Configuring E1 and E3 Interfaces


E1 is a standard WAN digital communication format designed to operate over copper facilities at a rate of 2.048 Mbps. E3 is a high-speed WAN digital communication technique designed to operate over copper facilities at a rate of 34.368 Mbps. Both are widely used outside North America. E1 is a basic time division multiplexing scheme used to carry digital circuits, and E3 is the time division multiplexing scheme used to carry 16 E1 circuits.

To configure E1-specific physical interface properties, include the e1-options statement:

 [edit interfaces  interface-name  ]  e1-options {   bert-error-rate  rate  ;   bert-period  seconds  ;   fcs (32  16);   framing (g704  g704-no-crc4  unframed);   idle-cycle-flag (flags  ones);   loopback (local  remote);   start-end-flag (shared  filler);   timeslots  time-slot-number  ; } 

To configure E3-specific physical interface properties, include the e3-options statement:

 [edit interfaces  interface-name  ]  e3-options {   bert-algorithm  algorithm  ;   bert-error-rate  rate  ;   bert-period  seconds  ;   compatibility-mode (digital-link  kentrox  larscom) <subrate  value  >;   fcs (32  16);   idle-cycle-flag  value  ;   loopback (local  remote);   (payload-scrambler  no-payload-scrambler);   start-end-flag  value  ; } 

You can configure an E1 or E3 interface to execute a bit error rate test (BERT) when the interface receives a request to run this test. You specify the duration of the test and the error rate to include in the bit stream by including the bert-period and bert-error-rate statements. For E3 interfaces, you specify the pattern to send in the bit stream by including the bert-algorithm statement:

 [edit interfaces  interface-name  e1-options] or  [edit interfaces  interface-name  e3-options] bert-algorithm  algorithm  ; bert-error-rate  rate  ; bert-period  seconds  ; 

For E3 interfaces, algorithm is the pattern to send in the bit stream. The algorithm for the E1 BERT procedure is pseudo-2e15-o151 (pattern is 2 15 “1, as defined in the CCITT/ITU O.151 standard). rate is the bit error rate. This can be an integer in the range 0 through 7, which corresponds to a bit error rate in the range 10 “0 (that is, 0, which corresponds to no errors) to 10 “7 (that is, 1 error per 10 million bits). The default is 0. seconds is the duration of the BERT procedure, in seconds. The test can last from 1 to 240 seconds; the default is 10 seconds.

To configure an E3 interface so that it is compatible with the channel service unit (CSU) at the remote end of the line, include the compatibility statement:

 [edit interfaces  interface-name  e3-options]  compatibility-mode (digital-link  kentrox  larscom)    <subrate  value  >; 

You can configure the interface to be compatible with a Digital Link, Kentrox, or Larscom CSU. The subrate of an E3 interface must exactly match that of the remote CSU. To specify the subrate, include the subrate option in the compatibility-mode statement. For Digital Link CSUs only, you can specify the subrate value as the data rate you configured on the CSU in the format x kb or x . x Mb . For a list of specificrate values, use the command completion feature in the CLI. The range is 358 kbps through 33.7 Mbps. Kentrox and Larscom CSUs do not support E3 subrate.

By default, E1 and E3 interfaces support a 16-bit checksum. You can configure a 32-bit checksum, which provides more reliable packet verification. However, some older equipment might not support 32-bit checksums. To configure a 32-bit checksum, include the fcs 32 statement:

 [edit interfaces  interface-name  e1-options] or  [edit interfaces  interface-name  e3-options] fcs 32; 

E3 HDLC payload scrambling, which is disabled by default, provides better link stability. Both sides of a connection must either use or not use scrambling. To configure scrambling on the interface, include the payload-scrambler statement:

 [edit interfaces  interface-name  e3-options]  payload-scrambler; 

By default, E1 and E3 interfaces transmit the value 0x7E in the idle cycles. To have the interface transmit the value 0xFF (all ones) instead, include the idle-cycle-flag statement, specifying the ones option:

 [edit interfaces  interface-name  e1-options] or  [edit interfaces  interface-name  e3-options] idle-cycle-flag ones; 

By default, E1 and E3 interfaces wait two idle cycles between sending start and end flags. To configure the interface to share the transmission of start and end flags, include the start-end-flag statement, specifying the shared option.

 [edit interfaces  interface-name  e1-options] or  [edit interfaces  interface-name  e3-options] start-end-flag shared; 

You can configure loopback capability between the local E1 or E3 interface and the remote channel service unit (CSU), as shown in Figure 6.1. You can configure the loopback to be local or remote. With local loopback, the E1 or E3 interface can transmit packets to the CSU but receives its own transmission back again and ignores data from the CSU. With remote loopback, packets sent from the CSU are received by the E1 or E3 interface but also are immediately retransmitted to the CSU.

Figure 6.1. Remote and Local E1 Loopback

graphics/06fig01.gif

To configure loopback capability on an E1 or E3 interface, include the loopback statement:

 [edit interfaces interface-name e1-options] or  [edit interfaces interface-name e3-options] loopback (local  remote); 

Packets can be looped on either the local router or the remote CSU. To turn off loopback, remove the loopback statement from the configuration.

On an E1 interface, to configure the number of time slots allocated to the interface, include the timeslots statement:

 [edit interfaces  interface-name  e1-options]  timeslots  time-slot-number  ; 

The slot number can be in the range 1 through 32. E1 interfaces have 32 time slots. You can designate any combination of time slots for usage. The default is to use all the time slots.



Juniper Networks Field Guide and Reference
Juniper Networks Field Guide and Reference
ISBN: 0321122445
EAN: 2147483647
Year: 2002
Pages: 185

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