Multiplex communications – Communication techniques for information carried in plural... – Adaptive
Reexamination Certificate
2000-02-29
2003-09-02
Ton, Dang (Department: 2661)
Multiplex communications
Communication techniques for information carried in plural...
Adaptive
C709S249000, C709S238000
Reexamination Certificate
active
06614809
ABSTRACT:
FIELD OF INVENTION
The present invention relates to data communications. More specifically, it relates to the transmission of packets over a communications link that crosses multiple types of networks.
BACKGROUND OF THE INVENTION
Connection oriented point-to-point communication links, such as a Layer
2
Tunneling Protocol (L
2
TP) tunnel, are an increasingly common feature of network infrastructures. Tunnels are prearranged connections established by agreement between internet service providers (ISPs). See Request for Comment (RFC) 2661 and
Layer Two Tunnelling Protocol
(L
2
TP), A. Valencia, et al., draft-ietf-pppext-12tp-16.txt, June 1999, herein incorporated by reference, available from the Internet Engineering Task Force (IETF) at www.ietf.org for more information.
FIG. 1
shows an architecture
10
involving an internet protocol (IP) network
70
to which tunnel initiator
30
is linked via network connection
32
, tunnel initiator
40
is linked via network connection
42
and tunnel endpoint
50
is linked via network connection
52
. A remote client
20
is linked to tunnel initiator
30
via communication link
22
that is tunneled through IP network
70
via tunnel connection
56
from tunnel initiator
30
to tunnel endpoint
50
. Another remote client
24
is linked to tunnel initiator
40
via communication link
26
that is tunneled through IP network
70
via tunnel connection
66
from tunnel initiator
40
to tunnel endpoint
50
. Tunnel endpoint device
50
is also connected to a Local Area Network
80
via network connection
54
. A server device
84
is linked to LAN
80
.
One example of a tunnel initiator or tunnel endpoint device is a network access server, such as that described in the patent to Dale M. Walsh et al., U.S. Pat. No. 5,528,595, which is fully incorporated by reference herein and describes an integrated network access server suitable for use in the present invention. Such a device has been commercialized widely by 3Com Corporation (previously U.S. Robotics Corp.) under the trade designation Total Control™ Enterprise Network Hub. Network access servers similar in functionality, architecture and design are available from other companies, including Ascend Communications, Livingston Enterprises, Multitech, and others. The invention is suitable for implementation in network access servers from the above companies, and other similar devices.
An L
2
TP tunnel typically provides a conduit for communications between a client device served by a tunnel initiator and a server device served by tunnel endpoint, i.e. tunnel connection
56
between tunnel initiator
30
and tunnel endpoint
50
that transports communication between remote client
20
and server
84
. Typically, a single tunnel slot provides the communication link between a client and server.
When a client device establishes a dial-up connection with a tunnel initiator (TI)
30
or
40
, then the TI typically recognizes the client device as a tunnel client by means of an authentication protocol, such as RADIUS, see Request For Comment (RFC)
2138
, herein incorporated by reference. An authentication, authorization and accounting (AAA) server
74
, such as a RADIUS server, may be connected to IP network
70
to provide AAA services to the tunnel initiators and other devices on the network. The authentication process can be adapted to provide an address for a tunnel endpoint device for the client. There exist other means for identifying a tunnel client, such as through the use of a mobile identification number (MIN) in mobile applications or, for protocols not directed toward mobile applications, the use of a Dial-up Number Information Service (DNIS) or Automatic Number identification (ANI), that can also be used to identify a tunnel endpoint for a client and establish a tunnel connection. Alternatively, the client device itself may provide the tunnel endpoint address. In still another approach, each TI may have a pre-constructed table containing entries that associate a client device identifiers with a tunnel endpoint address value. Independent of how the tunnel endpoint address is obtained, the tunnel initiator will establish a tunnel connection to the tunnel endpoint device.
FIG. 2
is a protocol stack diagram illustrating an example of the protocol relationships in a conventional tunnel structure. As is known in the art, the Open System Interconnection (“OSI”) model is used to describe computer networks. The OSI model consists of seven layers including from lowest-to-highest, a physical, data-link, network, transport, session, application and presentation layer. The physical layer, or layer
1
, transmits bits over a communication link. The data link layer, or layer
2
, transmits error free frames of data. The network layer, or layer
3
, transmits and routes data packets.
FIG. 2
illustrates an example of protocol stacks in each of the remote client
20
, tunnel initiator
30
, and tunnel endpoint
50
, and server
84
for tunnel connection
56
of FIG.
1
. Link
22
-for remote client
20
to tunnel initiator
30
can involve a wireless link protocol, such as the Radio Link Protocol (RLP), a dial-up type protocol, such as the Point-to-Point Protocol (PPP) or Serial Line Interface Protocol (SLIP), a network type protocol, such as the Media Access Control (MAC) protocol of Ethernet, or other types of links as the application demands. Thus, a layer
1
to layer
1
(L
1
) session is represented at the lowest level of the protocol stacks in
FIG. 2
between remote client
20
and tunnel initiator
30
. Because the link between the remote client and tunnel initiator is typically a serial link, a serial data link protocol session exists at layer
2
(L
2
) between remote client
20
and tunnel initiator
30
.
When a tunnel is established from tunnel initiator
30
to tunnel endpoint
50
, there are layer
1
(L
1
) and layer
2
(L
2
) sessions between the tunnel servers as well as a L
2
TP session that represents the tunnel connection
56
itself. Once the tunnel connection is established, a session between network layer peers, such as internet protocol (IP) peers, in the remote client
20
and tunnel endpoint
50
typically exists. A session also typically exists between transport layer peers in the remote client
20
and the server
84
. Transport layer protocols such as Transmission Control Protocol (“TCP”) and User Datagram Protocol (“UDP”) are often used over IP in computer networks. The Transmission Control Protocol provides a connection-oriented, end-to-end reliable protocol designed to fit into a layered hierarchy of protocols that support multi-network applications. The User Datagram Protocol provides a transaction oriented datagram protocol, where delivery and duplicate packet protection are not guaranteed.
A second IP (IP
2
) and UDP (UDP
2
) peer relationship exists for the routing of packets over the network
70
between the tunnel initiator
30
and the tunnel endpoint
50
. In addition, a PPP peer relationship typically exists between the remote client
20
and the tunnel endpoint
50
, where the PPP packets become the payload for the tunnel connection between the tunnel initiator
30
and tunnel endpoint
50
. PPP is described in further detail in RFC
1661
, herein incorporated by reference for all purposes.
Occasionally, a tunnel connection is desired between a remote client and a server where a tunnel initiator serving the remote client and a tunnel initiator serving the server reside on different types of networks.
FIG. 3
is a functional block diagram illustrating an architecture
100
where tunnel initiator
30
resides on IP network
70
and tunnel endpoint
150
serving server
84
resides on Asynchronous Transfer Mode (ATM) network
160
. A gateway device
140
is configured to recognize address on both the IP network
70
and the ATM network
160
and route traffic between the two networks.
In order to tunnel traffic between remote client
20
and server
84
, two tunnel connections must be established: a first tunnel
134
from tunnel initiator
30
to gatewa
Senthilnathan Janakiraman
Verma Madhvi
Verma Rohit
3Com Corporation
McDonnell & Boehnen Hulbert & Berghoff
Phan Tri H.
Ton Dang
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