WO2008118053A1

WO2008118053A1 - A method and a device for dynamic creation of virtual lans

Info

Publication number: WO2008118053A1
Application number: PCT/SE2007/050191
Authority: WO
Inventors: Staffan Bonnier
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2007-03-28
Filing date: 2007-03-28
Publication date: 2008-10-02

Abstract

The invention discloses a method (200) for use in a Broadband Network Gateway, BNG (160) to which at least one Access Node, AN (140), may be connected, the method (200) being used when a Customer Premises Equipment, CPE (130), which is connected to a customer port on the AN (140) sends a message to the BNG (160) requesting an IP-interface comprising a CPE IP-address and an IP-address of a default gateway IP- interface on the BNG, via which addresses a service may be accessed by the CPE (130). According to the invention, the BNG uses a first identity comprised in the message in order to identify said service and a second identity comprised in the message in order to identify the customer port, by means of which identities the requested IP-interface is set up by the BNG.

Description

A method and a device for dynamic creation of Virtual LANs.

TECHNICAL FIELD The present invention discloses a method and a device for the automated creation of multiple Virtual LANs, Local Area Networks, in a Broadband Network gateway, a BNG.

BACKGROUND In IEEE 802.1 Q, the notion of a Virtual Local Area Network, VLAN, is defined, which enables more than one VLAN to share one and the same physical infrastructure.

In IEEE P802.1ad, this notion is extended, enabling each Ethernet frame to simultaneously comprise information from two different VLANs, these two VLANs being referred to as the Customer VLAN, C-VLAN, and the Service VLAN, S-VLAN, respectively. The corresponding identities carried in the frame header are called the C-VID and S-VID respectively.

When an IP-interface on a C-VLAN is required on a Broadband Network Gateway, BNG, it is a desire to avoid manual configuration of the interface.

SUMMARY

As described above, there is a need and a desire for a method by which a BNG may automatically identify and configure an IP-interface for a C-VLAN.

This need is addressed by the present invention in that it discloses a method for use in a Broadband Network Gateway, BNG, to which at least one Access Node, AN, may be connected, the method being used when a Customer Premises Equipment, CPE, which is connected to a customer port on the AN sends a request to the BNG for a CPE IP-address and for an IP-address of a default gateway IP-interface on the BNG via which a service may be accessed .

According to the method of the invention, the BNG uses a first identity comprised in the message in order to identify the service, and a second identity comprised in the message in order to identify the customer port, by means of which identities the requested IP-interface is set up by the BNG.

Suitably, the first identity is the S-VID of the service, and the second identity is the C-Vl D of the C-VLAN .

Thus, by means of the invention, and as will also be realized when reading the more detailed description below, a BNG may configure an IP interface for a C-VLAN in an automated fashion.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described in more detail in the following, with reference to the appended drawings in which

Fig 1 shows a schematic view of a system in which the invention may be applied, and

Fig 2 shows the system of fig 1 , with the invention applied, and Fig 3 shows an event diagram of a method of the invention.

DETAILED DESCRIPTION

Fig 1 shows a very schematic block diagram of a system 100 in which the invention may be applied. The system comprises a number of Customer Premise Equipments, CPEs, two of which are shown in fig 1 , with one of them being referenced as 110.

Each of the CPEs in fig 1 is connected to the system 100 via an Access Node, AN₁ 130. An Aggregation Network, ANW, 140, connects the AN to a Broadband Network Gateway, BNG, 150.

As is shown in Fig 1 , the AN has a number of customer ports, two of which are indicated as "Port 1" and "Port 2".

As Fig 1 also shows, each CPE is connected to a customer port of the AN via a SERVICE ID, S-ID 120. The SERVICE ID specifies a SERVICE, 160, such as Internet connectivity or some other service. The connection to a SERVICE is made via a Service VLAN, S-VLAN, 170, which is configured in the AN, ANW, and BNG.

The AN associates the SERVICE ID with the S-VLAN, and the SERVICE ID may, e.g., be implemented by a physical port at the customer premise, connected to a virtual circuit over a DSL connection.

Within the Aggregation Network 140, the S-VLAN is identified by a Service VLAN Identity, S-VID, which is exemplified as 1288 in the example in Fig 1.

To each customer port in the AN, there is an associated Customer VLAN Identity, C-VID, for example C-VID 375 for Port 1 and C-VID 376 for Port 2 in Fig 1. A C-VID is used to identify a Customer VLAN, C-VLAN.

For each customer port, and for each S-VLAN to which a CPE may connect via that customer port, a Customer VLAN, C-VLAN, is established. The C- VLAN is identified by the C-VID associated with the customer port according to Fig 1. The combination of the S-VLAN and the C-VLAN is configured in the BNG, and there also exists an IP-interface in the BNG for the VLAN combination. This is illustrated in Fig 2, where C-VLAN is referenced by 180, and the IP-interface in the BNG is referenced by 190. The C-VLANs are typically used to separate the traffic received by or transmitted from CPEs connected to the same S-VLAN but to different AN- ports.

The CPEs shown in figs 1 and 2 use a DHCP client to retrieve their network configurations, such as an IP-address used by the CPE for the combination of the S-VLAN and the C-VLAN. The AN has a DHCP relay agent used to relay DHCP messages to and from the BNG. Moreover, the BNG is capable of handling such DHCP messages, either by acting as a DHCP server and directly responding to such messages, or by relaying such messages to a DHCP server external to the system.

The present invention makes it possible for the BNG to automatically sense a C-VLAN associated with an S-VLAN, and to automatically configure an IP interface such as 11 in Fig 2 via which a CPE may access the services connected to the S-VLAN.

The invention also makes it possible for the BNG to automatically remove the previously configured IP-interface.

Moreover, the invention makes it possible for the BNG to detect misconfigurations, for example if the same C-VID has been configured for the same S-VLAN on different AN customer ports.

When the user of a CPE tries to initiate a session with a service, for example, an Internet connection, the DHCP-client of his CPE sends an Ethernet message requesting this, referred to as DHCPDISCOVER, to the BNG via the route described above, i.e. CPE SERVICE ID -> AN -> S-VLAN ANW -> -> BNG.

The AN modifies the DHCPDISCOVER message, by attaching the C-VID associated with the AN customer port to which the CPE is connected, and the S-VID of the S-VLAN associated with the SERVICE ID to which the CPE connects. The C-VID and the S-VID are represented by fields in the Ethernet frame header. In a properly configured system, the (S-VID, C-VID) pair is unique for the customer port within the system 100.

Suitably, each C-VID associated with a customer port in the AN is divided into two parts: One part that is pre-configured when manufacturing the AN, and another part that is common to all customer ports within the AN. The second part is configured when the AN is deployed and S-VIDs of the different services accessible via the AN are configured.

The purpose of the division of C-VID into two parts is to ensure that an (S- VID, C-VID)-pair is unique for each AN customer port. Using this scheme, this is guaranteed within any AN, but not among customer ports on different Access Nodes.

The AN may optionally be configured to attach an identity that uniquely identifies the customer ports in the DHCPDISCOVER message (commonly referred to as DHCP Option 82 - note: the uniqueness typically spans the complete operator network, and hence all customer ports on all Access Nodes). BNG may use the DHCP Option 82 identity to determine whether some AN has been misconfigured: This is, for example, the case if the BNG observes the same (S-VID, C-VID)-pair in two DHCPDISCOVER messages with different Option 82 identities.

Thus, when a CPE issues a DHCPDISCOVER message, the Ethernet frame carrying the message is automatically tagged by the AN with the unique (S- VID, C-VID) pair, and then forwarded through the aggregation network to the BNG. The BNG listens to DHCPDISCOVER on all C-VLANs for each pre- provisioned S-VLAN, and may in this way automatically sense the C-VID when receiving the Ethernet frame.

If properly authorized for network access, a process during which the BNG may or may not use the C-VID in negotiation with AAA-servers (Access Accounting Authorization), the BNG then automatically configures an IP- interface for the (S-VID, C-VID) pair. The interface serves as default gateway for the CPE.

The procedure is illustrated by means of the event diagram of fig 3:

1. The DHCP client of a CPE 130 at a customer site issues a DHCPDISCOVER message. The CPE 130 is, as an example, connected to port 8 of the Access Node 140. According to the configuration of the AN 140, port 8 is, by way of example, associated with C-VID 3253 and the selected service is associated with S-VID 1.

2. The DHCPDISCOVER is forwarded (as broadcast or unicast) through the aggregation network to the BNG 160 with S-VID 1 and C-VID 3253. Since the

BNG listens to DHCPDISCOVER on S-VID 1 independently of the C-VID, the message is handled by the BNG.

3. The BNG extracts the DHCP Option 82 value if present in the DHCPDISCOVER message, and checks whether there is another IP- interface configured for the same (S-VID, C-VID) pair, but with another DHCP Option 82 value. If this is the case, the operator is appropriately notified, since this is an indication of a misconfiguration in an Access Node.

3. The BNG performs AAA-negotiations 4. Once the client has been authorized for network access, a DHCPOFFER is composed and sent on S-VLAN 1 and C-VLAN 3253 towards the Access Node 140.

5. The Access Node 140 removes the V-LAN (for S-VlD and C-VID) from the DHCPOFFER, and forwards the message to the client, i.e. to the CPE The DHCPOFFER includes a DHCP lease time, i.e., the time during which the client leases the IP-address included in the offer.

6. The client sends a DHCPREQUEST.

7. The DHCPREQUEST is forwarded in S-VLAN 1 and C-VLAN 3253.

8. The BNG 140 creates an IP-interface for S-VID 1 and C-VID 3253 and configures the offered IP-address as default gateway.

The DHCP-negotiation between the DHCP client in the CPE and the DHCP server or relay in the BNG then proceeds as specified in the system standard.

Another scenario, for automatically removing a previously created IP- interface, is exemplified as follows: When the negotiated DHCP lease time expires (possibly after several removals initiated by the client), or the DHCP client explicitly issues a DHCP release, the BNG removes the IP-interface configured on the (S-VID, C-VID) pair.

Claims

1. A method (200) for use in a Broadband Network Gateway, BNG (160) to which at least one Access Node, AN (140), may be connected, the method (200) being used when a Customer Premises Equipment, CPE (130), which is connected to a customer port on the AN (140) sends a message to the BNG (160) requesting an IP-interface comprising a CPE IP-address and an IP-address of a default gateway IP-interface on the BNG, via which addresses a service may be accessed by the CPE (130), the method being characterized in that the BNG uses a first identity comprised in the message in order to identify said service, and a second identity comprised in the message in order to identify the customer port, by means of which identities the requested IP-interface is set up by the BNG.

2. The method (200) of claim 1 , according to which the AN (140) is connected to the BNG (160) via an Aggregation Network (150).

3. The method (200) of any of claims 1 or 2, according to which said first identity is the S-VID of the AN, and said second identity is the C-VID of the C-VLAN.

4. The method of claim 3, according to which the C-VID of the C-VLAN consists of one part which identifies the port in the AN which is used by the CPE and one part which is unique for the AN in question within the S-LAN of which the AN is a part.

5. A Broadband Network Gateway, BNG (160) to which at least one Access Node, AN (140), may be connected, to which a Customer Premises Equipment, CPE (130), which is connected to a customer port on the AN (140) may send a message requesting an IP-interface comprising a CPE IP- address and an IP-address of a default gateway IP-interface on the BNG, via which addresses a service may be accessed by the CPE (130), the BNG (160) being characterized in that the BNG uses a first identity comprised in the message in order to identify said service and a second identity comprised in the message in order to identify the customer port, by means of which identities the BNG can set up the requested IP-interface.

6. The BNG (160) of claim 5, to which the AN (140) may be connected via an Aggregation Network (150).

7. The BNG (160) of claim 5 or 6, in which said first identity is the S-VID of the AN, and said second identity is the C-VID of the C-VLAN.

8. The BNG of claim 7, in which the C-VID of the C-VLAN consists of one part which identifies the port in the AN which is used by the CPE and one part which is unique for the AN in question within the S-LAN of which the AN is a part.