Chapter 2 Networking Fundamentals Network Classification Based on

Chapter 2 Networking Fundamentals

Network Classification • Based on Network Service • Data communication • Telecommunication • Based on Network Perspective • Network Infrastructure • Network Protocols • Network processors mostly deal with • Ethernet, MPLS and IP traffic • Less involvement in telecom equipment

Network Span and Speed

Network Hierarchy

Network Modeling (I) • Modeling Method 1. Data and communication protocols 2. Architecture and physical components 1. Data and Protocol Modeling • Layered architecture (network stack) • OSI model • TCP/IP model (Internet model)

Data Encapsulation • LLP & ULP • Interfacing entities vertically • PDU / Payload • Mux/Demux • Using headers

Network Modeling (II) 2. Architecture and Physical Modeling • Nodes and links • Hierarchical / functional model • Endpoint, Edge, Core or • Endpoint, Access, Dist. , Core

Network Technologies • Techniques that enable networks to functions • A number of them are applied in each layer of the network stack • And in each section of the network architecture • Network Processing Levels • Data plane • Actual data handling • Control plane • Making decisions about data handling

Data Networks • Telecom networks do not use NPs! • Data Networks • are more prevalent • Expanding & evolving faster • Two dominant technologies • Ethernet • Internet

Enterprise Ethernet • The most dominant L 2 protocol for LANs – more than 85% • Originally proposed by Xerox in 1970 s • Standardized by DEC, Intel and Xerox • Survived stiff competitions • From very powerful rivals • Wins due to its simplicity and price • Based on shared-medium interfacing of multiple hosts in a LAN • Modified into IEEE 802. 3 Interconnects in Top 500 supercomputers in Nov. 2018

The Ethernet Family • Operating in Data-link and physical layers • Multiple LAN standards, which cover • Many media types • A broad range of speeds (from 10 M to 400 G) • Various interfaces • All sharing CSMA/CD protocol

The Ethernet Evolution

Data Link Sublayers • Logical Link Control (LLC) • Interfaces between MAC and ULPs • Mux/Demux • E 2 E flow control and error mangement • Media Access Control (MAC) • Controls node access to media • Dictates frame format and data structure • Physical Layer • Defines bit rate, signal encoding,

Ethernet Physical Layer

Ethernet MAC Layer • Frame Size is less than 1536 • Jumbo Frames are < 9216

Ethernet Protocol Type (Ether. Type) Ether Type

Minimum Frame Size • The worst RTT of the frame on the LAN segment; • To detect collision by the transmitter. • Limited to 50µs (2. 5 Km of bit propagation in copper) • How many bytes for 10 Mb/s?

LLC Header & Sub. Network Access Protocol (SNAP) • LLC Header: the 1 st 8 bytes of frame data • Identify upper layer services and protocol ID • SNAP: To identify Ethertype, when the value is < 0 x 600

Ethernet Networking • Repeaters & hubs • Extend LAN diameter • Increase collision : non-scalable • Scalability solution • Limit LAN segments to be manageable • Attach them with bridges and switches • Separate physical LANs into virtual LANs (VLANs) • Carrier Class Ethernet

Bridges and Switches • Purpose: • Allowing scalability in a LAN: as many nodes as required • Reducing #hosts on shared medium to limit collision • Bridging is on L 2 • Separating collision domains on LANs (shared segments) • Two types: • Source routing • Transparent routing • Mixed (SRT)

Switches • Bridges with many ports • Can connect LANs of different broadcast domains • ASIC-based processing • Unlike SW-based on bridges • Broadcast Storm • Spanning tree requirement • Switching Mechanisms • Store-and-forward • Cut-through

Spanning Tree • Main processes in switching / Bridging • Construct the spanning tree • Learn MAC addresses • Perform packet forwarding • A tree spanning all nodes in a network • Loopless • Active network • Spanning Tree Protocol (STP) • A distance-vector alg. (nodes know their neighbors) • Port states: discarding, forwarding, learning

STP Algorithm • Identify a unique root bridge • Identify a unique root port on each bridge • Identify a designated bridge and port for each LAN • Preferred for connecting the LAN to others

STP Example

Virtual LANs (VLANs) • A method for sharing a medium between different networks • Each VLAN is a broadcasting domain • Host across VLANs are inaccessible • IEEE 802. 1 q standard • Frames are tagged with a VLAN tag to distinguish between networks • Tag = 0 : not a VLAN frame, • Tag = 0 x. FFF: for implementation use • Host to VLAN assignment: • Port-based (switch) • MAC-based • Application-based

VLAN Example

Spanning Trees in VLAN Networks • Per VLAN ST • Common ST • One ST for all • Multiple ST • Several active networks, each containing multiple VLANs • Learning Process • Independent (IVL) • Shared (SVL)

Internet Protocol • Using MACs for addressing is • Highly inflexible • Non-scalable • Need L 3 addressing • Internet Protocol • Standardized by IETF (RFCs) • IPv 4: 32 bit address • IPv 6: 128 bit address

IP Packet Routing • Routers • Connect Islands of local networks • Maintains a routing table • Routing entry: Destination address (prefix) , Egress port • Trie structures • Default entry • Packet forwarding • Data plane – performed for all packets • Examine IP header and make decision • Processing intensive • Routing protocols • Control plane • Exchange routing info among routers

Autonomous Systems • Divide Internet into partitions • Each partition (AS) handling routing internally • Interior Gateway Protocols • RIP, OSPF, EIGRP • Exterior Gateway Protocols • BGP • Shortest Path algorithms • Distance Vector (e. g. , BGP, RIP) • Uses Bellman-Ford • Link state (e. g. , OSPF) • Uses Dijekstra

Best Effort vs. Selective Routing • Best effort • Treat all packets equally • Insensitive to packet’s type and application • Selective routing • Consider type of service • Perform packet classification • Provide different service / resource levels per packet type

Selective Routing Models • Int. Serv • RSVP: Reserve resources (BW) for packet classes • Not scalable: needs reservation update in all routers • Diff. Serv • Per hop behavior (PHB) for routers • Queuing and BW levels • Multicast routing • Class D IP addresses: 224. 0. 0. 0 – 239. 0. 0. 0 (224. 0. 0. 0/4) • Data plane: FW packets to multiple destinations • Control plane: IGMP - Multicast groups and routing tables

Multicast Protocols • Mainly Experimental • Source-based trees • Extends OSPF (MOSPF) and Distance vector algs. (DVMRP) • Each router has a shortest path tree for each multicast group • Group-based trees • A core router has shortest path tree to all groups • This router only does multicasting • Example protocols: Core-Based-Tree (CBT)

Core-based Tree

ICMP Protocol • Control mechanism for IP networks

Internet Protocol Headers