SteelHead™ Deployment Guide : Satellite Optimization : Overview of SCPS
  
Overview of SCPS
This section describes SCPS. It does not cover the implementation of SCPS in the SteelHead. This section includes the following:
  • SCPS Benefits
  • Common Uses for SCPS
  • SCPS and SteelHeads
    • For information about how to implement SCPS and the SteelHead, see TCP Optimization for Satellite Environments.
     
    SCPS is a group of several protocol specifications developed by the consultative committee for space data systems (CCSDS) to address the limitations of communications in space. In the WAN optimization market, SCPS refers to the transport protocol specification, otherwise known as SCPS-TP. SCPS-TP is the most widely supported SCPS protocol. In the WAN optimization market, SCPS-TP is commonly called SCPS. The use of SCPS in SteelHeads is specifically referencing SCPS-TP. Definitions for all SCPS protocols are as follows:
  • SCPS-FP (file transfer protocol) - A set of extensions to FTP to make it more bit efficient and to add advanced features such as record update within a file and integrity checking on file transfers. This is an optional protocol.
  • SCPS-TP (transport protocol) - A set of transmission control protocol (TCP) options, such as selective negative acknowledgment (SNACK), selective acknowledgment (SACK), modified slow start algorithms, modified congestion avoidance algorithms, and Windows scaling. Additionally, SCPS-TP includes sender-side modifications to enhance the TCP performance in the stressed environments, such as long delays, high bit error rates, and significant asymmetries. For flow negotiation, SCPS uses TCP options that are registered with the Internet Assigned Numbers Authority (IANA). As a result, the SCPS-TP stack is compatible with other recognized TCP implementations.
  • SCPS-SP (security protocol) - Based on security protocol 3 (SP3) and network layer security protocol (NLSP), with reduced protocol overhead of header. SCPS-SP also provides integrity, confidentiality, authentication, and access control for the data transmitted over the network. SCPS-SP is an optional protocol, and is comparable to Internet Protocol Security (IPSec).
  • SCPS-NP (network protocol) - A bit-efficient network protocol that is analogous to IP. However, it is not compatible with IP. The protocol is designed for use in space systems. The protocol supports static or dynamic routing, precedence, and multiple routing options. This is an optional protocol.
    • For more information about SCPS-TP, go to http://public.ccsds.org/publications/archive/714x0b2.pdf.
    SCPS Benefits
    SCPS provides improved TCP performance in high-latency and high-loss environments, such as satellite networks. As a specification, SCPS enables third-party WAN optimization solutions that support SCPS, to provide TCP acceleration in a heterogeneous WAN optimization environment.
    SCPS is designed for use in dual-ended proxy (symmetric) scenarios. However, some SCPS devices also provide single-ended optimization. This enables a device to provide sender-side benefits even when there is no optimization appliance at the far end. However, not all SCPS solutions support single-ended proxy implementations.
    Common Uses for SCPS
    The three primary markets for SCPS are as follows:
  • Space agency space networks
  • Commercial satellite networks
  • Private government satellite networks
    • SCPS is a common request in large multiagency government satellite architectures in which a lowest common denominator approach to TCP acceleration is desirable. This enables the hub organization to provide basic TCP optimization to multiple agencies connecting into their teleports, without requiring a specific vendor solution.
    SCPS and SteelHeads
    SCPS is available in RiOS v7.0 or later. An SCPS license enables SteelHeads running RiOS v7.0 to negotiate SCPS optimization with another SteelHead or a third-party WAN optimizer or TCP-PEP. The SCPS license also enables the SCPS per connection and SCPS error-tolerant transport setting options. These two TCP stacks are tuned specifically for satellite networks. SteelHeads running RiOS v8.5 or later include a rate pacing mechanism to further tune the TCP. The mechanism can also negotiate compression with a third-party WAN optimizer or TCP-PEP.
    You can configure transport optimization used by the SteelHead separately from SCPS negotiation. This separation provides extensive flexibility for a broad range of environments.
    A SteelHead with SCPS, optimizing traffic to another SteelHead, uses the configured TCP stack and still performs standard RiOS optimization functions such as data reduction and application streamlining. The same SteelHead can negotiate SCPS with third-party TCP-PEP devices. This provides organizations with an approach for supporting third-party SCPS interoperability, while at the same time maximizing performance and productivity within their architectures with RiOS optimization.
    For more information about using SCPS in SteelHeads, see TCP Optimization for Satellite Environments and Licensing SCPS on a SteelHead.
    In RiOS v7.0 or later, you must license SCPS and restart the optimization service to enable SCPS negotiation service. This is irrelevant of which transport optimization method you select (for example, standard TCP, high-speed TCP, BW estimation, per connection, or error tolerant).