Transcript Sub4_1_4_multihoming_v2

4.1.4 multi-homing
introduction
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Multi-homing
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A host is said to be multihomed if it has multiple
network interfaces or IP address.
To increase the reliability of the network
applications.
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Some issues in using multi-homing
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path failure detection
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path exploration
path selection
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How to know the link condition?
Which link is better to transmit data?
path handover
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Handover scenario.
Transport layer multi-homing
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SCTP, Stream Control Transmission Protocol
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SCTP was originally designed for transmitting
PSTN signaling messages across the Internet.
TCP + multi-homing
SCTP overview
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SCTP is a new IETF standard transport protocol (RFC2960)
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Stream Control Transmission Protocol
Originally used in Signaling transport as like SS7
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doing telephone switching over IP networks
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highly reliable, timely delivery, high availability
Why ?
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TCP and UDP lacked some features that were needed
IP reference model(From Stewart/Xie)
Stream Control Transmission Protocol (SCTP)
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All about SCTP…
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Connection-oriented, reliable transport protocol
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Security features (4-way handshake, tags)
Message oriented (streams of messages/chunks)
Reliable in-sequence or out-of-sequence delivery
to upper layer
TCP-friendly flow/congestion control with selective ack.
Supports Multi-streaming and Multi-homing
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combination with TCP & UDP
one association can contain many logical streams
multiple physical or logical interfaces
Monitors peer and path reachability (heartbeats)
Reasonable overhead (typical 28 bytes for data)
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SCTP multi-homing
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Endpoints of a connection can consist of more
than one IP address
Data chunks are transmitted over primary path
and idle paths are alternative
Separate congestion control parameters for
different paths
SCTP multi-homing
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Multiple src/dest ip addresses
Use of different physical paths
not guaranteed
IP B2
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Peer reachability and
path status are monitored
(heartbeat)
IP A1
IP B3
IP A2
One selectable default
path
Parameters per path
(cwnd, RTT, RTO, PRL)
IP B1
IP network
SCTP Multihoming
A1
ISP
A2
ISP
Internet
ISP
B1
ISP
B2
Host A
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Host B
hosts choose 1 of 4 possible TCP connections:
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(A1,B1) or (A1,B2) or (A2,B1) or (A2,B2)
 one
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SCTP association
({A1,A2}, {B1,B2})
concept of “primary” destination
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Let B1 be Host A’s primary destination
Let A1 be Host B’s primary destination
network state (RTT, cwnd, ssthresh, …) maintained per
destination
Network layer multi-homing
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IPv4 multi-homing
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Network must have its own public IP address
range and an AS number
The routing over these connections is normally
controlled by a BGP enabled router.
In the case where one outgoing link from the
multihomed network fails, outgoing traffic will
automatically be routed via one of the remaining
links.
Data link multi-homing
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802.21
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IEEE 802.21 is developing standards to enable
handover and interoperability between
heterogeneous network types including both 802
and non 802 networks.
IEEE 802.21
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Media Independent Handover(HIM)
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Optimization of handovers between heterogeneous IEEE 802 system as well as
between 802 and cellular systems
Three mobility service
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Event Service
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Command Service
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換手事件觸發
相對應命令下達
Information Service
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蒐集interface資訊
14
802.21 architecture
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Session Initiation Protocol (SIP) + IEEE 802.21
 A mobile node with 2 WLAN interfaces.
 A session is running on one WLAN connection
initially.
 SIP uses IEEE 802.21 Media Independent
Information Service (MIIS) to acquire network
information and to configure the other WLAN
interface.
 When the first WLAN fails, SIP sends Re-Invite and
Registration message to switch the session to the
second WLAN interface.