AT-TLS supports the following negotiated functions:
This TLS function negotiates the maximum size of unencrypted data that can be sent in a single SSL fragment. Without this function, 16 K is the maximum fragment length. A TLS client can negotiate a size of 512, 1 K, 2 K or 4 K. Some clients need to use the smaller size because of memory or bandwidth limitations.
TLS cipher suites use the MAC construction HMAC with either MD5 or SHA-1 (RFC 2104) to authenticate record layer communications. The truncated HMAC function saves bandwidth by truncating the HMAC to 80 bits.