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4.1.4 multi-homing

4.1.4 multi-homing. introduction. Multi-homing A host is said to be multihomed if it has multiple network interfaces or IP address. To increase the reliability of the network applications. Some issues in using multi-homing path failure detection How to know the link condition?

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4.1.4 multi-homing

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  1. 4.1.4 multi-homing

  2. introduction • Multi-homing • A host is said to be multihomed if it has multiple network interfaces or IP address. • To increase the reliability of the network applications.

  3. Some issues in using multi-homing • path failure detection • How to know the link condition? • path exploration • path selection • Which link is better to transmit data? • path handover • Handover scenario.

  4. Transport layer multi-homing • SCTP, Stream Control Transmission Protocol • SCTP was originally designed for transmitting PSTN signaling messages across the Internet. • TCP + multi-homing

  5. SCTP overview • SCTP is a new IETF standard transport protocol (RFC2960) • Stream Control Transmission Protocol • Originally used in Signaling transport as like SS7 • doing telephone switching over IP networks • highly reliable, timely delivery, high availability • Why ? • TCP and UDP lacked some features that were needed

  6. IP reference model(From Stewart/Xie)

  7. Stream Control Transmission Protocol (SCTP) • All about SCTP… • Connection-oriented, reliable transport protocol • combination with TCP & UDP • 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 • 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)

  8. SCTP multi-homing • 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

  9. IP B2 IP B1 IP A1 IP B3 IP A2 IP network SCTP multi-homing • Multiple src/dest ip addresses • Use of different physical paths not guaranteed • Peer reachability and path status are monitored (heartbeat) • One selectable default path • Parameters per path (cwnd, RTT, RTO, PRL)

  10. ISP ISP Internet ISP ISP Host B Host A A1 B1 A2 B2 SCTP Multihoming • hosts choose 1 of 4 possible TCP connections: • (A1,B1) or (A1,B2) or (A2,B1) or (A2,B2) • one SCTP association • ({A1,A2}, {B1,B2}) • concept of “primary” destination • Let B1 be Host A’s primary destination • Let A1 be Host B’s primary destination • network state (RTT, cwnd, ssthresh, …) maintained per destination

  11. Network layer multi-homing • IPv4 multi-homing • 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.

  12. Data link multi-homing • 802.21 • IEEE 802.21 is developing standards to enable handover and interoperability between heterogeneous network types including both 802 and non 802 networks.

  13. IEEE802.21 • Media Independent Handover(HIM) • Optimization of handovers between heterogeneous IEEE 802 system as well as between 802 and cellular systems • Three mobility service • Event Service • 換手事件觸發 • Command Service • 相對應命令下達 • Information Service • 蒐集interface資訊 14

  14. 802.21 architecture

  15. 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.

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