Configuring ATM Interfaces


Asynchronous Transfer Mode (ATM) is a network protocol designed to facilitate the simultaneous handling of various types of traffic streams (voice, data, video) at very high speeds over the same physical connection. ATM relies on the concepts of virtual paths and virtual circuits. A virtual path, represented by a specific virtual path identifier (VPI), establishes a route between two devices in a network. Each VPI can contain multiple virtual circuits, each represented by a virtual circuit identifier (VCI).

For ATM physical interfaces, you can configure two ATM-specific physical device properties: the maximum number of virtual circuits (VCs) allowed on a virtual path (VP) and communication with directly attached ATM switches. You configure these properties by including the atm-options statement:

 [edit interfaces  interface-name  ]  atm-options {   vpi  vpi-identifier  maximum-vcs  maximum-vcs  ;   ilmi; } 

You configure the maximum number of virtual circuits allowed on a virtual path so that sufficient memory on the ATM PIC can be allocated for each VC. When configuring ATM interfaces on the router, you must include this statement. To configure the largest numbered VCs on a VP, include the vpi statement. The VP identifier can be a value from 0 through 255. You can configure a maximum number of 4,090 VCs per ATM interface; the largest value you can configure is 4,089.

You configure communication to directly attached ATM switches to enable querying of the IP addresses and port numbers of the switches. To configure communication between the router and its directly attached ATM switches, include the ilmi statement.

When you are using ATM encapsulation on an interface, you must map each logical interface to a VCI. You can optionally map logical interfaces to a VPI. An ATM interface can be a point-to-point interface or a point-to-multipoint (also called a multipoint nonbroadcast multiaccess [NBMA] connection).

To configure a VCI and a VPI on a point-to-point ATM interface, include the vci statement. For each VCI, you configure the VCI and VPI identifiers. The default VPI identifier is 0. The VCI identifier cannot exceed the highest numbered VC configured for the interface with the vpi statement. When you are configuring point-to-point connections, the MTU sizes on both sides of the connections must be the same.

 [edit interfaces  interface-name  unit  logical-unit-number  ]  vci  vpi-identifier.   vci-identifier  ; 

To configure a point-to-multipoint (NBMA) ATM connection, include the multipoint-destination statement:

 [edit interfaces  interface-name  unit  logical-unit-number  family  inet  address  address  ] multipoint-destination  destination  -  address  vci  vpi-   identifier.   vci-identifier  ; 

address is the interface's address. The address must include the destination prefix (for example, /24 ). For each destination, include one multipoint-destination statement. destination - address is the address of the remote side of the connection, and vci-identifier and vpi-identifier are the VCI and optional VPI identifiers for the connection. For point-to-multipoint connections, all interfaces in the subnet must use the same MTU size.

By default, ATM connections assume unicast traffic. If your ATM switch performs multicast replication, you can configure the connection to support multicast traffic by including the multicast-vci statement. You can configure multicast support only on point-to-multipoint ATM connections.

 [edit interfaces  interface-name  unit  logical-unit-number  ]  multicast-vci  vpi-identifier.   vci-identifier  ; 

You can configure ATM interfaces to support inverse ATM ARP, as described in RFC 2225.

When inverse ATM ARP is enabled, the router responds to received inverse ATM ARP requests by providing IP address information to the requesting ATM device. To configure a VC to respond to inverse ATM ARP requests , include the inverse-arp statement. You must configure ATM LLC-SNAP encapsulation on the logical interface to support inverse ARP. The other ATM encapsulation types are disallowed .

 [edit interfaces  interface-name  unit  logical-unit-number  ] or  [edit interfaces  interface-name  unit  logical-unit-number  family inet address  address  multipoint-destination  destination  ] inverse-arp ; 

When using an ATM encapsulation, you can configure a traffic-shaping profile that defines bandwidth utilization, which consists of either a constant rate or a peak cell rate with sustained cell rate, and burst tolerance; and maximum queue length. These values are used in the generic ATM cell -rate algorithm, which is a leaky bucket algorithm that defines the short-term burst rate for ATM cells, the maximum number of cells that can be included in a burst, and the long- term sustained ATM cell traffic rate. Each individual VC has its own independent shaping parameters.

By default, the bandwidth utilization is unlimited; that is, unspecified bit rate (UBR) is used. Also, by default, buffer usage by VCs is unregulated. To define limits to bandwidth utilization on a point-to-point interface or to limit buffer use, include the shaping statement. For point-to-point interfaces, include the shaping statement at the [edit interfaces interface-name unit logical-unit-number ] hierarchy level; for virtual circuits that are part of a point-to-multipoint interface, include it at the [edit interfaces interface-name unit logical-unit-number family family address address ] hierarchy level.

 shaping {   (cbr  rate  vbr peak  rate  sustained  rate  burst  length  );   queue-length  number  ; } 

For traffic that does not need to periodically burst to a higher rate, you can specify a constant bit rate (CBR) by including the cbr statement at the [edit interfaces interface-name unit logical-unit-number shaping] or [edit interfaces interface-name unit logical-unit-number family family address address multipoint-destination destination-address shaping ] hierarchy level:

 cbr  rate  ; 

To define variable bandwidth utilization (VBR), include the vbr statement at the [edit interfaces interface-name unit logical-unit-number shaping] or [edit interfaces interface-name unit logical-unit-number family family address address multipoint-destination destination-address shaping] hierarchy level:

 vbr peak  rate  sustained  rate  burst  length  ; 

When configuring VBR, you can define the peak rate, which is the top rate at which traffic can burst, the sustained rate, which is the normal traffic rate averaged over time, and the burst length, which is the maximum number of cells that a burst of traffic can contain and can be a value from 1 through 255 cells.

With an ATM encapsulation, you can configure the OAM F5 loopback cell period on virtual circuits, which is the interval at which OAM F5 loopback cells are transmitted. By default, no OAM F5 loopback cells are sent. To send OAM F5 loopback cells on a point-to-point interface, include the oam-period statement at the [edit interfaces interface-name unit logical-unit-number ] hierarchy level; to send them on a virtual circuit that is part of a point-to-multipoint interface, include the statement at the [edit interfaces interface-name unit logical-unit-number family family address address ] hierarchy level. The period can range from 1 through 900 seconds.

 oam-period (disable  seconds  ); 

With an ATM encapsulation, you can configure the OAM F5 loopback cell threshold on VCs, which is the minimum number of consecutive OAM F5 loopback cells received before declaring that a VC is up or lost before declaring that a VC is down. By default, when five consecutive OAM F5 loopback cells are received, the VC is considered to be up, and when five consecutive cells are lost, the VC is considered to be down. To modify these values on a point-to-point interface, include the oam-liveness statement at the [edit interfaces interface-name unit logical-unit-number ] hierarchy level, and to modify it on a virtual circuit that is part of a point-to-multipoint interface, include the oam-liveness statement at the [edit interfaces interface-name unit logical-unit-number family family address address ] hierarchy level. The cell count can be a value from 1 through 255 cells.

 oam-liveness {   up-count  cells  ;   down-count  cells  ; } 

See RFC 1483, Multiprotocol Encapsulation over ATM Adaptation Layer 5 .

For an ATM interface, the physical interface encapsulation can be ATM PVC, and ATM cell relay, which connects two remote virtual circuits or ATM physical interfaces with a label-switched path (LSP). For ATM PVC encapsulation, you can configure the logical interfaces with any ATM encapsulation. To configure the encapsulation on a physical interface, include the following encapsulation statement:

 [edit interfaces  interface-name]  encapsulation (atm-ccc-cell-relay  atm-pvc  cisco-hdlc  cisco-hdlc-ccc  frame-relay  frame-relay-ccc  ppp  ppp-ccc vlan-ccc); 

For ATM encapsulations , you also can configure the encapsulation type that is used inside the ATM cell itself by including the following encapsulation statement:

 [edit interfaces  interface-name  unit  logical-unit-number  ]  encapsulation (atm-ccc-cell-relay  atm-nlpid  atm-cisco- nlpid  atm-snap  atm-vc-mux  atm-ccc-vc-mux  frame- relay-ccc  vlan-ccc); 

To configure ATM E3 and T3 interfaces, include the following statements:

 [edit interfaces at-  fpc  /  pic  /  port  ]  e3-options {   atm-encapsulation (plcp  direct);   buildout <  distance  > (ft  m);   framing (g.751  g.832);   loopback (local  remote);   (payload-scrambler  no-payload-scrambler); } t3-options {   atm-encapsulation (plcp  direct);   buildout <  distance  > (ft  m);   (cbit-parity  no-cbit-parity);   loopback (local  remote);   (payload-scrambler  no-payload-scrambler); } 

See "Configuring E1 and E3 Interfaces," on page 215 and "Configuring T1 and T3 Interfaces," on page 257.

Some of the options and default values vary from those for the E3 and T3 interfaces:

  • atm-encapsulation ” PLCP is the default value. The E3 line-format option g.832 supports direct ATM encapsulation only.

  • buildout ” The default value is 10 feet. distance can be any integer value, followed by a unit specifier of ft or m . The range is 0 through 255 feet for E3 traffic or 0 through 450 feet for T3 traffic.

  • cbit-parity ” The default option is to enable C-bit parity.

  • framing ” There is no default option for E3 interfaces; T3 interfaces use the cbit-parity statement in place of framing .

  • loopback ” The default is no loopback.

  • payload-scrambler ” The default is to enable payload scrambling .

See "Configuring SONET/SDH Interfaces," on page 241.

In addition, the ATM E3 and T3 PICs support the clocking statement at the interface level, similar to the SONET PICs.

You must configure all the ports on an ATM E3 or T3 PIC with the same framing and encapsulation. Otherwise, all ports on the PIC are set to the slowest framing and encapsulating configuration. For ATM T3, this is PLCP and for ATM E3, this is G.751 PLCP.

When configuring ATM SONET/SDH interfaces, you also can include the following statements in the sonet-options statement to set SONET/SDH parameters on ATM interfaces:

 [edit interfaces at-  fpc  /  pic  /  port  ]  sonet-options {   aps {     advertise-interval  milliseconds  ;     authentication-key  key  ;     force;     hold-time  milliseconds  ;     lockout;     neighbor  address  ;     paired-group  group-name  ;     protect-circuit  group-name  ;     request;     revert-time  seconds  ;     working-circuit  group-name  ;   }   bytes {     e1-quiet  value  ;     f1  value  ;     f2  value  ;     s1  value  ;     z3  value  ;     z4  value  ;   }   fcs (32  16);   loopback (local  remote);   path-trace  trace-string  ;   (payload-scrambler  no-payload-scrambler);   rfc-2615;   (z0-increment  no-z0-increment); } 


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

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