2010年11月24日 星期三

C語言- incompatible types in assignment

如果使用陣列的方式宣告字串,則不可以直接使用=指定運算子另外指定字串
Ex.

char str[] = "hello";
str = "world";   // error, incompatible types in assignment

Reference:
http://caterpillar.onlyfun.net/Gossip/CGossip/PointerAndString.html

2010年11月16日 星期二

MSTP (Multiple Spanning Tree Protocol)

這篇很棒!  快速了解MSTP

Multiple Spanning Tree Protocol (IEEE 802.1s) is backwards compatible with STP/RSTP and addresses the limitations of existing spanning tree protocols (STP and RSTP) in networks to include the following features:
  • One Common and Internal Spanning Tree (CIST) that represents the entire network's connectivity.
  • Grouping of multiple bridges (or switching devices) into regions that appear as one single bridge on the network.
  • A VLAN can be mapped to a specific Multiple Spanning Tree Instance (MSTI). MSTI allows multiple VLANs to use the same spanning tree.
  • Load-balancing is possible as traffic from different VLANs can use distinct paths in a region. 

Purpose
  • To supplement VLAN insensitivity problem in STP/RSTP.

Edge Ports
  • Directly transition to forwarding, skipping learning states. 
  • Doesn’t generate topology changes when its link toggles. 
  • Become a normal spanning-tree port whenever receives a BPDU.


MST Instances
  • An MST bridge must be able to handle at least the following two instances 
    • One Common Internal Spanning Tree (CIST) 
    • One or more Multiple Spanning Tree Instance(s) (MSTIs) 
    • Cisco supports 16 instances: one CIST (instance 0) and 15 MSTIs


MST Instance
  • An MST Instance (MSTI) is a spanning tree instance. VLANs can be configured to run on a specific MSTI. Each created MSTI is identified by a unique number (known as an MST ID) known internally to a region. Thus an MSTI does not span across MST regions. 

Common and Internal Spanning Tree (CIST)
  • A CIST represents the connectivity of the entire network and it is equivalent to a spanning tree in an STP/RSTP. The CIST is the default MST instance (MSTID 0). Any VLANs that are not members of an MST instance are members of the CIST. In an MSTP-enabled network, there is only one CIST that runs between MST regions and single spanning tree devices. A network may contain multiple MST regions and other network segments running RSTP.

2010年11月11日 星期四

ThreadX

我想我現在稍微了解了點ThreadX在我們OS上的運作了...
也稍微了解了點產品的OS架構

期待下禮拜的training course學長的介紹!

拜託!! training course可不能打瞌睡阿!!!! 阿潘!!