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Datagram Congestion Control Protocol (DCCP)

Datagram Congestion Control Protocol (DCCP). Presented by Po-Chou Chen. Outline. Introduction Feature Important Differences from TCP DCCP Packets Packet Formats Congestion Control IDs Demo References. Introduction. RFC 4340 新傳輸協議 - 取代 UDP (Real-time) DCCP 定義了兩種擁塞控制機制

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Datagram Congestion Control Protocol (DCCP)

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  1. Datagram Congestion Control Protocol (DCCP) Presented by Po-Chou Chen

  2. Outline • Introduction • Feature • Important Differences from TCP • DCCP Packets • Packet Formats • Congestion Control IDs • Demo • References

  3. Introduction • RFC 4340 • 新傳輸協議-取代UDP (Real-time) • DCCP定義了兩種擁塞控制機制 • CCID2-TCP-like Congestion Control (RFC 4341) • CCID3-TCP-Friendly Rate Control (TFRC) (RFC4342)

  4. Feature • 使用Data和DataAck的數據傳輸 • Data-是純數據 • DataAck-可以有數據又有確認訊息 • 擁塞控制標記（CCID） • 多重連接(Multihoming)和移動通信(Mobility)中的應用。DCCP提供多重連接。在連接過程中可以通知對方位址或者端口的改變

  5. Important Differences from TCP • Packet stream (TCP :a byte stream protocol) • Unreliability • DCCP will never retransmit a datagram. Options are retransmitted as required to make feature negotiation and ack information reliable • Packet sequence numbers • Copious space for options (up to 1020 bytes) • Choice of congestion control • A<->B connection • data packets sent from A->B can use CCID 2 • data packets sent from B->A can use CCID 3

  6. Important Differences from TCP(Cont.) • No receive window • DCCP is a congestion control protocol, not a flow control protocol • Integrated support for mobility.

  7. DCCP Packets Client Server DCCP-Request (include CCID) DCCP-Response DCCP-Ack

  8. Packet Formats

  9. Packet Formats (Cont.) • Generic Packet Header • 12byte->16byte

  10. Packet Formats (Cont.)

  11. Congestion Control IDs • 0~1- Reserved • 2- TCP-like Congestion Control [RFC4341] • 3- TCP-Friendly Rate Control [RFC4342] • 4~255- Reserved

  12. Demo • Linux 2.6.14 and later include a DCCP stack • Demo OS: Fedora Core5(2.6.15-1.2054_FC5) • Run Server program: ./server –p DCCP • Run Client program: ./client –p DCCP 127.0.0.1

  13. References • RFC 4340 - Datagram Congestion Control Protocol (DCCP) • http://www.ietf.org/rfc/rfc4340.txt • RFC 4341 - Profile for Datagram Congestion Control Protocol (DCCP) Congestion Control ID 2: TCP-like Congestion Control • http://www.ietf.org/rfc/rfc4341.txt • RFC 4342 - Profile for Datagram Congestion Control Protocol (DCCP) Congestion Control ID 3: TCP-Friendly Rate Control (TFRC) • http://www.ietf.org/rfc/rfc4342.txt • Datagram Congestion Control Protocol (DCCP) • http://www.read.cs.ucla.edu/dccp/

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