Understanding Network Routing and WAN Technologies
1b.
Bandwidth – Throughput speed in bits per second ,Cost
– An arbitrary value assigned by an administrator for the intersecting of
Networks, Delay – Network latency caused by such factors as distance or
Congestion, Hop Count – The number of routers (hops) a packets passes
Through to its destination,Load – Measurement of traffic that flows
Through a router ,Reliability – Represents the amount of network
Downtime, that is, how reliable a network path is)
1c . Load Balancing- Routers will distribute packets equally
Among multiple equal-
cost paths.
1d. Administrative Distance-
It’s a numeric value that
Specifies the preference of a particular routing protocol.
1e. Distance Vector Protocol advantages: Lowest rource usage. Easiest Implementation and Maintenance. Link State Protocol: Fastest time to convergence, Greatest scalability.
1f. RIP – Routing
Information Protocol- Uses hop count metric
2A. Hello Process adjancies process-Connected int that are Using the same link state routing protocols will exchange hello packets. Once Router learn it has neighbor they form adjaceny. 2 ajacent neighbor will Exchange hello packets. These packets will serve as a keep alive function.
2B. Link-state update packets sents-When a router wants more Information about a particular set of links, it will send a link state request message to its neighbor. Neighbor will respond with link state update message Containng requested information.
2C.Contents of a link state update packet- When any link state Changes,( link goes up or down, cost changes, a router will flood a link state Update message to all other router in the area. Link state update contains one Or more link state advertisements (LSA’s) from the router. When any router Recieves a link update it checkes whiter this is a new update message. New lsu Message, this router will flood the message. If I t
2d Check.
OSPF path cost-
Eth int 10, fasteth int 1, gigeth int 1, serial int 64.
2 E. OSPF Hello interval- Ussually multicast (224.0.0.5) Sent every 10 sec in general. Sent every 30 sec for NBMA. Dead interval- This Is the time that must transpire before the neighbor is considered down. Default Time is 4 times the hello interval.
2 F. Purpose of OSPF Message – Hello- discovers neighbor and Builds adjanccies between them. Database- Checks for database synchronization Between routers. Link state request- requests specific link-state records from Router to router. Link state update- Sends specifically requested link-state Records.
2 G. Link state updates are flooded- When any router recieves a link state update message, it checks whether this Is a new update message. If it is a new lsu message then this router will flood The messge ( transmit a copy out all int Except the one it arrived on) if it is an old LSU message then this router will Drop the message.
2H- desigingate router
2I- Designated Router Elected- based on Priority Value. Backup Designated Router-is also elected and takes over if DR fails.
2J check- OSPF use path cost as metric for determining best route. Path cost- sum of Link costs on path to destination. Link cost-is based on bandwith of link Interface. Int bandwitch parameter can be changed by admin. It is not affected By clock rate command. Link cost= 10’8.
2k- How path cost for a route to a destination.
Wan Transmission circuits-
DSL
Up to 100 mbps
3b- Dslam- Located at the carriers central office, it Combines individual dsl connections from users into one high capacity link to An isp.
3C. DOCSIS-Data over Cable service interface specification- International standard developed by cablelabs. Test and certifies cable Equipment vendor devices. Defines the communication and operation support int Requirments for a data-over cable system. Specifies the OSI layer 1 and tlayer 2 requirements.
3D-
ISDN
Integrated Services Digital Network (ISDN) was a dial-up service developed in the 1980s for digital Network access.The Idea:
·Provides a fully-digital interface over telephone lines .Allows Customer to do both 64 Kbps dial-up and X.25 data over same ISDN line. Provides Intelligent signaling channel (D-channel) between customer equipment and Central Office
3E-Speed and application
3 f- T carrier- The most common T-carrier Implementations are T1 and T3, Signal level (DS0, DS1, etc.) ANSI standard for T-carrier technology that refers to its Physical layer electrical signaling Characteristics, DSO (digital signal, level 0), Equivalent of one voice channel (64 Kbps),Fractional T1 (FT1, n ×64K),Arrangement allowing an organization to Use only some channels on a T1 line, paying for what they use
3G- DS0- T1 1/24 0.64kbps , DS1 T1- 1 1.54 kbps, DS3 T1 28 44.376kbps.
3H- Sonnet- Fiber optic 0C-3 – 155 mbps , OC-12 –622 mbps. Metro gig ethernet 1 GBPS ,10 GBPS.
3I- OC-3 ≈ 3 × DS3 = 155M bps,-12 = 4 × OC-3 = 622M bps, OC-48 = 4 × OC-12 = 2.4G bps ,OC-192 = 4 × OC-48 = 10G bps, OC-768 = 4 × OC-192 = 40G bps
4A-
Leased Line / Dedicated / Private Line
Circuit
Always available, Guaranteed bandwidth and delay, Fixed cost per month, based on
Bandwidth and distance.
Circuit-Switched / Dial-up ,
Circuit set up by
Demand, Guaranteed bandwidth and delay, Fixed cost plus cost per minute Packet-Switched-
Customer
Data sent over carrier router backbone, Bandwidth is shared, delay is variable,
Typically fixed cost per month, based on access rate and performance parameters
4B- PPP Protocol – Layer 2 protocol based on HDLC ,PPP Services:,Defines frame formats,Negotiates link Establishment and data exchange, Defines network layer encapsulation, Enables Device authentication
4C- LCP -Establishes and terminates Link control, Used to negotiate options between devices at both ends. LCP Packets carry NO data – only used for setting up or tearing down communications Session. NCP- After link is established and authentication is complete, PPP Uses a Network Control Protocol (NCP) to ,Determine what Network Layer Protocol(s) can be sent across the link. Negotiate options for those Network Layer Protocols. Example: Internet Protocol Control Protocol (IPCP) is used to Configure a PPP link to carry IP data.
4D-x25 and frame rally
4E-
Frame Relay
Basic- Fixed Monthly cost based on, “Line charge” for access line between user site and Frame relay carrier location, “Port charge” for each connection into carrier Equipment, “PVC charge” for each PVC defined between ports ,Frame Relay is a Layer 2 protocol, so any layer 3 protocol (like IP, for example) can be carried Over a Frame Relay network
4F- Discard Eligible (DE) – Determines whether this frame can be discarded at network switches Forward Explicit Congestion Notification (FECN), Backward Explicit Congestion Notification (BECN) – Set by network switches if data congestion is detected
4G- CIR-For each PVC, customer pays For a Committed Information Rate (CIR):, CIR represents a guaranteed throughput For this PVC, Carrier also guarantees limited data delivery time if customer Does not exceed CIR ,Price of PVC is directly related to CIR, High CIR = high Monthly price, Low CIR = lower monthly price
4H= Metro Ethernet
4I- Metro Ethernet physical data – Physical data rate: 10 Mbps, 100 Mbps, 1 Gbps or 10 Gbps(Ethernet interface)
4J- Ethernet Virtual Circuits (EVCs) are defined to determine which sites can communicate
4k- E-Line services used for Corporate site interconnect, connect to ISP, Extranet partners, etc. Ethernet Virtual Private Line Service, Similar security and performance level to Frame Relay, Circuit Emulation Service over Ethernet, Fixed bit-rate service, Layer 2 Point-to-point VPN Service. E-LAN services used for intra-corporate site Interconnections. Transparent LAN Service ,Fully emulates Ethernet LAN within The WAN, Customer controls all VLANs and traffic flow, New VLANs can be added Without provider coordination, Multipoint VLAN Service, Carrier provides Encryption.
4l-Multi-Protocol Label Switching, A more efficient way to forward and route packets,Label Edge Router (LER)
Analyzes each packet on arrival to the MLPS network and puts on An MPLS subheader which tells each router where to forward the packet without Reading the IP header (just the MPLS subheader), MPLS subheader sometimes Called a wrapper.