By "gettreelevel" and "treelevel" you get the level of the merle tree with the hashes for the segments you want to download. You could request all the transaction hashes by specifying a very deep level. You could modify the proposal by removing the "level" byte in "gettreelevel" and always send the deepest level ie. The transaction hashes. Though by specifying the level you do not need to download all of the transaction hashes, only the hashes you need to verify each segment.
On 10 Sep 2012, at 16:14, Gregory Maxwell <
gmaxwell@gmail.com> wrote:
Why does this focus on actually sending the hash tree? The block
header + transaction list + transactions a node doesn't already know
(often just the coinbase) is enough.