Measuring NFS Performance in Wireless Networks

Abstract

Technological trends suggest that soon communication networks will consist of a high speed wired backbone with numerous wireless Local Area Networks. Mobile computing and wireless subnetworks are increasingly in demand. Mobile routing solutions provide wireless LANs with seamless connectivity to backbone wired systems. However, these solutions do not provide acceptable performance. Wireless networks have distinct transmission characteristics which present challenges to achieving efficient performance. Performance over wireless links is limited by high error rates, mobility, and low bandwidth. We have studied the performance of TCP and NFS over a wireless network. The prevalence of these protocols means that mobile hosts will frequently use them when communicating with stationary hosts. Measurements have been collected to determine the response of these protocols in the presence of various error patterns. These measurements show that NFS and TCP performance suffer extreme degradation due to these wireless link characteristics. Unexpectedly, NFS performance is not better than an TCP FTP file transfer. NFS performance over wireless links is limited by large packet sizes, long retransmission timeouts, and slow response to losses. Our goal is to understand the effects of wireless communication on these protocols and improve performance without requiring changes to the current network Infrastructure. (Also cross-referenced as UMIACS-TR-95-125)