You can limit the bandwidth used for downloading patches to ESXi 5.x hosts by using either the vSphere Client or the ESXi Shell. Limiting the patch download bandwidth prevents network congestion in slow networks.
You should not limit the download bandwidth when you upgrade hosts. When you start an upgrade remediation, ESX/ESXi hosts are put into maintenance mode, and a limited download rate might cause hosts to remain in maintenance mode for an extended period of time.
Patches are software updates that address a particular issue or enhancement on the host. Update Manager downloads patches for ESXi 5.x hosts from download sources on the Internet. The download sources can be provided by VMware or third-party vendors. To patch hosts by using Update Manager, you use patch baselines.
To upgrade ESX/ESXi 4.x, ESXi 5.0 or ESXi 5.1 host to ESXi 5.5, you must upload at least one ESXi 5.5 .iso image to the Update Manager repository and create a host upgrade baseline. For more information about different types of software updates, see Downloading Updates and Related Metadata.
In the Update Manager process, hosts download patches during remediation or staging operations. To prevent patch downloads from using all available bandwidth in slow networks, you can configure bandwidth throttling for ESXi 5.x hosts.