Interlude 11 bytes init packet wtf??

Hello!
in some interlude servers, first packet(init) length is about 11 bytes, when im expecting a more huge packet(about 186 bytes) containing:

protocolVersion (Integer)
sessionId(Integer)
rsaPublicKey (byte[128])
blowfishKey (byte[16])
gg1 (byte[4])
gg2 (byte[4])
gg3 (byte[4])
gg4 (byte[4])

do you know why??

Greetings