VPN MPLS overhead

Answered Question
Mar 12th, 2007
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Hi,


I have two questions:


a) Anybody know how can I calculate the overhead in VPN MPLS network ?


b) And about Voice over VPN MPLS, how much Kbps need I reserve to each voice channel ?


TIA

Correct Answer by mheusinger about 10 years 2 months ago

Hi,


there is a minimum of two MPLS labels (i.e. 8 Bytes) per VPN IP packet in most cases.

To calculate the VoIP bandwidth per call you need to account for the additional 8 Bytes. F.e. Voice with G.729(a) 8 kbps voice data, 20 ms (=Bytes) per packet

PPP on the link (8 Bytes L2 overhead), 48 Bytes of overhead for MPLS and L3/4 (2 MPLS labels + IP/UDP/RTP):

76 Byte per voip packet, 50 packets per second

gives you 30.4 kbps per call.

A different L2 encapsulation results in different bandwidth requirements.


Regards, Martin

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Correct Answer
mheusinger Mon, 03/12/2007 - 07:20
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Hi,


there is a minimum of two MPLS labels (i.e. 8 Bytes) per VPN IP packet in most cases.

To calculate the VoIP bandwidth per call you need to account for the additional 8 Bytes. F.e. Voice with G.729(a) 8 kbps voice data, 20 ms (=Bytes) per packet

PPP on the link (8 Bytes L2 overhead), 48 Bytes of overhead for MPLS and L3/4 (2 MPLS labels + IP/UDP/RTP):

76 Byte per voip packet, 50 packets per second

gives you 30.4 kbps per call.

A different L2 encapsulation results in different bandwidth requirements.


Regards, Martin

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