Backbone Provider Edge
bpe driver creates IEEE 802.1Q
Provider Backbone Bridge (PBB) networks by acting as a Backbone Edge Bridge
(BEB). PBB, also known as mac-in-mac, was originally specified in IEEE
802.1ah-2008 and became part of IEEE 802.1Q-2011.
A Provider Backbone Bridge Network (PBBN) consists of BEBs interconnected by Backbone Core Bridges (BCBs) to form an Ethernet network for the transport of encapsulated Ethernet packets. Where VLAN and SVLAN protocols add a shim to differentiate Ethernet packets for different networks but retain the Ethernet addresses of encapsulated traffic, PBB completely encapsulates Ethernet packets for transmission between BEBs on a PBBN. This removes the need for intermediate BCB devices on the backbone network to learn the Ethernet addresses of devices on the encapsulated network, but requires each BEB to maintain a mapping of addresses on the encapsulated network to peer BEBs.
A PBB packet consists of another Ethernet frame containing Ethernet addresses for BEBs and the PBB Ethernet protocol type (0x88e7), a 32-bit Backbone Service Instance Tag (I-TAG), followed by the encapsulated Ethernet frame. The I-TAG contains a 24-bit Backbone Service Instance Identifier (I-SID) to differentiate different PBBNs on the same backbone network
IEEE 802.1Q describes customer VLANs being encapsulated by PBB,
which in turn uses an S-VLAN service. This can be implemented with
vlan(4) using a
bpe interface as the parent,
and with the
bpe interface using
svlan(4) as the parent.
bpe itself does not
require this topology, therefore allowing flexible deployment and network
bpe driver implements a learning
bridge on each interface. The driver will learn the mapping of BEPs to
encapsulated Ethernet address based on traffic received from other devices
on the backbone network. Traffic sent to broadcast, multicast, or unknown
unicast Ethernet addresses will be flooded to a multicast address on the
backbone network. The multicast address used for each PBB Service Instance
will begin with 01:1e:83 as the first three octets, with the I-SID as the
last three octets. For example, a
bpe interface with
a vnetid of 1024 (0x400 in hex) will have a multicast group address of
01:1e:83:00:04:00. The address learning in
uses the Ethernet addresses of encapsulated traffic for its forwarding
decisions; it does not use VLAN or S-VLAN tags to differentiate
bpe interfaces can be created at runtime
create command or by setting up a
hostname.if(5) configuration file for
netstart(8). The interface itself can be configured with
ifconfig(8); see its manual page for more information.
bpe interfaces must be configured with a
parent Ethernet interface to operate, and a virtual network identifier for
use as the I-SID.
The I-TAG includes a priority field. By default, the value of the
priority field in a transmitted packet is based on the priority of packets
sent over the interface, which may be altered via
pf.conf(5); see the
prio option for more
txprio can set a
specific priority for transmitted packets.
bpe interfaces support the following
SIOCSIFPARENTstruct if_parent *
- Set the parent interface. The parent may only be configured while the virtual interface is administratively down.
SIOCGIFPARENTstruct if_parent *
- Get the currently configured parent interface.
SIOCDIFPARENTstruct ifreq *
- Delete the parent interface configuration. The parent may only be removed while the virtual interface is administratively down.
SIOCSVNETIDstruct ifreq *
- Set the virtual network identifier. Valid identifiers are 24-bit values in the range 0 to 16777215.
SIOCGVNETIDstruct if_parent *
- Get the currently configured virtual network identifier.
bridge(4), inet(4), ip(4), netintro(4), vlan(4), hostname.if(5), pf.conf(5), ifconfig(8), netstart(8)
IEEE 802.1Q standard, https://standards.ieee.org/standard/802_1Q-2018.html.
IEEE 802.1ah standard, Provider Backbone Bridges.
bpe driver first appeared in
David Gwynne <email@example.com>.