- The primary function of a BGP speaking system is to exchange network reachability information with other BGP systems.
- RIB: Routing Information Base
- The internet protocol implements two basic functions:
- The internet modules use the addresses carried in the internet header to transmit internet datagrams toward their destinations. The selection of a path for transmission is called routing.
- Open and Keepalive
- draft-ietf-pce-gmpls-pcep-extensions-11 不对称业务请求
- LMP主要用来邻居节点链路发现，OSPF通过洪泛发现拓扑，PCEP discovery(PCED)消息来找到pce位置
- RFC4657: stateful pce
- pce-initiation: draft-ietf-pce-pce-initiated-lsp-10 首节点建路
- pce-ls: draft-dhodylee-pce-pcep-ls-08 取代ospf,但有bgp-ls(RFC7752)
- The fastest way for a PCE to be updated on TED changes is via a direct interface with each network node and with incremental update from each network node with only the attribute that is modified.
- pce-cc: draft-ietf-teas-pce-central-control-05 改水平信令(串行发放)为垂直信令(并行发放)
- TE information is not exchanged across the domain boundaries.
- Motivation of a PCE-Based Architecture
2.1 CPU-Intensive Path Computation
2.2 Partial Visibility
- PCE is not considered to be a solution that is applicable to the entire Internet.
- New mechanisms must be developed to manage the data links, both in terms of link provisioning and fault management.
- component links are multiplex capable, whereas ports are not multiplex capable. This distinction is important since the management of such links(including, for example, resource allocation, label assignment, ant their physical verification) is different based on their multiplexing capability.
3.The link property correlation function of LMP is designed to
aggregate multiple data links (ports or component links) into a TE
link and to synchronize the properties of the TE link.
4.the Test message is the only LMP message that must be
transmitted over the data link.
5.The control channels
can be used to exchange control-plane information such as link
provisioning and fault management information (implemented using a
messaging protocol such as LMP, proposed in this document), path
management and label distribution information (implemented using a
signaling protocol such as RSVP-TE [RFC3209]), and network topology
and state distribution information (implemented using traffic
engineering extensions of protocols such as OSPF [RFC3630] and IS-IS
- OSPF is a link-state routing protocol.
- Each OSPF router maintains an identical db describing the AS’ topology. From this db, a routing table is calculated by constructing a shortest-path tree.
- OSPF recalculates routes quickly in the face of topological changes, utilizing a minimum of routing protocol traffic.
- Networks can be either transit or stub networks.
- stub networks: 桩网络，又叫末端网络，是指仅有一单个同路通过路由器连接到其他子网，或者仅有一个通路连接到其他网络。（https://www.2cto.com/net/201208/147516.html）
- Interfaces to point-to-point networks need not be assigned IP address. When interface addresses are assigned, they are modeled as sub links, with each router advertising a stub connection to the other router’s interface address.
- LSA: Link-State Advertisement(链路状态通告)
- SPF： short path first
- The topology of an area is invisible from the outside of the area. Conversely, routers internal to a given area know nothing of the detailed topology external to the area. This isolation of knowledge enables the protocol to effect a marked reduction in routing traffic as compared to treating the entire Autonomous System as a single link-state domain.
- Each area border router in an area summarizes for the area its cost to all networks external to the area. After the SPF tree is calculated for the area, routes to all inter-area destinations are calculated by examining the summaries of the are border routers.
- IP TOS field set to 0.
- The IP multicast datagrams used by OSPF never travel more than on hop.
- Supernetting has been proposed as one way to improve the scaling of IP routing in the worldwide Internet.
- OSPF simplifies this by requiring only adjacent routers to remain synchronized.
- The Designated Router is elected by the Hello Protocol.
- two-way receive: https://zhidao.baidu.com/question/1883741654782230828.html
- OSPF packet types:
- Hello Discover/maintain neighbors
- Database Description Summarize database contents
- Link State Request Database download
- Link State Update Database update
- Link State Ack Flooding ackownledgment