A method for migrating a content retrieval session associated with a content retrieval application at a host from a first server via a first interface to a second server via a second interface, the host comprising a client, the method comprising: caching content request messages sent by the content retrieval application by caching a first content request message sent via the first interface to the first content server, tracking content portions forwarded to the client by the first content server and in response to a trigger to switch from the first interface to the second interface creating a domain name server, DNS, request containing a uniform resource identifier, URI, retrieved from the earlier content request message; or caching content request messages sent by the content retrieval application by sending by the client a DNS request to a DNS via the first interface, caching the URI associated with the DNS request, tracking content portions forwarded to the client by the first content server and in response to a trigger to switch from the first interface to the second interface sending a copy of the cached DNS request or other indicator of the URI associated with the initial content request message via the second interface; establishing a transport connection with the second server using the second interface; the method further comprising: transmitting a content request message toward the second server via the second interface, said content request message including an identifier associated with content to be retrieved and an indication of content portions received by said content retrieval application, said content identifier within said content request message transmitted toward the second server via the second interface being derived from a cached content request message; analyzing a content bearing data stream received via said second interface to identify further content portions received by said content retrieval application; and forwarding, toward said content retrieval application, identified content portions not received by said content retrieval application. caching content request messages sent by the content retrieval application by caching a first content request message sent via the first interface to the first content server, tracking content portions forwarded to the client by the first content server and in response to a trigger to switch from the first interface to the second interface creating a domain name server, DNS, request containing a uniform resource identifier, URI, retrieved from the earlier content request message; or caching content request messages sent by the content retrieval application by sending by the client a DNS request to a DNS via the first interface, caching the URI associated with the DNS request, tracking content portions forwarded to the client by the first content server and in response to a trigger to switch from the first interface to the second interface sending a copy of the cached DNS request or other indicator of the URI associated with the initial content request message via the second interface; establishing a transport connection with the second server using the second interface; the method further comprising: transmitting a content request message toward the second server via the second interface, said content request message including an identifier associated with content to be retrieved and an indication of content portions received by said content retrieval application, said content identifier within said content request message transmitted toward the second server via the second interface being derived from a cached content request message; analyzing a content bearing data stream received via said second interface to identify further content portions received by said content retrieval application; and forwarding, toward said content retrieval application, identified content portions not received by said content retrieval application. transmitting a content request message toward the second server via the second interface, said content request message including an identifier associated with content to be retrieved and an indication of content portions received by said content retrieval application, said content identifier within said content request message transmitted toward the second server via the second interface being derived from a cached content request message; analyzing a content bearing data stream received via said second interface to identify further content portions received by said content retrieval application; and forwarding, toward said content retrieval application, identified content portions not received by said content retrieval application.