Is it possible to do Qos in Voip IPsec using TOS bit value.How VOIP packet send when using IPSEC means can we read TOS value in between devices.My requirement is that I have to do QOS but my in between device understand TOS value only.
first be aware that the IPSec standard does imply to copy the TOS byte of the encrypted header into the new header. This means in case your VoIP packets are already marked the marking will remain though you do not see the content of the IPSec packets.
Setup policies based on the TOS marking and your VoIP gets preferential treatment.
The second feature you might need to use - only available at the tunnel headend - is QoS pre-classify. There the encrypting router keeps a copy of the original header in memory along with the encrypted packet. This way you can use the original header to specify f.e. RTP traffic should be prioritized.
one more thing: make sure that you calculate with the proper bandwidth per VoIP call. In the case of VoIP over IPSec it will mainly be determined by the overhead. A good starting point for this topic is:
Table of ContentsIntroductionVersion HistoryPossible Future
UpdatesDocuments PurposeNAT Operation in ASA 8.3+ SectionsRule Types
Network Object NATTwice NAT / Manual NATRule Types used per SectionNAT
Types used with Twice NAT / Manual NAT and Network Obje...
Table of Contents Introduction:This document describes details on how
NAT-T works. Background: ESP encrypts all critical information,
encapsulating the entire inner TCP/UDP datagram within an ESP header.
ESP is an IP protocol in the same sense that TCP an...