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Cutting Through Opinions
Diagnosing Facts
Providing Resolution™
Interpath Technologies Resolves Long Standing Loss of Bandwidth Problem
A large financial corporate campus with two multiplexed T-1s. Everyone still had to go home and use his or her own Internet access to download anything over a Megabyte without hanging.
Client lived with this problem for nearly two years. Telco's' studies discovered no link errors. Client tried replacing Proxy Servers & several other devices - without a plan. Nothing worked. They didn’t study the environment — they threw changes at it.
Once engaged, Interpath Technologies designed a test — involving deployment of "taps" at key points along the campus to T-1's (Interpath). We monitored data as it moved from Physical layer up through Application Layer — for one day.
We discovered an extremely high rate of TCP Retransmissions between two points. They were caused by a timing problem between MUX & WAN Router.
Physical layer retransmissions cause delays of only microseconds — are a result of collisions where a sender knows a packet is destroyed. Retransmissions are instantaneous. TCP Retransmissions may cause delays of minutes. In TCP retransmissions, a sender thinks packet got through — has flushed that data. Compared to physical layer retransmissions — TCP retransmissions are ~10,000 times slower. It’s then up to a higher-level protocol to notice there’s no response. Client experienced over 90% TCP retransmissions before correction.
Client replaced the defective device. TCP Retransmissions dropped— performance immediately increased to appropriate levels.
For more information on this case study, Click Here.
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