client_body_buffer_size – use this directive to specify the client request body buffer size. The default value is 8k or 16k but it is recommended to set this as low as 1k: client_body_buffer_size 1k.
client_header_buffer_size – use this directive to specify the header buffer size for the client request header. A buffer size of 1k is adequate for most requests.
client_max_body_size – use this directive to specify the maximum accepted body size for a client request. A 1k directive should be sufficient but you need to increase it if you are receiving file uploads via the POST method.
large_client_header_buffers – use this directive to specify the maximum number and size of buffers to be used to read large client request headers. A large_client_header_buffers 2 1k directive sets the maximum number of buffers to 2, each with a maximum size of 1k. This directive will accept 2 kB data URI.