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Example: Configuring Packet Optical Networks with PTX Series Devices

 

This network configuration example configures three PTX3000 routers with 100 Gbps Ethernet interfaces, forward error correction (FEC), MPLS label-switched paths (LSP), preemptive fast reroute, and optical transport network (OTN) and wavelength-division multiplexing (WDM) parameters to show how these technologies support preemptive fast reroute with minimal traffic disruption due to link degradation in a converged supercore backbone router network.

Requirements

This example uses the following hardware and software components:

  • 3 PTX3000 routers (PTX5000 Series routers can also be used)

  • 3 FPC-SFF-P1A Flexible PIC Concentrators for the PTX3000 routers

  • 6 P1-PTX-2-100G-C-WDM-C 2-port 100G DWDM OTN PIC for the PTX3000 routers

  • Junos OS Release 14.2 R1 or later

Before you configure packet optical networking on the PTX Series routers, be sure that you have:

  • Installed all links and linecard hardware correctly

  • Configured all basic parameters such as router names

Overview

This network requires high-gigabit rate user traffic to be transported over a core of three PTX3000 routers from source interface to destination interface with very low latency, minimal nodal processing, and fast reroute of traffic in the case of link quality degradation. The best way to satisfy these requirements is to use OSPF as an interior gateway protocol (IGP), then use MPLS with LDP and Reservation Protocol with Traffic Engineering (RSVP-TE) to establish a label-switched path (LSP) from the ingress PTX Series router to the egress PTX Series router. Then primary and secondary LSPs are created among the PTX Series routers to enable preemptive fast reroute of traffic in case of a link degradation or failure.

Topology

This configuration example uses three PTX3000 routers named PTX3000-1, PTX3000-2, and PTX3000-3. Streaming traffic enters PTX3000-1 from the interface having IP address 192.168.1.1 and exits from PTX3000-2 to the interface having IP address 192.168.2.1. PTX3000-1 and PTX3000-2 are directly connected with a point-to-point fiber link. In case this link fails or exceeds an established error threshold, the streaming traffic can be routed from 192.168.1.1 to 192.168.2.1 through intermediate router PTX3000-3, which has direct links to both PTX-3000-1 and PTX3000-2.

Finally, packet optical parameters are established to detect primary path optical link degradation and to reroute traffic quickly onto the secondary LSP.

The topology used in the configuration example is shown in Figure 1.

Figure 1: Topology for the Packet Optical Network
Topology for the Packet Optical
Network

This example configures the following on all three PTX3000 routers:

  • Fiber optical interfaces—For the inter-PTX links, each interface establishes a jumbo frame size of 9192 bytes used for high-speed Ethernet interfaces, and sets the WDM wavelength at 1529.55 nanometers (nm), a wavelength used for 10-Gigabit or 100-Gigabit Ethernet Dense WDM (DWDM) interfaces only, part of the C-band ITU-Grid tunable optics standard. Setting optical wavelengths in device software instead of in an external device is a characteristic of packet topical networks. Then we set optical transport network (OTN) options: set the reporting interval in milliseconds (10) and establish the bit error rate (BER) thresholds for declaring the link degraded or failed (a pre-forward error correction (FEC) BER value of 5 .0e-3, or 1 bit in 1000) or cleared (5.0e-7, or 1 bit in 10 million). Note that FEC might still recover from many of these bit errors. For more information about FEC operation for OTNs on the PTX Series routers, especially BER threshold operation, see Understanding Pre-FEC BER Monitoring and BER Thresholds. Finally, this example configures preemptive fast reroute to enable monitoring of signal degradation and the feedback of the result to the source (MPLS LSPs are rerouted from the source). For more information about configuring 100-Gigabit Ethernet, see 100-Gigabit Ethernet OTN Options Configuration Overview.

  • OSPF as the IGP—All networks need to run a routing protocol to learn the network topology and to know what devices are reachable. This example configures OSPF as the IGP, but IS-IS could be used if preferred, as long as the same IGP is run throughout the network. The indirect route through PTX3000-3 is given a very high metric (10000) so that traffic does not use the link unless the direct link has failed.

  • LDP as MPLS signaling protocol—MPLS uses a signaling protocol to establish LSPs from source to destination routers. This example configures LDP, which automatically seeks out all possible routes in the network, as the basic MPLS signaling protocol. LDP uses the same metrics as established for the IGP (OSPF).

  • MPLS as the packet switching technology—MPLS establishes LSPs from ingress to egress router. In between, IP packets are encapsulated with an MPLS label and are switched, not routed. The nice thing about MPLS is that an LSP, no matter how many routers it passes through, looks like one hop at the IP layer. So LSP reroutes through PTX3000-3 look essentially the same to the source and destination systems.

  • RSVP-TE to set up the active and standby traffic engineering LSPs—This example uses RSVP-TE signaling to establish primary and standby LSPs in the network between PTX3000 routers. This example configures link protection on the inter-PTX Series router interfaces.

Configuration

Configuring packet optical networking in the PTX Series devices involves:

CLI Quick Configuration

To quickly configure this example, copy the following commands, paste them into a text file, remove line breaks, change any details such as interface designations and IP addresses to match your network, and then copy and paste the commands into the CLI at the [edit] hierarchy level.

PTX3000-1

PTX3000-2

PTX3000-3

Configuring Optical Interfaces

Step-by-Step Procedure

The following example requires you to navigate to various levels of the configuration hierarchy. For information about navigating the CLI, see Using the CLI Editor in Configuration Mode and CLI User Guide.

To configure optical interfaces and loopback on PTX3000-1:

  1. Configure the et-0/0/0 interface to PTX3000-2.
  2. Configure the et-0/0/1 interface to PTX3000-3.
  3. Configure the et-0/1/0 interface (the streaming traffic source).
  4. Configure lo0 interface (to Routing Engine).

Step-by-Step Procedure

To configure optical interfaces and loopback on PTX3000-2:

  1. Configure the et-1/0/0 interface to PTX3000-1.
  2. Configure the et-1/0/1 interface to PTX3000-3.
  3. Configure the et-1/1/1 interface (the streaming traffic destination).
  4. Configure lo0 interface (to Routing Engine).

Step-by-Step Procedure

To configure optical interfaces and loopback on PTX3000-3:

  1. Configure the et-2/0/0 interface to PTX3000-1.
  2. Configure the et-2/0/1 interface to PTX3000-2
  3. Configure lo0 interface (to Routing Engine).

Configuring OSPF

Step-by-Step Procedure

To configure OSPF on all interfaces:

  1. Enable OSPF on PTX3000-1.
  2. Enable OSPF on PTX3000-2.
  3. Enable OSPF on PTX3000-3.

Configuring LDP on PTX3000-1 and PTX3000-2

Step-by-Step Procedure

To configure LDP:

  1. Enable LDP on PTX3000-1 traffic and loopback interfaces.
  2. Enable LDP on PTX3000-2 traffic and loopback interfaces.

Configuring MPLS

Step-by-Step Procedure

To configure MPLS on PTX3000-1:

  1. Configure parameters and LSPs on PTX3000-1.
  2. Configure parameters and LSPs on PTX3000-2.
  3. Configure parameters and LSPs on PTX3000-3.Note

    This example configuration requires only minimal MPLS configuration on the “pass-through” router PTX3000-3, where no LSPs originate or terminate. In a production environment, the configuration would be more complex.

Configuring RSVP-TE LSPs

Step-by-Step Procedure

To configure RSVP-TE link protection:

  1. Configure link protection on PTX3000-1.
  2. Configure link protection on PTX3000-2.
  3. Configure link protection on PTX3000-3.

Results

From configuration mode, confirm your configuration by entering the show interfaces and show protocols commands. If the output does not display the intended configuration, repeat the instructions and in this example to correct the configuration.

Configuration for PTX3000-1

Configuration for PTX3000-2

Configuration for PTX3000-3

Verification

Confirm that the configuration is working properly.

Verifying That the Primary Path Is Working

Purpose

Confirm that the configuration is working properly between PTX3000-1 and PTX3000-2.

Action

From operational mode on PTX3000-1, enter the show interfaces extensive et-0/0/0 | match “Corrected|Uncorrected|alarms|Phy|FEC” command to make sure that the physical link is up with no alarms or errors.

user@ptx3000-1> show interfaces extensive et-0/0/0 | match “Corrected|Uncorrected|alarms|Phy|FEC”

Meaning

The link is up, there are no active alarms or defects, the default FEC mode is enabled, and there are no FEC alarms.

Verifying That the Link Fails When the BER Threshold Is Exceeded

Purpose

Confirm that the traffic no longer flows on the primary path if the BER exceeds the established threshold.

Action

From operational mode on PTX3000-1, enter the show interfaces extensive et-0/0/0 | match “Corrected|Uncorrected|alarms|Phy|FEC” command to make sure link is down with alarms or errors.

user@ptx3000-1> show interfaces extensive et-0/0/0 | match “Corrected|Uncorrected|alarms|Phy|FEC”

Meaning

The link is now down due to active alarms and defects.

Verifying That the Secondary Path Is Working with Fast Reroute

Purpose

Confirm that the traffic still flows on the secondary path through PTX3000-3.

Action

From operational mode on PTX3000-1, enter the monitor interface traffic command to make sure that the link to PTX3000-3 carries traffic.

user@ptx3000-1> monitor interface traffic

Meaning

The primary link is now down, but traffic is flowing on the secondary path. This reroute occurs due to exceeding the bit error threshold, not a physical link break.

Note

There are other commands that can be used to verify traffic flows before and after failures. The commands used in this section emphasize the physical link operation.