
Mobile Node sends Binding Updates to theHome Agent and to all the Nodes, he is connected to
Home Agent
R
R
R
R
Mobile Node moves
Network B
Network C
Network A Network D
CorrespondentNode
Mobile Node
InternetMobile Node
Home Agent 2
Home Agent 3
Mobile Node sends Binding Update to the Home-AgentsAnycast Address of its Home Network.
A Home Agent answers with Binding Acknowledgementwhich contains the Home Agents List
Home Agent 1
R
R
Dynamic Home Agent Address Discovery
Home Agent 3 9Home Agent 1 2Home Agent 2 -3
Home Agents List Priority
Mobile Node sends Binding Update to the first Home Agentfrom the Home Agents List
Binding Acknowledgement; Registration OK
Registration with selected Home Agent
InternetMobile Node
Home Agent 2
Home Agent 3
Home Agent 1
R
R
Home Agent 3 9Home Agent 1 2Home Agent 2 -3
Home Agents List Priority
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IPv6 Source AddressCare-of Address
IPv6 Destination Address
Destination OptionsHome Address OptionBinding Update Option
Payload
Packet Format Mobile IPv6
MN Correspondent Node
IPv6 Source Address
IPv6 Destination AddressCare-of Address
Routing HeaderHome Address
Payload
Correspondent Node MN
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Advantages Mobile IPv6
• Mobility already considered in design of IPv6• 128 bit IPv6-Addresses allows Mobile Node to
derive CoA from Router Advertisement easily• Stateless Address Autoconfiguration and
Neighbor Discovery make FAs and DHCP-Server superfluous
• IPv6 supports dynamically finding of HA efficiently by means of Anycast Address
• Integrated IPSec-Functionality in IPv6 makes Authentication of Mobile IPv6 Packets easier (in MIPv4 IPSec is optional, in MIPv6 mandatory)
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RFC
IP Mobility Support (RFC 2002)
IP Encapsulation within IP (RFC 2003)
Minimal Encapsulation within IP (RFC 2004)
Reverse Tunneling for Mobile IP (RFC 2344)
...
Internet Draft
Mobility Support in IPv6
Route Optimization in Mobile IP
Requirements on Mobile IP from a Cellular Perspective
...
Mobile IP in Standardization
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IPv6 in 3G Networks
IM DomainIPv6
PS DomainIPv4 or IPv6
Existing IPv4Internet
SGSN GGSN
Mobile Terminal
SIP ProxyServer
Media/SignallingGateway
PSTN
SIP Client
SIP ProxyServer
GTP OperatorsISP
WWW Server
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IPv6 in Broadband Networks
DSLAMATM
IP Core
Internet
BASInternet VC – Variable Bit Rate
SIP VC – Constant Bit Rate
IPv6 Multimedia Domain
SIP Serve
r
Other Operator’s Multimedia Domain
Globally routable IPv6 address(es)
IPv4 or IPv6 address
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Broadband/3G Integration• Unified infrastructure
– No interworking or gateways
• No addressing problems– Forecasted volumes easy to cater for
• Leverage application development for maximum returns
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MobileIPv6 Benefits• MobileIPv6 + Broadband ‘Direct’
model is a powerful enabler of IP mobility
• End-users running services are continuously on-line and contactable while roaming between broadband network access segments
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MobileIPv6 and Broadband
Without MobileIP, connections from UserA to UserB have to go via ISP A and ISP B
Inefficient routing Poor scalability Multiple single-points-
of-failure
ISP B
UserA
UserB
ISP A
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MobileIPv6 and Broadband
ISP B
UserA
UserB
ISP A
Initial traffic only passes through ISPs
Subsequent traffic direct to Care-of-address
Home Agent
Home Agent
Holds care-of-address of user B
Holds care-of-address of user A
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IPv6 Transition & Interworking
• Transition– how we migrate to IPv6
• Interworking– how we continue to operate with IPv4
• New networks have no transition requirements
• Transition requirements for core networks met through routine upgrades
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IPv6 Interworking
• Interworking multimedia domains– Enabling SIP application interworking– Deploy proxies at the network boundary
• Interworking network core– Dependent on type of address allocation to
end-user– Translation is required where user has no
IPv4 address
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IM DomainIPv6
PS DomainIPv4 or IPv6
Existing IPv4Internet
SGSN GGSN
Mobile Terminal
SIP ProxyServer
Media/SignallingGateway
PSTN
SIP Client
SIP ProxyServer
GTP OperatorsISP
WWW Server
Interworking Options
Potential points of IPv4/IPv6 interworking
support
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NAT-PT Translation
DSL Access Network
IP Network (IPv4)Access Router (IPv6)
End User Equipment(IPv6 only)
NAT-PT
IPv6 DNS
IPv4 DNS
DNS exchange initiates communication via translator
Communication with IPv4 via translator
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DSTM Support for native IPv4
DSL Access Network
IP Network (IPv4)
Access Router (IPv6)End User
Equipment(Initially IPv6
only)
DHCPv6End user discovers communication to IPv4 – requests temporary IPv4 address
Native communication with IPv4
IPv4 over IPv6 tunnel
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IPv4 GPRSContainer
RNC
WLAN BS2
Serial Router 2
Ultima202.140.100.18
202.140.100.22-30
HKLive IPv4
MAP202.140.100.20
Scenario 4: Fixed/Mobile
roaming
R520Ethernet
Scenario 3: Broadband MobileIPv6
Scenario 2: Wireless
broadband IPv6
WLAN BS1 Scenario 1: Fixed
broadband IPv6
VOD
Local Native IPv6 Network
HA
Hub 3
Hub 2
APPS(WWW, MP3, Quake, DNS)
202.140.100.17
PROXY202.140.100.19
CN
Hub 1
Router 1
Ethernet 6in4 tunnel202.140.100.21
PC 6in4 tunnelPrivate IPv4 addresses
PC
MIPv6
MIPv6
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Scenario 1: Broadband IPv6
Applications Server
DNS Server
HK IPv6 Network
WLAN
Quake IPv6 LocalInternet
IPv6 MP3 Audio
IPv6 VoD
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Scenario 2: IPv6 meets IPv4
DNS Server
IPv6 Network
IPv4 Internet
IPv6 Network
IPv6 Internet
IPv4Internet
IPv6 MP3 Audio
IP v4
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Scenario 3: MobileIPv6
Portal Server
Database Server
Home Agent
IPv4 InternetHK IPv6
Network
Local News & Weather
Home Domain
Office Domain
WLAN
Business News, Shares & Reminders
WLAN
MIPv6
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Scenario 4: Inter-technology handover
Portal Server
Database Server
Home Agent
IPv4 Internet
WLAN
HK IPv6 Network
GPRS
Business News, Shares & Reminders
Mobile Domain
Low Bandwidth
GPRS
Office Domain
High Bandwidth
Business News, Shares & Reminders
MIPv6
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Testbed System
InternetInternet
Mobile PAN
3G APs Advanced WLAN APs Beyond 3G APs
InternetInternet
Mobile PAN
3G APs Advanced WLAN APs Beyond 3G APs
SDR Terminals
Ring Core Network
Segment Network(Star Topology)
Segment Network(Bus Topology)
SignalingServer
Signaling Data
AAA Proxy
AAAServer
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IP Mobility Support• Basic idea of IP mobility management
– understand the issues of network-layer mobility support in IP network
– understand the basic design principles underlying all mobility support schemes
• Internet standard: mobile IPv4, Mobile IPv6– the operations of MIPv4– introduction to MIPv6
• Fast handover solutions
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Network Support for Mobility
• In TCP/IP, the host address plays two roles:– acts as an end-point identifier for connections involving
the host• a host address should always remain the same
– provides routing info for packets destined for the host• a host address should change whenever the host moves
• Goal: support mobility without having to change the protocols in all the millions of hosts currently on the Internet
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Two Tier Addressing• We need an address pair to identify a MH
at any time:– Home address for identification– current address for routing
• How to do two-tier addressing:– not physically done (which requires 8 bytes of
address per host)– perform address translation along the way by
some specialized agents that cache both addresses.
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Architecture to Support Mobility• Mobile host (MH): a host that moves
• Home address (HA): a location-independent address for a MH
• Home network: the network identified by the net id part of the HA of MH. A home net has some special agents for proxy-arp, packet forwarding, address translation etc. to support mobility
• When a MH moves within its home network, no network-level support is needed since packet forwarding is achieved by bridges
• When a MH moves across networks, the HA cannot be used for routing, though the HA has to be used for end-point identification by TCP
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Forwarding Agent
• Current address must refer to the foreign network when a MH is in a foreign network
• Packets destined for the MH contain the address of a Forwarding Agent (FA).
• FA forwards packets to the MH– If FA and MH are directly connected, FA simply replaces the
destination address with the Home Address of the MH
– otherwise, FA has to forward the packet to other FAs till the packet reaches the MH
• Note that the router/agent that is the last hop to the MH must be mobility aware, since it has to do the final address translation from FA to MH– example: base stations act as FAs
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Location Directory
• Location directory (LD) provides the mapping between the home address and forwarding address for a MH
• MH is responsible for sending updates to the LD when it moves
• LD is distributed
• Typically, the Home network maintains LD for its MHs, though parts of the LD are allowed to be cached by other foreign networks
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Address Translation
• When a source communicates with a MH, the MH puts its
HA in the destination address field.• Somewhere along the route, this has to pass thru an address
translation agent (ATA), which converts the HA to the forwarding address.
• Address Translation can be provided by 2 mechanisms:– IP-IP Encapsulation: encapsulate the original datagram within
another datagram that contains the FA address
– Loose source routing: indicates intermediate hops over which the datagram must travel to the final destination. In this case, the intermediate hop will be the FA, which then converts the packet address to the final destination
–
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Packet Forwarding• Source sends out packets that are addressed to HA
of MH• ATA intercepts packets and maps HA to FA
(using IPIP or LSR)• Packets arrive at FA• FA remaps address to HA and delivers packets
over the last hop• At the MH, the packet seems to arrive from
Source to HA; thus, transport layer is provided transparency
• What if the final FA and the MH were co-located ? Optimizations in this case ?
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Mobile IPv4: RFC2002
• Macro-management for mobility– less frequent than once per second– More concerned about long-term performance:
whether to allow seamless mobility or not
• Two scenarios for packet forwarding:– MH to a static host: as usual– a static host to a MH: needs Mobile IP
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A Quick Mapping for Mobile IPv4 to the Architecture
• Forwarding agent: co-located with foreign Agent or with MH (if DHCP is used)
• Location Directory: at home router only• Address Translation Agent: co-located with home
router• location update protocol: caching of LD is not
allowed; when a MH moves, only the primary copy is modified
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Basic Concepts
• Home agent: a router on a MH’s home network which tunnels datagrams for delivery to the MH when it is away from home, maintains LD for MH
• Foreign agent: a router on a MH’s visited network which provides routing services to the MH while registered. FA detunnels and delivers datagrams to the MH that were tunneled by the MH’s HA.
• Care-of Address: termination point of a tunnel toward a MH, for datagrams forwarded to the MH while it is away from home.– Foreign agent care-of address: the address of a foreign agent that
MH registers with– co-located care-of address: an externally obtained local address that
a MH gets.
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Protocol Overview• Mobility agents (FAs & HAs) advertise their presence• MH receives the agent advertisements & determines whether it
is on its home net or a foreign net– Home net: MH operates without mobility service– Foreign net: obtains a care-of address on the foreign net (via FA’s
agent advertisements or DHCP)
• if away from home, MH registers its new care-of address with its HA thru a registration request/response process (possibly via a FA).
• Datagram sent to the MH’s home address:– intercepted by its home agent, – tunneled by the HA to the MH’s care-of address, – detunneled at the tunnel endpoint (either a FA or MH itself), – and finally delivered to the MH
• In the reverse direction, using standard IP routing.
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Agent Discovery• Method used by a MH to determine whether it is in its home net
or a foreign net; may allow MH to determine the foreign agent care-of address
• Mobile IP extends ICMP router Discovery as its mechanism for Agent Discovery– agent advertisement & agent solicitation
• Agent advertisement: – lifetime: maximum length of time that the Advertisement is considered
valid in the absence of further Advertisement– if sends periodically, allows a MH to miss 3 Adv messages before deleting
the agent from its list.– If it can serve as a FA, must announce its FA care of address– HA must always be prepared to serve the MHs for which it is the HA.– FA may announce too busy to handle additional MHs, but must still
continually send out the Adv messages.
• Agent solicitation: must be implemented by a MH
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Registration• A mechanism for MHs to communicate their current
reachability info to their home agent• MHs use registration to
– request forwarding service when it is in a foreign network– inform their HA of their current care-of address– renew a registration which is due to expire– deregister when they return to home
• registration may be via a FA or directly from the MH.– Via a FA:
• If a MH is registering a FA care-of address• if a MH is using a co-located care-of address and receives an Agent Adv
from a FA if the “Registration required” bit is set in the Adv message
– directly with HA:• MH is using a co-located care-of address and not in the above case• when MH returns to home net,
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Registration OverviewVia FA:• MH sends a Registration Request to the FA • FA receives the request and relays it to the HA• HA sends a Registration Reply to the FA to grant/deny the
registration request• FA processes the Registration Reply and relays it to the
MHDirectly with HA:• exchanges Request/Reply with HA directly• After a successful registration:• HA creates/modifies the entry for the MH:
– MH’s care-of address, remaining lifetime of the registration, ID field from the Registration Reply
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Routing Consideration• Foreign Agent:– maintains a visitor list– when receives an encapsulated datagram, compare the inner destination
address to entries in its visitor list; route datagrams.
• Home Agent:– how to intercept any datagrams on the home net addressed to the MH when
the MH is away from home– use Proxy and gratuitous ARP:
• when a MH is registered on a foreign net, its HA uses proxy ARP to reply to ARP request that seeks the MH’s link-layer address
• when MH leaves/returns its home net, its HA uses gratuitous ARP to update the ARP caches of nodes on the home net, causing such nodes to associate the link-layer address of the HA with the MH’s home IP address
– Proxy ARP: an ARP reply sent by one node on behalf of another in response to an ARP request. The proxy supplies its own link-layer address in the reply.
– Gratuitous ARP: an ARP packet sent by a node to spontaneously cause others to update an entry in their ARP cache.
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Co-located care-off address via DHCP• DHCP (RFC1541):
– a generic protocol for dynamic host configuration– can be used to obtain care-of IP address, default router address, IP
subnet mask of a foreign net, domain, and DNS name– Each net is expected to provide either a DHCP server or relay
• Steps:– The DHCP client sends a DHCP_DISCOVER or DHCP_REQUEST
message– The DHCP server has a pool of available addresses. When it sees an
address request, it picks one of the addresses and responds with the DHCP_OFFER message, containing the home address.
– The DHCP client receives the address, and responds with a DHCP_REQUEST request confirming the address acceptance. The server then binds the address to the client. The server responds with a DHCP_ACK message.
– The DHCP client may proceed with its registration process.
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Route Optimization• Idea:
– Correspondent hosts can learn the current care-of address for a MH, and creates a valid binding (LD cache entry) for a MH, and becomes Address Translation Agents
– Host can encapsulate packets directly to the care-of address of MH (thus bypassing the HA), just as the HA does in the basic Mobile IP spec; host can also use minimal encapsulation as an abbreviated style of encapsulation (8 bytes addtion to the IP datagram)
• Two main issues:– updating binding caches
• only when it received and authenticated the MH’s mobility binding• when HA intercepts a datagram and tunnels it to the MH, HA sends a
Binding Update message to the sender• when FA sees that MH is not on its visitor list, it sends HA a Binding
Warning message, advising HA to send a Binding Update message to the MH
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Route Optimization (contd)• Foreign Agent Smooth Handoff (this is so-called fast
handover, to be talked further)– In basic Mobile IP, datagrams in flight may be lost during
handoff since HA forwarded those packets to the old FA.– Solution: old FA is notified of the MH’s new FA via a Binding
Update message from the new FA, and forwards datagrams in flight to the MH’s new care-of address
• Summary– Forwarding agent: same as basic mobile IP– Location Directory: correspondent hosts can cache LD entries– Address Translation Agent: colocated with correspondent hosts– Location update: HA is responsible for sending Binding Update
message
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IPv6 Mobility Proposal• Mobility support is a basic requirement for IPv6 design
• Key differences from Mobile IPv4:– support for route optimization becomes a fundamental part of the
protocol, not an optional part as in Mobile IPv4
– no need to deploy foreign agents any more
– packets sent to a MH while away from home are tunneled using an IPv6 Routing header (analogous to loose source routing in IPv4) rather than IP encapsulation
– MH is always responsible for delivering binding updates to its correspondence hosts
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Overview of Mobile IPv6• Forwarding agent: co-located with MHs
• Location directory: LD is maintained at home router. Cache entries are acquired thru Binding Update messages issued by MHs
• Address Translation Agent: colocated with all hosts and home routers
• Location Update: MH is responsible for updating the primary copy and all LD cache entries.
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Fast Handover• So far we only care about the long-term
performance, what about short-term transience during the handovers?– Will lose packets in flight, hard for TCP to
swallow– Handover across geographically adjacent
subnets happen most often in practice
• Fast handover seeks to solve this problem
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Idea behind fast handover• Set up a forwarding tunnel between the old
access router and the new access router
• The old access router forwards all the packets through the tunnel to the new access router, which delivers them to the MH
• Several solution proposals so far:– MAC bridge based– Proposal within MIPv6
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Summary• Forwarding agent: co-located with foreign Agent or
with MH (if DHCP is used)• Location Directory: at home router only• Address Translation Agent: co-located with home
router• location update protocol: caching of LD is not
allowed; when a MH moves, only the primary copy is modified
• Route optimization: never; – triangle routing problem– location info is NOT allowed to be cached due to
security concerns
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Linkhttp://www.ietf.org/rfc/rfc4260.txt?number=4260
http://www.ietf.org/rfc/rfc4283.txt?number=4283
http://www.ietf.org/rfc/rfc4285.txt?number=4285