An application layer firewall can also be called a proxy.
“A presentation layer gateway” is incorrect. A gateway connects two unlike environments and is usually required to translate between diffferent types of applications or protocols. This is not the function of a firewall.
“A session layer gateway” is incorrect. A gateway connects two unlike environments and is usually required to translate between diffferent types of applications or protocols. This is not the function of a firewall.
“A transport layer gateway” is incorrect. A gateway connects two unlike environments and is usually required to translate between diffferent types of applications or protocols. This is not the function of a firewall.
References: CBK, p. 467 AIO3, pp. 486 -490, 960