IS-IS TLV Attributes

CD

Within data communication protocols, optional information may be encoded as a type-length-value or TLV element inside a protocol. TLV is also known as tag- length-value.

The type and length are fixed in size (typically 1-4 bytes), and the value field is of variable size. These fields are used as follows:

-> Type. A binary code, often simply alphanumeric, which indicates the kind of field that this part of the message represents;

-> Length. The size of the value field (typically in bytes);

-> Value. Variable-sized series of bytes which contains data for this part of the message.

In Intermediate System to Intermediate System (IS-IS) routing protocol, a Type-Length-Value (TLV) is a data structure used to carry additional information in protocol messages.

A TLV has the following format:

• Type: specifies the type of information carried by the TLV
• Length: specifies the length of the value field in octets
• Value: carries the actual information or data

Now, coming to the question, the TLV used in IS-IS includes two attributes out of the options given:

A. Topology: The topology attribute in the TLV is used to carry information about the network topology, including the network's nodes, links, and their characteristics. This information is used by IS-IS routers to construct a topology database, which is used to compute shortest path routes.

D. Value: The Value attribute in the TLV is used to carry various types of information, including node and link attributes, administrative and operational parameters, and other protocol-specific information. The format and interpretation of the Value field depend on the Type field.

Therefore, the correct answer is A (topology) and D (value). The options C (length) and B (vector) are not attributes carried by IS-IS TLVs.