Jan 10, 2009

Drop and Insert(D&I)

The Drop and Insert (D&I) feature allows DS0 timeslots to be taken off one T1 interface and inserted into time slots of the other T1 interface. This feature is available in VIC and WIC applications.

    • Drop and Insert functionality does not support different framing and line coding on the two ports. Therefore, when a tdm-group is configured on the controller T1 or E1, the framing type between the two controllers must be the same. This is only for the tdm-group functionality of the VWIC card.

      Note: If you do configure two different framing types, this is the error message that the IOS sends to the console of the router:

      Voice_Router (config)#connect TDM t1 0/1 t1 0/2 %CONN TDM:  Framing type mismatch %CONN TDM: Endpoints are incompatible %CONN: Invalid Command
    • Drop and Insert timeslots do not need to be contiguous.

    • Drop and Insert of timeslots must be on the T1 controllers on the same 2-port VWIC, unless the gateway is Multiservice Interchange (MIX) enabled. When a gateway is MIX-enabled and the proper TDM network clock participation is configured, Drop and Insert of timeslots between T1 controllers on different VWICs is possible. Refer to Multiservice Interchange (MIX) for Cisco 3600 Series Multiservice Platforms for more details.

    • Drop and Insert uses tdm-groups.

    • Drop and Insert on a PRI can only be done if the entire PRI, including its D-channel is D&I'd. If individual channels must be D&I'd and other channel terminated, you cannot use PRI, you need to use CAS.

Non-Facility Associated Signaling(NFAS)

When a group of PRI interfaces are effectively bundled together, one D-channel can be used for the signaling data of all the combined B-channels, while the redundant D-channels can be used for data transmission. NFAS is only possible with a T1 PRI.

ISDN PRI NFAS是一種共用ISDN D channel(64 kb/s)的技術,而且只適用於T1 PRI。在NFAS中至少要設置一個Primary D channel,Backup D channel則是可有可無,如果有的話通常會將Primary & Backup D channel設置於不同的T1 controller上。假設在兩條T1上共有24 * 2 channels,我們可以只使用一條channel當共用的D channel來傳送控制訊號,剩下來的23 + 24 channels就可以當成B channels(64 kb/s)來傳送Data。

VoIP Router/Gateway Match Call Setup Element Parameters Order List

當我們在設定VoIP Gaetway時,我們必須要注意Router是如何match撥號內容來決定利用那一個dial-peer(很多人會誤解第一個檢查的是destination-pattern,事實上不然),甚至inbound和outbound dial peers也是完全不同的match rule:

Match Inbound Dial Peers Rule(by full string received in the setup request)

1. incoming called-number
首先Router或Gateway會嘗試去match call setup請求中被撥打的電話號碼(called number),因此會先檢查dail-peer中是否有設定incoming called-number參數。

2. answer-address
如果dial-peer中沒有incoming called-number參數符合被撥打的電話號碼(called number),Router或Gateway會嘗試去match call setup請求中的來電電話號碼(calling number)是否有符合某個dial-peer中設定的answer-address參數。

3. destination-pattern
如果dial-peer中沒有answer-address參數符合來電電話號碼(calling number),Router或Gateway會嘗試去match call setup請求中的來電電話號碼(calling number)是否有符合某個dial-peer中設定的destination-pattern參數。

4. port
如果incoming call setup請求來自於特定的voice port,利用這個voice port number來match inbound call leg中dial-peer設定的port參數。

5. Fist dial-peer added to the configuration(不是dial peer number最小的喔):
如果有多個dial peers設定了相同的voice port,Router或Gateway會match第一個加入到configuration中的dial peer。

6. dial peer 0
如果之前的步驟都沒有符合的條件,預設會進入到dial peer 0

PS: dial-peer 0無法改變預設參數。

Note: Dial peer 0 for inbound VoIP peers default configuration

  • any codec
  • ip precedence 0
  • vad enabled
  • no rsvp support
  • fax-rate service

Note: Dial peer 0 for outbound VoIP peers default configuration

  • no ivr application

Match Outbound Dial Peers Rule(by digit-by-digit basis)

1. destination-pattern
Router或Gateway利用dial-peer中設定的destination-pattern參數來決定要使用那一個dial peer進行路由。(The dial peer with closest match is selected)
2. 如果有多個dial peer符合情況相同,將會選擇擁有最小preference組態設定的dial peer。

3. 如果dial peer中的preference數值相同,那麼將會動態(dynamic)選擇任一個dial peer。

port or session target

- POTS dial peers使用port指令
- VoIP dial peers使用session target指令

#show dialplan number string
使用show dialplan number string指令來判斷那一個dial peer被matched特定撥號字串。這個指令會依照順序顯示所有已經被使用的matching dial peers。

Jan 8, 2009

我的第二張New Type CCIE獎牌(Service Provider)



New and Updated Cisco Certification Logos

目前網路上流傳兩個新版本的Cisco Certification Logo(如下圖),今天剛收到Cisco官方公告認證Logo即將更換的通知(如下文),可惜文中並沒有附上新Logo的圖片,所以也無法證實。連到Cisco認證中心去下載Logo,目前仍是舊的尚未更新,所以一切仍有待時間來證實。



08 January 2008

New and Updated Cisco Certification Logos

The Learning@Cisco organization is pleased to introduce new logos for its Cisco Career Certification Program. The logos were designed with input from the Cisco certified community, and represent the prestige and dedication defined by the program. Effective January 12, 2009, all certificates and plaques will include the new logos.

The new logos identify all levels of Cisco Career Certifications. In addition, all technology tracks are identified, allowing current and future professionals to distinguish themselves in the workplace and throughout the IT industry.

*Certified individuals can access the new logos for download by logging into the Certifications Tracking System at: www.cisco.com/go/certifications/login 

*All logo guidelines apply – new agreements must be signed to download the new images.

Jan 7, 2009

Clear Channel (G.Clear) Codec

G.Clear guarantees bit integrity when transferring a DS-0 through a gateway server, supports the transporting of nonvoice circuit data sessions through a Voice over IP (VoIP) network, and enables the VoIP networks to transport ISDN and switched 56 circuit-switched data calls. With the availability of G.Clear, ISDN data calls that do not require bonding can be supported.

In a transit application, because it is possible to have a mix of voice and data calls, not supporting G.Clear limits the solution to voice-only calls. The end-user application is in charge of handling packet loss and error recovery. This packet loss management precludes the use of clear channel with some applications unless the IP network is carefully engineered.

In an MGCP environment, the voice gateway backhauls the public switched telephony network (PSTN) signaling channel to the call agent. The call agent examines the bearer capability and determines when a G.Clear call should be established.


Note G.Clear codecs cannot be configured on a T1 channel associated signaling (CAS) trunk for incoming traffic. T1 CAS trunks use least significant bit-robbing for signaling, which causes the data to be incorrect and re-sent from high level protocols. Traffic on an incoming E1 R2 trunk can be configured.

If you configure the G.Clear codec under a VoIP dial peer, you cannot transmit and receive voice traffic with that dial peer on the voice gateway router. The G.Clear codec does not accommodate voice services like dial tone or ring-back tone.