Transcript Teenus_6 - Raadio- ja sidetehnika instituut

Kommunikatsiooniteenuste
arendus
IRT0080
Loeng 6
Avo Ots
telekommunikatsiooni õppetool,
TTÜ raadio- ja sidetehnika inst.
[email protected]
1
Access
Common
Core
Network
Multi-service
User Terminal
Basic Access
Network
2
Architectural Layout
Internet
IP backbone
Managed IP
Network
RANs
Multi-service User
Terminal (MUT)
Basic Access Network cells
3
Typical Broadband IP Model
Access PoP
ISP
L2TP Tunnel
Carrier IP core
ISP
Access PoP
INTERNET
4
Broadband ‘Direct’
ASP
Access PoP
BAS
Carrier IP core
ASP
Access PoP
INTERNET
5
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
IP Subnet: 160.243.x.x
BSS
BS
BS
BS
BS
BS
BS
BS
• BAN signaling not necessary
6
Root CCN
/Internet
Micro and Macro Mobility in IP
IP Core
Macro Domain/Region
IP Subnet: BSS
160.244.x.x
BSS
IP Subnet: BSS
160.241.x.x
BSS
IP Subnet:
160.242.x.x
IP Subnet:
160.243.x.x
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
BS
RAN
Micro Domain
BS
BS
BS
Subnets
7
Heterogeneous Wireless Networks
Internet
8
IP Protocol Stack
Application
Presentation
Telnet, FTP, RPC,
SIP, SAP, SDP, RTP/RTCP, RTSP
HTTP, SMTP, etc.
User Space
Session
Transport
TCP and UDP
Operating System
Network
IP/ICMP, Routing Protocols, Mobile IP, IP
Multicast/IGMP, etc.
Link
Ethernet, ATM, 802.11, HIPERLAN, UMTS,
Bluetooth, etc.
Device Drivers and
Hardware
Physical
9
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
10
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
11
IP Mobility Problem
Mobile Computer at Home Link:
Link A
129.187.109.xxx
Link C
204.71.200.xxx
129.187.109.40
Internet
Link B
129.187.222.xxx
12
IP Mobility Problem
Mobile Computer to Foreign Link:
Link A
129.187.109.xxx
Link C
204.71.200.xxx
129.187.109.40
Internet
Link B
129.187.222.xxx
13
IP Mobility Problem
Mobile Computer at Foreign Link:
Link A
129.187.109.xxx
Link C
204.71.200.xxx
Internet
Link B
129.187.222.xxx
Different
Subnet
129.187.109.40
Number
14
IP Mobility Problem
Mobile Computer at Foreign Link:
?
Link A
129.187.109.xxx
Link C
204.71.200.xxx
Internet
Link B
129.187.222.xxx
Different
Subnet
129.187.109.40
Number
15
IP Mobility –Mobile IP
Dual Adressing
Transparency
•
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)
IP
Home Address
Home Address
Home Address
Care-of Address
Home Address
Care-of Address
16
Terminology in Mobile IP
Mobile Node
A Node that can move from Access Point to Access Point
being always reachable for other nodes by his
Home Address.
Home Agent
a Router at the Home Network where the Mobile Node
can register its Care of Address.
Home Address
Static IP Address of the mobile Host in his Home Network
(e.g. used to identify TCP connections)
Care-of Address
Temporary IP Address that identifies the Mobile Node
in a visited Network (CoA)
Foreign Agent
The Router in the Foreign Network, that provides CoA
for visiting Mobile Nodes
Correspondent
Node
The node which is connected to the Mobile Node
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
Easy to use
• Mobility shall be as easy to handle as with
Mobile Phones in GSM
Routing
• Mobility shall be compatible to all Routing
Protocols and shall optimize routes
Security
• Mobility shall not decrease security in Internet
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
Link B
R
Foreign Agent
Home Link
Link A
R
Mobile Node
Internet
Home Agent
Link C
R
Node C
20
Mobile Node registers at its Home Agent
Link B
R
Home Link
Link A
2
Foreign Agent
Mobile Node
1
R
Internet
Home Agent
Link C
R
1
2
Mobile Node sends Binding Update
Home Agent confirms with Binding Acknowledgement
Host C
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Tunneling
Encapsulation
Source
Decapsulation
Destination
23
Mobile Node moves
Network B
R
Home Network
Network A
R
Mobile Node
Internet
Network C
Home Agent
R
R
Router
Correspondent
Node
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Mobile Node registers at its Home Agent
Network B
R

Network A 
R
Mobile Node
Internet
Home Agent
R
 Mobile Node sends Binding Update
 Home Agent confirms with Binding Acknowledgement
Network C
Correspondent
Node
25
Triangular Routing during Initial Phase
Network B
R
Network A 
R
Internet
Mobile Node

Home Agent
Network C
R

 Correspondent Node C initiates connection and sends
packets to the Home Address of the Mobile Node
 Home Agent intercepts packets and tunnels them
Correspondent
Node C
to the Mobile Node
 Mobile Node sends answer directly to Host C
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Normal Operation by Route Optimization
Network B
R

Network A
R
Internet
Home Agent
Mobile Node
Network C
R

 Mobile Node sends Binding Update to
Correspondent Node C
Correspondent
Node
 Now Correspondent Node can address the CoA of
the Mobile Node directly
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Mobile Node moves
Mobile Node
Network B
R
Network D
Network A
R
R
Internet
Home Agent

Network C
R
 Mobile Node sends Binding Updates to the
Home Agent and to all the Nodes, he is connected to
Correspondent
Node
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Dynamic Home Agent Address Discovery
Home Agents List
Priority
Home Agent 3
Home Agent 1
Home Agent 2
9
2
-3
R
Home Agent 3
R
Home Agent 1


Internet
Home Agent 2
Mobile Node sends Binding Update to the Home-Agents
Anycast Address of its Home Network.
A Home Agent answers with Binding Acknowledgement
which contains the Home Agents List
Mobile Node
Registration with selected Home Agent
Home Agents List
Priority
Home Agent 3
Home Agent 1
Home Agent 2
9
2
-3
R
Home Agent 3
R
Home Agent 1


Internet
Mobile Node
Home Agent 2
Mobile Node sends Binding Update to the first Home Agent
from the Home Agents List
Binding Acknowledgement; Registration OK
Packet Format Mobile IPv6
MN  Correspondent Node
Correspondent  Node MN
IPv6 Source Address
Care-of Address
IPv6 Source Address
IPv6 Destination Address
Destination Options
Home Address Option
Binding Update Option
IPv6 Destination Address
Care-of Address
Routing Header
Home Address
Payload
Payload
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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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Mobile IP in Standardization
RFC
Internet Draft







IP Mobility Support
(RFC 2002)
IP Encapsulation within
IP (RFC 2003)

Minimal Encapsulation
within IP (RFC 2004)
Reverse Tunneling for
Mobile IP (RFC 2344)

Mobility Support in IPv6
Route Optimization in
Mobile IP
Requirements on
Mobile IP from a
Cellular Perspective
...
...
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IPv6 in 3G Networks
IM Domain
IPv6
SIP Proxy
Server
PSTN
Media/
Signalling
Gateway
PS Domain
IPv4 or IPv6
Mobile
Terminal
GTP
SGSN
GGSN
Operators
ISP
Existing IPv4
Internet WWW Server
SIP Proxy
Server
SIP Client
34
IPv6 in Broadband Networks
Internet
IPv4 or IPv6
address
DSLAM
ATM
Internet VC –
Variable Bit Rate
BAS
IP Core
SIP VC –
Constant Bit Rate
Globally routable
IPv6 address(es)
IPv6
Multimedia
Domain
SIP
Serve
r
Other
Operator’s
Multimedia
Domain
35
Broadband/3G Integration
• Unified infrastructure
– No interworking or gateways
• No addressing problems
– Forecasted volumes easy to cater for
• Leverage application development for
maximum returns
36
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
37
MobileIPv6 and Broadband




User
Without MobileIP,
A
connections from UserA
to UserB have to go via
ISP A and ISP B
Inefficient routing
Poor scalability
Multiple single-pointsof-failure
User
B
ISP B
ISP A
38
MobileIPv6 and Broadband
User
A
User
B
Subsequent
traffic direct to
Care-of-address
ISP B
Home
Agent
Holds care-ofaddress of
user B
Initial traffic
only passes
through ISPs
ISP A
Home
Agent
Holds care-ofaddress of
user A
39
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
40
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
41
Interworking Options
IM Domain
IPv6
SIP Proxy
Server
PSTN
Media/
Signalling
Gateway
PS Domain
IPv4 or IPv6
Mobile
Terminal
GTP
SGSN
GGSN
Operators
ISP
Existing IPv4
Internet WWW Server
SIP Proxy
Server
SIP Client
Potential points of
IPv4/IPv6 interworking
support
42
NAT-PT Translation
End User
Equipment
(IPv6 only)
DSL Access
Network
Access
Router
(IPv6)
IP Network (IPv4)
NAT-PT
Communication
with IPv4 via
translator
IPv4 DNS
IPv6 DNS
DNS exchange
initiates
communication via
translator
43
DSTM Support for native IPv4
End User
Equipment
(Initially IPv6
only)
DSL Access
Network
Access
Router
(IPv6)
Native
communication
with IPv4
IPv4 over IPv6 tunnel
End user discovers
communication to IPv4 –
requests temporary IPv4
address
IP Network
(IPv4)
DHCPv6
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Ethernet 6in4 tunnel
202.140.100.21
PROXY
202.140.100.19
Router 1
IPv4 GPRS
Container
PC 6in4 tunnel
Private IPv4
addresses
PC
Hub 3
HK
Live IPv4
Ultima
202.140.100.18
202.140.100.22-30
MAP
202.140.100.20
Hub 2
MIPv6
Scenario 4:
Fixed/Mobile
roaming
Serial
R520
Ethernet
Router 2
Local Native IPv6 Network
WLAN BS2
MIPv6
CN
RNC
Scenario 3:
Broadband
MobileIPv6
Hub 1
WLAN BS1
HA
APPS
(WWW, MP3,
Quake, DNS)
202.140.100.17
VOD
Scenario 1:
Fixed
broadband
IPv6
Scenario 2:
Wireless
broadband
IPv6
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Scenario 1: Broadband IPv6
HK IPv6
Network
Applications
Server
DNS
Server
WLAN
Quake
IPv6 Local
Internet
IPv6 VoD
IPv6 MP3
Audio
46
Scenario 2: IPv6 meets IPv4
IPv6
Network
DNS
Server
IP v4
IPv4
Internet
IPv6
Network
IPv6
Internet
IPv6 MP3
Audio
IPv4
Internet
47
Scenario 3: MobileIPv6
IPv4
Internet
HK IPv6
Network
Database
Server
Portal
Server
WLAN
WLAN
Home Agent
Home Domain
Office Domain
MIPv6
Local News & Weather
Business News, Shares & Reminders
48
Scenario 4: Inter-technology handover
IPv4
Internet
HK IPv6
Network
Database
Server
Portal
Server
GPRS
GPRS
Home Agent
Office Domain
High Bandwidth
WLAN
Mobile Domain
Low Bandwidth
MIPv6
Business News, Shares & Reminders
49
Testbed System
50
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
51
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
52
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.
53
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 networklevel 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 endpoint identification by TCP
54
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
55
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
56
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
–
57
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 ?
58
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
59
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
60
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.
61
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.
62
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
63
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,
64
Registration Overview
Via 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
MH
Directly 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
65
•
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.
66
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.
67
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
68
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
69
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
70
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.
71
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
72
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
73
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
74
Link
http://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
75