fixup! Grammar fix

Author: Emilia Hane

discv5/discv5-theory.md

@@ -441,21 +441,24 @@ frequently have to re-establish sessions to its peers.
 
 ### Limiting resource consumption of peers behind symmetric NATs, useful for light-clients
 
-Peers with uncontactable ENRs do not get inserted into kbuckets. Nodes that are behind
+Peers with unreachable ENRs do not get inserted into kbuckets. Nodes that are behind
 symmetric NATs will naturally never succeed in pinpointing one external socket for peers
-to reach them on by [runtime address discovery] and therefore their uncontactable ENRs
-will never update to contactable ENRs. This means, these peers will never respond to
+to reach them on by [runtime address discovery] and therefore their unreachable ENRs
+will never update to reachable ENRs. This means, these peers will never respond to
 requests, as only peers in kbucktes are sent requests. This does not cohere with the
-p2p-model, rather the server-client model where the peer with a uncontactable ENR acts
+p2p-model, rather the server-client model where the peer with a unreachable ENR acts
 as the client. This misalignment is especially bothersome for well behaving (externally
 reachable) light-clients operating on limited resources. Discv5.2 corrects this
 side-effect of [runtime address discovery] by setting introducing a configurable limit to
-the number of sessions at a time with peers with uncontactable ENRs, the lower limit
-being 1. Nodes must accept sessions with at least one peer with a uncontactable ENR to
+the number of sessions at a time with peers with unreachable ENRs, the lower limit
+being 1. Nodes must accept sessions with at least one peer with a unreachable ENR to
 for [runtime address discovery] to be enabled on the discv5.2 network.
 
 ### Fault tolerance
 
+As was already the case in discv5, if a request to a node times out, (after the configured
+number of retries) that peer is considered unresponsive and the session can be failed.
+
 [EIP-778]: ../enr.md
 [identity scheme]: ../enr.md#record-structure
 [message packet]: ./discv5-wire.md#ordinary-message-packet-flag--0