Chapter
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Multicast route within the OSPF area: Used to know about multicast members
within various network segments, and construct right SPTs (Source network: S.
Group: G);
Multicast route between MOSPF areas: Used to gather the member relations in
an area and release the group member relationship records in the backbone
(Area 0) of the Autonomous System (AS); it also forwards multicast packets
between areas;
Multicast route between OSPF ASs: Used to forward cross-AS multicast
packets.
6.2.10 VBAS Protocol
6.2.10.1 Overview
By modifying authentication process, the VBAS protocol means that BAS queries
users’ physical location from the ZXDSL 9210 before BAS begins authentication, and
takes this value as the basis for physical locating and authentication of users. The
VBAS module functions are implemented by the AAA client on an embedded BAS.
6.2.10.2 Workflow of VBAS Protocol
Workflow of the VBAS protocol (Take the PPPoE access mode for example. Other
access authentication modes, such as 802.1X and DHCP+Web, have similar flows):
1. A user host broadcasts a session initiation packet (requesting for link
establishment), expecting a response from BAS (IP DSLAM may automatically
learn this user’s MAC address, and establish a physical port look-up table of
MAC and IP DSLAM);
2. After one or multiple BASs receive the broadcast, if they provide service users
need (PADI field), they send a service provision packet to the user host (The
user host may learn the MAC address of BAS according to this packet);
3. On certain principles (depending on specific implementation), the user host
selects a BAS and sends a unicast session request packet to this BAS;
4. Having received the session request packet, the selected BAS generates a unique
Session ID sends a confirmation packet (including Session ID) to the original
user host and enters the PPP session stage;
