add FAQ questions to federate.md

INSTALL.md

@@ -1,14 +1,14 @@
-* [Installing Synapse](#installing-synapse)
-  * [Installing from source](#installing-from-source)
-    * [Platform-Specific Instructions](#platform-specific-instructions)
-    * [Troubleshooting Installation](#troubleshooting-installation)
-  * [Prebuilt packages](#prebuilt-packages)
-* [Setting up Synapse](#setting-up-synapse)
-  * [TLS certificates](#tls-certificates)
-  * [Email](#email)
-  * [Registering a user](#registering-a-user)
-  * [Setting up a TURN server](#setting-up-a-turn-server)
-  * [URL previews](#url-previews)
+- [Installing Synapse](#installing-synapse)
+  - [Installing from source](#installing-from-source)
+    - [Platform-Specific Instructions](#platform-specific-instructions)
+    - [Troubleshooting Installation](#troubleshooting-installation)
+  - [Prebuilt packages](#prebuilt-packages)
+- [Setting up Synapse](#setting-up-synapse)
+  - [TLS certificates](#tls-certificates)
+  - [Email](#email)
+  - [Registering a user](#registering-a-user)
+  - [Setting up a TURN server](#setting-up-a-turn-server)
+  - [URL previews](#url-previews)
 
 # Installing Synapse
 
@@ -395,8 +395,9 @@ To configure Synapse to expose an HTTPS port, you will need to edit
   instance, if using certbot, use `fullchain.pem` as your certificate, not
   `cert.pem`).
 
-For those of you upgrading your TLS certificate for Synapse 1.0 compliance,
-please take a look at [our guide](docs/MSC1711_certificates_FAQ.md#configuring-certificates-for-compatibility-with-synapse-100).
+For a more detailed guide to configuring your server for federation, see
+[federate.md](docs/federate.md)
+
 
 ## Email
 

docs/federate.md

@@ -14,8 +14,8 @@ up and will work provided you set the ``server_name`` to match your
 machine's public DNS hostname, and provide Synapse with a TLS certificate
 which is valid for your ``server_name``.
 
-Once you have completed the steps necessary to federate, you should be able to 
-join a room via federation. (A good place to start is ``#synapse:matrix.org`` - a 
+Once you have completed the steps necessary to federate, you should be able to
+join a room via federation. (A good place to start is ``#synapse:matrix.org`` - a
 room for Synapse admins.)
 
 
@@ -98,6 +98,74 @@ _matrix._tcp.<server_name>``. In our example, we would expect this:
 Note that the target of a SRV record cannot be an alias (CNAME record): it has to point
 directly to the server hosting the synapse instance.
 
+### Delegation FAQ
+#### When do I need a SRV record or .well-known URI?
+
+If your homeserver listens on the default federation port (8448), and your
+`server_name` points to the host that your homeserver runs on, you do not need an SRV record or `.well-known/matrix/server` URI.
+
+For instance, if you registered `example.com` and pointed its DNS A record at a
+fresh Upcloud VPS or similar, you could install Synapse on that host,
+giving it a server_name of `example.com`, and it would automatically generate a
+valid TLS certificate for you via Let's Encrypt and no SRV record or
+`.well-known` URI would be needed.
+
+This is the common case, although you can add an SRV record or
+`.well-known/matrix/server` URI for completeness if you wish.
+
+**However**, if your server does not listen on port 8448, or if your `server_name`
+does not point to the host that your homeserver runs on, you will need to let
+other servers know how to find it. The way to do this is via .well-known or an
+SRV record.
+
+#### I have created a .well-known URI. Do I still need an SRV record?
+
+As of Synapse 0.99, Synapse will first check for the existence of a `.well-known`
+URI and follow any delegation it suggests. It will only then check for the
+existence of an SRV record.
+
+That means that the SRV record will often be redundant. However, you should
+remember that there may still be older versions of Synapse in the federation
+which do not understand `.well-known` URIs, so if you removed your SRV record you would no longer be able to federate with them.
+
+It is therefore best to leave the SRV record in place for now. Synapse 0.34 and
+earlier will follow the SRV record (and not care about the invalid
+certificate). Synapse 0.99 and later will follow the .well-known URI, with the
+correct certificate chain.
+
+#### Can I manage my own certificates rather than having Synapse renew certificates itself?
+
+Yes, you are welcome to manage your certificates yourself. Synapse will only
+attempt to obtain certificates from Let's Encrypt if you configure it to do
+so.The only requirement is that there is a valid TLS cert present for
+federation end points.
+
+#### Do you still recommend against using a reverse proxy on the federation port?
+
+We no longer actively recommend against using a reverse proxy. Many admins will
+find it easier to direct federation traffic to a reverse proxy and manage their
+own TLS certificates, and this is a supported configuration.
+
+See [reverse_proxy.rst](reverse_proxy.rst) for information on setting up a
+reverse proxy.
+
+#### Do I still need to give my TLS certificates to Synapse if I am using a reverse proxy?
+
+Practically speaking, this is no longer necessary.
+
+If you are using a reverse proxy for all of your TLS traffic, then you can set
+`no_tls: True`. In that case, the only reason Synapse needs the certificate is
+to populate a legacy 'tls_fingerprints' field in the federation API. This is
+ignored by Synapse 0.99.0 and later, and the only time pre-0.99 Synapses will
+check it is when attempting to fetch the server keys - and generally this is
+delegated via `matrix.org`, which is on 0.99.0.
+
+#### Do I need the same certificate for the client and federation port?
+
+No. There is nothing stopping you from using different certificates,
+particularly if you are using a reverse proxy. However, Synapse will use the
+same certificate on any ports where TLS is configured.
+
 ## Troubleshooting
 
 You can use the [federation tester](