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71 Cards in this Set
- Front
- Back
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Name 3 encapsulation methods |
HDLC ATM Frame Relay |
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Define fragmentation |
Network packet sizes can be converted based on both network's MTUs |
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What type of data is in a packet? |
Layer 4 (segment) |
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Define packet switching |
Data is chopped up into packets to be transmitted to a destination across a network |
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Name the 12 parts of an IP header and sizes, in bits (ignore this question) |
Version - 4 IHL (Internet Header Length) - 4 DS/ECN (Diff Svcs, Congestion) - 8 Length - 16 ID - 16 Flags - 3 FO (Frag Offset) - 13 TTL - 8 Protocol - 8 Checksum - 16 Source IP - 32 Dest IP - 32 |
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Define NAT |
Network Address Translation Converts private IP to public 1 for 1 |
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Define PAT |
Port Address Translation, AKA NAT overload Assigns unique port number to a private IP Can negotiate with many private IPs simultaneously |
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Define ACL |
Access Control List Blocks incoming/outgoing IPs based on the configuration Types: 1-99 standard, filters source IP only 100-199 extended, can filter: Source and destination TCP/UDP ports Protocol type (IP, ICMP) |
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No routing entry can be found for a packet, what does the router do? |
Sends ICMP (ping) back to the source |
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5 routing table entries |
Routing source (dynamic, static) Destination network Admin distance Metric Forward int/next hop |
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3 routing table lookup processes |
Longest match Admin distance Metric Load balancing (bonus) |
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Define admin distance |
Route trustworthiness Numeric value 0-255 Lower = better |
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Define metric |
Cost value for each routing protocol Lower = better |
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3 cases to use a static route |
Network has few routers Router directly connected to ISP Network is hub and spoke |
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Define default route |
When the route to a destination is not known, packet is forwarded out the default route |
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Define routed vs routing |
Routed = format of packet (ipv4, ipv6) Routing = router communication protocol (RIP, ospf) |
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Name 5 routing protocols |
RIP (routing info) OSPF IGRP (interior gateway) EIGRP (enhanced) BGP (border gateway) |
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Define interior vs exterior routing |
Interior = routing within an autonomous system Exterior = routing between two autonomous systems |
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4 IRP examples |
RIP OSPF IGRP EIGRP |
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ERP example |
BGP |
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Name 4 functions of dynamic routing |
Discovery of remote nets Maintain info Choose best path Find a newer best path |
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What routing protocol is most popular for transferring data in the same domain? |
RIP |
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How does RIP work? |
Lowest hop count 30 second updates Load balancing up to 6 paths Max 15 hops |
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Define OSPF |
Link state routing protocol Follows lowest cost 30 minute updates |
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How is cost calculated? |
Reference bandwidth (default 100Mb/s) ÷ actual bandwidth Low cost = better |
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Define BGP |
Allows communication between gateway routers 3 functionalities: neighbor acquisition Neighbor reachability Network reachability |
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Define neighbor acquisition |
Two routers directly connected exchange routing info |
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Define neighbor reachability |
Is the link still active (are you still there) Sends a keep alive message to maintain the connection |
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Define network reachability |
List of database of all networks a router can reach and preferred routes for each net |
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What connects customer equipment to carrier network |
Local loop |
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Name 5 WAN devices |
Router DSU/CSU Modem WAN switch Access server |
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Define modem |
Converts digital signal to analog Modulates signal using phone lines (300-3400Hz) |
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3 modem limitations |
Voice channel bandwidth Signal to noise ratio Noise encountered during conversions |
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V.34 modem max speed |
33.6 kbps |
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Define DSU/CSU |
Digital DCE that connects DTE to wan |
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Define DSU |
Data service unit Converts unipolar to bipolar (Eia 232 to AMI) |
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Define CSU |
Channel service unit Supports comms over digital ccts Located on customer premises Terminates electrical connection Generates keep alive signal |
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How many Ds0 channels are there |
24 |
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List the hierarchy of carrier signals for CSU (ignore this) |
0 - DS0 (1 channel, 64 kbps) First - DS1 (24 channels, 1.544 Mbps) Intermediate - T1C (48 ch, 3.152 Mbp Second - DS2 (96 ch, 6.312 Mbps) Third - DS3 (672 ch, 44.736 Mbps) |
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WAN operations focus on what 2 layers? |
1 and 2 |
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2 private infrastructure approaches |
Dedicated line vs switched network |
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What do you need for dedicated connections |
Point to point lines (PPP) on existing infrastructure |
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2 techs used in WAN switched nets |
Circuit switching Packet switching |
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Define circuit switching |
Dynamically establishes a dedicated comms path between 2 pts 3 phases: initialization Data tx Disconnect |
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2 examples of cct switched techs |
PSTN (public switched telephone net) ISDN (integrated Svcs digital net) |
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Define packet switching |
Breaking data into chunks and transmitting it in labelled packets through a switched net to the destination Packets may take different routes |
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3 examples of packet switching techs |
X.25 Frame Relay MPLS |
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Define local loop |
Transmission path that connects CPE to central office |
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Define demarcation pt |
Separates customer equipment from SVC provider equipment |
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Define CSU/DSU |
CSU Terminates the digital signal. Provides error correction and line monitoring DSU concerts T carrier from CSU into frames that the LAN can interpret |
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Define access server |
Concentrates dial in/out comms |
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Name 10 factors for choosing WAN techs |
Availability of svc Bandwidth Traffic type Dedicated or switched Cost Set up of private infrastructure Leased lines Data consumption QoS Security |
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7 types of mediums used in WANS |
Twisted pair Coax Fibre Terrestrial Microwave Sat Cellular BLOS |
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Name 2 organizations responsible for DTE to DCE comms |
EIA/TIA ITU |
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RS-232, 422, 423, 530, 612, 613, X21, v.35 Max speeds (ignore this one except RS-232 and V.35) |
RS-232: 20kbps TIA-422: 90Kbps @ 1200m, 10 Mbps @ 10 m TIA-423: 6.5Kbps @ 1200 m, 100kbps @ 100m 530: 2 Mbps V.35: 2.048 Mbps 612/613: 52 Mbps/45 Mbps X.21: 600 bps to 10 Mbps |
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Define T carrier |
Generic name for any several digitally mux'd carrier systems Used for digital data tx |
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How much data in one phone call |
64kbps AKA DS0 (Digital signal level 0) |
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T Carrier hierarchy (ignore this one) |
24 DS0s = T1 (1.544 Mbps) 2 T1 = T1C 2 T1C = T2 7 T2 = T3 6 T3 = T4 |
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6 data link control requirements |
Sync Flow ctrl Error ctrl Addressing Ctrl + data on same link Link mgmt |
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Key difference in a layer 2 WAN frame? |
Has a protocol field in the header for layer 3 multiprotocol support |
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What is Cisco hdlc |
Version of HDLC for multiprotocol support |
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What is PPP |
Multiprotocol support for transmission over serial lines |
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Main PPP advantage over HDLC |
Has link quality management feature |
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2 PPP authentication protocols |
PAP CHAP |
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3 main components of PPP |
HDLC: as basis for packet encapsulation Link ctrl protocol LCP: to establish, configure, test the link Network control protocol NCP: to establish and configure different network layer protocols |
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3 interfaces you can configure PPP |
Async serial Sync serial ISDN |
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Does PPP impose transmission rate restrictions? |
No |
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3 phases of PPP connection |
1) link establishment + negotiation 2) link quality det (optional) 3) network layer protocol config |
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Name 4 LCP options that PPP may include |
Authentication (pap, chap) Compression Error det Multilink (load balancing) |
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Define PAP |
2 way PPP authentication method No encryption Authenticates only once
Challenge message Accept/reject message |
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Define CHAP |
3 way handshake Challenge Response Accept/reject Periodic authentication Encrypted (MD5) |
