ZyXEL Communications VOP1372G-61 Manual

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VOP1372G-61
Support Notes
December 2011
Edition 1.0

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Content
Introduction ...............................................................................................................3
H.248 Signaling Procedures .....................................................................................11
VOP1372G-61...........................................................................................................17
H.248 application .....................................................................................................29
Debug guide .............................................................................................................37

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Introduction
What is VoIP?
Traditional voice switching business has long been the mainstay for a relatively small
group of global equipment suppliers. But times has changes, carriers are adopting a
standardized IP Multimedia Subsystem architecture for next-generation networks
with distributed softswitch call control and independent Media Gateways. In addition
to the legacy circuit switch equipment suppliers, the equipment market reshuffles
and opens to new vendors.
Media Gateway is a network element which packetizes voice traffic from POTS signals
to IP packets, and performs critical voice network features such as echo cancellation,
silence detection and suppression, etc. Softswitch is the one which provides call
control to Media Gateways in a packet voice network.
Through VOP1372G-61, ZyXEL transforms its IP DSLAM portfolio into multi-service
DSLAM and starts to enter the Media Gateway market worldwide.
VoIP is the sending of voice signals over the Internet Protocol. This allows you to
make phone calls and send faxes over the Internet at a fraction of the cost of using
the traditional circuit-switched telephone network.

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What is H.248?
H.248 protocol is a media gateway control protocol that enables Switched Circuit
Network (SCN) to transmit voice traffic over IP. H.248 protocol specifies
master/slave architecture for decomposed gateways. In the master/slave
architecture, Media Gateway Controller (MGC) is the master server and MGs are
the slave clients that behave as simple switches. One MGC can serve multiple MGs.
Network Diagram
H.248 protocol enables the creation, modification and deletion of media streams
across a media gateway, including the capability to negotiate the media formats to
be used.
Terminations and Contexts
The connection model (the figure below) for the H.248 protocol describes
the logical entities, or objects, within the MG that can be controlled by
the MGC. The main abstractions used in the connection model are
Terminations and Contexts.

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Example of H.248 connection model
Terminations
A Termination is a logical entity on a MG that sources and/or sinks
media and/or control streams. A Termination is described by a number of
characterizing Properties, which are grouped in a set of Descriptors that
are included in commands.
Terminations have unique identities (TerminationIDs), assigned by the MG
at the time of their creation.
There are two types of terminations: semi-permanent terminations and
ephemeral terminations. Terminations representing physical entities have
a semi-permanent existence. Terminations representing ephemeral
information flows, such as RTP flows, would usually exist only for the
duration of their use.
Contexts
A Context is an association between a number of Terminations. The

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Context describes the topology and the media mixing and/or switching
parameters if more than two Terminations are involved in the association.
There is a special Context called the null Context. It contains Terminations
that are not associated to any other Termination.
Contexts are identified by a Context_Id which is assigned by the MG and is
unique within the MG.
H.248 Message Structure
A message is an information unit sent or received by the H.248 protocol.
In the H.248 protocol, one or more commands are encapsulated in a
message.
The H.248 message mechanism is shown below.
H.248 Message Structure
Message

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Messages start with a header which is followed by several transactions.
The header contains a Message Identifier (MID) and a Version Number.
The MID identifies the sender of the message which may be a domain
address, domain name or device name. Domain name is a suggested
default. The Version Number identifies the version of the protocol the
message conforms to.
Transaction
A message contains one or more transactions. The transactions in a
message are treated independently. There is no order implied.
Transactions include requests and responses, and responses are
divided into two types: TransactionReply and TransactionPending.
TransactionRequest
The TransactionRequest is invoked by the sender. There is one
Transaction per request invocation. A request contains one or more
Actions, each of which specifies its target Context and one or more
Commands per Context.
The structure of Transaction Request is as
follows: TransactionRequest(TransactionId {
ContextID {Command … Command},
. . .
ContextID {Command … Command } })
The TransactionID parameter must specify a value for later
correlation with the TransactionReply or TransactionPending response
from the receiver.
TransactionReply
Transaction Reply is a response of the transaction receiver to the
Transaction Request. Every transaction should have its Reply. A
TransactionRequest stops being executed either if all commands in
the TransactionRequest have been carried out successfully or a
failure is encountered during the execution of a non-optional
command in the TransactionRequest.

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The structure of Transaction Reply is as
follows: TransactionReply(TransactionID {
ContextID { Response …Response },
. . .
ContextID { Response …Response } })
The TransactionID parameter must be the same as that of the
corresponding TransactionRequest.
TranctionPending
The receiver invokes the Transaction Pending. A Transaction Pending
indicates that the transaction is actively being processed, but has
not been completed. It is used to prevent the sender from assuming
the TransactionRequest was lost where the command will take some
time to complete.
The structure of Transaction Pending is as
follows:
TransactionPending(TransactionID{ } )
The TransactionID parameter must be the same as that of the
corresponding TransactionRequest.
Actions
Actions are related to Contexts. Actions are identified by a ContextID. In
an action, commands should be processed in order.
An action begins with the Context header in which ContextID is
contained for identifying the Context this action corresponds to.
ContextID is assigned by the MG and is unique within the scope of the
MG. The MGC shall use the ContextID in all subsequent transactions
relating to that Context.
Context header is followed by several commands, and these commands
are related to the Context identified by the ContextID.
Commands

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Commands are the major contents in an H.248 message. They control
the Context and Termination attributes including specifying the topology
structure of the Context and specifying the event reported by the
Termination, for example, what signals and actions can be imposed on
the Termination. A command is composed of the command header and
command parameters.
All commands as described in para 7.2 of ITU-T recommendation
H.248.1 version 2 shall be supported:
Add: To add adds a Termination to a Context. This shall also be used to a
Context when the first termination is added to a
Context.
Modify: To modify the properties, events, signals of an existing
termination.
Subtract: To remove a termination from its context. This command is
also used to delete a context when the last termination is removed
from the context.
Move: To atomically move a Termination to another
Context.
AuditValue: The AuditValue command returns the current state of
properties, events, signals and statistics of Terminations.
AuditCapabilities: The AuditCapabilities command returns all the
possible values for Termination properties, events and signals allowed
by the Media Gateway.
Notify: This command allows the MG to inform the MGC of the
occurrence of events in the MG.
ServiceChange: To allows the Media Gateway to notify the Media
Gateway Controller that a Termination or group of Terminations is about
to be taken out of service or has just been returned to service.
ServiceChange shall also be used by the MG to announce its availability
to a MGC (registration), and to notify the MGC of impending or
completed restart of the MG. The MGC may announce a handover to the

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MG by sending it a ServiceChange command. The MGC may also use
ServiceChange to instruct the MG to take a Termination or group of
Terminations in or out of service.
Descriptors
The parameters to a command are termed Descriptors. A descriptor
consists of a name and a list of items. Some items may have values. Many
commands share common descriptors. Descriptors may be returned as
output from a command. In any such return of descriptor contents, an
empty descriptor is represented by its name unaccompanied by any list.
In general, the text format of descriptors is as follows:
DescriptorName=<someID>{parm=value,
parm=value…}.
H.248 Packages
All the packages as per annex E of ITU-T recommendation H.248.1 version 2
are required to be supported by both MG and MGC.

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H.248 Signaling Procedures
The following part uses an example to illustrate a typical implementation of the
H.248 protocol. The diagrams of the call procedure abstractly display the interaction
between a media gateway and the media gateway controller instead of taking issues
like time graduation into account. The example is about a call set up between two
residential gateways. User A and User B are respectively connected to two residential
gateways RGW1 and RGW2, and the gateways are under the control of the same
media gateway controller. The example only describes a successful call, and it is
assumed that the gateways have registered on the media gateway controller. The
procedure is divided into two processes, namely call setup process and call backout
process.

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Call Setup Process
Call setup process

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1) MGC sends a Modify message to both gateways to detect the off-hook event on
the terminations.
2) It is assumed that User A hooks off first. After RGW1 detects the event, it sends to
MGC a Notify message in which the corresponding event information and detected
timestamp are contained. MGC returns a response message.
3) MGC sends a Modify command to RGW1, indicating to RGW1 to send dial tone to
User A. RGW sends dial tone to the user and meanwhile returns a response message.
4) User A hears the dial tone and begins to dial.
5) MGC receives the Notify message from RGW1 and begins to analyze the digits. It is
assumed that the called party is connected to RGW2 which is managed by the same
MGC. MGC creates a new context for RGW1 and adds a physical termination Term A
in it. If User B is idle, ring-back tone is sent to User A. At the same time, an
ephemeral termination is created and then added in the preceding context. The
connection domain IP address and the media domain port number of the ephemeral
termination are not specified. RGW1 creates a context whose ID is 1. The physical
termination Term A is added in the context. Meanwhile, an ephemeral termination
EphA is created and its IP address and port numbers are assigned. Then, RGW1
returns a corresponding response in which the IP address and the port number used
are indicated.
6) MGC sends a similar transaction to RGW2. RGW2 creates a context whose ID is2,
then it adds the physical termination Term B in the context; meanwhile,
RGW2creates an ephemeral termination EphB and returns a response message.
7) User B hooks off. RGW2 uses a Notify command requesting to report this event to
MGC. MGC also returns a Notify response.
8) MGC sends to RGW1 a message to stop sending ring-back tone to User A, and sets
the remote SDP information of EphA. The mode of both terminations is modified to
Send Recv (previously both created as RecvOnly mode). RGW1 returns a response
message indicating the success of the operation.
9) MGC sends a transaction to RGW2, indicating to stop ringing tone on Term B. After
the completion of the processing, RGW2 returns a response.

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10) The users can have a conversation. Once the call is terminated by either party,
the other party will hear busy tone.

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Call Backout Process
Call backout process
1) It is assumed that the calling party User A will terminate the call. RGW1 sends a
Notify message to MGC to report this event. MGC returns a response message of the
Notify command.
2) MGC generates a Modify command, indicating to RGW2 to play busy tone to User
B. The mode of both terminations is set to RecvOnly. RGW2 returns a response
indicating the success of the operation.
3) MGC directs RGW1 to remove both terminations from the context 1 and return
the statistics information of the ephemeral termination as the response.
4) User B hears busy tone and then hooks on. RGW2 reports a Notify message to

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MGC. MGC returns a corresponding response message.
5) The gateway sends a Subtract command to delete Term B and EphB from the
context 2. RGW2 also deletes the terminations from the context 2 and then returns a
response in which the statistics information of the ephemeral termination is
contained. Here, a call procedure ends. The terminations return to the initial status
and await a new call.

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VOP1372G-61
Overview
The VOP1372G-61 line card is designed to install with IES-6000/5112/5106M.
VOP1372G-61 provides aggregated 72 lines of Plain Office Telephone Service toward
PSTN network. Each telephone line interface, Foreign Exchange Subscriber (FXS)
connected with subscriber’s telephone set through copper wire ranged up to 5km.
The analog voice signal from subscriber was converted to packet voice and
transmitted toward called party through packet network. FXS line card uses H.248
protocol for network signaling to establish a voice call. Advance call features like
‘three-party conference call’, ‘call forward”, “call waiting”, etc. are integrated in the
Media Gateway Controller (MGC) to make NGN migration become easy in access
network deployment and management. Besides, to consider simplify access network
convergence toward unified IP packet network, FXS line interface can co-exists with
deployed ADSL or VDSL service in the same paired copper wire without disturbing
each other.
Parameters
The VOP1372G-61 line card is different from other xDSL series line cards. Following
table display the novel attributes in VOP1372G-61 only. Operators should be careful
with these parameters while deploying VoIP.
Item
Description
IP
An unique ip address for VOP1372G-61
DNS
Specify the ip address of domain name server
Route
Define the default routing entry and gateway of routing
VoIP H248 profile
1. Setup the ip address/domain name of MGC (Media Gateway
Controller). The default port number is 2944 but can be customized
in both MGC and line card.
2. “Transport” can be “UDP” or “TCP”, it’s used in order to choose
the data transport method configured on the media gateway
controller.
3. “Encode” is used to choose the text encoding method configured
on MGC.
4. “802.1P” (0~7) and “dscp” (Differentiated Service Code Point,
0~63) are used to define the QoS in VLAN tag and IP header
respectively.
5. “Inactivity timer” is a keep-alive timer from the MG to MGC. If

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there are no messages from the MGC to the MG, after each
inactivity-time out, the MG sends a notify packet to the MGC. The
units are 10 millisconds.
VoIP Interface
This setting allows operator to configure the system’s H.248
interfaces.
1. “Interface ID” is used in select the number of the H.248
Interface.
2. “Interface ID/Mask” is used in entering the H.248 interface’s IP
address and subnet mask, which could be the IP address to activate
signaling card in use to communicate with the MGC.
3. “VID” allows users to enter the number of the interface’s active
and backup signaling cards.
4. “MG name” allows users to enter a name for the media gateway,
could be up to 31 ASCII characters and spaces are not allowed.
5. “MG Port” is used to enter port number for the media gateway.
Each media gateway in an interface must use a different port. The
default port is 2944.
6.”H.248 Profile” allows users to select H.248 profile that media
gateway is going to use.
DSP profile
In this configuration operator can define what CODEC to use, how
much the play buffer and echo cancellation period.
1. Currently the available CODECs are G.711a, G.711mu, G.723,
G.726-16, G.726-24, G.726-32, G.726-40, G.729ab. Besides, both
caller and callee need to negotiate a consistent CODEC to be
applied in their voice conversation, thus the order of CODECs mean
the priority of selection.
2. “echotail” provides the echo cancellation period (i.e. 8, 16, 32
and 128 ms) to decrease the acoustic echo arising in circuit or
handset.
3. “playbuffer” is designed to store the received steaming and play
the audio, which can reduce the jitter. “min-delay” and “max-delay”
are the threshold of that buffer (10~500 ms, and max one ≧
mix.).
Country code
Some VOIP parameters/settings have different values according to
which country operator deploy the VOP1372G-61. To ease the
complexity of configuration, we build a list of packages for choice in
advance. If your country is not supported in the lists, please select a
similar region/nation.

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Configuration commands
Setup H.248 profile in IES-5106
To setup the VOP port, you need a template of H248 profile pre-configured, then,
apply it into specific port for phone communication.
Note: You should have a voice account already set up and have VoIP information
from your VoIP service provider prior to configure MG account on to the unit.
MSC1024GB> profile voip h248 set
usage: set <profile> <mgc-ip>|<mgc-dn>
[mgcport <mgc-port>]
[mgc2 off|{on <mgc2-ip>|<mgc2-dn>}]
[mgc2port <mgc2-port>]
[transport udp|tcp]
[encode long|short]
[pbit <pbit>]
[dscp <dscp>]
[it <it>] [prefix <prefix> <start-num> <suffix-len>]
[softswitch DEFVAL|zxss10-ss|nortel-cs1500|nortel-cs2000] [vbd off|on]
[rtpport <start-rtp-port> <end-rtp-port>]
[dmtimeout <start-timeout> <short-timeout> <long-timeout>]
[retrantime <init-retrantime> <min-retrantime>
<max-retrantime> <retran-window>]
[rfc2833 off|{on <payload-type>}] [t38 off|on][forcever off|on]

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<profile> : profile name, up to 31 characters
<mgc-ip> | <mgc-dn> : MGC IP or domain name, up to 63 characters
<mgc2-ip> | <mgc2-dn> : Secondary MGC IP or domain name, up to 63 characters
<mgc2-port> : Secondary MGC port, 1025~65535
<mgc-port> : MGC port number, 1025~65535
<transport> : transport protocol udp or tcp
<encode> : h248 coding type long or short
<pbit> : 802.1p bit for H.248 packet, 0~7
<dscp> : DSCP for H.248 packet, 0~63
<it> : inactivity timer, 0~65535 in unit of 10ms
<prefix> : ephemeral termination prefix, up to 31 characters
<start-num> : ephemeral termination suffix start number, up to 15
digits
<suffix-len> : ephemeral termination suffix number length,padding
zero at the front if not long enough.ranging from 0~15 zero to disable padding
<vbd> : VBD mode support enable/disable
<start-rtp-port> : Start of RTP port number, should be even, 4000~64000
<end-rtp-port> : End of RTP port number, should be even, 5000~65000
<start-rtp-port>~<end-rtp-port> at least 1000
<start-timeout> : digit map start timeout, 0~99 seconds
<short-timeout> : digit map short timeout, 1~99 seconds
<long-timeout> : digit map long timeout, 1~99 seconds
<init-retrantime> : initial retransmission timeout when the h.248 stack