DNS queries VPN

Session-level optimizations for wireless dataperformance improvement. HTTP pages generally havea large number of references to embedded objects thatare hosted in different domains. A Web browser mustperform a new domain name server (DNS) query for each domain name. Because the delay due to DNS responses ranges from 1 to 4 seconds, DNS queries canproduce a large overhead, especially across wirelesslinks. To eliminate this overhead, session-level optimization techniques based on URL rewriting have beenproposed. With URL rewriting, all embedded URLs in atop-level HTML page are rewritten to point to a singledomain name. (With an IPSS, they are rewritten topoint to a Web proxy on the IPSS.) As a result, onlyone DNS lookup will be made for all embedded objects;the IPSS will make multiple DNS requests, but they willbe made over a wireline network. The rewriting of thetop-level page at the IPSS is only possible because theapplication data are visible