Lecture 4 Routing Dan li CS Department, Tsinghua University 2021/1/31
Lecture 4 Routing 2021/1/31 1 Dan LI CS Department, Tsinghua University
Today's Lecture Inter-Domain Routing Reading list 2021/1/31
Today’s Lecture Inter-Domain Routing Reading list 2021/1/31 2
Inter-Domain Routing Routing hierarchy Internet structure EXternal BGP(E-BGP) Internal BGP (I-BGP 2021/1/31
Inter-Domain Routing Routing hierarchy Internet structure External BGP (E-BGP) Internal BGP (I-BGP) 2021/1/31 3
Routing Hierarchies Flat routing doesn'tscale Storage> Each node cannot be expected to store routes to every destination (or destination network) Convergence times increase Communication Total message count increases w Key observation Need less information with increasing distance to destination k Need lower diameters networks Solution area hierarchy 2021/1/31 4
Routing Hierarchies Flat routing doesn’t scale Storage → Each node cannot be expected to store routes to every destination (or destination network) Convergence times increase Communication → Total message count increases Key observation Need less information with increasing distance to destination Need lower diameters networks Solution: area hierarchy 2021/1/31 4
Areas Divide network into areas k areas can have nested sub-areas Hierarchically address nodes in a network Sequentially number top-level areas k Sub-areas of area are labeled relative to that area k nodes are numbered relative to the smallest containing area 2021/1/31
Areas Divide network into areas Areas can have nested sub-areas Hierarchically address nodes in a network Sequentially number top-level areas Sub-areas of area are labeled relative to that area Nodes are numbered relative to the smallest containing area 2021/1/31 5