 Now we are going to look at some more specifics of The flow state aware transport using the flow aggregates and we are going to look at the signaling aspect of it Then the network functions which perform the signaling The QS structure which is defined to exchange the signaling information between the end hosts as well as the network elements We will quickly look at the use case as well So now signaling Protocols which are used for the FSA transport in NGNs Are based on the extension or modification of existing protocols normally what happens is that the existing protocols at the Data link layer like Ethernet or at the network layer like IP have their own default headers now above These headers some additional information is encapsulated to exchange the QS information now this activity of using IP or Ethernet is Something known as in band signaling these additional fields actually provide some Parameters their values and some indication like request response Deny accept etc to implement the QS for each flow When when when this flow based QS service provisioning starts then there is a requirement to exchange the structure of the QS parameters Which has to be understood by both these parties? So there is a QS structure which is carried by the first packet now as we know that IP is Something that is connectionless and so is Ethernet So how exactly are we going to make sure that the packet carrying QS information is not lost? And the QS parameters are actually put across then some kind of retransmission strategy or timer mechanism can be introduced All we are discussing is the signaling in band which is implementing the flow state Aware QS provisioning through flow aggregates, but earlier if you recall we saw some explicit role of the network elements And the services such as the service control function in the service stratum and the resource and admission control functions at the Transport stratum. So our scope for now is the in band signaling Now there is a possibility that the flow state aware network, which is supposed to provide the Flows with certain QS may or may not support required QS It means some kind of plan B or an alternative arrangement should also exist so the QS requirements once transported from the end host to the network and to the destination may undergo some some change Once the QS requirements are not met by FSA or sometimes the FSA may deny or out altogether discard the packets containing the QS structure information Because the QS structure is not compatible or it is not provided by the network altogether So the network functions actually have to take into consideration the provisioning of service the Request to modify alter the service request or altogether discard it the QS structure Which is exchanged between the endpoints and the FSA aware network include the Available rate which is the rate assigned from the network to the flow So it means whatever user may request at the end of the day The user is going to receive what the network can offer then guaranteed rate is basically the rate which is the minimum Service requester is expecting to be provided Of course, it is the lower limit or the lower bound to the rate That a user cannot get anything other than this So it means that once the guaranteed rate is not provided Then there is a likelihood that this flow state aware QS provisioning might not happen altogether Then the preference priority is the priority of a flow within the flows Belonging to the same flow aggregate then we have the change or Direction basically it is a basically a request or a response mechanism that is implemented to Share information between these network elements and the endpoints then the type of flow state aware transport It actually involves the available rates the maximum rates provided by the network including ABR VBR CBR, etc. Then we have the second QS structure, which is attached now It is quite interesting sometimes the QS provisioning has to be Incorporated anyways so the end host knowing that QS could be denied by the network if it is not met Then can include a secondary QS structure just to make sure well if the network does not agree with the first one It can switch to the second one then we have the security structure in case some kind of security functionality such as confidentiality integrity and Authenticity is to be provided by the network then security structure has to be provided as well It is beyond the scope of QS, but these days QS actually is expected to contain Securities as well then the QS structure version because with IP version 4 IP version 6 Different QS structures can be implemented then it is the marker, which is a single bit once it is a zero It is set by the sender but if the Flow state aware node, which is part of the FSA network Changes the QS request then it it enables or sets the flag then we have the flow sender depth Usually what happens is when end-to-end request is sent from the end host to the FSA network It can enter into a network, which has proxies inside. It means that Whenever a network is entered, which has a proxy server Then the flow sender depth is set to a one and it is incremented So it means that the known more number of proxy based networks are entered It means that this counter is going to be incremented when the network is exited We know when we are talking about network. We are talking about the Aggregation network, which is a domain so a domain that is implementing the proxy service is Something that is going to increment the counter and vice versa So finally concluding. Let's look at a use case here. We have a sender Which is making a request At the maximum rate so it means maximum rate is the maximum Rate that the network can offer The The receiver is going to be a sent this request In the form of a QS structure the of course the receiver is going to be the end host but it is This QS structure is shared from the sender to the receiver via the FSA network with FSA enabled nodes So this is going to contain the type That is the maximum rate And the and the user insists that it's going to be guaranteed rate and it gives a preference priority for its own flow If a user does not get a response from the network It means that the FSA is not interested in providing it This service it is attempted three times It's it is empirical. Otherwise it can have any value, but for the sake of Implementation the default value is three If there is no response even after three times then the traffic the multimedia traffic is sent without the FSA enabled