This work looks at the issues involved in performing robust speech recognition over a packet-based network such as the IP network. This involves the combination of robust speech recognition together with a reliable method of sending speech data over the IP network. The format in which the speech is sent over the network is considered and results show that much better robustness is achieved when the front-end features are transmitted directly rather than encoding the speech with a codec. The problem of packet loss is addressed and a novel detection and estimation scheme for missing frames is introduced to overcome this problem. This is shown to recover performance with 50% packet loss from 33% to 90% which is only 3% below the no loss case.