Interfacing

E1/T1 Interface

Why not TDMoIP / CESoIP?

Usual E1/T1 over IP protocols use generic frames over IP transfer that makes more than 2 megabits constant rate with up to 8000 packets per second. That approach:

Fur such kind of integrations we prefer to have our own agent software on-site with hardware E1/T1 interfaces.

icE1usb

image.png

We have chosen Osmocom icE1usb as a primary interface for our projects for several reasons:

User manual can be found here.

NOTICE

Please be careful! Or your device will be damaged! Front-panel RJ45 connectors accepts 120 Om E1. Back-panel RJ45 is for GPIO and accepts TTL only. Don't try to connect the device to Ethernet. USB-C port should be connected to computer, since it's just an interface. Minijack connector is only to reprogram firmware. Also please configure properly internal jumpers to master (NE) or slave (NT) E1 mode.

PLEASE READ USER MANUAL FIRST.

Hardware configuration

Almost in all our cases you need this interface in NT (Network Termination) mode. In this mode the interface works as a network side and you can use a normal Ethernet cable for connection (no crossing required).

To change the mode, unscrew the 2 PH0 screws on the side with the 2 RJ45 jacks. You’ll also need to unscrew the nut on the SMA jack on the other side. After that, the cover plate and rubber gasket around the 2 RJ45 jacks can be removed. The PCB can be slid out of the case.

Then swap the jumpers so they match this picture:

R7EkjMk3OLkjHuoP-image.png

Driver installation

You can get Osmocom E1D from Osmocom's Debian repository (amd64, arm64). 

sudo apt install extrepo
sudo extrepo enable osmocom-latest
sudo apt update
sudo apt install -y osmo-e1d

Driver configuration

/etc/osmocom/osmo-e1d.cfg

log syslog daemon
 logging level force-all fatal
e1d
 interface 0 icE1usb
  usb-serial [interface serial number]
  line 0
  line 1

More information about logging section can be found here, here and here.
(If you care about configuration file format, please check the sources here).

How to find a serial number of connected icE1usb:

sudo lsusb -d 1d50:6145 -v 2> /dev/null | grep iSerial

Reload a service:

sudo systemctl restart osmo-e1d

You can also test your configuration from the command line:

sudo osmo-e1d -c /etc/osmocom/osmo-e1d.cfg

Recomended settings

/etc/rsyslog.d/99-e1d.conf 

if ($programname contains "osmo-e1d") and (($msg contains "Received Only 0 bytes") or ($msg contains "TS read underflow")) then {
  ~/dev/null
  stop
}

/etc/systemd/system/osmo-e1d.service.d/override.conf

[Service]
TimeoutStopSec=2s

Issues with the second E1 port

Please note that on many XHCI host controllers there seem to be implementation flaws in the XHCI host controller firmware preventing the activation of both icE1usb ports simultaneously. The XHCI controller firmware erroneously claims that there is insufficient bus bandwidth. However, the same icE1usb hardware/firmware works perfectly fine with OHCI, UHCI and EHCI host controllers. See https://osmocom.org/projects/e1-t1-adapter/wiki/Isochronous_USB_Issues for a user-maintained list of USB hosts / controllers and whether or not they work with two E1 ports.

In most installations it's not a real issue, because of need in a single port only.

We have tested it with following equipment:

FrameRelay over E1

FrameRelay-over-E1 Daemon (FRED)

Intro

Installation

sudo apt install extrepo
sudo extrepo enable osmocom-latest
curl http://packages.tetrapack.online/install/tools/Debian/add-repository.sh | bash
sudo apt install -y osmo-e1d fred

Configuration

Default configuration file is /opt/FRED/default.env

#
# Parameters for FRED binary
#

# E1D interface and line in format <interface number>.<line number>
FRED_LINE=0.0

# E1 slot list in format <first slot>-<last slot>
FRED_SLOT_LIST=1-31

# FrameRelay feature list in format <option>[,...]
# FRF.12-OUTER - outer frame sequence counting and fragmentation (incoming frames only supported)
FRED_FEATURE_LIST=

# DLCI list in format <DLCI>:<type>[,...]
# LMI-DCE-PVC
# IP  - IP bridge (RFC 2427 for IPv4, RFC 2590 for IPv6)
# ETH - Ethernet bridge (RFC 2427)
FRED_DLCI_LIST=0:LMI-DCE-PVC,16:IP,17:IP

# Path to configuration script to manage IP interface configuration on up and down
FRED_SCRIPT=./dimetra-hook.sh

#
# Parameters for dimetra-hook.sh
#

# Zone ID
DIMETRA_ZONE=1

# Local Site ID
DIMETRA_SITE=12

# FrameRelay DLCIs
DIMETRA_DLCI_PRIMARY=16
DIMETRA_DLCI_SECONDARY=17

# When set, routes will be added to FRR's OSPF prefix list
FRR_PREFIX_LIST=dimetra

Use with Dimetra

FRED package includes prepared scripts to establish connection between EBTS and Dimetra MPVPN network. 

sudo /opt/FRED/dimetra-setup.sh

Best settings for EBTS TSC will be:

.sitelink -e1
.e1config -crdStart 1 -crd 31 -ts16Skip off -portNo 1 -crc on
reset

Multiple instances

You can have several separated systems connected to a local Linux system. For such case you need to have several .env files for each configuration. use sudo ./setup.sh install to register all instances.

Also it's possible to run FRED in command line - sudo ./run.sh <configuration.env>