To reduce the bandwidth utilization, make Internet communications faster and accelerate page load times the use of a new two-layer HTTP-compatible protocol is growing in popularity. It is known as SPDY and is an encrypted (SSL) Session Layer protocol introduced for lightweight HTTP processing. SPDY is not an acronym; it is the full name of an open networking protocol for transporting web content. The goal of SPDY is to reduce web page load time by using a single TCP connection per domain. SPDY achieves this by allowing interleaved resource requests and prioritizing across resources.
SPDY provides a number of benefits over standard HTTP. It transmits fewer packets and therefore cuts down on packet loss and reduces buffer bloat on intermediate routers. It also requires fewer TCP connections and utilizes these connections more efficiently. For instance, redundant headers are removed, other headers are compressed, and it supports request prioritization. SPDY handles asynchronous interleaved requests to prevent router blocking. SPDY also achieves reduced latency through leveraging content compression. The resulting performance improvements over HTTP range from 27 to 60 percent in page load times with no encryption and from 39 to 55 percent with SSL. These gains are even more apparent when clients are seeing packet loss rates in excess of 2 percent common in mobile environments.
While most browsers support SPDY today the server/application infrastructures still largely run on HTTP. With the introduction of SPDY a number of problems arise from this mismatch: Layer 4 processing must take place; best security practices are broken; and capacity planning is impacted. The promises of this protocol go unfulfilled. A networking device which can transform messages from SPDY to HTTP is needed. This gateway feature enables Layer 7 optimization and provides time for datacenters to move to SPDY support. As SPDY slowly evolves into an increasingly popular protocol, web sites can adopt it without having to rebuild their existing infrastructure.
NetScaler Application Delivery Controllers provides full integration of this gateway feature in all software editions and platforms (MPX, SDX and VPX). These appliances acts as a proxy and ensure communications to both clients and servers in HTTP as well as SPDY and transform sessions between them. Incoming requests are stripped of their SPDY layer and the server responses have SPDY encapsulation added. No loss of functionality is incurred when running this gateway. For instance, full Layer 7 content switching along with data analytics continue to be available. NetScaler also supports Next Protocol Negotiation (NPN) which is required for SSL modules used with SPDY gateway functionality. Extensions for NPN TLS are also included.