EE469 Review 1

Layered Architecture Physical layer Data link layer Network layer Ethernet, WiFi Network layer IP Transport layer TCP, UDP Application layer (Web browser, email, VoIP)

Physical Layer Channel capacity: C=2H*BPSY, C=H*log(1+SNR) Baseband encoding NRZ, Manchester Modulation FSK, QPSK, QAM-4

Data Link Layer Framing Error detection sentinel, counter, clock (SONET) Error detection parity check, CRC, internet checksum

Data Link Layer Reliable transmission Stop and wait: ack/timeout/retransimission Sliding window protocol: sending a window’s worth of packet to make the pipeline full, rate = WS/ (RTT+ L/B) flow control, sender determines how much to send based on the bits in transit and receiver’s its buffer space sequence number for in-order delivery, n bits, 2W =< 2^n.

Shared Media Networks Ethernet CSMA/CD, exponential backoff Frame format: provides framing(preamble), addresses, CRC

Shared Media Networks Wireless Bluetooth (802.15.1), WiFi (.11), WiMax (.16) Physical layer: wide band, frequency hoping, CDMA (chips), OFDM Hidden state and exposed state problems 802.11 DCF/PCF: RTS/CTS/DATA/ACK

L2 Devices Bridges/Switches: connecting a number of LANs and reduce collision domain Self-learning algorithms: overhears the source address of passing frames to build forwarding tables (soft state with expiration time) Spanning tree algorithms to prevent loops

Network Layer: IPv4 Connectless (datagram), best-effort Packet format: 20 B fixed header + option, including TOS, packet id, fragment offset, TTL, addresses IP addresses: 4B, dotted decimal notation: 128.2.2.0 Class-based: A (0), B (10), C(110), D (1110, muticast); special addresses (all 0’s, 1’s). Subnet, subnet mask CIDR: slash notation to give more flexibility to address allocation

IPv6 Addresses: 16B, 8*4Hex: Header: D34H:123:…., short hand for IPv4: ::128.2.2.0 Header: More efficient (simpler), better support for QoS, security (extensions) 40B fixed + extensions, TOS, flow label (for circuits), TTL, addresses Put fragmentation in the extensions, no checksum (useless)

IP Associated Protocols ARP: given IP address, what is L2 address; broadcast query DHCP: lease IP addresses DNS: translate URL to IP address ICMP: echo message (ping), TTL exceeded (traceroute)

Routing Forwarding (lookup routing table) vs. routing (build the routing table) Objective: find lowest cost path between two nodes, cost can be hop, delay, etc.

Routing Distance vector (DV): RIP Exchange routing message among neighbors, while the message is entire routing table Not scalable, count to infinity problem Link state (LS): OSPF, IS-IS Routing message is broadcast to the entire network, while the message contains information about neighbors (link states). Dijstra’s algorithm

Routing in the Internet Internet consists of ASs stub, multihomed, transit IGP is used within AS, emphasis on cost. Typically LS EGP is used between AS, emphasis on policy. BGP, like DV, but listing the complete path

Multicast Group management (IGMP): create/destroy, join/leave group Multicast routing: tree based Can be a shared tree per group or one tree per source per group Build a sink tree (e.g., Dijstra’s alg.), then prune it

Mobile Networking Mobile hosts Mobile ad hoc networks Mobile IP: home agent, foreign agent (register to) Mobile ad hoc networks Route query/reply, on-demand AODV, DSR, DSDV