IBM SC30-3681-08 manual More Information About TLVs, Elan Type Policy, Max Frame Size Policy

When ELANs are spread over large geographic locations, the default timeout values for LE clients may be insufficient. These timeouts can be controlled for all LE clients by specifying their value in a TLV at the LECS.

Overview of LAN Emulation

This setup requires con®guring the LE clients with the correct ELAN Name.

vUse names for the LE clients

Each LE client can be given its own name. For example, you could create the policy values (Joe, LES_A) and (Mary, LES_A). Then, the LE clients con®gured with these names would be directed to the same LES. This method requires con®guring the ELAN name at each LE client and at the LECS. However, it allows Joe and Mary to move the client to a new location. Even though moving causes the client to have a new ATM address or MAC address, as long as you con®gure the new LE client with the same ELAN name, you retain membership in the original ELAN. This technique also offers a moderate amount of security if the names of each LE client are considered to be passwords.

ELAN Type Policy

ELAN type policy values are most useful for providing default ELANs. For example, the following policy values would ensure that every LE client is assigned to one of the LESs:

(Token-ring ELAN Type, LES_A)

(Ethernet ELAN Type, LES_B)

(Unspecified ELAN Type, LES_C)

In general, policies used for providing default ELAN assignments should be given a low priority, so that the more speci®c policies are considered ®rst.

Max Frame Size Policy

The max frame size policy can also be used to provide default ELAN assignments.

Duplicate Policy Values

Duplicates occur when the same policy value is associated with multiple LESs for a given policy. Duplicate policy values are allowed for the ELAN type and max frame size policies, but are not allowed for other policies. Duplicate values are useful only when combined with a different policy of the same priority.

For example, assume that there are three ELANs: an Ethernet ELAN with a max frame size of 4544 bytes, a Token-Ring ELAN with a max frame size of 4544 bytes, and another Token-Ring ELAN with a max frame size of 18190 bytes. LE clients could be assigned to the appropriate ELAN by setting the ELAN type and max frame size policies to the same priority level and de®ning the following policy values:

(Ethernet ELAN Type,	LES_1)	(Max Frame Size = 4544,	LES_1)
(Token-Ring ELAN Type,	LES_2)	(Max Frame Size = 4544,	LES_2)
(Token-Ring ELAN Type,	LES_2)	(Max Frame Size = 18190,	LES_2)

More Information About TLVs

TLVs are de®ned on an ELAN basis; therefore, the same set of TLVs is returned to all LE clients that are assigned to a particular ELAN. When a TLV is included in a con®guration response, the LE clientmust use the value speci®ed in the TLV as an operating parameter (if the LE client recognizes the ELAN type). A few examples of situations where TLVs might be bene®cial are as follows:

v

Chapter 20. Overview of LAN Emulation 263