DDN Network Service and user Inbound speed

I. Network Service category

DDN network services are divided into three types: dedicated circuit, frame relay, and compressed voice/G3 fax services. DDN's main business is to provide users with medium and high-speed, high-quality point-to-point and point-to-point digital circuits (dedicated circuits); based on dedicated circuits, the Frame Relay Service Module (FRM) is introduced to provide frame relay services with permanent virtual circuit (PVC) connections. The voice service module (VSM) is introduced to the user's inbound network) provides the compressed voice/G3 Fax Service. On DDN, The Frame Relay Service and the compressed voice/G3 Fax Service can be considered as value-added services based on the dedicated circuit service. For the compressed voice and G3 fax services, the network value can be added, or the user value can be added.

1. dedicated circuit business
(1) Basic dedicated circuit

The basic dedicated circuit provided by DDN is a point-to-point dedicated circuit with a specified speed.

(2) Special circuits with specific requirements

To meet the special needs of users, the DDN network can also provide dedicated circuits with specific requirements, such:

① High Availability TDM Circuit
For important users, DDN networks should improve the availability of TDM circuits through measures such as path backup and high priority.
② Dedicated circuit with low transmission latency
For dedicated circuits that require low transmission latency, DDN networks are connected by selecting the ground path to avoid the introduction of additional transmission latency of satellite circuits.
③ Dedicated Timing Circuit
The User agrees with the network on the connection time and end time of the dedicated circuit, and uses the dedicated circuit regularly.
④ Dedicated multi-point circuit
Dedicated circuit service between N users. When N is greater than 2, it is called multi-point dedicated circuit service. Multi-Point dedicated circuits can be divided into multiple broadcast points, two-way multi-point and N-direction multi-point dedicated circuits.

(A) Dedicated broadcast multi-point circuit
A dedicated broadcast multi-point circuit is a transmission path that only has one broadcast source user. For example, you can use this service to publish a stock market.
(B) Bidirectional Multi-point dedicated circuit
There is a control station user, and the others are the auxiliary station users. The information sent by the control station is received by the auxiliary station. The information sent by any auxiliary station is received by the control station, and there is no information path between the auxiliary stations. Using Bidirectional Multi-Point circuit service, you can build a computer network in training/selection mode.
(C) N-direction multi-point dedicated circuit
Among N users, any user sends messages to all other users. The N-direction multi-point dedicated circuit is used for conference business. DDN must be able to provide broadcast multi-point and bidirectional multi-point dedicated circuit services. For N-direction multi-point dedicated circuit, you can add a multi-point control unit device when the DDN node is not available.

2. Frame Relay Service
(1) equivalent frame relay network in DDN

The Frame Relay Service on DDN is implemented by setting the frame relay module on the DDN node, between Frame Relay modules (FRM), and FRM and frame mounting/dismounting (FAD) modules are interconnected through basic dedicated circuits. FRM, FAD, and dedicated circuits between them are specifically used for Frame Relay services. Their settings can be independent of the attached DDN network, that is, they can be based on the distribution of Frame Relay users and the needs of Frame Relay business, set the FRM, FAD, and their capacity at the selected DDN node. The dedicated circuit and capacity between FRM and FAD are also set according to the needs of the Frame Relay Service, instead of setting FRM and FAD for each DDN node, not each digital channel must have a dedicated circuit for the Frame Relay Service. In this way, from the perspective of Frame Relay Service alone, it can be considered that a frame relay network exists logically in DDN.

(2) Access of Frame Relay users

There are two types of anti-frame service users: one is the user with the ITU-T recommendation Q.922 "frame-based bearer service ISDN data link layer specification" interface, called the anti-frame service user. The other type is non-Q.922 users. Frame Relay users can directly connect to FRM, while non-Frame Relay users are connected to FRM through FAD. FAD performs frame loading and splitting and protocol conversion. FRM performs the frame relay function, that is, it stores the forwarding frames according to the data link connection identifier (DLCI) in the frame header of the frame.

(3) Frame Relay PVC route table

The frame relay PVC route table is a comparison table between the physical paths on frm and the dlci in each frame transmitted. The frame relay PVC route table is uniformly formulated by the network management control center and installed into each FRM.

The DLCI values used between FRM instances are defined in the PVC routing table by the Network Management Control Center. Each FRM performs DLCI Conversion Based on the route table to form virtual channel connections between users.

3. compressing voice/G3 fax services

DDN provides this service by setting the voice service module (VSM) in the user's inbound network. Between VSM, the DDN Network provides end-to-end full digital connections, that is, the number/mode conversion components for voice encoding and signaling processing are no longer introduced in the middle. VSM can be set on a node in DDN or on your own.

　

Ii. User Inbound speed

For the above businesses, the user network access rate provided by DDN and the connection between users are shown in the following table. For dedicated circuits and circuits that enable voice/G3 fax services, the network access rate must be the same for interworking users. For frame frames, the FRM in DDN has the function of storing and forwarding frames, allows users with different inbound speeds to communicate with each other.

　

Business type	User Inbound speed (kbit/s)	Connections between users
Dedicated Circuit	2048 N × 64 (N = 1 ~ 31) Sub-rate: 2.4, 4.8, 9.6, 19.2	TDM connection
Frame Relay	9.6, 14.4, 19.2, 32, 48 N × 64 (N = 1 ~ 31) 2048	PVC connection
Voice/G3 Fax (note)	User's 2/4-line analog inbound (DDN provides additional signaling information transmission capacity) 8, 16, and 32 kbit/s channels	TDM connection with signaling transmission capability

NOTE: For the conversation audio/G3 Fax Service, the 8, 16, and 32 kbit/s listed in the table refer to the voice compression encoding rate. After the transmission signaling and control information are attached, the actual usage rate of each voice encoding path is slightly higher. For example, to add 0.8 kbit/s, the TDM connection rate with signaling transmission capability on DDN is 8.8 kbit/s, 16.8 kbit/s, and 32.8 kbit/s.