Avaya Configuring Frame Relay Services Manual de usuario descargar pdf (Pagina 54)

Configuring Frame Relay Services

3-8 117376-A Rev. A

Selecting Address Type and Length

You can specify the DLCI address type and length that the router and the frame

relay network use to direct packets to their destinations. The address type for the

router and for the switch must be the same.

Selecting a DLCI Address Type

Your options for the DLCI address type follow:

• ADDR Q922 selects addressing as speciﬁed in the ﬁnal version of the Q.922

standard. Q.922 provides for FECN, BECN, DE, and EA bits. While most

Q.922 addresses are included within a 2-octet ﬁeld, the standard allows for

3- and 4-octet address ﬁelds. This is the default.

• The November draft of ADDR Q922 differs from ADDR Q922 in dropping

the D/C bit from the extended (3- and 4-byte) forms. The D/C bit (DLCI or

DL-Core Control Indication) is always 0.

• The March draft of ADDR Q922 differs from ADDR Q922 in deﬁning an

11-bit DLCI and dropping the DE bit from the second octet of the address

ﬁeld.

• ADDR Q921 differs from ADDR Q922 MARCH 90 in that it does not use

FECNs or BECNs, which means that it does not provide congestion control.

Selecting Address Length

Your options for the DLCI address length are 2, 3, or 4 bytes. See the illustrations

of frame relay headers in F

igure 2-2 and Figure 2-3 to understand the distinctions

among these types. To specify address length, complete the tasks in the following

table.

1 2 ... 49 50 51 52 53 54 55 56 57 58 59 ... 93 94

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Avaya Configuring Frame Relay Services Manual de usuario Pagina 54