Learning IOS and JUNOS

In-path Networks The Steelhead appliance can be physically connected to access both ports and trunks. When the Steelhead appliance is placed on a trunk, the In-path interface has to be able to tag its traffic with the correct VLAN number. The supported trunking protocol is 802.1q (“Dot1Q”). A tag can be assigned via the GUI or the CLI. The CLI command for this is: HOSTNAME (config) # in-path interface inpathx_x vlan

Interface Naming Conventions The interface names for the bypass cards are a combination of the slot number and the port pairs ( _ , _ ). For example, if a four-port bypass card is located in slot 0 of your appliance, the interface names are: lan0_0 , wan0_0 , lan0_1 , and wan0_1 respectively. Alternatively, if the bypass card is located in slot 1 of your appliance, the interface names are: lan1_0, wan1_0, lan1_1, and wan1_1 respectively.

Peering Rules Configuring peering rules defines what to do when a Steelhead appliance receives an autodiscovery probe from another Steelhead appliance. As such, the scope of a peering rule is limited to a server-side Steelhead appliance (the one receiving the probe). Note that peering rules on an intermediary Steelhead appliance (or server-side) will have no effect in preventing optimization with a client-side Steelhead appliance if it is using a fixed-target rule designating the intermediary Steelhead appliance as its destination (since there is no auto-discovery probe in a fixed-target rule).

Different Types and Their Function • Pass Through. Pass through rules identify traffic that is passed through the network unoptimized. For example, you may define pass through rules to exclude subnets from optimization. Traffic is also passed through when the Steelhead appliance is in bypass mode.(Passthrough might occur because of in-path rules, because the connection was established before the Steelhead appliance was put in place, or before the Steelhead service was enabled.) • Fixed-Target. Fixed-target rules specify out-of-path Steelhead appliances near the target server that you want to optimize. Determine which servers you want the Steelhead appliance to optimize (and, optionally which ports), and add rules to specify the network of servers, ports, port labels, and out-of-path Steelhead appliances to use. Fixed-target rules can also be used for in-path deployments for Steelhead appliances not using EAD. • Auto Discover. Auto-discovery is the process by which the Steelhead applian

Common Ports Ports Used by RiOS Port Type 7744 Data store sync port 7800 In-path port 7801 NAT port 7810 Out-of-path port 7820 Failover port for redundant appliances 7830 Exchange traffic port 7840 Exchange Director NSPI traffic port 7850 Connection Forwarding (neighbor) port 7860 Interceptor Appliance 7870 Steelhead Mobile

NFS Optimization You can configure Steelhead appliances to use Transaction Prediction to perform application level latency optimization on NFS. Application-level latency optimization improves NFS performance over high latency WANs. NFS latency optimization optimizes TCP connections and is only supported for NFS v3. You can configure NFS settings globally for all servers and volumes, or you can configure NFS settings that are specific to particular servers or volumes. When you configure NFS settings for a server, the settings are applied to all volumes on that server unless you override settings for specific volumes. • Read-ahead and read caching (checks freshness with modify date) • Write-behind • Metadata prefetching and caching • Convert multiple requests into one larger request • Special symbolic link handling

自2009年6月24日開始，CCNA Voice認證分為兩種選項。一個叫做commercial option，另一個則是enterprise option。 CCNA Voice Certification enterprise option ： 只要你擁有CCNA認證並且通過CVOICE 6.0考試(642-436)就可以取得CCNA Voice認證資料。 CCNA Voice Certification commcerical option ： 只要你擁有CCNA認證並且通過IIUC考試(640-460)就可以取得CCNA Voice認證資料。 所以…如果各位有心要取得CCVP認證的話，事實上是可以不用先考CCNA Voice(IIUC)的，因此我就無緣無故地突然收到了Cisco寄來的CCNA Voice證書(之前考過CVOICE 6.0)。 On June 24th, 2009, Learning@Cisco announced program changes to the CCNA Voice certification. There are now two options available for candidates wishing to achieve their CCNA Voice certification: A commercial option and an enterprise option. The new CCNA Voice Certification enterprise option assesses skills/knowledge related to the Cisco Unified Communications Manager 6.0 (CUCM 6.0). It is typically employed by large organizations such as governments, large companies, and colleges. Passing the CVOICE #642-436 exam will meet the requirements for this option. The CCNA Voice Certification commercial option continu

Nagle's algorithm From Wikipedia, the free encyclopedia Nagle's algorithm , named after John Nagle , is a means of improving the efficiency of TCP/IP networks by reducing the number of packets that need to be sent over the network. Nagle's document, Congestion Control in IP/TCP Internetworks ( RFC896 ) describes what he called the 'small packet problem', where an application repeatedly emits data in small chunks, frequently only 1 byte in size. Since TCP packets have a 40 byte header (20 bytes for TCP, 20 bytes for IPv4 ), this results in a 41 byte packet for 1 byte of useful information, a huge overhead. This situation often occurs in Telnet sessions, where most keypresses generate a single byte of data which is transmitted immediately. Worse, over slow links, many such packets can be in transit at the same time, potentially leading to congestion collapse . Nagle's algorithm works by coalescing a number of small outgoing messages, and sending them all at o

2009-07-28 工商時報 【林淑惠】 　一直以來，市場對於WiMAX前景，始終不抱樂觀，甚至對於政府推動M台灣，想讓台灣藉由WiMAX、在國際電信市場建構特有的優勢產業、都不見得認 同，但幾年下來，透過政府主動搭橋、民間團體從旁協助，確實也讓台廠掙得不少不少從WiMAX湧出的訂單及商機，尤其是大陸及新興市場，隱藏的商機更為可 觀。 　例如，中國移動從今年起，在各省分公司積極推動結合TD、WiFi、WLAN等無線技術服務的「無線城市」計畫，光從中移動廣東分公司與廣州市政府簽署「資訊廣州」策略合作協定內容來看，中移動 未來 3至5年內便將投入180億人民幣建設無線城市網路。 　不僅如此，中移動還準備投資66億人民幣在廣州建設一個整合研發與人才培訓的技術研發中心、準備拉進500家全球先進資訊服務供應商進駐，初估 未來 將進一步帶動200億人民幣的產業鏈商機，台商從這裡，應當可以找到不少商機。 　另外，中國移動河南分公司（河南移動）也與鄭州市政府簽訂合作協議，要在未來5年投資90多億人民幣打造「無線城市」，總計大陸為期3到5年的「無線城市」建設期，將是繼大陸電信三雄開展3G服務之後，最讓人 眼睛 一亮的大建設，而且就在8月，中國移動總裁王建宙來台時，也準備就這塊終端設備、進行商務考察，並拜訪多家網通廠。

Half Open connections Connections that haven’t been completely established yet are in the "Half-open" state. Every new connection starts off in the half open state but quickly transitions to the established/flowing state if there are no errors in connecting to the peer SH and endpoint server. Thus, this count should typically be low. However in the case of a SYN or probe attack, the SFE times out (TCP connection establishment timeout) attempting to connect to the fictitious endpoint server, the half open connections will exist for the duration of the connection attempt. The same holds true when there is a network partition between the SFE and server or when the server fails to respond. If the Half-Open connection count on a Steelhead are consistently high and an issue is suspected, please provide a sysdump to help facilitate investigating the issue. Half closed connections Intercepted connections that are tearing down or where the client/server has performed a TCP half-close