H3C Technologies H3C S12500 Series Switches - Manual (Page 11)

3
LSDB
A link state database (LSDB) contains the states of all links in an SPBM network.
MAC-in-MAC
SPBM encapsulates Ethernet frames into MAC-in-MAC frames by using 802.1ah PBB encapsulation. For
more information about the MAC-in-MAC frame format, see " Data paths ."
Customer frames are encapsulated in MAC-in-MAC format at edges of the SPBM network before they are
forwarded from one customer site to another.
PW
Pseudo wires (PWs) are MAC-in-MAC tunnels established over the SPBM network for transmitting
customer traffic.
PWs are established between BEBs. BCBs do not set up PWs.
SPB VSI
An SPB virtual service instance (SPB VSI) provides MAC-in-MAC tunnel service for Ethernet service
instances. Each SPB VSI is uniquely identified by an I-SID. For more information about VSIs, see VPLS in
MPLS Configuration Guide.
SPBM packet types
SPBM packets include ISIS-SPB control packets and SPBM data packets.
ISIS-SPB control packets
ISIS-SPB control packets include hello, LSP, and SNP. All SPBM control packets are encapsulated in
802.1q.
Hello
SPBM neighbors send IS-IS hello (IIH) PDUs to establish and maintain adjacencies.
LSP
Adjacent SPBM neighbors send link state PDUs (LSPs) to advertise topology data.
SNP
Adjacent SPBM neighbors exchange sequence number PDUs (SNPs) for LSDB synchronization.
SNPs include complete SNP (CSNP) and partial SNP (PSNP).
• CSNP—Contains the digest of each LSP in the LSDB. Adjacent routers exchange CSNPs to maintain
LSDB synchronization.
• PSNP—Contains the sequence numbers of recently received LSPs. An SPBM node uses a PSNP to
acknowledge LSPs or to request needed LSPs from a neighbor.