How to know flow of packet after be compressed

Asked by nguyen trong cuong on 2013-05-22

Hi, you can tell me how to send packet compressed in network, if the network devices (such as routers) do not support ROHC, can it be sent? i have problem to understand operation when compressed RTP/UDP/IP header of packet without ip header can be sent between 2 networks. Plz help me.

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rohc Edit question
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Last query:
2013-05-22
Last reply:
2013-05-23

Hello,

The way you transmit the ROHC packets on your network is up to you. It depends of your network and your use case. In general, you will transmit the ROHC packets above the link layer. On an Ethernet network, you might transmit them as payload of Ethernet frames. On a PPP link, you might want to transmit ROHC packets in PPP frames. In a satellite network, you might want to transmit then in ATM, MPE, ULE, GSE... frames.

If you want to transmit ROHC packets over the Internet, you need a way to tunnel the ROHC packets. IP hosts and routers won't understand the ROHC headers so they can not handle ROHC traffic directly. You can use an IP-IP, GRE, or even IP-UDP tunnel. The ROHC over UDP tunnel [1] performs the third option. The IP/ROHC tunnel [2] performs the 1st option.

Regards,
Didier

[1] http://rohc-lib.org/wiki/doku.php#rohc_over_udp_tunnel
[2] http://rohc-lib.org/wiki/doku.php#ip_rohc_tunnel

Atik (atik) said : #2

Hi Didier

As far as my understanding we cant use IP/ROHC tunnel behind NAT? so if i want to use ROHC behind nat i need UDP tunnel, right? is there any plan for udp tunnel to make as IP/ROHC Client/Server architecture.

Regards
Atik

> As far as my understanding we cant use IP/ROHC tunnel behind NAT?
> so if i want to use ROHC behind nat i need UDP tunnel, right? is there
> any plan for udp tunnel to make as IP/ROHC Client/Server architecture.

It depends on the NAT gateway. If IP packets with protocol field set to 142 are accepted, it should work.

For the ROHC over UDP tunnel application that is located in the app/tunnel/ directory in the sources of the ROHC library, there is no plan to make it more robust. It is a demo application.

If you require tunneling over UDP, you may enhance the IP/ROHC application to support UDP encapsulation in addition to IP. That could be an interesting feature. Changes would be limited. I would agree to merge them in the IP/ROHC sources.

Regards,
Didier

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