Learning IOS and JUNOS

資料來源：IPv6 Forum Taiwan Mobile IP通訊協定架構 Mobile IP的主要目的為可以使得主機使用一個固定的IP位址，和一個暫時位址來連接到網際網路。對於使用者而言，並不會感覺到暫時位址的存在，因此原先所作到一半的事情就不會被干擾而中斷。以下我們將簡單介紹Mobile IP的運作原理。 Mobile IP網路系統架構 Mobile IP網路架構與各子系統如下圖所示，當中： Mobile Host： 在網際網路上，一台主機如果常常改變其對網路的接點(point of attachment)，稱為Mobile Host。接點的改變可能發生在網路正在通信中的狀態。但是通常假設接點的變化時間比通訊協定反應的時間來得慢。 Home Network： 對Mobile Host有管理權的網路，對網際網路上的其他主機而言，Mobile Host不論其目前的位址為何，"似乎"是接在此處。 Home Address： 和其他固定主機的位址一樣，此位址是固定的，由Home Network的管理者提供給Mobile Host。當傳送資料給Mobile Host時，只須知道此位址，不須知道Mobile Host目前的暫時位址。 Home Agent ： 在Home Network上的某一台主機，能夠使得Mobile Host對網路上的其他主機而言，是隨時都可以存取的。 Foreign Network ： 對任一Mobile Host而言，任一個除了Home Network之外，允許其接上的網路，就稱為Foreign Network。 Care-of-Address： 一個表示當Mobile Host不在Home Network時，在網路上接點的IP位址。 Foreign Agent： 在Foreign Network上的主機，能使封包傳送到Care-of-Address。 Register： Mobile Host告知Home Agent其Care-of-Address。 -------------------------------------------------------------------------------- 基本工作原理 Mobile IP是由IETF所制定的RFC 2002,

Peering is voluntary interconnection of administratively separate Internet networks for the purpose of exchanging traffic between the customers of each network. The pure definition of peering is settlement-free or "sender keeps all," meaning that neither party pays the other for the exchanged traffic, instead, each derives revenue from its own customers. Marketing and commercial pressures have led to the word peering routinely being used when there is some settlement involved, even though that is not the accurate technical use of the word. The phrase "settlement-free peering" is sometimes used to reflect this reality and unambiguously describe the pure cost-free peering situation. Peering requires physical interconnection of the networks, an exchange of routing information through the Border Gateway Protocol (BGP) routing protocol and is often accompanied by peering agreements of varying formality, from "handshake" to thick contracts. How peering works The

Tier 1 network A Tier 1 Network is an IP network (typically but not necessarily an Internet Service Provider) which connects to the entire Internet solely via Settlement Free Interconnection, commonly known as peering. Another name for a Tier 1 network is "transit-free", because it does not receive a full transit table from any other network. Although there is no formal definition of the "Internet Tier hierarchy", the generally accepted definition among networking professionals is: ‧Tier 1 - A network that peers with every other network to reach the Internet. ‧Tier 2 - A network that peers with some networks, but still purchases IP transit to reach at least some portion of the Internet. ‧Tier 3 - A network that solely purchases transit from other networks to reach the Internet. Politics There are many reasons why networking professionals use the "Tier Hierarchy" to describe networks, but the most important one is better understanding of a particular networ

What is IGMPv1? IGMPv1使用Query-Response模型來允許Multicast Router和Multi-Layer Switch來確定在本網段內哪個Multicast Group是啟動的。在這個模型中，Router或Switch充當IGMP Querier，週期性(每隔60秒)地發送IGMPv1 Membership Query給224.0.0.1。啟用Multicast的所有主機監聽該位址並接收Query Packet。主機以IGMPv1 Membership Report回覆，表示它要接收特定Group的Multicast Traffic；該網段中的Router或Switch就可以了解Multicast Group中有哪些接收者。 主機可以通過發送一個或多個主動的Membership Report封包表明加入(Join)一個Multicast Group。如: 某個主機主動發送一個Report封包表明要接收Multicast Group(224.1.1.1)的流量。 主機通過停止處理Multicast Group Traffic以及不回應IGMP Query的方式來離開Multicast Group。 IGMPv1依靠L3的IP Multicast Routing Protocol(PIM、DVMRP等)來解決同一網段中哪個Router或Multi-Layer Switch成為Querier。Querier Router發送IGMPv1的Query來確定哪個Multicast Group是啟動的。通常Designated Router會被選擇為Querier。 IGMPv1的封包有2種： - Member Query(224.0.0.1, 每60秒查詢一次) - Member Report What is IGMPv2? IGMPv2的Query和Membership Report與IGMPv1類似。它們的差別在於： (一) IGMPv2的Query分為兩部分： - General Query(功能與IGMPv1的Query相同) - Group-Specific Query(僅查詢特定Group的資訊) (二) IGMPv1和IGMPv2的Membership Report使用不同的類型代碼。 IGMPv2的新特性包括： 1）Que

在Link-State Routing Protocol兩兄弟OSPF, IS-IS之間，有很多地方相似及相異之處，我這次特別將OSPF Designated Router(DR)/Backup Designated Router(BDR)及IS-IS Designated Intermediate System(DIS)這兩個同為SPF algorithm中在MultiAccess網路中必須存在的角色分別說明它們之間的相異點，希望可以為大家省去一一比對的麻煩。(如附圖)