Were you disgusted at ATM adaptation layer?

Well, the material of the study of today's chief telecommunications engineer is an ATM, too. The ATM and the adaptation layer call AAL for short today. AAL is a layer that hits the sub-layer in OSI reference model's data link layer. When you allow me to quote the explanation of the type of AAL from Wiki easily

AAL1 connection type and constant bit rate. Standard for communication of mass animation such as video conferencing telephones. To use one octet of payloads for the control of the order of transmitting the cell, real data becomes 47 octets. It is used in premises LAN.

AAL2 connection type and variable bit rate. Standard for low-speed voice sign. It is allowed to multiplex two or more traffic to one cell to decrease jitter's (swing the delay) influence by assembly and the restoration of the cell, and to send before the cell is filled.

AAL3/4 connectionless type and constant bit rate. Standard for for data communication. AAL3 and AAL4 were integrated by moving the connection setting to a high-ranking layer though it originally proposed AAL3 as a connection type and AAL4 was proposed as a connectionless type. To use four octets of payloads for high-ranking layer PDU information, real data becomes 44 octets.

AAL5 connectionless type and variable bit rate. Standard by which AAL3/4 is simplified. All payloads can be used for real data by assuming a positional detecting function of a high-ranking layer to be only a finality part. It is widely used as large area LAN with Ethernet over ATM, IP over ATM, and PPPoA (Point-to-Point Protocol over ATM). ･･･. It is so. Then, it is based and today's material is [kochira] ↓↓.




- ATM adaptation layer (AAL)



The leased circuit service etc. are used to communicate on the ATM network being classified into service class A pseudo.. resemblance of existing line service for the communication of the fixed speed type. AAL type 1

These sentences are correct.
- AAL type 1 It communicates like the leased circuit service etc. on the ATM network being classified into service class A for the communication = fixed speed type by pseudo.. resemblance of existing line service.



AAL type 2 is used to communicate of the real time character's at a changeable speed not being demanded ..for a low-speed voice-data communication...

These sentences are wrong.
- AAL type 2 is for a low-speed voice-data communication, and real time AAL for the communication from which the character is demanded at a changeable speed.
- Type 2 is low-speed though type 1 is a fixed speed at a changeable speed ･･･ However, the character is in real time demanded naturally because it uses it for the voice-data communication.




AAL type 3/4 is hardly used from becoming of AAL type 5 with few overheads or more the main current for the data communication for the data communication.

These sentences are correct.
- The AAL type is hardly used from becoming of AAL type 5 with few overheads or more the main current for the data communication for 3/4= data communication.



Isn't today's problem comparatively comprehensible?However, correct sentences that become livers of the layer, changing sentences for a moment in the part like "Extra", and setting questions do doing by being ･･･ Then, around here today

Outline of connected processing of SIP used with VoIP net

Well, because the knowledge of SIP has the part that is already common sense in the network industry and the telecom industry, the chief telecommunications engineer's examination knows the minimum any more though thinks the problem of SIP to be frequent occurrence.

And, it is not the one that today's material judges "Corrections of sentences" as usual, and it is good ..only reading for the time being... The level level of today's problem doesn't become work as written at the beginning though the substantial request message of SIP if it doesn't know.

I do not understand the meaning even as for the packet capture because it will not satisfactorily use the protocol analyzer. Then, today's material is [kochira] ↓↓.



- Outline of connected processing of SIP used with VoIP net



The message of SIP includes request (demand) message and response (response) messages. As for the request message, six kinds are standardized by RFC3261 among these.

- There is request (demand) message and response (response) message = messages of SIP.



The request message of SIP is said 【 method 】 in general, and the main usage is as follows.

- In general, the request message of SIP is said 【 method 】.



A:　INVITE is the first request message used to establish the session between user agent.

- The first request message used to establish the session between INVITE = user agent



B:　【ACK】 is a request message used to confirm the response message to INVITE was received, and the media session can be established by 【ACK】 for the communication.

- 【ACK】 In the request message used to confirm the response message to = INVITE was received, the media session can be established by 【ACK】 for the communication.



C:　BYE can be sent from either the caller or the receiver by the request message used to end the set media session.

- It is possible to send it from either the caller or the receiver by the request message used to end the media session BYE = set.



D:　CANCEL corresponds to breaking the connection before the other party responds when calling it before the media session is established by the request message used to discontinue setting.

- It corresponds to breaking the connection before the other party responds when calling it before the media session is established CANCE L = by the request message used to discontinue setting.



E:　When the user agent registers 【URI】 that is my location information (location information) and Internet Protocol address to the SIP network, RESISTER is used.

- When RESISTER = user agent registers 【URI】 that is my location information (location information) and Internet Protocol address to the SIP network, it is used.



F:　When the user agent inquires the ability and the state to other user agent and 【 proxy 】 server, OPTIONS is used.

- When OPTIONS = user agent inquires the ability and the state to other user agent and 【 proxy 】 server, it is used.



Well, how though this blog is not considerably seen easily because the table is not used? ..sleep.. then, a person not good at the problem related to SIP : around here today because there might be a hindrance also in the business not to mention the examination if it doesn't come to be able to judge the state by seeing "CallingSequence" though it was a problem of the request message of SIP ..study hard...

About VP and VC of the ATM

Yes, I think that today's chief telecommunications engineer's material also goes by the ATM. In today's problem, virtual passing VC is a virtual channel in VP in VP and VC of the ATM. Is VP (virtual pass) a virtual transmission line in short and it only have to be thought the transmission line of the ATM and SDH?It is a group of a logical virtual line that mutually connects the edge tune. VC (virtual channel) is a road to put it briefly as shown in data. A few VC can be passed through one VP and good transmission of efficiency can be done. Then, today's material is [kochira] ↓↓.



- VP of ATM (virtual passing) and VC (virtual channel)



In the sending terminal, the VCI value in which the receiving terminal that is the address is indicated directly is set to the VCI field of the ATM cell.

These sentences are wrong.
- VCI doesn't indicate the address directly. VCI decentralization only arranges and is used only to distinguish the channel that each cell belongs in the done each switch.
- Only the VCI value shows the channel, and even the terminal is not shown.



In the method of setting VC, there is PVC method set like the SVC method and the lease line, etc. of the setting at each communication based on the contract.

These sentences are correct.
- Method of setting only SVC = to communicate, and liberating virtual channel with end of communication
- Method of assuming virtual channel to be to be remain set for a long term by PVC = contract etc.



In the ATM network where the VP crossing connection was used, VC is set with the ATM switch in the terminal of VP.

These sentences are correct.
- Naturally, the setting of VC is a switch in the terminal of VP.



VC accommodated by VP besides VC accommodated by a certain VP of the output port of the ATM switch can use the same VCI value.

These sentences are correct.
- Yes, it is possible to use it.



さて、いかがでしたか？明日からの週末も気を抜かずに伝送交換の勉強がんばってくださいね。それでは今日はこの辺で。