Question: What are the transmission speed for Cat 5, Cat 5e, Cat 6 network cable?
Cat 5 and Cat 5e UTP cables can support 10/100/1000 Mbps Ethernet. Although Cat 5 cable may support to some degree in Gigabit Ethernet (1000 Mbps), it performs below standard during high-data transfer scenarios, so I do not recommend you to use Cat 5 cable in Gigabit Ethernet, use Cat 5e instead (of course Cat 6 is the best).
Cat 6 UTP cable is manufactured targeting on Gigabit Ethernet and backward compatible with 10/100 Mbps Ethernet. It performs better then Cat 5 cable with higher transmission rate and lower transmission error.
If you plan to have Gigabit network, look for Cat 5e or Cat 6 UTP cables.
Note: Cat 3 UTP cable? Forget about it... It's not popular anymore since it can only support 10 Mbps Ethernet.