d. Discover subnet masks and e. Report routing failures br> Many different kind of routing failures can be reported via the Destination Unreachable ICMP frame (type 3). Masks can be found using the Address Mask Request and Reply ICMP frames (type 17, 18). TTL (Time to live) and Redirection exist at the Network layer (IP) rather than the Transport layer (TCP, UDP).
Reference: Comer, Internetworking with TCP/IP, Chapter 9.