Delta Electronics Sonet OC-48/SDH User Manual download pdf (Page 10)

Interface Properties

and changes is exhausting, but a few values are more commonly used than others. These proper-

ties include the following:

Description A user-defined text description is available for all interfaces. This is often used

to describe the interface’s purpose.

Diagnostic characteristics Circuit-testing capabilities, such as loopback settings or Bit Error

Rate Test (BERT) tests, are user-configured on a per-physical interface basis. (We discuss these

tools in the “Useful Interface Commands” section later in this chapter.)

Encapsulation Options for encapsulation types vary for different media types.

Frame check sequence (FCS) This field is used for error-checking received packets. You

can change the default value from a 16-bit field to a 32-bit mode.

Interface clock source Point-to-point interfaces require a clocking source for synchronization

purposes. Options here include internal (the default) or external.

Interface MTU size The maximum transmission unit (MTU) of the physical interface can be

changed. Each interface has a different default value; the possible range is 256 to 9192 bytes.

Keepalives A keepalive is a physical-layer mechanism that is used to determine whether

the interface is operating correctly. With the exception of ATM interfaces, each interface uses

keepalives by default. You can disable this function.

Payload scrambling Scrambling is a mechanism used for long-haul communications to

assist in an error-free transmission. Most interfaces in the JUNOS software use a default value

of payload-scrambler, but you can disable this function as well.

Connecting to Another Vendor’s Router

When two Juniper Networks routers are connected, the default physical properties allow the

network link to operate normally. However, the physical interface defaults do not always match

the operational parameters of another vendor. In situations like this, you must change the oper-

ation of one side of the link to allow the connection to fully function.

One good example of this is connecting a SONET point-to-point link to a router from Cisco Sys-

tems. The default encapsulation type for a SONET link within the JUNOS software is the Point-

to-Point Protocol (PPP). A Cisco Systems router, on the other hand, uses a Cisco proprietary for-

mat of the High-Level Data Link Control (HDLC) protocol. The JUNOS software supports this

HDLC format on point-to-point interfaces using the keyword cisco-hdlc. Once configured,

your Juniper Networks router and Cisco Systems router can interoperate and pass user data

traffic.

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Delta Electronics Sonet OC-48/SDH User Manual Page 10