METRO ETHERNET

  1. TLS provides a transparent access-link connection to the carrier's network, where the carrier's connection appears as a logical segment. TLS doesn't scale well because of the use of access link connections. With 802.1Q, you are limited to 4,096 VLANs.

  2. DVS provides a trunk link into a service provider, where the provider's infrastructure is seen as a single logical switch. It provides more flexibility, but presents problems with connecting multiple customers with multiple VLANs. 802.1Q-in-Q tunneling is used to overcome this issue.

  3. SONET, which uses fiber-optic cabling, can carry multiple transports, including Ethernet, IP, ATM, and other services. It supports a dual-ring topology for redundancy. Its main disadvantage is that it uses bandwidth inefficiently.

  4. DWDM supports multiple wavelength frequencies on a single strand of fiber (up to 200). It supports very high data rages (Gbps). One advantage that it has over SONET is that SONET uses TDM, which wastes bandwidth. CWDM is a last-mile technology and supports up to 16 wavelength frequencies. It is used for short distances, such as customers located in the same building.

  5. Q-in-Q (tag stacking) is proprietary to Cisco and is 802.1Q enhancement. Q-in-Q is accomplished by inserting another 802.1Q tag (the service provider's) into your 802.1Q tagged frame. The advantage of Q-in-Q is that the provider's VLAN numbering scheme is transparent to your own numbering scheme. Q-in-Q allows STP BPDUs and CDP information to be tunneled.

  6. EoMPLS extends MPLS by tunneling Layer 2 Ethernet frames across a service provider's Layer 3 core. EoMPLS has more scalability because it has a Layer 3 core and Layer 2 information, including STP, can be tunneled through the service provider. EoMPLS scales much better than Q-in-Q.



BCMSN Exam Cram 2 (Exam Cram 642-811)
CCNP BCMSN Exam Cram 2 (Exam Cram 642-811)
ISBN: 0789729911
EAN: 2147483647
Year: 2003
Pages: 171
Authors: Richard Deal

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