TLA ID field (Top-Level Aggregation Identifier):
Top-Level Aggregation Identifier, containing toppest address routing information. It refers to
the maximum route information in the inter-working. It is 13 bits long and can provide up to
8192 different top level routes.
RES field (Reserved for future use):
Reservation field, 8 bits. It will possibly be used to expand the top level or the next level
aggregation identifier field.
NLA ID field (Next-Level Aggregation Identifier):
Next-Level Aggregation Identifier, 24 bits. This identifier is used to control the top-level
aggregation to arrange the address space by some institutions. In other word, these
institutions (such as the large-sized ISP) can separate the 24-bit field according to the
addressing level structure themselves. For instance, a large-sized ISP can separate it into 4
internal top-level routes by 2 bits, other 22 bits of the address space is assigned to other
entities (such as the small-sized local ISP). If these entities obtain enough address space,
the same measure can be taken to subdivide the space assigned to them.
SLA ID field (Site-Level Aggregation Identifier):
Site-Level Aggregation Identifier, used to arrange internal network structures by some
institutions. Each institution can use the same way as that in the IPv4 to create the level
network structure themselves. If the 16 bits are taken as the plane address space, there are
up to 65535 different subnets. If the former 8 bits are taken as the higher-level of routes
within this organization, 255 large-scale subnets are allowed. Furthermore, each large-scale
subnet can be subdivided into up to 255 small-scale subnets.
Interface Identifier field (Interface Identifier):
It is 64 bits long and contains the 64 bit value of IEEE EUI-64 interface identifiers.
2. Link Local Addresses
The format of the link-level local addresses is shown as follows:
| 10 |
| bits | 54 bits | 64 bits |
+-------------+----------------------------------+--------------------------------------+
|1111111010| 0 | interface ID |
+-------------+----------------------------------+--------------------------------------+
The link-level local address is used to number the host on the single network link. The
address of former 10-bit identification for the prefix is the link-level local address. The router
will not forward the message of the source address of the destination address with the
link-level local address forever. The intermediate 54-bit of this address is 0. The latter 64
indicates the interface identifier, this part allows the single network to connect to up to 2
64
-1
hosts.
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