reference will now be made in detail to various embodiments of the present invention , example of which is illustrated in the accompanying drawings . referring to the drawings , and initially to fig1 , one embodiment of a computer system indicated generally by the reference numeral 10 comprises a public network 12 connecting various devices . the devices connected to the network 12 may include a wireless transmitter / receiver 16 , which may define a hotspot 18 or may be , for example , part of a cellular network providing general wireless coverage , a printing system comprising a print server 20 controlling a printer 22 , and an enterprise network 23 comprising an enterprise server 24 . the print server 20 may include application software capable of interpreting data file formats from common application programs and a printer driver for the printer 22 so that the printer 22 and print server 20 together can receive , interpret , and print a file that is received in the user data saving format of common application programs such as word processors , spreadsheets , graphics packages , etc . in an embodiment , the public network 12 is , includes , or is in communication with , the internet , and the enterprise network 23 may be anywhere on the internet . the enterprise network 23 is protected by a firewall 26 , which may be implemented as a separate device or may be a logical function of the enterprise server 24 . the enterprise server 24 may be part of an enterprise intranet ( not shown ) behind the firewall 26 . the enterprise server 24 stores files including a document 28 . a mobile user equipment 30 , which may be , for example , a smart phone , may be present in the hotspot 18 , and may be in communication with the transmitter / receiver 16 and thereby with the network 12 . alternatively , the user equipment 30 may be connected to the public network 12 in another way , for example , by a wired connection . as shown in fig1 , especially in the case of the hotspot 18 , the printer 22 may be near to the transmitter / receiver 16 . alternatively , the printer 22 may be anywhere on the network 12 , especially if a document to be printed is for the use of a person other than a user of the user equipment 30 . the user equipment 30 is trusted by the firewall 26 , and is equipped to establish and maintain a secure connection with enterprise server 24 , shown symbolically by a chain - dotted line 32 in fig1 . the secure connection 32 may form a virtual private network ( vpn ) effectively extending the enterprise network 23 to include the user equipment 30 . once the secure connection 32 is established and the user equipment 30 has authenticated itself to the firewall 26 , the user equipment 30 is permitted to access and retrieve the document 28 . the user equipment 30 is also equipped to establish connections with other devices on the network 12 , for example , with the print server 20 . referring now to fig2 , in a method embodiment of the invention , a user equipment 30 , for example , a wireless e - mail device , first connects itself to the public network 12 . the connection process may comply with the standard protocols of the network and , in the interests of simplicity , is not shown in fig2 . in step 52 the user equipment 30 establishes a ip connection with a print server 20 that controls a printer 22 in step 54 , the user equipment 30 authenticates itself to the firewall 26 and establishes a vpn connection 32 with the enterprise server 24 . steps 52 and 54 may occur in either order . for example , the user of the user equipment 30 may be connected to the enterprise server 24 to check e - mail , and may connect to the print server 20 only when the user finds that he or she needs to print out a document 28 that is an e - mail attachment . for example , the user equipment 30 may be attached to the network 12 , including a nearby printer 22 , for purposes that do not require the vpn connection 32 , and may establish the vpn connection 32 only when it becomes necessary for the user to access the document 28 . for example , the user may already know about the document 28 , and may establish the connection to the print server 20 and the vpn connection 32 to the enterprise server 24 only when the user wishes to print out the document . in step 56 , the user equipment 30 optionally obtains a reference identifying the document 28 , which may comprise a filename for the document 28 and a location of the document 28 within the vpn comprising the enterprise server 24 . in the embodiment shown in fig2 , the user equipment contacts the enterprise server 24 to obtain , or at least verify , the existence and location of the document 28 , so step 56 is shown as following step 54 . alternatively , the user equipment 30 may receive a precise reference to the document 28 before establishing the secure connection to the enterprise server 24 in step 54 . for example , the location of the document 28 may already be stored on the user equipment 30 or known to the user of the user equipment 30 . in step 58 , the user equipment 30 sends to the print server 20 instructions to print the document 28 and a reference to the document 28 located on the enterprise server 24 . the reference sent to the print server 20 includes the current address of the user equipment 30 within the public network 12 . the reference sent to the print server 20 may also include the filename and address of the document 28 within the enterprise network 23 . alternatively , the reference sent to the print server 20 may be in a form meaningful only to the user equipment 30 , in order not to disclose publicly unnecessary information about the internal structure of the private network . in step 60 , the print server 20 sends to the user equipment 30 a request for the enterprise server 24 to supply the print server 20 with a copy of the document 28 . in the request , the print server 20 identifies the document 28 by the reference provided in step 58 . the user equipment 30 , which is acting effectively as part of the enterprise network 23 , may read the message to confirm that it consists solely of a proper request for the document 28 , and no undesirable content has been added by the print server 20 or by any intermediate device between the print server 20 and the user equipment 30 . if the reference to the document 28 in the request does not contain the location and filename of the document 28 on the enterprise server 24 , the user equipment provides that information . the user equipment 30 then sends the request on to the enterprise server 24 . the enterprise server 24 receives the request , and perceives the request as coming from the user equipment 30 . the user equipment 30 is within the enterprise network 23 and entitled to obtain the document 28 , so the enterprise server 24 complies with the request and sends the document 28 . when the document 28 arrives at the user equipment 30 , the user equipment 30 routes the packets of the document 28 to the print server 20 . in the embodiment shown in fig2 , a large file is transmitted as a stream of packets , each of which is sufficiently small to be handled by the user equipment 30 . the user equipment 30 receives the packets from the enterprise server 24 and forwards the packets to the print server 20 as they are received , without attempting to treat the document 28 as a whole . the user equipment 30 can thus route an indefinitely large document 28 from the enterprise server 24 to the print server 20 without being constrained by the limited memory capacity of the user equipment 30 . in addition , the document 28 may be stored on the enterprise server 24 in an editable format , which may be small compared with , for example , a rasterized printer format . the user equipment 30 can pass the packets forming the document 28 out without prejudicing the security of the enterprise network 23 . the user equipment 30 does not permit any packets or other messages to enter the enterprise network 23 . if return packets are required for verification as part of the transmission protocol being used , then the user equipment 30 receives the verification packets from the print server 20 independently of sending verification packets to the enterprise server 24 . in step 62 , the print server 20 converts the document 28 , if necessary , into a printer format , and sends the document 28 to the printer 22 . the printer 22 prints the document . once the entire document 28 has arrived at the print server 20 , the vpn connection 32 between the enterprise server 24 and the user equipment 30 , and / or any communication channel between the user equipment 30 and the print server 20 , may be closed . alternatively , one or both of those connections may be kept open for future use and / or for other uses . various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention . for example , in the interests of simplicity , fig1 does not show in detail components of network 12 that merely serve to route messages between the print server 20 , the enterprise server 24 , and the user equipment 30 , but such components may be present . similarly , additional servers that may be consulted to obtain address or routing information , or that may contain location data about available printers 22 , are not shown but may be present . in fig1 , the transmitter / receiver 16 and the print server 20 are shown as being independently connected to the network 12 . in a hotspot 18 , the transmitter / receiver 16 and the print server 20 may physically be in a single unit with a common point of connection to the network 12 , or may be in a smaller network with a common point of connection to the network 12 . in fig1 , the printer 22 and the print server 20 are shown as separate units . the print server 20 may alternatively be a functionality of the printer 22 . thus , it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents .