Chapter 1 Networking Technologies
Topology
• Point-to-point
• Star – 10BaseT Ethernet
• Bus – 10Base5, 10Base2
• Ring – FDDI(Fiber Distributed Data Interface)
| | Physical Topology | Logical Topology |
| Ethernet | Bus, Star, p2p | Bus |
| Token Ring | Bus | Ring |
| FDDI | Ring | Ring |
Meshing - partially or fully
Types
• LAN
o Ethernet, Fast Ethernet (FE), Gigabit Ethernet (GE), Token Ring, FDDI
• WAN
o circuit-switched
temp or backup
analog dialup
ISDN
o cell-switched
cell - fixed length packets
expensive, QoS
ATM, Switched Multi-megabit Data Services(SMDS)
o packet-switched
variable length packets
cost-effective, less QoS
Frame Relay, X.25
o dedicated connections
o cable and DSL modem – always connected, cable share logical bus topology
o channel service units(CSU)/data service units(DSU), NT1, routers, carrier switch, modem, firewall
• MAN(Metropolitan)
o hybrid of LAN and WAN
o SONET(Synchronous Optical Network)
o SDH(Synchronous Digital Hierarchy)
o high-end router, ATM switch, optical switch
• SAN(Storage)
o fiber channel, over 1Gbps
o high cost
• Content Networks(CN)
o aware OSI 4-7
o content distribution, routing, switching, management, delivery
o intelligent network services- QoS, security, multicasting, VPN
o caching downloaded info
o distributing traffic load across servers
Intranet, Extranet and Internet
• extranet provides services for known external users, via VPN
o VPN provides authentication, confidentiality, integrity
• internet provides services for unknown users
Chapter 2 Networking Concepts
OSI – Open System Interconnection Reference Model
• application
o Interface to users of network aware apps.
o telnet, FTP, HTTP, SMTP
• presentation
o data and info representation
o ASCII, EBCDIC, BMP, GIF, JPEG, WAV, AVI, MPEG
• session
o initiating the setup and teardown of connections
o differentiating among multiple connections
o RPC, NFS
• transport
o actual mechanics of connections
o reliable – error detection and correction
o unreliable – error detection, no correction
o TCP – Transmission Control Protocol
o IPX’s SPX – Sequenced Packet Exchange
o UDP – User Datagram Protocol
• network
o logical topology
o layer-3 addresses
o router functions in the layer
o TCP/IP, IPX, AppleTalk
• data link
o MAC - media access control
o layer 2 frame
o error detection, normally no error correction
o LAN IEEE 802.2, 802.3, 802.5 Ethernet II, FDDI
o WAN ATM, Frame Relay, HDLC, PPP, SLDC, SLIP, X.25
o switch, bridge, NIC function in the layer
• physical
o RJ-45, DB-9, UTP, fiber
o Data communication equipment – DCE
o Data Terminal equipment – DTE
o repeater, hub function in the layer
Fiber cabling
• multi-mode – multiple LED
• single-mode – one laser, 100Gbps
• not effected by electromagnetic interference, unlike copper cabling
• WDM – wave division multiplexing
• DWDM – dense WDM
• SONET, SDH
• IOR – index of refraction, loss factor, connector loss, microbending, macrobending
| | SONET(US) | SDH(itnl.) | Mbps |
| OC-1 | STS-1 | - | 51.84 |
| OC-3 | STS-3 | STM-1 | 155.52 |
| OC-12 | STS-12 | STM-4 | 622.08 |
| OC-48 | STS-48 | STM-16 | 2488.32 |
| OC-192 | STS-192 | STM-64 | 9953.28 |
Wireless
• narrowband 900MHz, 2.4G, 5G, use spread spectrum to increase bandwidth
• broadband – lower bandwidth, broader coverage
• circuit/packet data solutions
• infrared provide high data rates over very small range
• satellite - cost and latency
• WEP – Wired Equivalency Privacym. 40/128 bits, weak
• 802.1x/EAP(extensible authen. protocol)
| | 802.11a | 802.11b | 802.11g |
| Mbps | 54 | 11 | 54 |
| GHz | 5 | 2.4 | 2.4 |
| feet | 25-75 | 100-150 | 100-150 |
L2 - Data Link Layer
L2 must be same media type
MAC
• 48bits or 12 digits, first 6 digits called OUI (organizationally unique id)
• hexadecimal
• only need unique in a broadcast domain
• broadcast address FFFF.FFFF.FFFF
Ethernet
• CSMA/CD, < style="">
• Carrier Sense Multiple Access/Collision Detection
• collision domain, bandwidth domain
• Ethernet II comparing to IEEE
o no sub-layer LLC/MAC
o a type field instead of length field
> 1500 Ethernet II frame
<= 1500 802.3 Frame
| Data Link | | | |
| Top | LLC(Logical Link Control) | 802.2 | How to multiplex multiple network layer protocol in frame, software using SAP(Service Access Point) |
| Bottom | MAC | 802.3 | Framing, MAC addressing, hardware |
802.3 Frame
| Preamble | 8 bytes |
| Dest MAC | 6 bytes |
| Src MAC | 6 bytes |
| Length | 2 bytes |
| Data | |
| FCS | 4 bytes |
LLC use SAP or SNAP field to differentiate layer-3 payloads. With SNAP frame, SAP fields are set to 0xAA; type field is used to indicate layer-3 protocol.
| | Physical topology | Logical topology | |
| 10Base5 | Bus | Bus | 500m |
| 10Base2 | Bus | Bus | 185m |
| 10BaseT | Star | Bus | 100m |
| 100BaseTX | Star | Bus | 100m |
| 100BaseFX | Star | Bus | Half 400m Full 2Km |
| 100BaseT4 | Star | Bus | 100m |
Gigabit Ethernet – IEEE 802.3z
L2 device - Bridge
• learn
• forward
o unknown unicast address, broadcast and multicast address are always flooded
• remove loop with STP(Spanning Tree Protocol)
• each port connected to a bridge is a separate collision domain, but the whole is broadcast domain because bridge floods
L2 device – Switch
• more features than Bridge
• Bridge and Switch are used to solve collision and bandwidth problem, and Router works in L3 can do so but more expensive.
L3 Network Layer
• logical network address
• Find path to dest.
• connect different data link types together
IPX address – 80bits, 32bits network number, 48 bits host address
Routers make routing decisions based on network numbers in L3 address, like IP address. Locations of networks are stored in a routing table. Unknown unicast destinations are dropped.
• L3 address can build large hierarchical networks
• stop broadcast and multicast
• find better path with rich metric structure
• connect different media type
• can switch packets on the same interfaces using VLAN
• implement QoS
L4 Transport Layer
• setup and maintain session connection
• reliable/unreliable delivery via seq# and acknowledgement
• flow control over ready/not ready signal or windowing
o ready/not ready signal not efficient
o Windows size can negotiate dynamically, how many segments can send before waiting for ack from dest.
• Multiplex connections to allow multiple applications send/receive data at the same time – by using source/destination port and L3 address, socket.
Connection-oriented always start with 3-way handshake
• SYN ->
• SYN/ACK <-
• ACK ->
PDU – Packet Data Unit terms
• Data L7-5
• Segment L4
• Packet L3
• Frame L2
• Bits L1
Cisco hierarchical network
• Core
o high-speed L2 switching and typically don’t manipulate packets
• Distribution
o L3 routing, provides a logical boundary between access and core layers
o stop broadcast
o logical addressing, filtering and QoS
o security
o connect different media types
• Access
o provide user’s initial access to network via hubs or switches
• make upward connection
o Do access -> distribution, distribution -> core
o Do NOT access -> access, distribution -> distribution
Chapter 3 IP Addressing
TCP/IP stack
• application(L7,6,5)
• transport(L4)
o TCP
flow control (windowing and ack)
reliable connections (seq# and ack)
Use PAR to recover lost segments, resending them with a delay between transmissions, until ack received.
header 20bytes
| source port | 16 |
| dest port | 16 |
| Seq# | 32 |
| Ack# | 32 |
| Header length | 4 |
| Reserved field | 6 |
| Code bits | 6 |
| Window size | 16 |
| Checksum | 16 |
| Urgent field | 16 |
| Options | 0-32 |
| data | |
IANA assign well-known TCP ports, FTP 20/21, HTTP 80, SMTP 25, telnet 23
o UDP ports
| source port | 16 |
| dest port | 16 |
| Length | 16 |
| Checksum | 16 |
| data | |
IANA assign well-known UDP ports, DNS query 53, RIP 520, SNMP 161, TFTP 69
• Internet(L3)
o header 20bytes
o TTL to limit hops a packet travel
o ICMP, ARP, RARP, OSPF
o Internet Control Massage Protocol, ping, traceroute
ARP and RARP
Address Resolution Protocol
With a router in between, L2 use default router’s MAC as dest, but IP is the remote dest and router won’t change it.
Reverse ARP, common used in DHCP and BOOTP
IP Addressing
Dotted decimal
Class
| A | 8bits | 0 | 1-126 | 0000001-01111111 |
| B | 16bits | 10 | 128-191 | 1000000-10111111 |
| C | 24bits | 110 | 192-223 | 1100000-11011111 |
| D | multicast | 1110 | 224-239 | 1110000-11101111 |
| E | reserved | 11110 | 240-254 | 1111000-11110111 |
Private networks address
• 10.0.0.0-10.255.255.255 1 A network
• 172.16.0.0-172.31.255.255 16 B network
• 19.168.0.0-192.168.255.255 256 C network
• need NAT to access public network
0.0.0.0 All IP address
255.255.255.255 local broadcast address
Each network has two reserved address – network number(1st one) and directed broadcast address (last one).
Subnet Masks
• Dotted decimal 192.168.1.0 255.255.255.0
• Number of networking bits 192.168.1.0/24
• first and last subnet called subnet 0 may not be used
Network numbers are incrementing by in the interesting octet: 256 – subnet mask value = increment value
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