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... - Allow TLS clients and servers to negotiate the maximum fragment
length to be sent. This functionality is desirable as a result of
memory constraints ...
... client to
indicate which server it is contacting. Section 3.2 describes the
extension that provides maximum fragment length negotiation. Section
3.3 describes the extension that allows client certificate URLs.
...
... TLS specifies a fixed maximum plaintext
fragment length of 2^14 bytes. It may be desirable for constrained
clients to negotiate a smaller maximum fragment ...
... fragment length of 2^14 bytes. It may be desirable for constrained
clients to negotiate a smaller maximum fragment length due to memory
limitations or bandwidth limitations.
...
... bandwidth limitations.
In order to negotiate smaller maximum fragment lengths, clients MAY
include an extension of type "max_fragment ...
... fragment lengths, clients MAY
include an extension of type "max_fragment_length" in the (extended)
client hello. The "extension_data" field of this extension SHALL
...
... } MaxFragmentLength;
whose value is the desired maximum fragment length. The allowed
values for this field are: 2^9, 2^10, 2^11, and 2^12.
...
... Servers that receive an extended client hello containing a
"max_fragment_length" extension MAY accept the requested maximum
fragment length by including an extension of type
...
... "max_fragment_length" extension MAY accept the requested maximum
fragment length by including an extension of type
"max_fragment_length" in the (extended) server hello ...
... fragment length by including an extension of type
"max_fragment_length" in the (extended) server hello. The
"extension_data" field of this extension SHALL contain a
...
... "extension_data" field of this extension SHALL contain a
"MaxFragmentLength" whose value is the same as the requested maximum
fragment length.
If a server receives a maximum fragment length negotiation ...
... fragment length.
If a server receives a maximum fragment length negotiation request
for a value other than the allowed values, it MUST abort the
handshake ...
... alert. Similarly, if a client
receives a maximum fragment length negotiation response that differs
from the length it requested, it MUST also abort the handshake with
...
... alert.
Once a maximum fragment length other than 2^14 has been successfully
negotiated, the client and server MUST immediately begin fragmenting
...
... client and server MUST immediately begin fragmenting
messages (including handshake messages), to ensure that no fragment
larger than the negotiated length is sent. Note that TLS already
...
...
The maximum fragment length takes effect immediately, including for
handshake messages. However, that does not introduce any security ...
... Note that as described in Section 3.2, once a non-null cipher suite
has been activated, the effective maximum fragment length depends on
the cipher suite and compression method ...
... cipher suite and compression method, as well as on the negotiated
max_fragment_length. This must be taken into account when sizing
buffers, and checking for buffer ...