VoIP

Relation Specification:
RFC3261 Session Initiation Protocol
ITU-T recommendation H.33

1. Throughput
2. Packet Loss
3. Jitter
4. Pcaket Delay

SpectraLink

SpectraLink has two types of operations
point-to-point as in I call you
Push-To-Talk (PTT) which is like a walky-talky
#1 uses unicast SPR packets
#2 use multicast UDP packets
SpectraLink says that #1 MUST be higher priority than #2
So, #1 goes in the Voice queue and #2 goes in the Video queue

What is ToS.

How the DHCP flow

DHCP protocol flows are different with, getting a new address and getting the previously assigned address. Figure2 shows the first case:

1. DHCP client broadcasts a DhcpDiscover. The client may specify preference of a lease and/or an IP address.
2. DHCP server receiving the DhcpDiscover may return DhcpOffer or may not return (Many servers may receives the DhcpDiscover). If a server decides to respond, server puts an available address into yiaddr field and broadcasts the DhcpOffer. At this point, there is no agreement of an assignment between the server and the client.
3. Client gets one or more DhcpOffers and chooses one server from them. The client puts the IP address of the server into the Server identifier option of a DhcpRequest and broadcasts it to a server.
4. The server checks the Server identifier option. If it does not match with its own address, the server considers it as an implicit decline. The selected server sends the DhcpAck (if its address is available) or the DhcpNak (for example, the address is already assigned to another client).
5. The client that gets the DhcpAck starts using the IP address. If it gets DhcpNak, it restarts from step 1.
6. The client finds a problem with the assigned address of DhcpAck, it sends DhcpDecline to the server, and restarts from step 1.
7. The client can release the address before its lease expires by DhcpRelease. This process is not absolutely required.

ARP Protocol flow

VLAN fromat header

IGMP Packet Format

1, IGMP V1: 支持包类型, 两种 query 和report; router 等待超时时间才知道组成员已经不存在;
2,IGMP V2: 支持包类型, 三种, query,report和Leave, 增加Leave包的目的是,当组中最后一个成员离开时,通知路由器,快速收敛. 而且Query包也分为两种, 一为正常的Query,查询所有的组是否有成员(类似于V1);一种为特殊的query,在收到Leave包后, 路由器所发出的只查询该组的query包;
3,IGMP V3: 支持包的类型,两种, query和report. 增加Source filtering功能, host可以通知路由器,指定只收或者不收,某些特定的组和原地址的包. 防止了Unkonw host的DOS攻击. query分为三种, 查询所有组的/特殊组的/特殊组和特殊源地址的;
关于V3为什么要取消Leave这个有助于快速收敛的包呢? 其实他将V2的Leave包的功能加入到report包中来了, 当host有任何变动且认为应该通知Router时,他就会发送report包.
http://www.commsdesign.com/showArticle.jhtml?articleID=52200253
224.0.0.0 － Base address
224.0.0.1 － 网段中所有支持多播的主机
224.0.0.2 － 网段中所有支持多播的路由器
224.0.0.4 － 网段中所有的DVMRP路由器
224.0.0.5 － 所有的OSPF路由器
224.0.0.6 － 所有的OSPF指派路由器
224.0.0.7 － 所有的ST路由器
224.0.0.8 － 所有的ST主机
224.0.0.9 － 所有RIPv2路由器
224.0.0.10 － 网段中所有支的路由器
224.0.0.11 － Mobile-Agents
224.0.0.12 － DHCP server / relay agent.
224.0.0.13 － 所有的PIM路由器
224.0.0.22 － 所有的IGMP路由器
224.0.0.251 － 所有的支持组播的DNS服务器

IPv4 and V6 Header