Patent Application
20100158026
Often, there is a desire to introduce a new network element into an existing network such as 3GPP network. This desire could be driven by many diverse requirements, such as improving network performance, monitoring network conditions, improvement of user experience, improving security aspects of the network or the user or for any of the myriad of things that are possible. Such a device may need to be placed logically as a “bump in the wire” in the network, in the sense that it is placed between two devices and both devices are unaware of the newly introduced device. Such a placement of the new device could be either physically in-line between the two devices or logically in-line, such that the traffic is routed through the new device.
Protocol standards define one or more layers of control protocol interactions between two devices over a connected interface. These control protocol operations define actions to be performed by each device while interacting with an adjacent device, or neighbor for managing user data-plane sessions. Examples of such operations include establishing, modifying, and terminating a user data plane session, such as Packet Data Protocol (PDP) context, or creating, modifying, and terminating a Radio Access Bearer (RAB) for active PDP context in 3GPP/UMTS mobile network. When a “bump in the wire” type device, as described above, is placed between two standards-defined communication devices, this new device will be operating outside the scope of the corresponding control protocol standards. Thus, the new device does not have any identity in the respective protocol framework. The interfaces shown (IuB, IuPS etc.) in the accompanying figures are logical protocol interfaces and may be transported through ATM or IP transports per 3GPP/UMTS standards. The interface protocol standards define both the control protocols for managing user sessions through the mobile network, as well as the user plane packet encapsulation protocols. The focus of the current invention is control plane protocols on these interfaces.
b represents the placement of the new device 9 physically inline within the network shown in
Many types of bridges exist. For example, protocol bridges, such as Layer 2 Ethernet bridges (IEEE 802.1D, 802.1Q), operate by intercepting Ethernet Layer 2 MAC Header, and using these headers to build internal forwarding tables to associate Layer 2 MAC Addresses with 1 or more forwarding ports within the Bridge. The goals of such a bridge are to extend the interconnectivity between the connected devices (i.e. the number of nodes that can participate in the Layer 2 network), extend the network reach beyond the Ethernet Physical Layer, and increase the total Bandwidth among a number of nodes by providing simultaneous packet transfer operations. These Layer 2 bridges forward packets received from one interface to one or more interfaces based on their Layer 2 Header without modifying the packet contents.
Layer 3 forwarding devices, such as IP routers, intercept packets from one or more interfaces, and forward them to one or more interfaces. Depending on the type of lower layer transport they are connected to, these devices may modify the Layer 2 headers. The goal of such devices is to extend the Network Connectivity at Layer 3 among a number of devices, and increase the Bandwidth among a large number of devices.
Repeaters, such as Ethernet Repeaters, extend the physical reachability of the two devices that they connect to (i.e. the distance between devices is increased). They terminate or extend the corresponding link layer protocols and forward upper layer packets from one interface to another.
Each of these prior art devices simply forwards existing packets to one or more destinations. In some embodiments, the device modifies the packet, typically at the Layer 2 or Layer 3 level to expand the network. However, it may be desirable and advantageous to introduce new messages into the network, or to terminate other flows.
The current invention describes a device and method for intercepting multi-layer control protocols and selectively bridge (relay packets from one interface to another without modification), or inject or terminate certain streams, or modify certain protocol contents. The objective of the current invention is to extend Peer-to-Peer protocols between two standard network devices in a transparent way, in the sense that the presence of new device is unknown to the two peers.
In some embodiments, this new device can then offer enhanced features such as monitoring, new session initiation for delivering locally cached content, etc. Some of these value-added benefits are described in co-pending U.S. patent application Ser. No. 12/536,537, entitled “Content Caching is a Radio Access Network”, the disclosure of which is herein incorporated by reference in its entirety.
This new device is termed a “Multi-Protocol Transparent Proxy (MPTP)”. The MPTP device intercepts one or more control protocols on the interface that it connects to. Depending on the device configuration and supported features, the MPTP forwards (relays packets from one interface to another without modification), injects or terminates certain protocol packets, thus operating as proxy, or receives certain protocol packets from one interface, modifies the packet contents and forwards to the other interface.
The methods and procedures per the current invention are exemplified using Control protocols on the IuPS interface (IuPS-CP) between RNC and SGSN in UMTS Radio Access Network. However, they apply to other protocol interfaces, such as IuB, Gn, GI interfaces in the UMTS network, or other network protocols such as in LTE, 3GPP2, and WIMAX network Architectures, and therefore are not limited to one specific embodiment.
a shows a RAN network of the prior art;
b shows the RAN network of
c shows the logical placement of the device in
a shows the RNC SGSN interface control plane protocols for ATM transport option;
b shows the RNC SGSN interface User Plane Protocols for both ATM and IP transport options;
When viewed from an external network, the GGSN 3 appears as a router to a sub-network, because the GGSN 3 hides the GPRS infrastructure from the external network. When the GGSN 3 receives data addressed to a specific user, it checks if the user is active. If it is, the GGSN 3 forwards the data to the SGSN 4 serving the mobile user. However if the mobile user is inactive, the data are discarded, or a paging procedure is initiated to locate and notify the mobile device. For data originated within the GPRS network, the GGSN 3 routes these mobile-originated packets to the correct external network.
The GGSN 3 converts the GPRS packets coming from the SGSN 4 into the appropriate packet data protocol (PDP) format (e.g., IP or X.25) and sends them out on the corresponding packet data network. For incoming packets, the PDP addresses are converted to the GSM address of the destination user. The readdressed packets are then sent to the responsible SGSN 4. In order to accomplish this function, the GGSN 3 stores the current SGSN address of the user and its associated profile in its location register. The GGSN 3 is responsible for IP address assignment and is the default router for the connected user equipment (UE) 7. The GGSN 3 also performs authentication functions.
A Serving GPRS Support Node (SGSN) 4 is responsible for the delivery of data packets from and to the mobile stations within its geographical service area. Its tasks include packet routing and transfer, mobility management (attach/detach and location management), logical link management, and authentication and charging functions. The location register of the SGSN 4 stores location information and user profiles of all GPRS users registered with this SGSN 4.
The Radio Network Controller (or RNC) 5 is a governing element in the radio access network and is responsible for controlling the Node Bs 6 that are connected to it. The RNC carries out radio resource management, some of the mobility management functions and is the point where encryption is done before user data is sent to and from the mobile. The RNC 5 connects to the SGSN (Serving GPRS Support Node) 4 in the Packet Switched Core Network.
Node B 6 is a term used to denote the base transceiver station (BTS) in the UMTS/3GPP Architecture. As in all cellular systems, such as GSM, Node B (or BTS) 6 contains radio frequency transmitter(s) and the receiver(s) used to communicate directly with the user equipment, which move freely around it.
The user equipment (UE) 7 comprises all user equipment, including handsets, smart phones and computing equipment. A Node B is likely to be connected to a plurality of user equipment. Thus, a single Node B may communicate with multiple mobile clients, each utilizing one or more UE 7.
The following examples shows the insertion of the new device between the RNC and the SGSN, as shown in
3GPP Technical Specifications [1-4] define Control Plane and User Plane protocols for IuPS interface between RNC (Radio Network Controller), and SGSN (Serving Gateway Service Node). The Control Plane protocols are shown in
In operation, software operates at each level to parse the information required at that level. After the protocol information for that layer has been stripped off, the remainder of the packet is forwarded to the next higher protocol layer. This process continues until the packet has been fully decomposed. In the case of pass-through traffic, the packet is then reconstructed by appending protocol information as the packet is passed down the layers. In other words, packet headers are reattached in the opposite order in which they are removed, such that the L1 information is the first to be removed on an incoming packet and the last to be appended on an outgoing packet.
b illustrates the User Plane Protocols that exist on the IuPS interface in 3GPP/UMTS network, as shown in
There are a number of embodiments that can be used to insert a new device into this network. The first embodiment, also known as monitor mode interception, is shown in
In this mode, the new device 9a monitors (sniffs) the physical interface between two nodes, such as the RNC 5 and the SGSN 4, and decodes any packets transmitted on that interface and propagates these packets to higher level applications. The new device 9a is physically inserted into the ATM network 11, using a physical interface tap 12. The protocol stack may be a pared down, or reduced, version, in the sense that it does not hold any active data.
Though this mode can help implement the new device quickly, it has serious limitations in terms of its ability to inject and modify protocol messages. This limitation comes in due to the limitations of “tapping”. “Tapping” is typically a one-way process used to listen to or observe communication on a physical interface 11. As such, it is difficult to insert messages into the stream even if that tap 12 is two-way at the physical layer. This is due to the complexity of correctly guessing various protocol sequence numbers and timing within that protocol.
In other words, as packets are passing between two devices, such as RNC 5 and SGSN 4, over the network 11, each packet carries one or more sequence numbers, which allow the receiving node to confirm that packets are sequential and none have been lost. Attempting to insert packets into this stream requires that the new packets contain sequence numbers that match those expected by the receiving node. Furthermore, since the sending node is unaware of this new device, it will also use those sequence numbers, thereby resulting in lost of corrupted data.
A second embodiment, referred to as back-to-back mode, is shown in
Though this method gives tremendous flexibility in terms of various features the new device 9b can implement, it suffers from several significant drawbacks in terms of network scalability and deployment. These drawbacks include:
A third embodiment, known as multi-protocol transparent proxy (MPTP) is identified in the current invention and is shown in
First, the intermediate (or newly inserted) device 9c does not need a network identity. It merely intercepts the physical interface and bridges messages at each layer. Bridging, in this context, means forwarding a given protocol packet to the peer after minor (or no) modifications to make it acceptable to the peer. These modifications include, but are not limited to, sequence number adjustments, checksum updates and other parameter updates depending upon the specific protocol layer. However, it does not terminate the communication protocol, as is done in the previous embodiment.
The MPTP device 9c performs the above operations at each of the protocol layers.
A packet may reach the device 9c such as via ATM network 15. The packet is passed upward through the associated protocols on one protocol stack 17a. While processing the protocol layers, the MPTP device 9c simply relays the messages from one interface to the other (such as across from stack 17a to stack 17b) if it is not of interest or if it is not understood. Thus, it does not suffer from the drawback described with the back-to-back mode, in the case of new or not understood protocol messages.
This model allows for network applications to be incorporated into the MPTP device 9c. The various protocol layers provide information about the connections and the remote devices. In some embodiments, the MPTP 9c will also present some of the protocol messages to an application resident on the new device. This helps the new device 9c understand and act upon the protocol exchange in order to implement any additional features that may be of interest. Applications can control the layers to enable presentation of only a certain set of messages. Further sections explore various embodiments of this filtering mechanism.
Depending on the feature requirements and application needs, MPTP 9c can also inject messages into the protocol stream 17a, 17b (on either side). When messages are injected, the protocol stack may adjust the protocol parameters (such as, but not limited to, sequence numbers, and checksum) before propagating the messages to the other device.
Implementation of the MPTP mode can be defined in terms of two types of components; a Bridge Application/Control component 20 and a Protocol Bridging Component 21.
For example, a local network interconnect, or a shared memory structure can be used to exchange information between the components. Other mechanisms are known and within the scope of the invention.
In other embodiments, a processor is shared between two or more components. For example, the bridging components 21a-f may utilize a single processing unit, where the instructions are organized such that each protocol layer represents a different task or routine executing on the processing unit. In other embodiments, the bridge application/control component 20 shares a processing unit with one or more of the bridging components 21.
The instructions to be executed can be written in any suitable programming language. Furthermore, the operating system employed by the processing unit (if any) is application specific, and is not limited by the present invention.
This bridge application/control component 20 drives the functionality of the new device 9c. To do this, the component 20 interfaces with one or more bridging components 21a-e (as shown in
The bridge application/control component 20 determines the specific messages or classes of messages that it would like to receive. In one embodiment, it configures the bridging components 21a-e with the appropriate configuration information. This configuration information could be a complex filtering criterion that could include information from the message headers, message body or the transport information for a specific message. The bridge application/control component 20 may generate multiple filter criteria per protocol layer, and different filter criteria at each protocol layer if desired.
Having determined and configured the bridging components to intercept certain messages, the bridge application/control component 20 may also instruct the bridging components 21 as to the action to be taken upon detection of a message matching the selected parameters.
For example, the bridge application/control component 20 may instruct the bridging component 21 to perform one of the following functions, including but not limited to:
The bridge application/control component 20 may also receive and process messages that the bridging component forwards/redirects towards this component 20. This processing may include modifying certain elements and forwarding to the other protocol stack, completely consuming the packet within the component 20, or simply discarding the packet.
In addition to processing packets received by the MPTP 9c, the bridge application/control component 20 may also inject new messages into a particular layer. These messages could be completely new messages, responses to previously intercepted messages, or blank messages to synchronize protocol or transport level messages such as to maintain proper sequence numbers. For example, the bridge application may be a web cache, which has a storage element filled with commonly used web pages. In response to a request for an uncached website, the bridge application/control component 20 would simply allow the request to pass through the MPTP 9c. If, however, the requested web page were resident in local memory, the bridge application 20 would intercept the request and respond to it, as if it were the remote web server.
The bridge application/control component 20 may also modify messages received from the bridging component 21. In some embodiments, the bridge application/control component modifies an information element, where an information element is any data within the packet such as that which describes the client, user session or specific transaction. For example, during the establishment of a new user session, the bridge application/control component 20 may modify various parameters, including but not limited to QOS parameters, service class, and priority. In the case of a previously established user session, the bridge application/control component 20 may modify parameters including Radio Access Bearer.
Bridging component 21 interfaces with the bridge application/control component 20 and protocol layers on each side, and performs the following operations.
The bridging component 21 stores local data including protocol states, sequence numbers, configuration and control information. In certain implementations, this local data may not exist.
Optionally it maintains statistics and error information concerning the particular layer.
The bridging component 21 provides a management interface to control and view logs, statistics and errors. In certain implementations, this functionality could be omitted completely.
As explained above, the bridging component 21 receives the control/configuration information from bridge application/control component 20 that instructs it as to which messages are of interest, and what action to take on these messages. The bridging component 21 filters messages based on this received configuration. The possible actions of the bridging component 21 include:
In some embodiments, the bridging component 21 may have default or additional logic contained within it. In this embodiment, the bridging component 21 may operate using this additional logic, in addition to the above-described filters. For example, if, based on context, the bridging component 21 determines that a message need not be inserted into the peer stream, this bridging component 21 might simply discard it.
In the scenario where the bridge application/control component 20 decides to inject a new message into the stream, the message is formatted per the corresponding protocol and sent to the appropriate protocol stack and appropriate protocol layer by the bridging component 21. The bridge application/control component 20 is aware of the protocol layer that the new message utilizes, and therefore knows the appropriate bridging component 21 to send the packet to.
The bridging component 21 is also responsible for ensuring that the messages are coherent or “sane” with respect to that protocol. This might include adjusting information within the messages such as sequence numbers, checksum, information consistency and formatting.
It is important to note that the bridging component 21 above may be an independent component located between the two protocol stacks (as shown in
There are various advantages of the multi-protocol transparent proxy. For example, as explained above, the new device does not need a network identity, thus preserving precious network resources. In addition, deployment of the MPTP is trivial, as the network operator does not need to modify the configuration of existing devices. Since the device does not have an identity, it is invisible to its neighbors. Similarly, removing a MPTP from a network is straightforward, since no modifications were made during deployment. Additionally, the MPTP has complete access to all the protocol messages. This enables it to implement any value added features. This solution does not break the compatibility between the existing devices.
The Multi-Protocol Transparent Proxy device and methods defined herein facilitate the insertion of new devices transparently into a protocol stack. This allows enhanced features such as monitoring, business intelligence gathering, content insertion, and protocol enhancements on one interface without affecting the other interface.
To do this, the new device intercepts and selectively performs one or more of the following operations:
Having defined one physical embodiment and the various features of the transparent proxy, the following describes the operation of the proxy. As described above, the protocol stack in
For example, the bridge application/control component may determine, based on messages in the control protocol, the capabilities of a particular mobile client, such as its device type and associated screen size. Similarly, it can determine the services to which the mobile client is entitled, such as its QoS and service plane attributes. Based on this, the bridge application/control component may attempt to enhance the experience of a specific mobile client by creating a secondary PDP context. However, it may only perform this if the client device is a particular device, such as a interconnect card for a laptop or portable computer, and if the subscriber is authorized to receive the enhanced experience.
An example of the operation of the present invention is in the creation of a new secondary user plane session (Secondary PDP Context) for viewing video, where the video may be resident locally in the device.
Creating such a user session requires RANAP protocol operations through the RNC to the UE. When the bridge application determines such a new secondary user session needs to be created, it need to insert new RANAP messages for this particular UE connection. All other messages that are not relevant to this UE are forwarded as Copy and Forward. In other words, the proxy device 9 needs to create new control plane messages which are required before a user session can be established. Referring to
RANAP Messages are carried over the SCCP transport connection that maintains sequenced message delivery using message sequence numbers, and retransmission. In other words, each message has a unique sequence number and these numbers are guaranteed to be sequential to allow the recipient to know when a message has been lost.
Before the device 9 inserts any new messages for the newly created connection, sequence numbers will be identical on the two interfaces 17a, 17b in each direction. In other words, messages received on one interface are always forwarded to the second interface. Thus, there is a one-to-one correspondence between RANAP messages received on one interface and sent on the second interface.
However, when the device 9 generates a new RANAP message, that message is directed only toward the RNC 5. Therefore, there are RANAP messages that exit the device toward the RNC 5, which were not generated by the SGSN 4. Since these are not received or sent on the interface to SGSN 4, the sequence numbers for this specific UE on the two interfaces no longer match.
Thus, future messages that use this specific UE SCCP connection would be transmitted by the bridging component after the sequence numbers are adjusted to match the expected sequence numbers by the remote peer on each interface.
After the new RANAP message is inserted by the device 9 as described above and sent to the RNC 5, the remote peer returns a response message. Since the original RANAP message was not received from the SGSN interface, the response message received on the RNC/IuPS interface is processed by the device 9. Since the network upstream is unaware of this response, the message is consumed by the MPTP device, so that it is not forwarded to the SGSN 4.
The connection-oriented transport by SCCP uses sequence numbers and packet retransmissions. Thus, the remote peer retransmits a packet with the same sequence number. If the local protocol/bridging entity recognizes this packet as a duplicate, it may discard the message depending on the protocol state. Similarly, the remote peer may request retransmission of a message if it detects a missing packet. Such a packet may be a locally inserted packet, or a packet received from remote device and forwarded. By maintaining a sequence number map that defines whether the specific packet is locally inserted or forwarded on each interface, the MPTP device 9 determines whether the retransmission request needs to be forwarded or responded to locally.
This example shows the four basic operations of the device, when manipulating messages in the control plane. First, the device 9 can simply choose to bridge the message between the RNC 5 and the SGSN 4. In this mode, the device 9 may or may not modify the message (such as manipulating the sequence number) as it bridges the message. Second, the device 9 can choose to copy the message and forward it.
This allows the device to track the control plane state. Third, the device 9 can insert messages, as described above. Finally, the device can delete or discard messages, such as those that are terminated within the device.
Though this disclosure focuses on a specific interface (Iu on ATM), the methods and procedures are applicable to any interface protocol between any pair of devices. Other embodiments include:
This application claims priority of U.S. Provisional Patent Application Ser. No. 61/140,165, filed Dec. 23, 2008, the disclosure of which is herein incorporated by reference in its entirety.
| Number | Date | Country | |
|---|---|---|---|
| 61140165 | Dec 2008 | US |
