Joint ITU-T/IEEE Workshop on Carrier-class Ethernet

Transcription

1 Joint ITU-T/IEEE Workshop on Carrier-class Ethernet Carrier Bridge Architecture Stephen Haddock Chief Technology Officer Extreme Networks

2 802.1 Bridging Architecture for Carrier Ethernet from D & Q bridges to Provider Bridges and Provider Backbone Bridges

3 In the Beginning 802.1D Transparent, connectionless frame relay. Architecture creates a independent Service Access Point at the ISS. Allows relay to forward frames between different technologies. Higher Layer Entities Protocols (e.g. Spanning Tree) Relay LAN B LAN A Packet Forwarding, Filtering, Learning Internal Sublayer Service (ISS) interface Media Dependent Convergence Functions (to create independent interface at ISS) Media Access Control Functions (e.g /Ethernet, 802.5/Token Ring, FDDI)

4 Enter VLANs 802.1Q VLANs allow different communities to share a physical Local Area Network infrastructure. Provide connectivity within a community but isolation between communities. Each packet carries a VLAN tag that identifies the community to which it belongs. Higher Layer Entities VLAN-aware packet Forwarding, Filtering, Learning tag Relay tag Enhanced Internal Sublayer Service (EISS) interface All ISS parameters plus: {VID VLAN identifier, DE drop_eligibility} VLAN tagging/untagging functions Internal Sublayer Service (ISS) interface Parameters: {DA -- destination_address, SA -- source_address, PRI -- priority, MSDU -- mac_service_data_unit}

5 VLANs had Carrier appeal Enabled a Service Provider to offer a multipoint Transparent LAN Service to customers using Layer 2 Ethernet switches. VLANs provided customer isolation. VLAN tags identified customer packets. But some customers were already using VLANs in their own networks Who owned the VLAN ID space, the customer or the provider? Really needed separate VLAN tags for the customer and the provider.

6 Provider Bridging 802.1ad Defines a new Service VLAN tag type specifically for use in provider networks. Semantics of Service VLAN tag are identical to the customer VLAN tag. Distinguished by a new Ethertype value. Service VLAN tag can be stacked on top of customer VLAN tag. A basic Provider Bridge (S-VLAN Bridge) operates only on the Service VLAN tag. A Customer Bridge (C-VLAN Bridge) operates only on the customer VLAN tag.

7 Provider Edge Bridges Desire to allow a customer to access multiple distinct service instances through a single physical port (service multiplexing). Customer VLAN tag used for service selection. Means some bridges at the edge of a Provider Bridged Network need to operate on both Customer VLAN tags and Service VLAN tags. Introduce concept of bridge components: A bridge component is a full set of bridge functionality (including port interface stacks, relay, and higher layer entities) where the port interface stacks are not necessarily connected to external LANs. A Provider Edge Bridge contains a C-VLAN component per customer with an internal connection per service instance to an S-VLAN component.

8 Provider Edge Bridge Model S-VLAN Component C-VLAN Component C-VLAN Component Higher Layer Entities Relay Higher Layer Entities Relay S-tag S-tag C-tag C-tag Internal link

9 Limitations of Provider Bridges Service VLAN ID is overloaded Used both for service identification and for VLAN forwarding in the Provider Network. VLAN functionality doesn t scale: Control Protocols (MSTP, MVRP) Per-VLAN Port state and counters Limits number of services to 4K. Customer addresses used in Provider Network Customer adds/moves/changes affect state in core of Provider Network May result in very large address tables in core of Provider Network

10 Provider Backbone Bridging (802.1ah) Separate service identification and VLAN identification Service Identifier used for filtering at edges of Backbone Network, but not used for forwarding through the Backbone core. Allows number of services to scale to 16M Backbone VLAN tag used for forwarding in core of Backbone Network Backbone VLAN tag format, ethertype, and semantics are all identical to S-VLAN tag. Allows use of Provider Bridges in Backbone core -in- encapsulation Customer frames encapsulated with new header at edges of Backbone Network. New header contains addresses of the Bridges at the ingress and egress edges of the Backbone Network. Forwarding in Backbone based only on Backbone addresses Customer addresses never learned in Backbone core

11 Backbone Edge Bridges Need to map Service VLAN IDs to Extended Service Instance Identifiers (I-SIDs). Need to operate on both Customer addresses with Service VLAN IDs and Backbone addresses with Backbone VLAN IDs. Need to learn associations between Customer addresses and Backbone addresses. May need to operate on several distinct Service VLAN spaces. Modeled with multiple bridge components (analogous to Provider Edge Bridges)

12 Backbone Edge Components I-component: Relay forwards/filters/learns customer addresses with S-VLAN identifiers. Associations between customer addresses and backbone addresses stored in learned database. Is an S-VLAN component with I-tagging functions in interface stack connecting to Backbone Network. I-tag includes 24 bit service instance identifier and encapsulated customer addresses. header containing backbone addresses added when I-tag is created. B-component: Relay forwards/fliters/learns backbone addresses with B-VLAN identifiers Is an S-VLAN component with I-tag specific functions in interface stack at edge of Backbone Network.

13 Backbone Edge Bridge Model B- Component I- Component I- Component Higher Layer Entities Relay Higher Layer Entities Relay S-tag S-tag S-tag S-tag I-tag filter I-tag add/remove Internal link

14 Observations The basic 802.1D bridging model has shown remarkable longevity and flexibility. Architectural partitioning and internal interfaces permit building upon existing functionality. Adapted to support 802.1Q VLANs while maintaining interoperability with existing bridges, end stations, and LAN standards. Extended to support 802.1ad Provider Bridging with minimal change for core bridges (recognizing new Ethertype), and concentrating more complex functionality in edge ports. Tremendous improvement in carrier scalability with 802.1ah Provider Backbone Bridging, utilizing basic Provider Bridges in the backbone core and again concentrating more complex functionality in edge ports.