added language about server connection migration

draft-ietf-quic-load-balancers.md

@@ -799,7 +799,12 @@ packet. The comments signify the range of acceptable values where applicable.
 } routing_algorithm_config;
 ~~~
 
-# Load balancer chains
+# Additional Use Cases
+
+This section discusses considerations for some deployment scenarios not implied
+by the specification above.
+
+## Load balancer chains
 
 Some network architectures may have multiple tiers of low-state load balancers,
 where a first tier of devices makes a routing decision to the next tier, and so
@@ -813,6 +818,19 @@ to the correct forwrading address. Note that this solution is extensible to
 arbitrarily large numbers of load-balancing tiers, as the maximum server ID
 space is quite large.
 
+## Moving connections between servers
+
+Some deployments may transparently move a connection from one server to another.
+The means of transferring connection state between servers is out of scope of
+this document.
+
+To support a handover, a server involved in the transition could issue CIDs that
+map to the new server via a NEW_CONNECTION_ID frame, and retire CIDs associated
+with the new server.
+
+Alternately, if the old server is going offline, the load balancer could simply
+map its server ID to the new server's address.
+
 # Security Considerations {#security-considerations}
 
 QUIC-LB is intended to prevent linkability.  Attacks would therefore attempt to