IEEE 802.1ah-2008

Ethernet was developed as a packet data technology that combines a small number of computers located in close proximity to each other in a single local network . Subsequently, Ethernet became one of the most popular data link technologies used for data transfer, not only for organizing local networks, but also for organizing regional , city , and sometimes global networks . The development of Ethernet has created the need to separate the domains of Ethernet networks between users and providers . For this purpose, a new S-Tag field ( English Service Tag - provider network tag), consisting of four bytes, was added to the Ethernet frame. With the addition of a new S-Tag field, switching in the domain of the provider's network is based on the value of the S-Tag field and the MAC address of the Ethernet frame receiver, and C-Tag is used to create VLAN domains for user networks. This technology is known as QinQ or Q tunneling and is described in the IEEE 802.1ad standard.

QinQ does not allow you to fully separate the domains of user and provider networks, but only allows you to overcome the limit on the number of VLAN identifiers in the network. This can help in separating the domains of user networks and the domain of the provider's management network when using technologies such as tunneling management protocols or PVSTP . In addition to the problem of the lack of a complete separation of the domains of the user networks and the provider, QinQ also has too little control over the MAC addresses in Ethernet frames transmitted in the domain of the provider network. It is not possible to solve the problem of MAC address control using only one QinQ technology, since Ethernet frame switching in the provider's network domain is based on MAC addresses from the client network. All these problems require more effective mechanisms for separating the domains of user and provider networks.

The main idea of ​​PBB is to isolate the domains of user and provider networks by encapsulating the user's Etheret frame into the Ethernet provider frame. To implement this idea, a new Ethernet frame header is introduced. The new frame title may look different, but the main fields of the title are:

• Main header fields:
  • The recipient address of the trunk network frame (B-DA, Backbone Destination Address - the receiver's trunk address); takes six bytes.
  • The sender address of the trunk network frame (B-SA, Backbone Source Address - the sender trunk address); takes six bytes.
  • EtherType field ; fixed value equal to 0x88A8 and occupying two bytes.
  • VLAN indicator of the backbone network, (B-TAG, English Backbone tag - the backbone tag, and B-VID, English Backbone tag VLAN Identificator - the backbone VLAN identifier); takes two bytes.
• Service Data Encapsulation Fields:
  • EtherType field; fixed value equal to 0x88E7 and occupying two bytes
  • A flag field consisting of a priority flag, a packet processing indicator (DEI, English Drop Eligible Indicator - an indicator indicating the possibility of packet loss) and a non-user network domain address designation (NCA, English No Customer Address indication - non-user address designation ) ; (the so-called OA&M frames).
  • Service Identifier (I-SID, English Identifier Service Identificatior - identifier identifying the service); takes up three bytes.
• Original Ethernet User Frame:
  • The recipient address of the user network frame; takes six bytes.
  • Sender address of the user network frame; takes six bytes.
  • EtherType field, a fixed value of 0x8100 and occupying two bytes.
  • User Network VLAN ID takes two bytes.
  • EtherType field, a fixed value, typically 0x0800, spanning two bytes.
  • User frame title.

The PBB introduces an additional 48 bits of B-DA and 48 bits of B-SA to indicate the MAC address of the receiver and sender of the trunk network. In addition to these 96 bits, PBB introduces an additional 12 bits of B-VID (VLAN identifier of the trunk) and 24 bits of I-SID (VLAN identifier of the trunk network). Switching in the PBB domain of the provider's network is based on the values ​​of the B-DA and B-VID fields.

PBB is based on PBB-TE technology, described in IEEE 802.1Qay and standardized in 2009 ^[1]

• Qinq
• Metro Ethernet
• Carrier ethernet
• IEEE 802.1
• IEEE 802-1aq - Shortest Path Bridging (SPB)

• IEEE 802.1ah-2008 Standard Page