How does cRTP works between multiple routers ?

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Oct 21st, 2008
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Hi,


I understand the cRTP work link-by-link basis. Could anyone clarify me how does this works on the following senarios.


---R1---------R2---------R3---

1.

i. cRTP enabled on the interface of the R1 connected to R2.

ii. cRTP does not enabled on the R2 interfaces connected to R1 and R3

iii. cRTP enabled on the interface of the R3 connected to R2.


Will the R2 relay the cRTP packet from the R1 with out uncompressing the packet to R3 ?


2.

i. cRTP enabled on the interface of the R1 connected to R2.

ii. cRTP enabled on the R2 interfaces connected to R1

iii. cRTP does not enable on the R2 interfaces connected to R3.

iii. cRTP enabled on the interface of the R3 connected to R2.


Will the R2 relay the cRTP packet from the R1 with out uncompressing the packet to R3 ?


3. Does all the router interface ( R1,R2 and R3) must be configured for cRTP, for cRTP to work properly ?


Thanks.



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Istvan_Rabai Tue, 10/21/2008 - 07:31
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Hi Sathasivam,


"cRTP works on a link-by-link basis" means that you have to enable cRTP on BOTH ends of any link.


cRTP must be enabled on the both ends of the link between R1 and R2 and on both ends of the link between R2 and R3.


R2 will not relay cRTP packets to R3, it will normally route IP packets to R3, if properly configured.


If cRTP is enabled on both ends of the link between R1 and R2 only, then R2 will reestablish the original IP packet from R1 and normally route it to R3.


If cRTP is enabled on the both ends of the link between R1 and R2 and on both ends of the link between R2 and R3, then the following happens:


1. R1 router decides to route the original IP packet through the interface towards R2.

2. R1 will use cRTP to compress the packet header and will send it to R2.


3. R2 receives the cRTP packet and reestablishes the original IP packet.

4. R2 decides to route the original IP packet through the interface towards R3.

5. R2 will use cRTP to again compress the packet header and will send it to R3.


6. R3 receives the cRTP packet and reestablishes the original IP packet.

7. R3 decides to route the original IP packet through the interface towards its destination.


Cheers:

Istvan





ragulan_dms Tue, 10/21/2008 - 18:24
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Thanks a lot. In this case if we are going to make use of cRTP over the WAN IP link then Service provider also need to do the cRTP on their site in order to work properly, is it ?


Thanks..

Istvan_Rabai Tue, 10/21/2008 - 21:02
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If you enable cRTP on the WAN link to the Service Provider, then yes, the Service Provider has to enable cRTP on their side of the link as well.


You need to negotiate this with the Service Provider.


Cheers:

Istvan

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