faq.rst revision 758aff32 
1**************************
2Frequently Asked Questions
3**************************
4
5API/Design
6==========
7
8*Why have a separate engine for server and client?  Surely traffic
9could be differentiated as much as it needs to be internally in one
10engine?*
11
12The traffic *cannot* be differentiated for gQUIC versions Q046 and Q050.
13This is because in these versions, the server never includes a connection
14ID into the packets it sends to the client.  To have more than one
15connection, then, the client must open a socket per connection: otherwise,
16the engine would not be able to dispatch incoming packets to correct
17connections.
18
19To aid development, there is a :macro:`LSQUIC_FORCED_TCID0_VERSIONS` that
20specifies the list of versions with 0-sized connections.  (If you, for
21example, want to turn them off.)
22
23Once gQUIC becomes deprecated in the future, there will remain no technical
24reason why a single engine instance could not be used both for client and
25server connections.  It will be just work.  For example, the single
26engine settings :type:`lsquic_engine_settings` will have to be separated
27into client and server settings, as the two usually do need to have
28separate settings.
29
30Example Programs
31================
32
33*http_client does not work with www.google.com, www.facebook.com, etc.*
34
35Check the version.  By defaut, ``http_client`` will use the latest supported
36version (at the time of this writing, "h3-31"), while the server may be using
37an older version, such as "h3-29".  Adding ``-o version=h3-29`` to the
38command line may well solve your issue.
39
40There is an `outstanding bug`_ where lsquic client does not perform version
41negotiation correctly for HTTP/3.  We do not expect this to be fixed, because
42a) this version negotiation mechanism is likely to become defunct when QUIC v1
43is released and b) version negotiation is not necessary for an HTTP/3 client,
44because the other side's version is communicated to it via the ``Alt-Svc`` HTTP
45header.
46
47.. _`outstanding bug`: https://github.com/litespeedtech/lsquic/issues/180
48