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ETH-QoS Facts
MPLS-ETH-QoS Facts
| Question | Answer |
|---|---|
| Ethernet standard spans what two layers? | Physical Layer & Data Link |
| What layer/standards apply to the Ethernet standard? | Physical & Data Link. IEEE802.3 = Physical & Media Access Controller. IEEE802.2 = Logical Link Controller (Upper Data Link) |
| How fast is "Fast Ethernet"? What physical Medium? | 100Mbps. Typically UTP. |
| What medium is required for 10 Gigabit Ethernet? Range of Sx versus Lx? | Fiber. Sx Range = 200m. Lx range = 5km |
| Ethernet Naming Convention. What is Baseband versus Broadband? | Speed_Tx Technique_Physical Medium Baseband = One signal sent at a time Broadband = Multiple signals simultaneously |
| Length of MAC Address? Number of possible addresses? How is address split up? | EUI 48 = 48 bits in length --> 2^48 Possible Addresses. NOTE: Read right to Left in Hex First 24 bits = Company ID Second 24 bits = Extension Identifier |
| Describe structure of Ethernet Frame | 1)Preamble/SFD (8bits) 2)Dest MAC Address (6 bytes) 3)Source MAC Address (6 bytes) 4)Type (2 bytes) [0800 HEX = IP packet] 5)Data 6)Frame Check Sequence (FCS)(4 bytes) |
| How do switches vs bridges accomplish switching differently? | Bridge = Software Switching Switch = Hardware Switching |
| What are the advantages of one host collision domains? | No collisions & Full Duplex Operation! |
| What is the broadcast address used by switches? | All Hex F's = FF.FF.FF.FF.FF.FF |
| What are the ports involved in STP? And what are the port states? What are the messages sent? | Ports = Root Port, Designated Port, Blocking Port Port States = Blocking, Listening, Learning, Fowarding Messages = BPDUs |
| RSTP reduces convergence for what types of links? | Reduced for: Point to Point & Edge Type Links. NOT reduced for Link Type Shared (Hub) |
| What are the ports involved in RSTP? Port States? | Ports = Designated, Root, Backup (for Des), Alternative (for Root), Disabled Port States = Discarding, Learning, Forwarding |
| What is a Trunk link? Works using ___ ____? What is an Access port? | Link between switches that can carry traffic for any VLAN! _VLAN _Tags! Access port connects to end users. Carries traffic for one VLAN. |
| What is the standard for VLAN tagging? | IEEE802.1Q |
| What is in an 802.1Q tag? | 1) Tag Protocol ID 2) Tag Control Info a] VID = VLAN Identifier b] PCP = Priority Code Point c] CFI = Canonical Format Identifier (1 bit) |
| Advantages of Link Aggregation (two)? | Increased Link Speed. Increased Redundancy. |
| LACP can use a max of _____ ports and only ____ can be active at any one time. Link Aggregation Requirements? | 16 ports, 8 active Requirements = All links full duplex, point to point, same speed |
| What VLANs are used in Ethernet Ring Protection? | --1 Control VLAN (Spans whole ring and can enter Secondary port) --Multiple Data VLANs |
| ERP response to "Link Down"? | Open Secondary Ports & send "Flush Forwarding Database Message" on Control VLAN |
| ERP response to "Switch Down"? | Unblock Secondary Ports |
| Total VLANs available using 802.1Q? | 4096 (VLAN tag = 12 bits in length) |
| QinQ Scalability Formula | (#Services)*(#Sites per Service)*(#Hosts per Site) |
| What standard governs MAC-IN-MAC Provider Backbone Bridging? | IEEE802.1AH |
| What 3 components make up the Service Provider MAC header? | 1)Backbone Destination 2)Backbone Source 3)Backbone TAG |
| What standard governs Connection Oriented Traffic Engineering? | 802.1QAY |
| What are the 4 requirements on a network? | Throughput, Delay, Jitter, Loss |
| Name the IP Precedence classes. How many bits in IP Precedence? | 3 bits = 8 classes 0) Routine 1) Priority 2) Immediate 3) Flash 4) Flash Override 5) Critical 6) Internetwork Control** 7) Network Control** **Reserved for router messages (ICMP, etc) |
| How does DiffServ improve on IP Precedence? | 6 bits = 64 classes (>8) --Includes weighting for drop probability |
| What are Behavior Aggregates (BAs)? | Packets in a network traveling in the same direction with the same DSCP marking. They will be mapped to a Per Hop Behavior (PHB). |
| What is a DS Region? | Group of one or more contiguous DS domains (domains can have different PHB policies and mappings). Use TCAs to agree between the edge routers. |
| Name the 2 types of Traffic Identifiers. | 1) BA Identifier - Classifies packets based ONLY on the DSCP value. 2) Multi-Field (MF) Classifier - Examines a combination of header fields. |
| How is Differv's DSCP compatible with IP precedence? | First 3 bits defites the class = same 8 possible classes. Additional 3 bits define drop probabilities (low, medium, high). EF - Expedited Forwarding (1) AF - Assured Forwarding (4) BE/Default - Best Effort (1) |
| Name the DiffServ Ingress & Egress Functions. | Ingress = Classification, Marking, Policing Egress = Queuing, Scheduling, Congestion Avoidance |
| Formula for rate in Token bucket model? | Rate = (Burst in bits)/(Time Committed in seconds) |
| What kind of Token Buckets can be stacked? | Conforming Burst [Green] Committed Burst (almost conform)[Yellow] Excessive Burst [Red] |
| Once queue depth is achieved (full), what is the probability of drops? How does queue depth affect performance? | 1 or 100% tail drop probability Too big = Big Packet Delay Too small = Tail Drops |
| How does QoS in L2MPLS work? | QoS info is stored in the MPLS header using the 3 bit EXP field to correspond with the IP Precedence in the IP Header (3 MSb's of the DSCP field) |
| How does QoS in L2Ethernet work? | 3 MSb's of the DSCP field propagated into the 3 bit PCP field in the Ethernet header. Governed by 802.1p standard. |
Created by:
glarsen117
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