for other control processes, and a short header that may be used for data transmission in an established connection.  While the long header always exposes some information (such as the version and <del> Connection IDs), the short header only optionally exposes a single Connection ID. Given that exposing this information may make it possible to associate multiple addresses with a single client during rebinding, which has privacy implications, an application may indicate to not support exposure of certain information after the handshake. Specifically, an application that has additional information that the client is not behind a NAT and the server is not behind a load balancer, and therefore it is unlikely that the addresses will be re- bound, may indicate to the transport that is wishes to not expose a </del> <ins> Connection IDs), the short header exposes at most only a single </ins> Connection ID. 6.1. QUIC supports a server-generated Connection ID, transmitted to the client during connection establishment (see Section 6.1 of QUIC). <del> Servers behind load balancers should propose a Connection ID during the handshake, encoding the identity of the server or information about its load balancing pool, in order to support stateless load balancing.  Once the server generates a Connection ID that encodes its identity, every CDN load balancer would be able to forward the packets to that server without needing information about every specific flow it is forwarding. Server-generated Connection IDs must not encode any information other that that needed to route packets to the appropriate backend server(s): typically the identity of the backend server or pool of servers, if the data-center's load balancing system keeps "local" state of all flows itself.  Care must be exercised to ensure that the information encoded in the Connection ID is not sufficient to identify unique end users.  Note that by encoding routing information in the Connection ID, load balancers open up a new attack vector that allows bad actors to direct traffic at a specific backend server or pool.  It is therefore recommended that Server-Generated Connection ID includes a cryptographic MAC that the load balancer pool server is able to identify and discard packets featuring an invalid MAC. </del> <ins> Servers behind load balancers may need to propose a Connection ID during the handshake, encoding the identity of the server or information about its load balancing pool, in order to support stateless load balancing.  Once the server generates a Connection ID that encodes its identity, every CDN load balancer would be able to forward the packets to that server without retaining connection state. Server-generated connection IDs should seek to obscure any encoding, of routing identities or any other information.  Exposing the server mapping would allow linkage of multiple IP addresses to the same host if the server also supports migration.  Furthermore, this opens an attack vector on specific servers or pools. The best way to obscure an encoding is to appear random to observers, which is most rigorously achieved with encryption. </ins> 6.2. <ins> While sufficiently robust connection ID generation schemes will mitigate linkability issues, they do not provide full protection. Analysis of the lifetimes of six-tuples (source and destination addresses as well as the migrated CID) may expose these links anyway. In the limit where connection migration in a server pool is rare, it is trivial for an observer to associate two connection IDs. Conversely, in the opposite limit where every server handles multiple simultaneous migrations, even an exposed server mapping may be insufficient information. The most efficient mitigation for these attacks is operational, either by using a load balancing architecture that loads more flows onto a single server-side address, by coordinating the timing of migrations to attempt to increase the number of simultaneous migrations at a given time, or through other means. 6.3. </ins> QUIC provides a Server Retry packet that can be sent by a server in response to the Client Initial packet.  The server may choose a new Connection ID in that packet and the client will retry by sending