Efficiently processing messages at a proxy without intermediary copying increases a proxy's capabilities since fewer resources are expended on operations, such as intermediary copying. A proxy determines which data of a message received into memory will be maintained. The proxy indicates, in an ordered encoding, locations of the determined data and of update data. The update data may be a new message segment, session identifier, etc. The ordered encoding, which indicates the data in order as they will occur in the forwarded message, is used to forward the message with the maintained data and the update data.