When would a connection persist through a filter chain change?

Title: When would a connection persist through a filter chain change?

Description:

Hi Envoy devs, apologies if this sounds an uninformed question. Doc [1] says that network filter changes will result in connection draining, and I do see that happen for network filter changes. But it seems that route changes via RDS in HTTP connection manager doesn't drain connections. So I'm wondering what is the logic under the hood: Are all http level config changes eligible to escape draining? Or is it because the protobuf message happen to be the same in the RDS case? So if ECDS is specified [2] would the connection also survive, even though ECDS may push new configs? Thanks!

Relevant Links:

[1] https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/listeners/network_filter_chain#filter-chain-only-update [2] https://www.envoyproxy.io/docs/envoy/latest/api-v3/extensions/filters/network/http_connection_manager/v3/http_connection_manager.proto#envoy-v3-api-field-extensions-filters-network-http-connection-manager-v3-httpfilter-config-discovery