Mesh topology

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1. Mesh topology

Example 1 – Mesh topology

Fig. 1.1: Example 1 – Mesh topology


1.1. Description

The first example shows how BABEL can be used to propagate RipEX2’s LANs automatically instead of static routes. The topology allows every device to directly see each other resulting in a situation that all communication goes directly between two particular RipEX2 units. There is no dedicated repeater or another technology such as LTE or Fibre optics.

1.2. RipEX_A configuration

Start with unit’s Name and Mode. Go to the SETTINGS – Device – Unit menu. Select the “Router” mode, because it is not possible to configure dynamic routing protocols in the Bridge mode. Set the name to “RipEX_A”.

RipEX_A – Mode and name

Fig. 1.2: RipEX_A – Mode and name


You can also set a correct time in the unit, either via a working NTP server or just manually update it by the time in your browser (“Update in device” button and a check-box “Use browser time”). This is useful in general and mainly for debugging purposes (Statistics, monitoring, …). It is not required by BABEL protocol.

RipEX_A – Time

Fig. 1.3: RipEX_A – Time


Configure a correct Ethernet IP address 192.168.1.1/24 (bridged on all ETH ports).

RipEX_A – Ethernet IP address

Fig. 1.4: RipEX_A – Ethernet IP address


Go to the Radio submenu and configure the Radio interface. You can accommodate most of the parameters to suit your needs, but be consistent throughout this application note and all its examples.

RipEX_A – Radio interface settings

Fig. 1.5: RipEX_A – Radio interface settings


Settings:

Radio protocol

Flexible

IP / Mask

10.10.10.1/24

Radio protocol

Flexible

ACK

On

Retries

3

TX/RX frequencies

415.500.000 MHz

Antenna configuration

Single (Tx/Rx)

RF power PEP

20 dBm (testing on the desk, lowest power)

Channel spacing and OBW

25 kHz

Modulation and its type

QAM, 16DEQAM

FEC

Off

[Note]Note

Using the Flexible Radio protocol via a simplex channel (half-duplex operation) might result in a FULL MESH organized network. When BDP Radio protocol is set, using the BABEL dynamic routing results in a self-configuring network with a STAR topology. There is no Encryption set, neither any Individual link options within these examples.

The most important menu is SETTINGS – Routing – BABEL. Activate the protocol and set the Router ID to unique 1.1.1.1 and enable Routing offering so that it forwards received routes to other neighbor.

RipEX_A – BABEL common settings

Fig. 1.6: RipEX_A – BABEL common settings


Go to the Network panel and create a new Wireless network.

RipEX_A – BABEL Network settings

Fig. 1.7: RipEX_A – BABEL Network settings


Interface must be “radio” (interface name) and its type “Wireless” (it is a radio channel). Change the Rx cost from default 128 to 100.

Increase the Hello interval to 30 seconds. This is important so that BABEL does not send too many overhead packets on the radio channel. Decision on this (and other) parameters is always a “tradeoff”. Lower the interval, quicker protocol operations such as topology changes detection or complete routing propagation, but in a cost of higher Radio channel utilization.

Keep in mind that if you run low FSK or even low QAM modulation, the primary goal is still correct SCADA operation and not overhead data.

Another parameter to be set is Update interval multiplier and is set to default 4. This number multiplies the Hello interval (in our example it is 4×30 seconds = 2 minutes). Router updates packets are sent in ~ 2 minutes intervals.

This setup, the same in all 4 RipEX2 units, results in approximately 1 BABEL packet per 10 second, i.e., 100 bps. The topology change can be detected and spread across a network within quite a long interval, ranging from 30 seconds to several minutes. Optimize these values to suit your topology, used modulation type and SCADA traffic.

Go to another panel “Static rules” and configure advertised network 192.168.1.0/24 with default metric equal to 0.

RipEX_A – Static rules settings

Fig. 1.8: RipEX_A – Static rules settings


Go to another panel “Import filter” and create a new rule. The only non-default parameter we need to set is “Local preferred source address” (LPSA) – set it to 192.168.1.1 (Ethernet IP of RipEX_A). This is a preferred source IP address for locally generated packets.

RipEX_A – Import filter settings

Fig. 1.9: RipEX_A – Import filter settings


We do not configure anything in the “Export filter” panel.

The configuration is complete. Go to the “Changes” menu (upper right corner button) and save the changes.

1.3. RipEX_B, RipEX_C and RipEX_D configuration

Other units share most of the settings we configured in RipEX_A. We just highlight the differences compared to RipEX_A setup.

RipEX_B

Unit name

RipEX_B

Ethernet IP

192.168.2.1/24

Radio IP

10.10.10.2

BABEL routing

 

Router ID

2.2.2.2

Static rules

192.168.2.0/24

Import filter LPSA

192.168.2.1

RipEX_C

Unit name

RipEX_C

Ethernet IP

192.168.3.1/24

Radio IP

10.10.10.3

BABEL routing

 

Router ID

3.3.3.3

Static rules

192.168.3.0/24

Import filter LPSA

192.168.3.1

RipEX_D

Unit name

RipEX_D

Ethernet IP

192.168.4.1/24

Radio IP

10.10.10.4

BABEL routing

 

Router ID

4.4.4.4

Static rules

192.168.4.0/24

Import filter LPSA

192.168.4.1

1.4. Diagnostics and Testing

Once configured, you can wait until the network converges to the correct routing, or you can also reboot all the units so the protocol starts from scratch.

1.4.1. Routing

Go to the DIAGNOSTICS – Routing menu and check the BABEL panel. Let’s go through individual tables.

BABEL diagnostics – Interfaces

Fig. 1.10: BABEL diagnostics – Interfaces


In the 1 st table, we can see all interfaces on which BABEL is either configured or found. If the interface is missing, but should be there, it probably failed while initialization (e.g., because of missing link IPv6 address).

State

Interface state, either “up” or “down”

Rx cost

It displays configured received cost (for other neighbor)

Nbrs

Number of detected neighbors on particular interface

Time

Number of seconds until next BABEL Hello or Update transmission

Nexthop

What “next-hop” address the router offers to neighbors (IPv4 and IPv6)

  • Can be useful in case of configured 0.0.0.0 – to check if correct IP is really used

BABEL diagnostics – Neighbors

Fig. 1.11: BABEL diagnostics – Neighbors


IP address

Neighbor’s IPv6 link address

Interface

Interface on which the neighbor was found

Metric

Current metric for receiving from neighbor

Routes

Number of routes received from neighbor

Hellos

Number or received Hello packets (from up to 16)

Expires [s]

Time until reception of another expected Hello packet from neighbor

BABEL diagnostics – Routes

Fig. 1.12: BABEL diagnostics – Routes


A list of all routes from all neighbors. It may even consist “loops” for routes which are not currently used, but once the protocol switches to them, loops are solved and “fixed”. Or in other words, such routes are are not considered as “candidates”.

Prefix

Range of destination IP addresses for a particular rule

Nexthop

Next-hop address

Metric

Current cost to the destination

F

* for currently active rule, + for feasible next candidate for active rule

Seqno

Update packet sequence number which announced the rule

Expires [s]

Time until the rule expires

BABEL diagnostics – Entries

Fig. 1.13: BABEL diagnostics – Entries


Prefix

Prefix of routed address range

Router ID

Router ID – first 4 Bytes either zeros, or randomized. Second 4 Bytes equal to Router ID set in the configuration

Metric

Current cost to the destination

Seqno

Number of various routing rules for particular prefix/subnet

Routes

Time until the rule expires

Sources

Number of various routers which export a particular prefix to BABEL network

BABEL diagnostics – Table babel_ipv4

Fig. 1.14: BABEL diagnostics – Table babel_ipv4


The table consist of advanced and detailed information of all routes from BABEL table.

1.4.2. Tools

Now, check the remote unit’s IP accessibility. Go to the DIAGNOSTICS – Tools – ICMP ping menu.

RipEX_A – Diagnostics – Tools – ICMP Ping

Fig. 1.15: RipEX_A – Diagnostics – Tools – ICMP Ping


Fill in the Destination IP field with required IP (try all remote LAN IPs). Check if it gets through. If not, check the Routing diagnostics for available routes.

You can also check what route is used for particular destination in another panel “Routing”.

RipEX_A – Diagnostics – Tools – Routing

Fig. 1.16: RipEX_A – Diagnostics – Tools – Routing


You can debug issues further in Statistics and/or Monitoring menus.