DOCS-12574 specify format for hostnames when using +srv connection string (#2595) (#3286)

* DOCS-12574 specify format for hostnames when using +srv connection string

* internal review comments

* external review

Author: jmd-mongo

source/reference/connection-string.txt

@@ -244,8 +244,32 @@ query the DNS for the record to determine which hosts are running the
    (or the equivalent :urioption:`ssl`) option to ``false`` with
    ``tls=false`` (or ``ssl=false``) in the query string.
 
-The following example shows a typical connection string for a DNS
-:term:`seed list` connection string:
+When using the ``+srv`` format, you must specify the ``hostname``, 
+``domain``, and ``top-level domain (TLD)`` in the following format: 
+``<hostname>.<domain>.<TLD>.`` This table shows how the placeholders
+correspond to example values:
+
+.. list-table::
+   :header-rows: 1
+   :widths: 50 50 
+
+   * - Placeholder
+     - Example
+
+   * - ``<hostname>``
+     - ``server``
+
+   * - ``<domain>``
+     - ``example``
+
+   * - ``<TLD>``
+     - ``com``
+
+   * - ``<hostname>.<domain>.<TLD>``
+     - ``server.example.com``
+
+This example shows a DNS :term:`seed list` connection string that 
+correctly uses the ``<hostname>.<domain>.<TLD>`` format.
 
 .. code-block:: none
 
@@ -259,6 +283,9 @@ The corresponding DNS configuration might resemble:
    _mongodb._tcp.server.example.com. 86400 IN SRV   0        5      27317 mongodb1.example.com.
    _mongodb._tcp.server.example.com. 86400 IN SRV   0        5      27017 mongodb2.example.com.
 
+Individual SRV records must be in 
+``_mongodb._tcp.<hostname>.<domain>.<TLD>`` format.
+
 When a client connects to a member of the :term:`seed list`, the client 
 retrieves a list of replica set members it can connect to. Clients 
 often use DNS aliases in their seed lists which means the host may
@@ -275,6 +302,17 @@ replica set config.
    the parent domains and hostname do not match, you will not be able to
    connect.
 
+This example shows a DNS seed list connection string that is missing
+the ``<hostname>``. This is incorrect and raises an error. 
+
+.. code-block:: none
+   :copyable: false
+
+   # This connection string is missing the <hostname> and raises a connection error
+
+   mongodb+srv://example.com/       
+
+
 Like the standard connection string, the DNS seed list connection string
 supports specifying options as a query string. With a DNS seed list
 connection string, you can *also* specify the following options via a