GPRS and PPP

From: http://topic.csdn.net/t/20030528/15/1845691.html

 

Using GPRS modem to access the Internet, the current implementation method is to use PPP as a transit, the GPRS transmission layer is like this:
--------
IP/X.25
--------
Sndcp
--------
LLC
----------------
RLC
----------------
Mac
----------------
RF
----------------
 
Ms is on the left and BS is on the right. For Ms, IP support can be provided, either in me, Ta, or te, as long as there is an interface. However
Currently, no one will expose the sndcp interface for external use.
The modem is integrated with an IP address, while the IP address is a network-layer protocol that can communicate with the IP address of the network. The me IP address can be obtained through the internal GPRS protocol.
What about DTE communication? IP communication fails if you do not know the IP address of the DTE. Therefore, GPRS
The modem integrates the PPP protocol internally, so that the DTE can obtain the IP address from the GPRS Modem through PPP, while the GPRS
Modem acts as a forwarding rule. To put it bluntly, PPP is a bridge here.
The IP address obtained by modem is transferred to DTE. For more detailed and accurate information, check the GPRS protocol text.

 

After GPRS Modem supports PPP, on the DTE side, as long as ATD * 99 # (or other similar dial-up strings), it will immediately receive connect, and then GPRS
The modem is transferred to the PPP state machine and acts as a PPP
Server, DTE can obtain the IP address according to the common PPP operation, and then you can use the IP address operation. GPRS
The modem sends the IP packets obtained from PPP to the network through the internal GPRS protocol, and then the ggsn forwards the packets to the destination IP address.

 

The GPRS protocol is available in ETSI, such as 01.60/01.61/02.60/03.60/03.64/04.60/04.64.

 

The discussion is very lively. In fact, the essence of the problem lies in the conversion between various protocols and their timing. For GPRS itself, it can directly support IP, GPRS
There is no PPP channel between the modem and ggsn, but for DTE <-> GPRS Modem
Modem data transmission function, it provides PPP form of external (for DTE) interface is more reasonable, so that the original DTE resources can support GPRS without too much Modification
Modem. For example, you only need to establish a dial-up connection in the win series.
Remember, the GPRS Modem itself does not need to obtain the IP address from the server through PPP. It is the PDP thing, but it assigns this IP address to the DTE through PPP.
For xiaosheng80:
1. Is there an internal IP address first, which is sending an IP packet (? PPP package) process?
It is basically correct, but it is not an internal IP address. How can I use IP addresses for communication without IP addresses?

2. According to the old cat, GPRS Modem uses the PPP protocol to obtain an internal IP address and then acts as a PPP server.
Server to obtain an internal IP address, I would like to ask is that the future IP package also needs PPP encapsulation through GPRS
Is the modem sent out? Does Ms require a PPP client role to send a PPP package to BS?
Incorrect. GPRS
The modem does not use PPP to obtain the IP address. For DTE, the future IP package still needs to pass through the PPP package through GPRS
Sent by modem. The situation in MS is different, because you can obtain the IP address without PPP, and in MS, there are usually corresponding interfaces for you to directly send IP data.

3. Can you tell me what DTE actually means? (I feel fuzzy)
DTE (data (or digital ?) Terminal Equipment)
DCE (data (or digital ?) Circuit Equipment)