1 / 20

SIP over SCTP performance analysis

SIP over SCTP performance analysis. Gonzalo.Camarillo@ericsson.com Schulzrinne@cs.columbia.edu Raimo.Kantola@hut.fi. Outline. Problem statement: signalling transport Introduction to SCTP SCTP performance analysis SCTP vs UDP SCTP vs TCP. Signalling Transport (SIGTRAN).

selina
Download Presentation

SIP over SCTP performance analysis

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. SIP over SCTP performance analysis Gonzalo.Camarillo@ericsson.com Schulzrinne@cs.columbia.edu Raimo.Kantola@hut.fi

  2. Outline • Problem statement: signalling transport • Introduction to SCTP • SCTP performance analysis • SCTP vs UDP • SCTP vs TCP

  3. Signalling Transport (SIGTRAN) • Providers want to transport telephony signalling over IP • IP trunking • Let us try to use existing transport protocols PSTN IP PSTN SG SG SG: Signalling Gateway

  4. Traditional transports: UDP and TCP • UDP (User Datagram Protocol) • Unreliable transfer of datagrams • Demultiplexing based on port numbers • Checksum • Example: RTP • TCP (Transmission Control Protocol) • Reliable transfer of streams of bytes • Congestion control: network friendly • Example: HTTP, FTP, Telnet

  5. TCP limitations • Carry every SS7 call on top of a TCP session • Every SS7 call is affected by the TCP three-way handshake • Multiple SS7 calls on top of a single TCP session • TCP provides a stream service: Head of the line blocking problem

  6. UDP limitations • Use UDP and application level retransmissions • No flow control: Congestion • Large amount of state information in the application • In a slightly different context, this solution was adopted by SIP

  7. Stream Control Transmission Protocol (SCTP) • SIGTRAN is chartered to develop a transport protocol that fulfils signalling transport requirements • October 2000; RFC 2960: Stream Control Transmission Protocol • A connection in SCTP terminology is an “association” • Four-way handshake (avoids DoS attacks) SCTP TCP

  8. Stream Control Transmission Protocol (SCTP) • SCTP allows multihoming • A receiver can be reachable at multiple IP addresses • Robustness rather than load balancing • SCTP is a message-based protocol • Easier parsing • No need of application specific boundaries

  9. Stream Control Transmission Protocol (SCTP) • SCTP allows multiple streams within an association • Flow control performed on association basis (TSN) • Delivery performed on stream basis (no head of the line blocking) STREAM 0 TSN:Transmission Sequence Number

  10. Stream Control Transmission Protocol (SCTP) • SCTP uses TCP SACK congestion and flow control mechanisms (per association) • Slow start, congestion avoidance, fast retransmit, fast recovery • SCTP provides two services (per stream) • Ordered message delivery • Unordered message delivery • It also provides unordered messages within an ordered stream

  11. SIP over SCTP • Two ways of transporting SIP over SCTP • Send all SIP requests and responses over a single unordered SCTP stream. • Send requests and responses belonging to the same SIP transaction over the same SCTP stream. • Stream ID can be used as a lightweight transaction identifier instead of the Call-ID, From, To, Via and Cseq header fields • Server side: Incoming ACKs (non-2xx) and CANCELs • Client side: Incoming responses

  12. Simulations: SCTP performance analysis We implemented SCTP in the network simulator (ns) We only analyzed the SIP hop-by-hop handshake (INVITE-100 Trying) 15 ms 15 ms 15 ms

  13. SCTP vs. UDP Fast retransmit detects losses much faster than UDP-based timeouts UDP lacks congestion control Delay (ms) Time a packet is generated (ms)

  14. SCTP transport layer fragmentation • Every fragment a different TSN • Begin and End bits are used for reassembling • Once an SCTP packet is sent it cannot be re-fragmented again • Sudden changes in the path MTU trigger IP fragmentation • Problems with NATs and firewalls SCTP DATA chunk TSN = 1 10 TSN = 2 00 TSN = 3 01

  15. SCTP and TCP window-based congestion control • Congestion window (cwnd) limits the data rate at the sender • Slow start: exponential growth of cwnd • Congestion avoidance: linear growth of cwnd • When the data rate at the sender is limited by the application rather than by cwnd, the congestion window grows dramatically • Bursts of traffic produce heavy congestion

  16. Head Of the Line (HOL) blocking Comparison between ordered SCTP (which behaves like TCP SACK) and unordered SCTP Time a packet is received (ms) Time a packet is generated (ms)

  17. 15 ms 15 ms 15 ms Measuring HOL: buffer limited router

  18. 15 ms 15 ms 15 ms Measuring HOL: induced packet loss

  19. 15 ms 15 ms 15 ms Measuring HOL: competing traffic

  20. Conclusions • UDP is not a suitable protocol for proxy to proxy communications • SCTP offers some advantages over TCP • Protection against DoS attacks • Multihoming • Message based • Lightweight transaction identifiers • HOL avoidance • Supposedly the biggest advantage of SCTP • Only significant gain when anyway the delay is unacceptable • SCTP has some limitations • Transport layer fragmentation • Window-based congestion control

More Related