Hi thr,

I have few doubts on ppp0 interface and Ethereal tool which are listed as below.

1. When we connect data card or phone as a modem to our laptop then where does ppp0 interface gets established?
In my reading I found that ppp0 interface is established between computer and data card.

2. Once the ppp0 interface gets established and if we run ethereal tool on the laptop which packet it logs. The packet that are sent/receive from/to kernel to data card or the packet that are sent/receive from/to data card or traffic sent/receive between data card and socket?

3. In Fedora core 3 if I send icmp packet of size greater than 5780 bytes on ppp0 interface I get message "ping: sendmsg: No buffer space available". What does this error means? Where buffer gets full? Whether it is kernel buffer, data card buffer or socket buffer of sender.
Who generates this error ping, kernel, socket or data card.
But in wireline n/w I am able to send packet of size 65535 bytes. Then who genereates above message in case of ppp0 interface?

4. What happens exactly when ping sends a packet of any size? Who creates packet of specified size? whether it ask kernel to create packet of specified size and then kernel write into socket or ping program creates a packet.

5. In my experiments on ppp0 interface for higher packet size say 5780 bytes where 100 packets are sent ping statistics show 100 packets sent on sender machine. But Ethereal log shows less than 100 packets are sent. Why Ethereal did not log all 100 request packets?

This is what I think. Please tell me if I am correct or wrong.
Etheral listens traffic between socket and data card. Ping write packets to socket. According to ping ping sends all 100 packet but may be buufer in the socket gets full and it is not able to send all 100 packets and it drops the packet and hence Etheral did not log all 100 packets. When the buffer in socket gets full it sends "ping: sendmsg No buffer space available message"

But then the question arises how come in wireline n/w socket is able to send packet of size 65000 bytes.

6. Does socket has its own buffer size? If yes then What is the default socket buffer size?

If anyone has answer to any of the above questions please reply me.

Thanks in advance
Regards,
Kavita