T 1327/19 (Load balancing and failover in layer-2 networks) 27-10-2021
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HASH-BASED MULTI-HOMING
Divisional application - added subject-matter (no)
Divisional application - after amendment
Amendments - added subject-matter (no)
Amendments - after amendment
Claims - clarity
Claims - main request (yes)
Remittal to the department of first instance
I. The appeal is directed against the examining division's decision to refuse the European patent application. The present application is a divisional application of the earlier (parent) application EP 07827358.8.
II. The examining division decided that the application did not fulfil the requirements of Articles 76(1), 123(2) or 84 EPC, nor those of Rule 43 EPC.
III. In its statement of grounds of appeal, the appellant (applicant) requested that a patent be granted on the basis of the claims according to either a main request or an auxiliary request, both of which were submitted with the statement of grounds of appeal. A corrected version of the auxiliary request was filed on 4 June 2019.
IV. The board issued summons to oral proceedings. In a communication, it provided its preliminary opinion on the case (Article 15(1) RPBA 2020).
The board held that claim 1 of the main request fulfilled the requirements of Article 84 EPC but that some of the dependent claims did not. As to the issues under Articles 76(1) and 123(2) EPC, the board held that neither the main request nor the auxiliary request complied with the requirements.
Finally, the board indicated its intention to remit the case to the examining division should the raised objections be overcome.
V. In a reply dated 18 August 2021, the appellant provided amendments to the requests. In response to the objections pursuant to Articles 76(1) and 123(2) EPC, arguments as well as supporting passages of the description were provided.
VI. In a communication dated 4 October 2021, the board indicated that it considered that the objections raised in its previous communication with respect to the main request had been overcome by the appellant's amendments and arguments. As to the auxiliary request, however, the board held that the requirements of Article 84 EPC had not been met.
The board maintained its intention to remit the case to the examining division should the objections be overcome, as the examining division did not assess in its decision whether the application met the requirements of Articles 54 and 56 EPC.
VII. Oral proceedings were held on 27 October 2021. The appellant requested that the decision under appeal be set aside and that a patent be granted on the basis of the set of claims of the main request or, alternatively, that of the auxiliary request, both of which were filed with the appellant's letter dated 18 August 2021.
VIII. The appellant's final requests were that the decision under appeal be set aside and that the case be remitted to the examining division for further prosecution.
IX. Claim 1 of the main request includes the following features (as labelled by the board):
A method for providing Layer-2 communication paths using third and fourth nodes for transporting Ethernet frames between a first node (24) in a first network and a second node (28) in a second network (32), by using the third node (36A) that comprises a first port (40A) associated with a first index value (50), and the fourth node (36B) that comprises a second port (40B) associated with a second index value (50) that is different from the first index value, the first and second ports are cooperatively part of a group, and the first and second ports are part of different communication paths, the method comprising:
receiving (52) a first Ethernet frame addressed to the second node from the first node over the first network, the first Ethernet frame comprises a first header value in a header field; and
receiving (52) a second Ethernet frame addressed to the second node from the first node over the first network, the second Ethernet frame comprises a second header value in the header field;
characterized in that
the method further comprising
applying a hash function to the first and second header values resulting in respective first and second hash values and comparing the results with the first and second index values;
responsive to the first hash value being equal to the first index value, sending (58) the received first Ethernet frame to the second node only via the first port of the third node over the second network; and
responsive to the second hash value being equal to the second index value, sending (58) the received second Ethernet frame to the second node only via the second port of the fourth node over the second network.
Independent claim 18 of the main request is directed to a corresponding system.
X. The main request's dependent claims considered by the board read as follows:
4. The method according to claim 1, for use with multiple nodes cooperating as a group, each of the nodes comprises at least one port, so that there are P active ports, where P>3, each of the ports is associated with a distinct index value (50) from the group (0, 1, 2, ... P-1), the method comprising:
receiving (52) a third Ethernet frame addressed to the second node from the first node over the first network, the third Ethernet frame comprises a third header value in the header field;
applying a hash function to the third header value resulting a third hash value; and
sending (58) the received first Ethernet frame to the second node over the second network only via a port that is associated with an index value that is equal to the third hash value.
9. The method according to any one of the preceding claims, further preceded by associating (50) the first and second index values to the respective first and second ports, and wherein the third or fourth node is defined as edge node in the first or second network according to Spanning-Tree Protocol, STP, standard, Multiple Spanning-Tree Protocol, MSTP, standard, or Rapid Spanning-Tree Protocol, RSTP, that is according to IEEE 802.1D standard.
10. The method according to any one of the preceding claims, wherein the first or second network supports or provides Virtual Private Local Area Network Services, VPLS, that is identified in the header field, or wherein the received first or second Ethernet frame is associated with a Virtual LAN, VLAN.
12. The method according to claim 10, wherein the received first or second Ethernet frame is part of multiple VLANs deployed in a hierarchical structure, which includes an outer VLAN, identified with an outer VLAN Identifier, VID, encapsulating an inner VLAN identified with an inner VID, wherein the received first or second Ethernet frame header comprises the outer VID and the inner VID, each according to IEEE 802.lQ standard, and wherein each of the first and second header values is based on, or uses, the inner VID and the outer VID.
13. The method according to any one of the preceding claims, the method further comprising by the third node:
detecting activity or failure of the second port; and
responsive to the detecting:
receiving (52) a third Ethernet frame addressed to the second node from the first node over the first network, the third Ethernet frame comprises a third header value in the header field;
applying the hash function to the third header value resulting a third hash value; and
responsive to the third header value being included in the second set, sending (58) the received third Ethernet frame to the second node via the first port over the second network.
17. The method according to any one of claims 1-12, wherein the first and second ports are respectively part of first and second distinct communication paths between the first and second nodes, the method further comprising providing protection against failures or providing traffic load balancing by using the first and second communication paths, and wherein the protection is according to ITU-T G.8031 June 2006 standard, Institute of Electrical and Electronics Engineers, IEEE, IEEE 802.1 standard, or IEEE 802.3 Clause 43 standard.
1. The present application concerns load balancing and failover by using alternative communication paths between end points in layer-2 networks, implemented by means of intermediate nodes.
2. Main request
2.1 Admissibility (Article 13(1) RPBA)
The main request was filed in reaction to the board's preliminary opinion. Since the amendments prima facie overcome the board's objections, the board decided to admit the main request into the proceedings.
2.2 Support by the description (Article 84 EPC)
In the impugned decision, the examining division held that independent claim 1 and independent claim 18 (former claim 14) of the main request were missing features essential for the definition of the invention. Therefore, the requirements of Article 84 EPC were not fulfilled.
2.2.1 As a first essential feature, the examining division identified the feature that "the first port of the third node and second port of the fourth node are assigned to serve as member ports of a Multi-Homing Group, MHG".
The examining division argued that this was essential "since these ports act as a multi-homing group to choose one distinct path to the destination node".
The appellant countered that omitting this feature constituted an allowable generalisation. Furthermore, the technical problems solved by the application related to "alternative communication paths" and thus did not rely on any group in general or a "Multi-Homing Group (MHG)" in particular.
The board notes that Article 84 EPC requires, amongst other things, that the claims indicate all the essential features of the invention. Any features that are necessary in order to obtain the desired effect or, in other words, that are necessary in order to solve the technical problem with which the application is concerned are to be considered essential features (see decision T 32/82). In the present case, the problem solved by the application concerns providing "alternative communication paths [having] no single point of failure" (see page 5, lines 10-12).
The board considers that claim 1 already mentions the fact that "the first and second ports are part of different communication paths", i.e. what the examining division argued was missing. Therefore, the board considers that the feature under scrutiny is not an essential feature of the invention.
2.2.2 As a second essential feature, the examining division identified the feature that "all the frames transmitted from the first node in the first network and destined to the second node in the second network are received at the third and fourth nodes".
The examining division argued that this was essential since "the third and fourth node both apply the hash function and are responsible for choosing the right path among the alternative paths to the destination node".
The appellant asserted that the examining division did not point out any passage in the description which would require all frames transmitted by the first node to the second node to be handled by both intermediate nodes.
The board considers that the description (see, e.g., page 13, lines 17-23) discloses that the sending of all frames to all intermediate nodes is only performed during the "MAC learning process", and not during regular operation. Hence, the description discloses that the technical problem is also solved if only certain frames are received at both the third and fourth nodes. Therefore, this feature cannot constitute an essential feature of the invention.
2.2.3 As a further essential feature, the examining division identified the feature of "responsive to the first (second) hash value being equal to the first (second) index value, sending the received first (second) Ethernet frame to the second node via the first (second) port of the third (fourth) node over the second network and discarding the first Ethernet frame by the fourth (third) node".
The examining division argued that this was essential as "the first frame has to be discarded at the other ports since only one port is chosen according to the hash function for forwarding the first Ethernet frame".
The board concurs with the appellant that these features are already implied by the formulation "sending ... via the first (second) port". Hence, adding these features into claim 1 would effectively not alter its scope.
2.2.4 In view of the above, the board holds that the features identified in the impugned decision as allegedly being missing are either not essential or are already reflected in the wording of claim 1, which thus fulfills the requirements of Article 84 EPC.
The same applies to independent claim 18.
2.3 Clarity (Article 84 EPC)
The board asserts that the amendments to dependent claims 10 and 12 overcome the objections regarding the lack of clarity raised by the board, as the unclear terms have been deleted. The board thus holds that the dependent claims are clear, as mandated by Article 84 EPC.
Aside from that, the board notes that the objection pursuant to Rule 43(4) EPC raised in the impugned decision has been overcome by the renumbering of the previous independent claim 14 to become the present claim 18.
2.4 Added subject-matter (Articles 76(1) and 123(2) EPC)
2.4.1 To support the subject-matter of claims 4, 10 and 12, the appellant provided - in its letter dated 18 August 2021 - passages of the description as originally filed. The description as originally filed is identical to the description of the parent application as originally filed. Therefore, conformity with the requirements of Articles 76(1) and 123(2) EPC may be examined jointly.
The conditions mentioned in claim 4 are notably disclosed on page 11, lines 22-29, although the parameter "M" is used therein for the number of active member ports and "P" is used for the priority index (claim 4 uses "P" for the number of active member ports, rather than "M"). The board could identify the "receiving" step on page 10, lines 17-19, and the "applying" step on page 5, lines 13-18 (the terminology "third" Ethernet frame, "third" header value and "third" hash has been added, but this does not alter the technical teaching in the present context). The "sending" step could be identified on page 10, lines 30-32.
The subject-matter of claim 10 could be identified notably on page 10, lines 5-12.
The subject-matter of claim 12 could be identified notably on page 8, lines 23-28.
2.4.2 As to claims 9, 13 and 17, the board asserts that the amendments overcome the objections regarding added subject-matter raised by the board, as the incriminating features have been deleted.
2.4.3 Consequently, the claims of the main request fulfill the requirements of Articles 76(1) and 123(2) EPC.
2.5 In view of the above, the board holds that the grounds for refusing the main request provided in the impugned decision have been overcome by amendments and/or arguments.
3. Consequently, the decision under appeal must be set aside.
4. Remittal (Article 11 RPBA 2020)
Under Article 11 RPBA 2020, the board may remit the case to the department whose decision was appealed if there are special reasons for doing so.
The board notes that the examining division decided on the issues of added subject-matter (Articles 76(1) and 123(2) EPC) and lack of support/lack of clarity (Article 84 EPC). Novelty and inventive step were not assessed in the impugned decision.
Under these circumstances, the board does not consider it appropriate to decide on the issues of novelty and inventive step without a decision of the examining division. Thus, the board holds that special reasons exist for remitting the case to the department of first instance.
For these reasons it is decided that:
The decision under appeal is set aside and the case remitted to the examining division for further prosecution.