Transparent LAN Services via MAC Learning Distribution
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Solution Overview
Problem
Packet carrier networks face scalability issues with VLANs due to limited VID space and the need for edge bridges to learn and store MAC addresses of all customers, leading to large routing tables and difficulties in OAM operations.
Innovation Solution
Distributing MAC address learning to customer premises equipment (CPEs) and using a dual table system with a fast forwarding database for reduced forwarding states and a slow storage database for original addresses, enabling Transparent LAN Services without requiring core or edge bridges to learn client MAC addresses.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If VLANs are used for customer network segmentation, then network scalability is improved through logical grouping, but the limited VID space (4096 unique VIDs) restricts the number of supported customers and services in carrier networks
Solution Approach 1:
The patent segments the VLAN identification function into two parts: a Customer VLAN ID (C-VLAN ID) that identifies the customer's virtual LAN, and a Service VLAN ID (S-VLAN ID) that identifies the service provider's virtual LAN. This segmentation allows the C-VLAN to remain transparent to the service provider network while the S-VLAN provides the necessary scalability for carrier networks, effectively resolving the VID space limitation by separating customer-specific identification from provider-specific identification.
2Reliability
If edge bridges learn and store MAC addresses of all customers in VLAN filtering databases, then transparent LAN services are provided, but routing tables become large and OAM operations become difficult
Solution Approach 1:
The patent extracts the MAC address learning and storage function from the service provider's edge bridges and relocates it to the customer's CPE equipment. The service provider network only needs to learn and store the MAC addresses of edge bridges, not individual customer MAC addresses. This extraction dramatically reduces the routing table size in provider bridges while maintaining transparent LAN service functionality, as the CPE handles customer MAC address management locally.
Solution Approach 2:
The CPE acts as an intermediary between customer end stations and the service provider network. It performs MAC address learning for customer devices and translates between customer VLAN tags and provider VLAN tags. This intermediary role allows the provider network to operate with simplified routing tables containing only edge bridge MAC addresses, while the CPE maintains the detailed customer MAC address information needed for transparent LAN services.
3Quantity of substance
If Q-in-Q VLAN stacking is used to extend VID space, then provider VLAN identification is improved, but the number of supported customers per Service VLAN remains limited to 4094
Solution Approach 1:
The patent segments the VLAN identification into two independent 12-bit fields: C-VLAN ID for customer identification and S-VLAN ID for service identification. Unlike Q-in-Q which stacks VLAN tags sequentially, this segmentation allows any C-VLAN ID (0-4095) to be combined with any S-VLAN ID (0-4095), providing 4096 service VLANs × 4096 customer VLANs = 16.7 million unique customer-service combinations, vastly exceeding the Q-in-Q limitation.
4Adaptability or versatility
If all MAC addresses of customers' end stations are learned and stored by each bridge within a VLAN, then VLAN to VLAN communication is enabled, but the quantity of addresses to be learned increases significantly
Solution Approach 1:
The patent extracts the MAC address learning function from provider bridges and relocates it to customer CPE equipment. Provider bridges only need to learn edge bridge MAC addresses, not individual customer MAC addresses. The CPE performs MAC address learning for customer end stations and uses this information to make forwarding decisions, eliminating the need for provider bridges to store large numbers of customer MAC addresses while maintaining VLAN to VLAN communication capability.
Data Source
AI summary
A network apparatus includes a customer network portion having a customer premises equipment (CPE) bridge configured to connect to internal network entities of the customer network portion and to edge bridges of a provider network portion interconnecting separate customer network portions. The CPE bridge is configured to determine a transparent local area network service (TLS) for a packet received from one of the internal network entities based on a media access control (MAC) address of a destination of the packet in a different separate customer network portion. The CPE bridge is also configured to modify the packet to indicate the determined TLS, for the provider network portion to utilize to transmit the packet based on the determined TLS to a second CPE bridge associated with the destination, without the provider network utilizing the destination MAC address.