Electrical computers and digital processing systems: support – Multiple computer communication using cryptography – Packet header designating cryptographically protected data
Reexamination Certificate
1999-02-05
2002-11-05
Peeso, Thomas R. (Department: 2132)
Electrical computers and digital processing systems: support
Multiple computer communication using cryptography
Packet header designating cryptographically protected data
C713S168000, C713S171000, C380S247000
Reexamination Certificate
active
06477644
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to mobile internet access and in particular to a method and apparatus for sending a security key to a mobile host for use in internet access.
BACKGROUND OF THE INVENTION
Corporate users have traditionally accessed the internet from a fixed location within a Local Area Network (LAN), a user's LAN often being referred to as his “home” network (HN). The user interface to the internet is typically a personal computer (the “host”). As is illustrated in
FIG. 1
, the home network is connected to an internet service provider which routes internet data, so-called “datagrams”, between the home network and the internet, the internet in turn comprising other routers and service providers which route data to and from other “foreign” networks (FN).
In order to be able to transmit and receive datagrams to and from the internet, a host requires an internet address. A corporate home network is typically allocated a set of internet addresses by a national authority and the home network can assign these either fixedly or dynamically to hosts attached to the home network (using for example the Dyriamic Host Configuration Protocol DHCP). The allocated set of internet addresses comprise a common prefix portion which identifies the home network, whilst a suffix portion identifies the destination host. When a datagram is received by a home network, a router (R) of the home network polls the attached hosts to determine which host corresponds to the internet address conveyed with the datagram. The datagram is then forwarded by the router to the identified host.
With the recent rapid advances in mobile communication technology, and in particular of wireless technologies, there has come a desire to gain internet access from mobile hosts or terminals, for example a laptop computer coupled to a cellular telephone. At present, this is available via certain digital telephone networks (e.g. GSM). As with conventional fixed line internet access, a mobile host may have a fixedly or dynamically assigned internet address, allocated by a service provider who is usually the cellular telephone network operator. In the case of mobile internet access, a communication channel between the mobile host and the network is reserved for the duration of the call. Internet data destined for the mobile host is received by the network and is sent to the host over the reserved channel.
This system works satisfactorily whilst a mobile host remains within one homogeneous network. However, it does not provide for “roaming” between different types of networks or between networks operated by different operators. When a mobile host “de-registers” with one network and registers with a new network, there is no mechanism for forwarding internet datagrams, addressed to the old network, to the new network as the communication channel between the mobile host and the old network no longer exists. It is therefore necessary to open a new communication channel between the mobile host and the new network. All datagrams addressed to the old network and not yet received by the mobile host are lost as a result of this channel change.
The desire for roaming is likely to increase in the near future as the provision of corporate wireless LANs becomes commonplace. A corporate user will have the opportunity to make wireless voice and data calls from a mobile terminal via the corporate LAN whilst he is inside the coverage area of that LAN. When the user leaves that area, he will then be able to connect to a digital cellular telephone network. In addition, so-called “hot-spot” LANs are likely to be provided in areas where high data capacity is required, e.g. airports, shopping centres. In all probability, hot-spot LANs will be operated by the cellular network operators although they may of course be operated by the property owners themselves.
A mobile internet access protocol which provides for roaming is currently being standardised by the Internet Engineering Task Force (IETF). This protocol is known as RFC2002. A mobile internet protocol is also described in EP556012. These protocols make use of a “home agent”, located in a mobile host's home network, to keep track of the host when it leaves the home network. A mobile host is fixedly allocated an internet address corresponding to the home network.
When a mobile host is registered to its home network, the functionality of the network's home agent is off for that host (i.e. the host is “deregistered” with the home agent) so that the home agent does not alter the flow of datagrams from the internet to the network's router and the mobile host (as indicated by reference numeral
1
in FIG.
2
). When the mobile host leaves its home network and contacts a foreign network (FN), the host is registered with a foreign agent (FA) of that network. The foreign agent then transmits to the mobile host an internet address of the foreign agent, and the mobile host in turn transmits the received internet address to the home network's home agent, together with a registration instruction. The home agent registers the new status of the mobile host and records the newly allocated internet address as a “care-of-address” for the host. Whenever the mobile host registers with a new foreign network, a new care-of-address is sent to the home network's home agent to replace the previously registered care-of-address.
It will be appreciated that, as a mobile host has a fixed internet address allocated to it, datagrams destined for the host will always be sent to the home network. If a mobile host has an active internet connection when it passes from its home network to a foreign network, and a datagram destined for the host subsequently arrives at the home network, the home agent determines that the mobile host is registered with a foreign agent and forwards the datagrams to the registered care-of-address. A communication channel will have been reserved between the mobile host and the foreign agent, and the redirected datagram can be sent to the mobile host over this channel. Similarly, if a mobile host initiates a new internet access when registered with a foreign network, the host continues to use its allocated internet address. The home agent has already received the care-of-address and can again forward datagrams destined for the mobile host to the foreign agent for transfer to the host.
In some cases, the foreign network may dynamically assign an internet address to a visiting mobile host, e.g. if the foreign network does not have a foreign agent. This address is sent to the mobile host which in turn sends it to the home network's home agent as a care-of-address. Rather than just merely redirecting datagrams to the care-of-address, the home agent actually replaces the old internet address contained in the datagram with the co-located care-of-address before retransmitting the datagram. This particular form of care-of-address which identifies the mobile host as the “tunnel” end-point for the redirected datagrams, rather than a foreign agent, is known as a “co-located care-of-address”. It is noted however, that when the mobile host is accessing the internet via the foreign network, it still uses its fixedly allocated internet address. It will therefore be appreciated that regardless of whether the home agent receives a care-of-address or a co-located care-of-address all datagrams directed to a mobile host pass through the home network's home agent (as indicated by reference numeral
2
in FIG.
2
).
In a modification to the mobile internet access protocol described above, roaming of a mobile host from a home to a foreign network may be achieved by assigning a new internet address, in said second network, to the mobile host when the host leaves the home network for the foreign network. This new address is then transmitted from the mobile host to the home network's home agent where the new address is registered as a care-of-address or co-located care-of-address for the mobile host. Datagrams addressed to the new internet address are se
Nokia Mobile Phones Limited
Peeso Thomas R.
Perman & Green LLP
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