Showing posts from 2009

New CCIE Voice Locations in Asia

New CCIE Voice Locations in AsiaIn recognition of the demand for CCIE skills development in Asia, the CCIE program is pleased to announce new CCIE Voice lab exam test center openings in three major cities:
BeijingHong KongBangaloreThe CCIE program serves a growing number of worldwide candidates by covering all major regions with the latest test center resources. In addition to the three new locations, CCIE Voice lab exam locations include:
San JoseRTP (North Carolina)BrusselsSydneyTokyo

Hierarchical Packet Fair Queueing (H-PFQ) vs Hierarchical Fair Service Curve (H-FSC).

While most of the previous research has focused on providing Quality of Service (QoS) on a per session basis, there is a growing need to also support hierarchical link-sharing, or QoS guarantees for traffic aggregate (such as those belonging to the same organization, service provider, or application family). Supporting QoS for both single sessions and traffic aggregates is difficult as it requires the network to meet multiple QoS requirements at different granularities simultaneously. This problem is exacerbated by the fact that there are no formal models that specify all the requirements.

We have developed an idealized model that is the first to simultaneously capture the requirements of the three important services in an integrated services computer network: guaranteed real-time, adaptive best-effort, and hierarchical link-sharing services. We then designed two hierarchical scheduling algorithms, Hierarchical Packet Fair Queueing (H-PFQ) and Hierarchical Fair Service Curve (H-FSC).…

EMC Data Domain

Data Domain提供給客戶的是建立Disk Staging備份架構中的一種以硬碟為備份資料儲存及恢復的Hardware Appliance. 它以串列SATA硬碟技術為主, 並提供DD OS作業系統軟體, 使得它不只是一種含有RAID 6功能的低價位高性能磁碟陣列外, 並且它的 "容量最加化存儲技術(Capacity Optimized Storage)" 大量減少實際資料所需的儲存空間 和 "資料零缺點架構(Data Invulnerability Architecture)"技術, 提供前所未有的資料多重保護功能. 更近一步的將 "容量最加化存儲技術" 發揮在建立異地備援架構上的資料複製, 讓客戶不在為了傳統資料保護架構缺點而煩惱, 這三大獨特功能更是讓每GB資料儲存成本接近磁帶自動化備份設備, 但卻能提供給客戶比傳統資料保護更完善的機制與架構. 簡單說, 它是一種為了符合專業備份及恢復設備的特殊要求而設計的產品.

容量最加化存儲技術(Capacity Optimized Storage)-備份資料拆解-只儲存獨特的資料碎片, 大幅減少所需的空間需求及成本-

EMC Avamar

EMC Avamar是一套針對遠端辦公室備份環境,內建重複資料刪除技術的備份軟體,透過前端代理程式的處理,可刪除備份資料中的冗餘,大幅降低備份資料傳輸佔用的網路頻寬,並節省儲存媒體的消耗量。

系統支援非常廣泛,代理程式可支援Windows、Linux、Solaris、HP-UX、AIX等主要Unix平臺,Mac OS X以及VMware等作業環境,另外也能支援DB2、Exchange、SQL Server、Oracle等應用程式。可適應大多數的企業IT環境。

Avamar源自Avamar被EMC併購前的Axion,是一套很典型的集中控管式備份軟體,採用「用戶端—伺服器端」的架構。Avamar伺 服器端的主程式必須安裝在IA32平臺的Red Hat Enterprise Linux AS/ES 3.0上,而用戶端代理程式的支援就非常廣。安裝完成後,可由管理者從Avamar伺服器上,啟動裝有代理程式的前端系統,執行備份作業,將指定的資料經 網路送到Avamar伺服器控制的儲存設備上。除了由伺服器端發起備份外,也能由前端系統的使用者自行啟動備份。管理者還能從其他電腦透過瀏覽器登入 Avamar伺服器,執行各項作業。

由於Avamar本質上是一套備份軟體,除了重複資料刪除這個功能外,其餘功能均與一般軟體類似,如作業狀態監控介面、報表、儲存區管理功能等, 操作算是相當簡便。為簡化建置與維護的問題,EMC銷售時可提供預載了Avamar的應用伺服器,原廠本身也驗証過IBM、HP、Dell等廠商數款市售 伺服器的硬體相容性。

冗餘資料的刪減是Avamar的最大特色,透過區塊級的比對能有效剔除資料底層中的重複部份。由於比對動作是由代理程式執行,因此送到網路上的資 料已經是經過De-Dupe,故能大幅縮減對傳輸頻寬的需求;而且代理程式不僅只是比對前端主機上的資料,還能將前端資料的特徵值,比對已儲存在伺服器上 的現有資料的特徵值,因此比對範圍是整個Avamar的儲存區域,這也就是所謂的「全域壓縮」。


Riverbed Steelhead QoS Class Queue Methods

Optionally, select one of the following queue methods for the class from the drop-down list:
SFQ. Shared Fair Queueing (SFQ) is the default queue for all classes. Determines Steelhead appliance behavior when the number of packets in a QoS class outbound queue exceeds the configured queue length. When SFQ is used, packets are dropped from within the queue in a round-robin fashion, among the present traffic flows. SFQ ensures that each flow within the QoS class receives a fair share of output bandwidth relative to each other, preventing bursty flows from starving other flows within the QoS class.FIFO. Transmits all flows in the order that they are received (first in, first out). Bursty sources can cause long delays in delivering time-sensitive application traffic and potentially to network control and signaling messages.MXTCP. Has very different use cases than the other queue parameters. MX-TCP also has secondary effects that you need to understand before configuring:When optimized traff…

Riverbed Steelhead QoS Classification for the FTP Data Channel

QoS Classification for the FTP Data Channel
When configuring QoS classification for FTP, the QoS rules differ depending on whether the FTP data channel is using active or passive FTP. Active versus passive FTP determines whether the FTP client or the FTP server select the port connection for use with the data channel, which has implications for QoS classification.

Active FTP Classification
With active FTP, the FTP client logs in and issues the PORT command, informing the server which port it must use to connect to the client for the FTP data channel. Next, the FTP server initiates the connection towards the client. From a TCP perspective, the server and the client swap roles: The FTP server becomes the client because it sends the SYN packet, and the FTP client becomes the server because it receives the SYN packet.
Although not defined in the RFC, most FTP servers use source port 20 for the active FTP data channel. For active FTP, configure a QoS rule on the server-side Steelhead appliance…

Riverbed Steelhead Adaptive Data Streamlining Modes

Default This setting is enabled by default and works for most implementations. The default setting: Provides the most data reduction.Reduces random disk seeks and improves disk throughput by discarding very small data margin segments that are no longer necessary. This Margin Segment Elimination (MSE) process provides network-based disk defragmentation.Writes large page clusters.Monitors the disk write I/O response time to provide more throughput.SDR-Adaptive Specify to include the default settings and also.Balances writes and reads.Monitors both read and write disk I/O response and, based on statistical trends, can employ a blend of disk-based and non-disk-based data reduction techniques to enable sustained throughput during periods of high diskintensive workloads. Important: Use caution with this setting, particularly when you are optimizing CIFS or NFS with prepopulation. Please contact Riverbed Technical Support for more information.SDR-M Performs data reduction entirely in memory,…

Riverbed Steelhead In-Path Rule - Neural Framing Mode

Optionally, if you have selected Auto-Discover or Fixed Target, you can select a neural framing mode for the in-path rule. Neural framing enables the system to select the optimal packet framing boundaries for SDR. Neural framing creates a set of heuristics to intelligently determine the optimal moment to flush TCP buffers. The system continuously evaluates these heuristics and uses the optimal heuristic to maximize the amount of buffered data transmitted in each flush, while minimizing the amount of idle time that the data sits in the buffer. You can specify the following neural framing settings:
Never. Never use the Nagle algorithm. All the data is immediately encoded without waiting for timers to fire or application buffers to fill past a specified threshold. Neural heuristics are computed in this mode but are not used.Always. Always use the Nagle algorithm. All data is passed to the codec which attempts to coalesce consume calls (if needed) to achieve better fingerprinting. A timer …

TCP Vegas

TCP 的傳送端利用RTT 針測由傳送端到接收端之間queue的長度並藉此調整congestion window 的值,主要修改的部份有三點:
Slow Start: 大約2 個RTT時間,cwnd 才會增加一倍;Congestion Avoidance:Vegas 藉由比較預期的速率與實際傳送的速率算出Diff 的值,並限制Diff 的值必須介於alpha 與beta 之間,若Diff < alpha,則增加傳送的速率,反之,若Diff > beta,則減少傳送的速率;藉由觀察RTT 的值比判斷是否已經有packet timeout

When Are ICMP Redirects Sent?

How ICMP Redirect Messages Work

ICMP redirect messages are used by routers to notify the hosts on the data link that a better route is available for a particular destination.
For example, the two routers R1 and R2 are connected to the same Ethernet segment as Host H. The default gateway for Host H is configured to use router R1.Host H sends a packet to router R1 to reach the destination on Remote Branch office Host
Router R1, after it consults its routing table, finds that the next-hop to reach Host is router R2.
Now router R1 must forward the packet out the same Ethernet interface on which it was received. Router R1 forwards the packet to router R2 and also sends an ICMP redirect message to Host H.
This informs the host that the best route to reach Host is by way of router R2.
Host H then forwards all the subsequent packets destined for Host to router R2.

Markov Model

What is a Markov Model?
Markov models are some of the most powerful tools available to engineers and scientists for analyzing complex systems. This analysis yields results for both the time dependent evolution of the system and the steady state of the system.

For example, in Reliability Engineering, the operation of the system may be represented by a state diagram, which represents the states and rates of a dynamic system. This diagram consists of nodes (representing a possible state of the system, which is determined by the states of the individual components & sub-components) connected by arrows (representing the rate at which the system operation transitions from one state to the other state). Transitions may be determined by a variety of possible events, for example the failure or repair of an individual component. A state-to-state transition is characterized by a probability distribution. Under reasonable assumptions, the system operation may be analyzed using a …

Out-of-Band (OOB) Splice

What is the OOB Splice?
An OOB splice is an independent, separate TCP connection made on the first connection between two peer Steelhead appliances used to transfer version, licensing and other OOB data between peer Steelhead appliances. An OOB connection must exist between two peers for connections between these peers to be optimized. If the OOB splice dies all optimized connections on the peer Steelhead appliances will be terminated.
The OOB connection is a single connection existing between two Steelhead appliances regardless of the direction of flow. So if you open one or more connections in one direction, then initiate a connection from the other direction, there will still be only one connection for the OOB splice. This connection is made on the first connection between two peer Steelhead appliances using their in-path IP addresses and port 7800 by default. The OOB splice is rarely of any concern except in full transparency deployments.
Case Study In the example below, the Client is…


RIVERBED ANNOUNCES STEELHEAD MOBILE 3.0 Mobile Solution Complements Broader Steelhead Appliance Deployment and Speeds Enterprise IT Infrastructure Performance; Provides Acceleration for Windows 7 and 64-bit Systems SAN FRANCISCO – November 02, 2009 – Riverbed Technology (NASDAQ: RVBD), the IT infrastructure performance company for networks, applications and storage, today announced upcoming enhancements to its Mobile WAN optimization solution to address the productivity challenges global organizations face when managing remote and mobile workforces. Riverbed® Steelhead® Mobile increases employee productivity while on the road, working from home or connected wirelessly in the office by providing application performance improvements. With this release, Riverbed will provide acceleration for Windows 7 and 64-bit systems for mobile end users. In addition, organizations will be able to take advantage of improved flexibility and simplified manage ment functionality to provide mobile worker…

Riverbed Cascade Gateways vs Cascade Profiler vs Cascade Sensor

Cascade Gateways collects network flow data already existing in an organization’s network provides intelligent de-duplication retaining information on where each flow was recorded, and sends this condensed data to the Cascade Profiler. Cascade Profiler complements this information with layer 7 application and response time data retrieved from a Cascade Sensordeployed in the datacenter. These records are then further enhanced with user identification information provided by active directories, switch port information, QoS, and SNMP data. The result is a complete view of a business application flow from the back end server to the users desktop. Cascade also provides an extensive set of integrations, with management systems typically deployed in an IT environment to further streamline workflows and provide value across multiple operations teams.

EIGRP: Packet from ourselves ignored

本週在上ICND2的時候,有同學突然問了我一個問題,他在測試debug eigrp時出現了一個 log message
02:36:26: EIGRP: Packet from ourselves ignored
一下子我還真的無法回答上來,後來趁著休息時間上網找了一些資料,終於在CCIE Practical Studies: Security (CCIE Self-Study)這本書中找到相關說明(感謝Google圖書館)。
原來是因為在Router上建立的loopback interface啟動了EIGRP,EIGRP Router也會在loopback interface上發送hello的封包,然後又被自己接收到,EIGRP知道這個hello封包是由自己送出的,因此忽略它不再嘗試去建立neighbor關係。
解決方案就是如果有類似的情況又不想看到這樣的訊息,可以試著加上passive-interface的指令來讓EIGRP router不要在loopback interface上送出hello封包。

BGP Best Path Criteria

Updated from Cisco 360 Workshop 1 Vol.1
1. Highest weight(default=0) 2. Highest local preference(default=100) 3. Locally originated(Next hop:, weight=32768) 4. Shortest AS path length 5. Lowest origin code(IGP < EGP < incomplete) 6. Lowest MED(default=0) 7. EBGP over IBGP 8. If internal, prefer path with lowest IGP metric to next hop 9. If external, consider multipath (NEW!) 10. If external, prefer old one 11. Lowest router ID or originator ID 12. Minimum cluster list length (NEW!) 13. Lowest neighbor address

Understanding BGP TTL Security - Packet Life

Understanding BGP TTL Security - Packet Life
By default, IOS sends BGP messages to EBGP neighbors with an IP time-to-live (TTL) of 1. (This can be adjusted with ebgp-multihopattached to the desired neighbor or peer group under BGP configuration.) Sending BGP messages with a TTL of one requires that the peer be directly connected, or the packets will expire in transit. Likewise, a BGP router will only accept incoming BGP messages with a TTL of 1 (or whatever value is specified by ebgp-multihop), which can help mitigate spoofing attacks.
However, there is an inherent vulnerability to this approach: it is trivial for a remote attacker to adjust the TTL of sent packets so that they appear to originating from a directly-connected peer. By spoofing legitimate-looking packets toward a BGP router at high volume, a denial of service (DoS) attack may be accomplished.
A very simple solution to this, as discussed in RFC 3682, is to invert the direction in which the TTL is counted. The maximum value o…

What is Multicast Designated Router (DR) ?

晚上閒來無事檢查一下e-mule的成果,看到了一份古早的multicast course slide + content的PDF,真的有點衝動想要把它整本印出來,裏面的內容真的很詳細很棒,但是現在完全沒有教這些來龍去脈,所以我想現在的學生就算是考過CCNP/CCIP對於multicast也只是一知半解。

在文章裏面我剛好看到了一個也出現在BSCI課文中的一個專有名詞 Designated Router/Querier,更重要的是…Cisco BSCI 教科書中那段文章還是錯的,它把highest IP寫成了lowest IP...(心中OS:習慣就好 習慣就好 教書教了三年還真的仍不習慣~)

• Designated Router (DR)
– For multi-access networks, a Designated Router (DR) is elected. In PIM Sparse mode networks, the DR is responsible for sending Joins to the RP for members on the multi-access network and for sending Registers to the RP for sources on the multi-access network. For Dense mode, the DR has no meaning. The exception to this is when IGMPv1 is in use. In this case, the DR also functions as the IGMP Querier for the Multi-Access network.

• Designated Router (DR) Election
– To elect the DR, each PIM node on a multi-access network examines the received PIM Hello messages from its neighbors and compares the IP Address of its interface with the IP Address of its PIM Neighbors. The …

Configure RSVP Agents in Cisco IOS Software

CIPT2 Vol. 1 Page 3-59 shows how to configure a Cisco IOS router to enable RSVP-agent functionality.

sccp local FastEthernet 0/0
sccp ccm identifier 1 version 6.0
sccp ccm group 1
associate ccm 1 priority 1
associate profile 1 register HQ-1_MTP
dspfarm profile 1 mtp
codec pass-through
maximum sessions software 20
associate application SCCP

interface Serial0/1
description IP-WAN
ip address
duplex auto
speed auto
ip rsvp bandwidth 40

Implementing Cisco Unified Mobility

今天是我自2000年來Cisco筆試第二次的fail紀錄(上一次是 DCN,這一次是CIPT2),現在voice的筆試有很多需要強記的觀念及步驟,今天就遇到一題要求我將所有的指令依序排列(內容完全跟課本中某個slide完全相同),但是我實在沒有什麼機會作lab因為不熟練所以沒有得分。另外一題則是觀念問題,要我把Mobility Connect 以及 Mobile Voice Access步驟選出來,這也是完全要考驗考生對Lab的實作能力,但是這部份的內容在課本說得並不清楚,所以我在這邊把CIPT2 Lab中的步驟大綱點出來,方便各位快速查詢:
Mobile Connect Task 1: Add the Mobility Softkey to IP Phones a. Configure a Softkey Template with the Mobility Softkey b. Assign the Softkey Template to the IP Phone
Task 2: Associate an End User Account with the IP Phone and Enable the Use of Mobility a. Configure an End User for Device Mobility b. Configure the Office Phone to be Owned by the End User
Task 3: Configure Remote Destination Profiles and Remote Destinations a. Configure a Remote Destination Profile b. Configure a Remote Destination
Mobile Voice Access Task 4: Enable Cisco Unified Mobile Voice Access a. Activate the Cisco Unified Mobile Voice Access Service b. Configure Cisco Unified Mobility Service Parameters c. Configure End Users to Be Allowed to Use Cisco Unif…

New Video Certifications Track and Cisco 360 Learning Program for CCIE Voice

Cisco Announces New Video Certifications Track and Cisco 360 Learning Program for CCIE Voice
In response to sharply increasing market demand for advanced video and collaboration solutions, Cisco is pleased to announce the release of two forthcoming Video specialist certifications and the new Cisco 360 Learning Program for CCIE® Voice.
The Cisco TelePresence Installation and Cisco TelePresence Solutions Specialist certifications offer IT professionals and students a career opportunity to integrate, operate and manage Cisco TelePresence systems and solutions. Both certifications will be made available in early 2010.
The Cisco 360 Learning Program for CCIE Voice provides experienced network engineers with an effective, job-relevant, and proven program to build expert-level skills and to prepare for the rigorous Cisco CCIE Voice lab exam. The Cisco 360 Learning Program for CCIE Voice will be made available on December 7, 2010.
For more information access the Cisco Learning Network.

Understanding Denial-of-Service Attacks

You may have heard of denial-of-service attacks launched against websites, but you can also be a victim of these attacks. Denial-of-service attacks can be difficult to distinguish from common network activity, but there are some indications that an attack is in progress.
What is a denial-of-service (DoS) attack?
In a denial-of-service (DoS) attack, an attacker attempts to prevent legitimate users from accessing information or services. By targeting your computer and its network connection, or the computers and network of the sites you are trying to use, an attacker may be able to prevent you from accessing email, websites, online accounts (banking, etc.), or other services that rely on the affected computer.
The most common and obvious type of DoS attack occurs when an attacker "floods" a network with information. When you type a URL for a particular website into your browser, you are sending a request to that site's computer server to view the page. Th…

DISA (Direct Inward System Access)

The DISA, Direct Inward System Access, application allows someone from outside the telephone switch (PBX) to obtain an "internal" system dialtone and to place calls from it as if they were placing a call from within the switch.

DISA plays a dialtone. The user enters their numeric passcode, followed by the pound sign (#). If the passcode is correct, the user is then given system dialtone on which a call may be placed.

My First Riverbed Certification - RCSP


Connect to E911 via PRI or CAMA trunk?

There are two types of circuits an enterprise can use to route 911 calls to the proper PSAPs (public safety answering points) and deliver the 10-digit caller ID: ISDN PRIs or Centralized Automatic Message Accounting (CAMA) trunks.

"ISDN is the wea port of choice from our perspective," says Guy Clinch, Avaya's government solutions director and a member of the National Emergency Number Association's PBX/multi-line telephone system technical subcommittee, because you can fit more phone lines in a PRI and assign each of those numbers to represent a separate ERL. In short, you can map your location and send more granular location information to the PSAP.

But as many as 85% of enterprises choose instead to retrofit their IP PBXs using legacy analog CAMA trunks for entry into the public safety system, Clinch says. It's cheaper, because the CAMA trunk is equivalent to on phone number, so they get charged only once.

The downside: CAMA trunks cannot deliver a custom caller ID…

Cisco Monitor Director

Cisco Monitor Director, a centralized proactive solutions-management tool for Cisco channel partners to offer multicustomer outsourced 24-hour network management services. It communicates with the Cisco Monitor Manager residing on a customer's premises to provide comprehensive, real-time monitoring, alerting and reporting to help troubleshoot and fix issues remotely. Combining these management tools helps enable Cisco channel partners become trusted advisers to their customers.

The Smart Phone Control Protocol (SPCP)

The Smart Phone Control Protocol, or SPCS, is an addition to the Simple Call Control Protocol (SCCP) that is only supported on the CP-500 phones and the SPA525 phone.79XX phones register with their SCCP call control using a proprietary handshake that consists of a series of messages. During the registration phase a number of things happen:1. Phone (Station) sends a Registration Request2. Request is acknowledged by the Call Control (CME/UC500)3. Capabilities are advertised4. Button template, Softkeys, Line Status, Display message, Speed dials Time and date are requested by the phone and sent by CME/UC500When the phone is a 500 series phone, two additional messages precede all this handshake, namely an SPCP Token Request and an SPCP Token Acknowledgement (if successful) or Token rejection (if unsuccessful). A Token ACK can only be sent by UC500, while an ISR will always send a Token Reject. This prevents the phone from registering to any call control different than UC500.





4-bytes Autonomous System Number

迎戰台灣大 遠傳擬買中嘉

工商時報 2009-09-23【朱漢崙/台北報導】  為迎戰台灣大跨足有線電視,遠東集團旗下遠傳電信已密商韓系知名私募基金安博凱(MBK),要買下中嘉!外資圈權威消息人士透露,遠傳數月前已接觸安博凱,希望買下中嘉,上週台灣大哥大搶先一步買下凱擘的東森系統台,加深遠傳鞏固市場優勢的警覺,與安博凱的協商已進入緊鑼密鼓階段,近期可望傳出佳音。  而遠東集團、富邦集團的電信事業對決,也將因彼此都拿下有線電視系統台,而進入新的里程碑。  先前台灣大買下有線電視目前市佔率第一名的東森系統台,出價568億元,據了解,遠傳此次買下安博凱所有的中嘉,目前雙方談判的成交價,以中嘉收視戶120萬戶,而每戶約5萬元的市場行情估算,上看600億元。  消息人士說,遠傳早已對此布局,而台灣大接手凱擘為一道有力「觸媒」,促使遠東集團對此案,從鴨子划水開始加速進行,包括遠傳董事長徐旭東、安博凱的台灣區代表人龔國權,已有所接觸。  中嘉曾是有線電視系統台的龍頭,儘管目前已被東森追上,名列第二,但市佔率仍以20%緊追東森系統台的22%,若電信「二哥」遠傳成功拿下中嘉,將可避免「一哥」台灣大拿下東森系統台之後,挾電信業結盟有線電視的優勢,擴大彼此差距。  在財務規劃上,據消息人士透露,成交價上看600億元的這起交易,是採全數現金交易,或換股、現金各半,尚未決定;若全採現金交易,則遠傳擬向外募集的資金,約在350億元左右,若採取現金、換股各半的模式進行交易,則對外募資金額,將可大幅降低,至於以承接負債來抵減部分交易金額的方式,也在考慮之列。  安博凱2年半前以14.35億美元,約台幣470億元的價格,取得中嘉所屬11個系統台60%股權。若雙方交易以上看600億元的價格底定,那不到3年時間,安博凱就淨賺130億元。  中嘉目前有三股勢力,最大的就是這次談判主體安博凱,全球媒體大王梅鐸與中信集團辜濂松家族,各持股20%,股東結構比起東森系統台較複雜,不過由於安博凱持有過半股權,一旦成交,遠東集團將入主中嘉。

Wide area file services (WAFS)

Wide area file services (WAFS) products allow remote office users to access and share files globally at LAN speeds over the WAN. Distributed enterprises that deploy WAFS solutions are able to consolidate storage to corporate datacenters, eliminating the need to back up and manage data that previously resided in their remote offices. WAFS uses techniques such as CIFS and MAPI protocol optimization, data compression, and sometimes storing recurrent data patterns in a local cache.
WAFS is a subset of WAN optimization, which also caches SSL Intranet and ASP applications and elearning multimedia traffic as well, to accelerate a greater percentage of WAN traffic.

Advanced TCP Implementation(HS-TCP vs S-TCP vs BIC-TCP)

以下的內容是節錄自Cisco Press Application Acceleration and WAN Optimization Fundamentals中的章節,由於這幾個協定可以說是各家廣域網路加速器都會參考的標準,用以改善原有TCP設計運作上的缺陷,所以我把它們整理出來加以分較,希望對各位有所幫助!
HS-TCP(High Speed TCP)High-Speed TCP is a advanced TCP implementation that was developed primarily to address bandwidth scalability. HS-TCP uses an adaptive cwnd increase that is is based on the current cwnd value of the connection. When the cwnd value is large, HS-TCP uses a larger cwnd increase when a segment is successfully acknowledged. In effect, this helps HS-TCP to more quickly find the available bandwidth, which leads to higher levels of throughput on large networks much more quickly.
HS-TCP also uses an adaptive cwnd decrease based on the current cwnd value. When the cwnd value for a connection is large, HS-TCP uses a very small decrease to the connection's cwnd value when loss of a segment is detected. In this way, HS-TCP allows a connection to…

Cisco Networkers 2009 - CCIE Lunch Invitation

等了很久,終於等到這一封邀請信 - CCIE Lunch Invitation。
傳聞在Cisco Networker活動中都會有一場聚會,與會人員是來自世界各地的CCIE,主持人通常是Cisco金字塔高層主管,可以想見這個活動一定是意義非凡(如果各位是比較資深的CCIE應該也曾經參加過台灣思科主辦的CCIE Club活動,可惜的是無以後繼,CCIE Club就這樣地悄悄消失於地球的表面,只留下每人一只Cisco Logo紀念錶)

台灣大買凱擘吃東森 將躍居有線電視龍頭


【經濟日報╱記者費家琪、黃晶琳/台北報導】 2009.09.16 03:59 am 台灣大哥大可望買下有線電視第二大系統台凱擘,最快今(16)日召開董事會討論,傾向以現金交易,一舉吃下110萬戶的有線電視用戶與東森電視的十個頻道,躍居台灣最大的有線電視系統台與頻道業者,併購金額上看600億元。至截稿為止,尚無法聯絡上台灣大與凱擘的發言管道。消息來源透露,台灣大一直有意擴張有線電視經營版圖,之前對麥格理經營的台灣寬頻有興趣,經過評估後,則相中在台北市布局甚深的凱擘,要藉此切入消費實力最高、又最難布線的地區。此外,凱擘還掌握東森電視台的十個頻道,包括新聞台、幼幼台、戲劇台等,這對有心跨足數位內容的富邦金董事長蔡明忠、台灣大董事長蔡明興而言,更是吸引力十足。不過,雙方之前一直卡在價格問題,台灣大有意以手中持有21%庫藏股和凱擘交換,原本去年底可望交易,但台灣大當時的股價滑落,近期股價逐步回升。在雙方協調過程中,仍傾向於全部以現金併購,或半換股與半現金的交易方式。以凱擘約110萬用戶推算約500多億元,加上凱雷持有約64%的東森電視台股權,投入約五、六十億元,併購金額上看600億元。台灣大可望今天召開董事會討論此事,台灣大昨天收盤價約51.9元,小跌0.1元。之前有線電視併購案的用戶數價格屢屢推高,一度高達每戶4.7 萬元。但在金融風暴後,雖然市場景氣回溫,價格要再創新高不易,傳言每戶金額約在4萬至5萬元。值得注意的是,台灣大有線電視用戶數約60萬戶,居於市場第四大,凱擘達到110萬戶,是市場第二大,兩者合計達到170萬用戶數,居有線電視市場龍頭。不過,政府目前對有線電視用戶數仍有不得高於三分之一的限制,雙方如何以轉投資架構布局,也有待觀察。台灣大目前擁有600多萬手機用戶,又經營購物頻道momo 台與親子台,希望藉由行動電話、有線電視、頻道內容等全方位的經營,擴大市場版圖。目前電信市場的龍頭業者是中華電,也是台灣大最大的對手,中華電最近在推動隨選視訊(MOD)上著力甚深,達到70萬用戶,雙方競爭激烈,台灣大有意藉由更廣的布局,深入用戶的客廳,與中華電全面開戰。 【2009/09/16 經濟日報】@

Cisco 360 Learning Program for CCIE R&S: Cisco Lab Safe Promotion

Together, the Cisco 360 Learning Program for CCIE Routing and Switching and the Cisco Lab Safe promotion allow qualifying learners who do not pass their first Cisco CCIE® R&S lab exam attempt to retake the CCIE lab exam at no additional cost (a $1,400 US value).To be eligible for this promotion, individuals must meet these requirements: Obtain their instructor’s recommendation Complete the Cisco 360 Learning Program for CCIE R&S Essentials Package or a CIERS instructor-led workshopScore 80 percent or better on at least one of the performance assessments that are listed belowOnly select Cisco Authorized Learning Partners offer the Cisco 360 Learning Program curriculum and Cisco Lab Safe promotion, which combined provide you with added assurance in the quality and value of your training investment.